Animal feed composition comprising half-burned dolomite

Abstract

The present invention relates to an animal feed composition comprising half-burned dolomite in an amount of at least 10 wt.-%, based on the total weight of the composition, an animal feed formulation comprising the animal feed composition, as well as the use of half-burned dolomite in a feed formulation for animals, preferably poultry, ruminants, polygastric and monogastric animals such as cows, horses, sheeps, goats, swines and the like, and fish.

Description

[0001]Animal feed composition comprising half-burned dolomite The present invention relates to an animal feed composition comprising half-burned dolomite in an amount of at least 10 wt.-%, based on the total weight of the composition, an animal feed formulation comprising the animal feed composition, as well as the use of half-burned dolomite in a feed formulation for animals, preferably poultry, ruminants, polygastric and monogastric animals such as cows, horses, sheeps, goats, swines and the like, and fish. Technological Background The supplementation of calcium and magnesium in animals, preferably ruminants, is widelyused in animal nutrition and health for various reasons. In particular, calcium and magnesium areessential nutrients in animals and typically needed beyond basic feed requiring the addition of calciumand magnesium to their feed ration. Furthermore, calcium and magnesium have a buffering effect onrumen pH and thus may reduce the likelihood of ruminal acidosis caused by feeding high concentratediets. The most common approach is supplementing animals with a selection or combination ofCaCO3, MgO, brucite, dolomite, and (NaHCO3 / Na2CO3). Another approach uses a product of marineorigin (typically Lithothamnium calcareum) which comprises a porous structure consisting of 85%calcium carbonate and 15% magnesium carbonate. A further approach uses ready-to-use feedsupplements comprising a mixture of natural, ultra-finely ground calcium carbonate (about 77%) andmagnesium oxide (about 19%) compacted with a sugar cane molasses binder (4%) and pressed intogranular form, which is e.g. commercially sold under the tradename OmyaFeed® C MgO.However, each of these approaches have several drawbacks. For example, the quality / purityof the available raw materials is not satisfactory for e.g. MgO and brucite. Furthermore, theiravailability is limited due to the current geopolitical situation, price, and high dusting level of theproducts provided in powder form. Moreover, dolomite provides a poor reactivity and pH impact of theraw material. As regards the products of the marine origin, these products are unsustainable productdue to the excavation of coral reefs from the seafloor and destruction of marine environment.Furthermore, there are difficulties to obtain mining permits as well as limited availability of deposits ofsufficient quality. In addition thereto, these products may be contaminated with heavy metals,especially As. As regards the above-mentioned ready-to-use feed supplement, there are restrictionson the purity of the available raw magnesium oxide materials. Furthermore, there are concerns on thereactivity of magnesium oxide and further complicated manufacturing process.In view of the foregoing, there is still a need in the art for an animal feed providing the macronutrients calcium and magnesium. More precisely, there is a need for an animal feed comprisingcalcium and magnesium that provides a buffering capacity in animals, preferably ruminants, combinedwith a high bioavailability. Accordingly, it is an objective of the present invention to provide an animal feed that has ahigh buffering capacity in animals, preferably ruminants, such that the risk of rumen acidosis may bereduced. It is a further objective of the present invention to provide an animal feed that has a highbioavailability. It is another objective of the present invention to provide the macronutrients calciumand magnesium in animal feed. It is a further objective of the present invention to provide an animalfeed comprising calcium and magnesium that are obtained from raw materials of high quality / purityand without restrictions on the sustainability of the raw material sources. These and other objectives of the present invention can be solved by the inventive animal feedcomposition, the animal feed formulation comprising the animal feed composition as well as the use ofhalf-burned dolomite in a feed formulation for animals. Summary of the Invention According to one aspect of the present invention, an animal feed composition is provided. The animal feed composition comprises half-burned dolomite in an amount of at least 10 wt.-%, based on the total weight of the composition. Asecond aspect of the present invention relates to an animal feed formulation comprising theanimal feed composition as defined herein. A third aspect of the present invention relates to the use of half-burned dolomite in a feed formulation for animals, preferably poultry, ruminants, polygastric and monogastric animals such as cows, horses, sheeps, goats, swines and the like, and fish. The inventors surprisingly found out that the animal feed composition provides a high andsufficient buffering capacity in animals, such as ruminants, and thus the risk of rumen acidosis isreduced. Furthermore, the half-burned dolomite in the animal feed provides a high and sufficientbioavailability. In addition thereto, the animal feed provides the macronutrients calcium and magnesiumin animal feed. Furthermore, half-burned dolomite included in the animal feed composition can beobtained from a raw material of high quality / purity and without restrictions on the sustainability of the raw material sources Advantageous embodiments of the present invention can be found in the corresponding dependent claims. In one embodiment of any one of the aspects of the present invention, the half-burned dolomite has a magnesium oxide (MgO) content of ≥ 15 wt.-%, preferably from 15 to 50 wt.-%, more preferably from 20 to 35 wt.-% and most preferably from 20 to 30 wt.-%, based on the total weight of the half-burned dolomite. In another embodiment of any one of the aspects of the present invention, the half-burneddolomite has a calcium carbonate (CaCO3) content of ≥ 39 wt.-%, preferably from 39 to 85 wt.-%, more preferably from 50 to 80 wt.-% and most preferably from 65 to 75 wt.-%, based on the total weight of the half-burned dolomite. In yet another embodiment of any one of the aspects of the present invention, the half-burneddolomite has a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably ≤ 3.5 wt.-%, based on the total weight of the half-burned dolomite. In one embodiment of any one of the aspects of the present invention, the half-burneddolomite has a weight median particle size d50 in the range from 1 to 200 µm, preferably from 1 to 150µm, more preferably from 1 to 100 µm, and most preferably from 5 to 50 µm, as determined by laserdiffraction, and / or the half-burned dolomite has a BET specific surface area in the range from 1 to 20m2 / g, preferably from 1 to 15 m2 / g, and most preferably from 2 to 10 m2 / g, measured using nitrogenand the BET method according to ISO 9277:2010.In another embodiment of the animal feed composition of the present invention, the half-burned dolomite is present in an amount ranging from 10 to 100 wt.-%, preferably from 20 to 100 wt.- %, more preferably from 40 to 100 wt.-% and most preferably from 65 to 100 wt.-%, based on the total weight of the composition. In yet another embodiment of the animal feed composition of the present invention, thecomposition further comprises one or more agent(s) comprising anions selected from the group comprising oxides, hydroxides, carbonates, hydrogen carbonates, sulfates, chlorides and the like, and / or cations selected from the group comprising magnesium, calcium, sodium, potassium and mixtures thereof. In one embodiment of the animal feed composition of the present invention, the compositioncomprises the one or more agent(s) in a total amount ranging from 0 to 90 wt.-%, preferably from 0 to 80 wt.-% and most preferably from 0 to 35 wt.-%, based on the total weight of the composition. In another embodiment of any one of the aspects of the present invention, the composition further comprises a binder, such as molasses, clays, lignosulfonates, sodium alginate, in an amount ranging from 1 to 10 wt.-%, preferably from 1 to 5 wt.-% and most preferably from 1 to 3 wt.-%, based on the total weight of the composition. In yet another embodiment of the animal feed composition of the present invention, the composition is in form of a compacted composition such as granules, preferably granules having an average particle size of 0.5 to 10 mm, more preferably 2 to 6 mm. In one embodiment of the animal feed formulation of the present invention, the formulationfurther comprises ingredients such as vitamins, minerals, trace elements, roughage, sugar, aminoacids, proteins, bentonite, zeolite, yeasts, flavorings, colorants, preservatives, oils, probiotics,prebiotics, antioxidants, emulsifiers, regulators, digestability enhancers and mixtures thereof.In another embodiment of the animal feed formulation of the present invention, the formulationhas a content of half-burned dolomite ranging from 0.1 to 10 wt.-%, preferably from 0.1 to 5 wt.-%,more preferably from 0.25 to 3 wt.-%, and most preferably from 0.5 to 2 wt.-%, based on the total weight of the formulation. In one embodiment of the use of the present invention, the half-burned dolomite is used asmagnesium and calcium ion source and / or pH control agent. Where the term “comprising” is used in the present description and claims, it does not exclude other elements. For the purposes of the present invention, the term “consisting of” is considered to be a preferred embodiment of the term “comprising”. If hereinafter a group is defined to comprise at least acertain number of embodiments, this is also to be understood to disclose a group, which preferablyconsists only of these embodiments. Whenever the terms “including” or “having” are used, these terms are meant to be equivalent to “comprising” as defined hereinabove. Terms like “obtainable” or “definable” and “obtained” or “defined” are used interchangeably. This, for example, means that, unless the context clearly dictates otherwise, the term “obtained” does not mean to indicate that, for example, an embodiment must be obtained by, for example, the sequence of steps following the term “obtained” though such a limited understanding is always included by the terms “obtained” or “defined” as a preferred embodiment When in the following reference is made to embodiments or technical details of the inventive animal feed composition, it is to be understood that these embodiments or technical details also refer to the inventive animal feed formulation and the inventive use. The animal feed composition The inventive animal feed composition comprises half-burned dolomite. It is specificallyrequired that the animal feed composition comprises half-burned dolomite in an amount of at least 10wt.-%, based on the total weight of the composition. In the meaning of the present invention, raw “dolomite” is a naturally occurring double carbonate consisting of a structural arrangement of calcium carbonate CaCO3 and magnesiumcarbonate MgCO3. For the purposes of the present invention, any available variety of dolomite can beused. However, in one preferred embodiment, the dolomite is white dolomite representing a relatively pure dolomite. In order to convert the magnesium compounds and / or calcium compounds, i.e. thecarbonates, contained in said dolomite at least partially into magnesium and calcium oxide, thedolomite is usually calcined at high temperatures, wherein said calcining step can be carried out byany conventional calcining process known to the skilled person. For example, dolomite can be calcined at temperatures of between 900°C and 1200°C and more preferably at a temperature of between 1000°C and 1100°C in order to obtain burned dolomite (MgO · CaO). Alternatively, dolomite is calcined at temperatures of between 600°C and 900°C, more preferably of between 600°C and 800°C and most preferably at a temperature of about 750°C in order to obtain half-burned dolomite (MgO · CaCO3). The chemical characteristics such as reactivity of the half-burned or burned dolomite, i.e. of the obtained magnesium oxide, depend mainly on the temperatures and calcining processes used which are well known to the skilled person. For instance, if the dolomite is calcined at a temperature in the range of 1000°C to 1100°C in order to obtain burned dolomite, said temperature is preferably maintained for a period of time of between 30 min to 120 min and most preferably for a period of time of between 45 min and 90 min, for example for about 60 min. It is appreciated that “half-burned dolomite” in the meaning of the present invention refers to dolomite that has been subjected to a calcining at a temperature of between 650°C and 950°C, morepreferably of between 750°C and 950°C and most preferably at a temperature of between 800 and900°C, e.g. a temperature of between 800 and < 900°C. For instance, if the dolomite is calcined at atemperature in the range of 650°C and 950°C, more preferably in the range of 750°C and 950°C andmost preferably in the range of 800 and 900°C, e.g. in the range of 800 and < 900°C, in order to obtainhalf-burned dolomite, said temperature is preferably maintained for a period of time of between 20 minand 100 min and most preferably for a period of time of between 20 min and 70 min, for examplebetween 30 min and 45 min.As already mentioned above, the half-burned dolomite comprises magnesium oxide. Forexample, the half-burned dolomite has a magnesium oxide (MgO) content of ≥ 15 wt.-%, based on the total weight of the half-burned dolomite. In one embodiment, the half-burned dolomite has a magnesium oxide (MgO) content from 15 to 50 wt.-%, more preferably from 20 to 35 wt.-% and most preferably from 20 to 30 wt.-%, based on the total weight of the half-burned dolomite. In view of the calcining temperature used for obtaining the half-burned dolomite, the half- burned dolomite further comprises specific amounts of calcium carbonate. For example, the half- burned dolomite has a calcium carbonate (CaCO3) content of ≥ 39 wt.-%, based on the total weight of the half-burned dolomite. In one embodiment, the half-burned dolomite has a calcium carbonate (CaCO3) content from 39 to 85 wt.-%, more preferably from 50 to 80 wt.-% and most preferably from 65 to 75 wt.-%, based on the total weight of the half-burned dolomite. Additionally or alternatively, the half-burned dolomite thus comprises calcium oxide. Forexample, the half-burned dolomite has a calcium oxide (CaO) content of ≤ 5 wt.-%, based on the total weight of the half-burned dolomite. In one embodiment, the half-burned dolomite has a calcium oxide (CaO) content of ≤ 4 wt.-%, and most preferably ≤ 3.5 wt.-%, based on the total weight of the half-burned dolomite. In one embodiment, the calcium oxide (CaO) content of the half-burned dolomite is ≤3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the half-burned dolomite. In view of the above, it is appreciated that the half-burned dolomite comprises specific amounts of magnesium oxide and calcium carbonate. In one embodiment, the half-burned dolomite thus has a) a magnesium oxide (MgO) content of ≥ 15 wt.-%, preferably from 15 to 50 wt.-%, morepreferably from 20 to 35 wt.-% and most preferably from 20 to 30 wt.-%, based on the total weight of the half-burned dolomite, and b) a calcium carbonate (CaCO3) content of ≥ 39 wt.-%, preferably from 39 to 85 wt.-%,more preferably from 50 to 80 wt.-% and most preferably from 65 to 75 wt.-%, based on the total weight of the half-burned dolomite. Additionally or alternatively, the half-burned dolomite comprises specific amounts of magnesium oxide and calcium oxide. In one embodiment, the half-burned dolomite thus has a) a magnesium oxide (MgO) content of ≥ 15 wt.-%, preferably from 15 to 50 wt.-%, morepreferably from 20 to 35 wt.-% and most preferably from 20 to 30 wt.-%, based on the total weight of the half-burned dolomite, and b) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1wt.-%, based on the total weight of the half-burned dolomite. Additionally or alternatively, the half-burned dolomite comprises specific amounts of calciumcarbonate and calcium oxide.In one embodiment, the half-burned dolomite thus has a) a calcium carbonate (CaCO3) content of ≥ 39 wt.-%, preferably from 39 to 85 wt.-%,more preferably from 50 to 80 wt.-% and most preferably from 65 to 75 wt.-%, based on the total weight of the half-burned dolomite, and b) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1wt.-%, based on the total weight of the half-burned dolomite. Preferably, the half-burned dolomite comprises specific amounts of magnesium oxide, calcium carbonate and calcium oxide. In one embodiment, the half-burned dolomite thus has a) a magnesium oxide (MgO) content of ≥ 15 wt.-%, preferably from 15 to 50 wt.-%, morepreferably from 20 to 35 wt.-% and most preferably from 20 to 30 wt.-%, based on the total weight of the half-burned dolomite, and b) a calcium carbonate (CaCO3) content of ≥ 39 wt.-%, preferably from 39 to 85 wt.-%,more preferably from 50 to 80 wt.-% and most preferably from 65 to 75 wt.-%, based on the total weight of the half-burned dolomite, and c) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1wt.-%, based on the total weight of the half-burned dolomite.It is appreciated that the half-burned dolomite in the animal feed composition should have ahigh bioavailability. Thus, it is preferred that the half-burned dolomite has a weight median particle sized50 in the range from 1 to 200 µm, as determined by laser diffraction. Preferably, the half-burneddolomite has a weight median particle size d50 in the range from 1 to 150 µm, preferably from 1 to 100µm, and most preferably from 5 to 50 µm, as determined by laser diffraction.Additionally or alternatively, the half-burned dolomite has a top cut particle size d98, as determined by laser diffraction, of ≤ 400 µm. Preferably, the half-burned dolomite has a top cut particlesize d98 in the range from 50 to 400 µm, more preferably from 50 to 300 µm, and most preferably from50 to 200 µm, as determined by laser diffraction .Throughout the present document, the “particle size” of all materials is described by itsdistribution of particle sizes on a volume base. Volume determined median grain diameter d50 (ord50(vol)) and the volume determined top cut particle size d98 (or d98(vol)) was evaluated using a Malvern Mastersizer 3000 Laser Diffraction System (Malvern Instruments Plc., Great Britain) equippedwith an Aero S attachment. The d50(vol) or d98(vol) value indicates a diameter value such that 50 % or98 % by volume, respectively, of the particles have a diameter of less than this value. The methods and instruments are known to the skilled person and are commonly used to determine particle sizedistributions of fillers and pigments.In one embodiment, the half-burned dolomite has a weight median particle size d50 in therange from 1 to 200 µm, preferably from 1 to 150 µm, more preferably from 1 to 100 µm, and mostpreferably from 5 to 50 µm, as determined by laser diffraction, or a top cut particle size d98 in the rangefrom 50 to 400 µm, preferably from 50 to 300 µm, and most preferably from 50 to 200 µm, asdetermined by laser diffraction. Preferably, the half-burned dolomite has a weight median particle sized50 in the range from 1 to 200 µm, preferably from 1 to 150 µm, more preferably from 1 to 100 µm,and most preferably from 5 to 50 µm, as determined by laser diffraction, and a top cut particle size d98in the range from 50 to 400 µm, preferably from 50 to 300 µm, and most preferably from 50 to 200 µm,as determined by laser diffraction. Additionally or alternatively, the half-burned dolomite has a BET specific surface area in therange from 1 to 20 m2 / g, preferably from 1 to 15 m2 / g, and most preferably from 2 to 10 m2 / g,measured using nitrogen and the BET method according to ISO 9277:2010. The “specific surface area” (expressed in m2 / g) of a material as used throughout the present document can be determined by the Brunauer Emmett Teller (BET) method with nitrogen as adsorbing gas and by use of a ASAP 2460 instrument from Micromeritics. The method is well known to the skilled person and defined in ISO 9277:2010. Samples are conditioned at 100 °C under vacuum for a period of 30 min prior to measurement. The total surface area (in m2) of said material can be obtained by multiplication of the specific surface area (in m2 / g) and the mass (in g) of the material. In one embodiment, the half-burned dolomite has a weight median particle size d50 in therange from 1 to 200 µm, preferably from 1 to 150 µm, more preferably from 1 to 100 µm, and mostpreferably from 5 to 50 µm, as determined by laser diffraction, or the half-burned dolomite has a BETspecific surface area in the range from 1 to 20 m2 / g, preferably from 1 to 15 m2 / g, and most preferablyfrom 2 to 10 m2 / g, measured using nitrogen and the BET method according to ISO 9277:2010.Preferably, the half-burned dolomite has a weight median particle size d50 in the range from 1to 200 µm, preferably from 1 to 150 µm, more preferably from 1 to 100 µm, and most preferably from 5to 50 µm, as determined by laser diffraction, and the half-burned dolomite has a BET specific surface area in the range from 1 to 20 m2 / g, preferably from 1 to 15 m2 / g, and most preferably from 2 to 10 m2 / g, measured using nitrogen and the BET method according to ISO 9277:2010. In one embodiment, the half-burned dolomite has a weight median particle size d50 in therange from 1 to 200 µm, preferably from 1 to 150 µm, more preferably from 1 to 100 µm, and mostpreferably from 5 to 50 µm, as determined by laser diffraction, and a top cut particle size d98 in therange from 50 to 400 µm, preferably from 50 to 300 µm, and most preferably from 50 to 200 µm, asdetermined by laser diffraction, and the half-burned dolomite has a BET specific surface area in therange from 1 to 20 m2 / g, preferably from 1 to 15 m2 / g, and most preferably from 2 to 10 m2 / g,measured using nitrogen and the BET method according to ISO 9277:2010.It is appreciated that the particle size distribution, i.e. the weight median particle size d50 andthe top cut particle size d98, as well as the BET specific surface area can be adjusted by any method orinstrument known to the skilled person. For example, the particle size distribution, i.e. the weightmedian particle size d50 and the top cut particle size d98, as well as the BET specific surface area canbe adjusted by milling the half-burned dolomite for a sufficient time, e.g. in the presence or absence of grinding media. It is further required that the animal feed composition comprises the half-burned dolomite in an amount of at least 10 wt.-%, based on the total weight of the composition. In one embodiment, the half-burned dolomite is present in an amount ranging from 10 to 100 wt.-%, preferably from 20 to 100 wt.-%, more preferably from 40 to 100 wt.-% and most preferably from 65 to 100 wt.-%, based on the total weight of the composition. In a preferred embodiment, the half-burned dolomite is present in an amount ranging from 10 to 99 wt.-%, preferably from 20 to 99 wt.-%, more preferably from 40 to 99 wt.-% and most preferably from 65 to 99 wt.-%, based on the total weight of the composition. Alternatively, the half-burneddolomite is present in an amount ranging from 10 to 97 wt.-%, preferably from 20 to 97 wt.-%, morepreferably from 40 to 97 wt.-% and most preferably from 65 to 97 wt.-%, based on the total weight ofthe composition. Alternatively, the half-burned dolomite is present in an amount ranging from 10 to 95 wt.-%, preferably from 20 to 95 wt.-%, more preferably from 40 to 95 wt.-% and most preferably from 65 to 95 wt.-%, based on the total weight of the composition. Alternatively, the half-burned dolomite is present in an amount ranging from 10 to 92 wt.-%, preferably from 20 to 92 wt.-%, more preferably from 40 to 92 wt.-% and most preferably from 65 to 92 wt.-%, based on the total weight of the composition. Preferably, the half-burned dolomite is present in an amount ranging from 10 to 90 wt.-%, preferably from 20 to 90 wt.-%, more preferably from 40 to 90 wt.-% and most preferably from 65 to 90 wt.-%, based on the total weight of the composition. In view of the above, the animal feed composition preferably has a magnesium oxide (MgO) content of ≥ 1.5 wt.-%, based on the total weight of the animal feed composition. In one embodiment, the animal feed composition has a magnesium oxide (MgO) content from 1.5 to 50 wt.-%, more preferably from 2.0 to 35 wt.-% and most preferably from 2.0 to 30 wt.-%, based on the total weight of the animal feed composition. Additionally or alternatively, the animal feed composition has a calcium carbonate (CaCO3)content of ≥ 3.9 wt.-%, based on the total weight of the animal feed composition. In one embodiment, the animal feed composition has a calcium carbonate (CaCO3) content from 3.9 to 85 wt.-%, more preferably from 5.0 to 80 wt.-% and most preferably from 6.5 to 75 wt.-%, based on the total weight of the animal feed composition. Additionally or alternatively, the animal feed composition has a calcium oxide (CaO) content of ≤ 5 wt.-%, based on the total weight of the animal feed composition. In one embodiment, the animalfeed composition has a calcium oxide (CaO) content of ≤ 4 wt.-%, and most preferably ≤ 3.5 wt.-%,based on the total weight of the animal feed composition. In one embodiment, the calcium oxide(CaO) content of the animal feed composition is ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the animal feed composition. In view of the above, it is appreciated that the animal feed composition comprises specific amounts of magnesium oxide and calcium carbonate. In one embodiment, the animal feed composition thus preferably hasa) a magnesium oxide (MgO) content of ≥ 1.5 wt.-%, preferably from 1.5 to 50 wt.-%,more preferably from 2.0 to 35 wt.-% and most preferably from 2.0 to 30 wt.-%, based on the total weight of the animal feed composition, and b) a calcium carbonate (CaCO3) content of ≥ 3.9 wt.-%, preferably from 3.9 to 85 wt.-%,more preferably from 5.0 to 80 wt.-% and most preferably from 6.5 to 75 wt.-%, based on the total weight of the animal feed composition. Additionally or alternatively, the animal feed composition comprises specific amounts of magnesium oxide and calcium oxide. In one embodiment, the animal feed composition thus preferably hasa) a magnesium oxide (MgO) content of ≥ 1.5 wt.-%, preferably from 1.5 to 50 wt.-%,more preferably from 2.0 to 35 wt.-% and most preferably from 2.0 to 30 wt.-%, based on the total weight of the animal feed composition, and b) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the animal feed composition. Additionally or alternatively, the animal feed composition comprises specific amounts ofcalcium carbonate and calcium oxide.In one embodiment, the animal feed composition thus preferably has a) a calcium carbonate (CaCO3) content of ≥ 3.9 wt.-%, preferably from 3.9 to 85 wt.-%,more preferably from 5.0 to 80 wt.-% and most preferably from 6.5 to 75 wt.-%, based on the total weight of the animal feed composition, and b) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the animal feed composition. Preferably, the animal feed composition comprises specific amounts of magnesium oxide, calcium carbonate and calcium oxide. In one embodiment, the animal feed composition thus preferably has a) a magnesium oxide (MgO) content of ≥ 1.5 wt.-%, preferably from 1.5 to 50 wt.-%,more preferably from 2.0 to 35 wt.-% and most preferably from 2.0 to 30 wt.-%, based on the total weight of the animal feed composition, and b) a calcium carbonate (CaCO3) content of ≥ 3.9 wt.-%, preferably from 3.9 to 85 wt.-%,more preferably from 5.0 to 80 wt.-% and most preferably from 6.5 to 75 wt.-%, based on the total weight of the animal feed composition, and c) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the animal feed composition. In a preferred embodiment, the animal feed composition has a) a magnesium oxide (MgO) content of ≥ 3.0 wt.-%, preferably from 3.0 to 50 wt.-%,more preferably from 4.0 to 35 wt.-% and most preferably from 4.0 to 30 wt.-%, based on the totalweight of the animal feed composition, and b) a calcium carbonate (CaCO3) content of ≥ 7.8 wt.-%, preferably from 7.8 to 85 wt.-%,more preferably from 10.0 to 80 wt.-% and most preferably from 13.0 to 75 wt.-%, based on the totalweight of the animal feed composition, and c) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the animal feed composition. In a preferred embodiment, the animal feed composition has a) a magnesium oxide (MgO) content of ≥ 6.0 wt.-%, preferably from 6.0 to 50 wt.-%,more preferably from 8.0 to 35 wt.-% and most preferably from 8.0 to 30 wt.-%, based on the totalweight of the animal feed composition, and b) a calcium carbonate (CaCO3) content of ≥ 15.6 wt.-%, preferably from 15.6 to 85 wt.-%, more preferably from 20.0 to 80 wt.-% and most preferably from 26.0 to 75 wt.-%, based on thetotal weight of the animal feed composition, and c) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the animal feed composition. In a preferred embodiment, the animal feed composition has a) a magnesium oxide (MgO) content of ≥ 9.75 wt.-%, preferably from 9.75 to 50 wt.-%,more preferably from 13.0 to 35 wt.-% and most preferably from 13.0 to 30 wt.-%, based on the totalweight of the animal feed composition, and b) a calcium carbonate (CaCO3) content of ≥ 25.35 wt.-%, preferably from 25.35 to 85wt.-%, more preferably from 32.5 to 80 wt.-% and most preferably from 42.25 to 75 wt.-%, based on the total weight of the animal feed composition, and c) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the animal feed composition. The half-burned dolomite can be used in the animal feed composition as magnesium andcalcium ion source and / or pH control agent. For example, the half-burned dolomite is used in theanimal feed composition as magnesium and calcium ion source or pH control agent. It is appreciatedthat the half-burned dolomite is preferably used in the animal feed composition as magnesium and calcium ion source if the animal feed composition is mainly considered for monogastrics. Alternatively,the half-burned dolomite is preferably used in the animal feed composition as pH control agent if theanimal feed composition is mainly considered for polygastrics, i.e. ruminants. Preferably, the half-burned dolomite is used in the animal feed composition as magnesium and calcium ion source and pHcontrol agent. For example, the half-burned dolomite is used in the animal feed composition asmagnesium and calcium ion source and pH control agent for polygastrics, i.e. ruminants. The wording “pH control agent” in the meaning of the present invention refers to an agent that buffers the pH according to the optimal physiological pH of the stomach. For example, the pH control agent is generally suitable for buffering the pH in a range between 2 and 6.4. In a preferred embodiment, the pH control agent is suitable for buffering the pH in a range between 5.8 and 6.4,especially if the animal feed composition is used for ruminants.In view of the above, it is appreciated that the animal feed composition may be free of further agent(s). That is to say, the animal feed composition consists of the half-burned dolomite. In one embodiment, the animal feed composition comprises one or more agent(s) that aretypically included in the products to be prepared. For example, the animal feed composition further comprises one or more agent(s) comprising anions selected from the group comprising oxides, hydroxides, carbonates, hydrogen carbonates, sulfates, chlorides and the like. Additionally or alternatively, the animal feed composition further comprises one or more agent(s) comprising cations selected from the group comprising magnesium, calcium, sodium, potassium and mixtures thereof. In one embodiment, the animal feed composition further comprises one or more agent(s) comprising anions selected from the group comprising oxides, hydroxides, carbonates, hydrogen carbonates, sulfates, chlorides and the like and cations selected from the group comprising magnesium, calcium, sodium, potassium and mixtures thereof. Preferably, the animal feed composition further comprises one or more agent(s) selected fromthe group comprising, preferably consisting of, magnesium hydroxide, calcium hydroxide, magnesiumoxide, calcium oxide, sodium hydroxide, potassium hydroxide, calcium carbonate, magnesium carbonate, dolomite, magnesium chloride, calcium chloride, sodium chloride, potassium chloride,calcium hydrogen carbonate, magnesium hydrogen carbonate, sodium hydrogen carbonate,magnesium sulfate, calcium sulfate, and the like. In a further preferred embodiment, the animal feedcomposition further comprises one or more agent(s) selected from the group comprising, preferablyconsisting of, magnesium oxide, calcium oxide, calcium carbonate, magnesium carbonate anddolomite. For example, the animal feed composition further comprises one or more agent(s) selected from the group comprising, preferably consisting of, magnesium oxide, calcium oxide, calciumcarbonate and magnesium carbonate.In one embodiment, the animal feed composition further comprises one agent selected fromthe group comprising, preferably consisting of, magnesium hydroxide, calcium hydroxide, magnesiumoxide, calcium oxide, sodium hydroxide, potassium hydroxide, calcium carbonate, magnesiumcarbonate, dolomite, magnesium chloride, calcium chloride, sodium chloride, potassium chloride, calcium hydrogen carbonate, magnesium hydrogen carbonate, sodium hydrogen carbonate,magnesium sulfate, calcium sulfate, and the like. In a further preferred embodiment, the animal feedcomposition further comprises one agent selected from the group comprising, preferably consisting of,magnesium oxide, calcium oxide, calcium carbonate, magnesium carbonate and dolomite. Forexample, the animal feed composition further comprises one agent selected from the groupcomprising, preferably consisting of, magnesium oxide, calcium oxide, calcium carbonate andmagnesium carbonate. Alternatively, the animal feed composition comprises a mixture of the above agents. That is to say, the animal feed composition further comprises two or more, e.g. two or three, agents selected from the group comprising, preferably consisting of, magnesium hydroxide, calcium hydroxide, magnesium oxide, calcium oxide, sodium hydroxide, potassium hydroxide, calcium carbonate, magnesium carbonate, dolomite, magnesium chloride, calcium chloride, sodium chloride, potassium chloride, calcium hydrogen carbonate, magnesium hydrogen carbonate, sodium hydrogen carbonate, magnesium sulfate, calcium sulfate, and the like. In a further preferred embodiment, the animal feed composition further comprises two or more, e.g. two or three, agents selected from the groupcomprising, preferably consisting of, magnesium oxide, calcium oxide, calcium carbonate, magnesiumcarbonate and dolomite. For example, the animal feed composition further comprises two or more, e.g. two or three, agents selected from the group comprising, preferably consisting of, magnesium oxide, calcium oxide, calcium carbonate and magnesium carbonate. If the animal feed composition further comprises calcium carbonate, the calcium carbonate ispreferably ground calcium carbonate (GCC). The ground calcium carbonate preferably has a weightmedian particle size d50 in the range from 1 to 200 µm, preferably from 1 to 150 µm, more preferablyfrom 1 to 100 µm, and most preferably from 5 to 50 µm, as determined by laser diffraction.If the animal feed composition further comprises dolomite, the dolomite is preferably grounddolomite. The ground dolomite preferably has a weight median particle size d50 in the range from 1 to200 µm, preferably from 1 to 150 µm, more preferably from 1 to 100 µm, and most preferably from 5 to50 µm, as determined by laser diffraction. It is to be noted that the animal feed composition comprises half-burned dolomite acting as pH control agent. In a preferred embodiment, the animal feed composition is thus free of one or more pH control agent(s) differing from half-burned dolomite. If the animal feed composition comprises such one or more agent(s), the one or more agent(s)are preferably present in a total amount of up to 90 wt.-%, preferably up to 80 wt.-% and mostpreferably up to 35 wt.-%, based on the total weight of the composition. Thus, the animal feed composition comprises the one or more agent(s) in a total amount ranging from 0 to 90 wt.-%, preferably from 0 to 80 wt.-% and most preferably from 0 to 35 wt.-%,based on the total weight of the composition. Preferably, the animal feed composition comprises theone or more agent(s) in a total amount ranging from 10 to 90 wt.-%, preferably from 10 to 80 wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. In one preferred embodiment, the animal feed composition thus comprises a) half-burned dolomite in an amount ranging from 10 to 90 wt.-%, preferably from 20 to90 wt.-%, more preferably from 40 to 90 wt.-% and most preferably from 65 to 90 wt.-%, based on the total weight of the composition, and b) one or more agent(s) in a total amount ranging from 10 to 90 wt.-%, preferably from 10to 80 wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. For example, the animal feed composition comprises a) half-burned dolomite in an amount ranging from 10 to 90 wt.-%, preferably from 20 to90 wt.-%, more preferably from 40 to 90 wt.-% and most preferably from 65 to 90 wt.-%, based on the total weight of the composition, and b) ground calcium carbonate in a total amount ranging from 10 to 90 wt.-%, preferablyfrom 10 to 80 wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. Alternatively, the animal feed composition comprises a) half-burned dolomite in an amount ranging from 10 to 90 wt.-%, preferably from 20 to90 wt.-%, more preferably from 40 to 90 wt.-% and most preferably from 65 to 90 wt.-%, based on the total weight of the composition, and b) ground dolomite in a total amount ranging from 10 to 90 wt.-%, preferably from 10 to80 wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. In one embodiment, the animal feed composition comprises a) half-burned dolomite in an amount ranging from 10 to 90 wt.-%, preferably from 20 to90 wt.-%, more preferably from 40 to 90 wt.-% and most preferably from 65 to 90 wt.-%, based on the total weight of the composition, and b) ground calcium carbonate and ground dolomite in a total amount ranging from 10 to90 wt.-%, preferably from 10 to 80 wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. In one embodiment, the animal feed composition comprisesa) half-burned dolomite in an amount ranging from 10 to 90 wt.-%, preferably from 20 to90 wt.-%, more preferably from 40 to 90 wt.-% and most preferably from 65 to 90 wt.-%, based on the total weight of the composition, and b) magnesium oxide in a total amount ranging from 10 to 90 wt.-%, preferably from 10 to80 wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. Alternatively, the animal feed composition comprises a) half-burned dolomite in an amount ranging from 10 to 90 wt.-%, preferably from 20 to90 wt.-%, more preferably from 40 to 90 wt.-% and most preferably from 65 to 90 wt.-%, based on the total weight of the composition, and b) calcium oxide in a total amount ranging from 10 to 90 wt.-%, preferably from 10 to 80wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. In one embodiment, the animal feed composition comprises a) half-burned dolomite in an amount ranging from 10 to 90 wt.-%, preferably from 20 to90 wt.-%, more preferably from 40 to 90 wt.-% and most preferably from 65 to 90 wt.-%, based on the total weight of the composition, and b) magnesium oxide and calcium oxide in a total amount ranging from 10 to 90 wt.-%,preferably from 10 to 80 wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. Alternatively, the animal feed composition comprises a) a magnesium oxide (MgO) content of ≥ 1.5 wt.-%, preferably from 1.5 to 45.0 wt.-%,more preferably from 2.0 to 31.5 wt.-% and most preferably from 2.0 to 27.0 wt.-%, based on the totalweight of the animal feed composition, and b) a calcium carbonate (CaCO3) content of ≥ 3.9 wt.-%, preferably from 3.9 to 76.5 wt.-%, more preferably from 5.0 to 72.0 wt.-% and most preferably from 6.5 to 67.5 wt.-%, based on thetotal weight of the animal feed composition, and c) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the animal feed composition, and d) one or more agent(s) in a total amount ranging from 10 to 90 wt.-%, preferably from 10to 80 wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. In a preferred embodiment, the animal feed composition comprises a) a magnesium oxide (MgO) content of ≥ 3.0 wt.-%, preferably from 3.0 to 45.0 wt.-%,more preferably from 4.0 to 31.5 wt.-% and most preferably from 4.0 to 27.0 wt.-%, based on the totalweight of the animal feed composition, and b) a calcium carbonate (CaCO3) content of ≥ 7.8 wt.-%, preferably from 7.8 to 76.5 wt.-%, more preferably from 10.0 to 72.0 wt.-% and most preferably from 13.0 to 67.5 wt.-%, based on thetotal weight of the animal feed composition, andc) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the animal feed composition, and d) one or more agent(s) in a total amount ranging from 10 to 90 wt.-%, preferably from 10to 80 wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. In a preferred embodiment, the animal feed composition comprises a) a magnesium oxide (MgO) content of ≥ 6.0 wt.-%, preferably from 6.0 to 45.0 wt.-%,more preferably from 8.0 to 31.5 wt.-% and most preferably from 8.0 to 27.0 wt.-%, based on the totalweight of the animal feed composition, and b) a calcium carbonate (CaCO3) content of ≥ 15.6 wt.-%, preferably from 15.6 to 76.5 wt.-%, more preferably from 20.0 to 72.0 wt.-% and most preferably from 26.0 to 67.5 wt.-%, based on thetotal weight of the animal feed composition, and c) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the animal feed composition, and d) one or more agent(s) in a total amount ranging from 10 to 90 wt.-%, preferably from 10to 80 wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. In a preferred embodiment, the animal feed composition comprisesa) a magnesium oxide (MgO) content of ≥ 9.75 wt.-%, preferably from 9.75 to 45.0 wt.-%,more preferably from 13.0 to 31.5 wt.-% and most preferably from 13.0 to 27.0 wt.-%, based on thetotal weight of the animal feed composition, and b) a calcium carbonate (CaCO3) content of ≥ 25.35 wt.-%, preferably from 25.35 to 76.5wt.-%, more preferably from 32.5 to 72.0 wt.-% and most preferably from 42.25 to 67.5 wt.-%, basedon the total weight of the animal feed composition, and c) a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably≤ 3.5 wt.-%, e.g. ≤ 3 wt.-%, preferably ≤ 2.5 wt.-%, more preferably ≤ 2 wt.-%, and most preferably ≤ 1 wt.-%, based on the total weight of the animal feed composition, and d) one or more agent(s) in a total amount ranging from 10 to 90 wt.-%, preferably from 10to 80 wt.-%, more preferably from 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. It is appreciated that the animal feed composition may be provided in any form that is considered suitable for the products to be prepared. Thus, the animal feed composition can be for example provided in form of a powder, a compacted form such as granules, aqueous solution, aqueous dispersion and the like. In one embodiment, the animal feed composition is in form of a compacted composition suchas granules. This is of advantage as it provides the animal feed composition as a uniform and dust-free composition and thus improves the handling of the animal feed composition. The granules may have any size and form that is considered suitable for the products to beprepared. For example, the granules have an average particle size of 0.5 to 10 mm, more preferably 2to 6 mm If the animal feed composition is provided in form of a compacted composition such as granules, the composition may further comprise a binder in order to improve the result of thecompaction process. If present, the composition comprises a binder in an amount ranging from 1 to 10wt.-%, preferably from 1 to 5 wt.-% and most preferably from 1 to 3 wt.-%, based on the total weight of the composition. As a binder, every compound may be used that is considered suitable for the products to beprepared. For example, the binder may be selected from the group comprising, preferably consistingof, molasses, clays, lignosulfonates, sodium alginate, and mixtures thereof. If molasses is used asbinder, the molasses is preferably sugar cane molasses. If clays are used as binder, the clay may beselected from the group comprising bentonite, clinoptilolite, kaolinite, sepiolite and mixtures thereof.Preferably, the binder is molasses. In this embodiment, the animal feed composition thus preferably comprises a) half-burned dolomite in an amount ranging from 90 to 99 wt.-%, preferably from 93 to99 wt.-%, more preferably from 95 to 99 wt.-% and most preferably from 97 to 99 wt.-%, based on the total weight of the composition, and b) a binder in an amount ranging from 1 to 10 wt.-%, preferably from 1 to 7 wt.-%, morepreferably from 1 to 5 wt.-% and most preferably from 1 to 3 wt.-%, based on the total weight of the composition. In one embodiment, the animal feed composition may thus comprise half-burned dolomite together with one or more agent(s) and a binder. Preferably, the animal feed composition thus comprises, preferably consists of,a) half-burned dolomite in an amount ranging from 13 to 89 wt.-%, more preferably from35 to 89 wt.-% and most preferably from 62 to 89 wt.-%, based on the total weight of the composition, and b) one or more agent(s) in a total amount ranging from 10 to 80 wt.-%, more preferablyfrom 10 to 60 wt.-% and most preferably from 10 to 35 wt.-%, based on the total weight of the composition. c) a binder in an amount ranging from 1 to 7 wt.-%, more preferably from 1 to 5 wt.-%and most preferably from 1 to 3 wt.-%, based on the total weight of the composition. In view of the above, it is preferred that the animal feed composition is preferably a base composition that is added to a final animal feed formulation that is applied to animals. Thus, the animal feed composition is preferably more concentrated than the final animal feed formulation. However, it is also possible that the animal feed composition is provided to animals such that it is not further diluted. This may have the advantage that the animal feed composition is provided in more concentrated form and lower volume. The animal feed formulation In a second aspect of the present invention, an animal feed formulation is provided. The animal feed formulation comprises the animal feed composition as defined herein. With regard to the definition of the animal feed composition and preferred embodiments thereof, reference is made to the statements provided above when discussing the technical details of the animal feed composition. The animal feed formulation comprises the animal feed composition such that the content ofhalf-burned dolomite is adjusted to the specific animal feed formulation to be prepared.In one embodiment, the animal feed formulation has a content of half-burned dolomite rangingfrom 0.1 to 10 wt.-%, based on the total weight of the formulation. In another embodiment, the animal feed formulation has a content of half-burned dolomite ranging from 0.1 to 5 wt.-%, more preferably from 0.25 to 3 wt.-%, and most preferably from 0.5 to 2 wt.-%, based on the total weight of the formulation. For example, the animal feed formulation has a) a magnesium oxide (MgO) content of ≥ 0.015 wt.-%, preferably from 0.015 to 5.0 wt.-%, more preferably from 0.02 to 1.75 wt.-%, and most preferably from 0.1 to 0.6 wt.-%, based on thetotal weight of the animal feed formulation, and b) a calcium carbonate (CaCO3) content of ≥ 0.039 wt.-%, preferably from 0.039 to 8.5wt.-%, more preferably from 0.05 to 4.0 wt.-% and most preferably from 0.325 to 1.5 wt.-%, based onthe total weight of the animal feed formulation, and c) a calcium oxide (CaO) content of ≤ 0.005 wt.-%, preferably ≤ 0.004 wt.-%, and mostpreferably ≤ 0.0035 wt.-%, e.g. ≤ 0.003 wt.-%, preferably ≤ 0.0025 wt.-%, more preferably ≤ 0.002 wt.- %, and most preferably ≤ 0.001 wt.-%, based on the total weight of the animal feed formulation.In view of the above, the animal feed formulation preferably comprises the animal feed composition in amounts ranging from 0.1 to 20 wt.-%, more preferably from 0.25 to 15 wt.-%, and most preferably from 0.5 to 10 wt.-%, based on the total weight of the formulation. As already noted above, the final animal feed formulation is applied to animals. Thus, it isappreciated that the animal feed formulation can include further ingredient(s) that is / are typicallypresent in the products to be prepared. The further ingredient(s) is / are not restricted to a specific typeof ingredient(s). In general, any kind of ingredient(s) that is / are suitable for animal feeding can beadded to the animal feeding formulation of the present invention. More precisely, any ingredient(s) thatis / are suitable for the desired animal feed formulation can be used in the formulation.Furthermore, it is to be noted that the ingredient(s) may be also adapted to the specific kind of animal for which the animal feed formulation is considered. For example, the animal feed formulation is for animals, preferably poultry, ruminants, polygastric and monogastric animals such as cows, horses, sheeps, goats, swines and the like, and fish. The further ingredient(s) may be selected from the group comprising vitamins, minerals, trace elements, roughage, sugar, amino acids, proteins, bentonite, zeolite, yeasts, flavorings, colorants, preservatives, oils, probiotics, prebiotics, antioxidants, emulsifiers, regulators, digestability enhancers and mixtures thereof. It is appreciated that the animal feed formulation can comprise one or more of such ingredient(s).The wording “one or more” ingredient(s) indicates that the further ingredient(s) may compriseone further ingredient or a mixture of two or more ingredients. Preferably, the further ingredient(s)comprise a mixture of two or more ingredients. For example, the further ingredient(s) are a mixture comprising at least two ingredients selectedfrom the group comprising vitamins, minerals, trace elements, roughage, sugar, amino acids, proteins, bentonite, zeolite, yeasts, flavorings, colorants, preservatives, oils, probiotics, prebiotics, antioxidants,emulsifiers, regulators and digestability enhancers.The animal feed formulation may comprise the further ingredient(s) in amounts that are typicallyused for the products to be prepared and further depends on the further ingredient(s) added to theanimal feed formulation. For example, the animal feed formulation comprises the further ingredient(s) ina total amount of up to 99.9 wt.-%, based on the total weight of the formulation. In one embodiment, the animal feed formulation comprises the further ingredient(s) in a total amount ranging from 90 to 99.9 wt.-%, preferably from 95 to 99.9 wt.-%, more preferably from 97 to 99.75 wt.-%, and most preferably from 98 to 99.5 wt.-%, based on the total weight of the formulation. Preferably, the animal feed formulation thus comprises a) a content of half-burned dolomite ranging from 0.1 to 10 wt.-%, preferably from 0.1 to 5wt.-%, more preferably from 0.25 to 3 wt.-%, and most preferably from 0.5 to 2 wt.-%, based on the total weight of the formulation, and b) further ingredient(s) in a total amount ranging from 90 to 99.9 wt.-%, preferably from 95to 99.9 wt.-%, more preferably from 97 to 99.75 wt.-%, and most preferably from 98 to 99.5 wt.-%, based on the total weight of the formulation. In view of the very good results achieved for the half-burned dolomite in animal feeding, the present invention refers in another aspect to the use of half-burned dolomite in a feed formulation for animals, preferably poultry, ruminants, polygastric and monogastric animals such as cows, horses, sheeps, goats, swines and the like, and fish. It is appreciated that the half-burned dolomite is used as magnesium and calcium ion sourceand / or pH control agent in animal feeding. For example, the half-burned dolomite is used as magnesium and calcium ion source or pHcontrol agent. Preferably, the half-burned dolomite is used as magnesium and calcium ion source inanimal feeding for monogastrics. Alternatively, the half-burned dolomite is used as pH control agent inanimal feeding for polygastrics, i.e. ruminants. Preferably, the half-burned dolomite is used asmagnesium and calcium ion source and pH control agent in animal feeding. For example, the half-burned dolomite is used as magnesium and calcium ion source and pH control agent in animal feeding for polygastrics, i.e. ruminants. It is to be noted that the half-burned dolomite used in animal feeding is preferably provided in form of the animal feed composition and / or the animal feed formulation of the present invention. With regard to the definition of the animal feed composition, the animal feed formulation, the half-burned dolomite and preferred embodiments thereof, reference is made to the statements provided above when discussing the technical details of the animal feed composition and the animal feed formulation. Brief description of the Figures Fig.1 shows the pH profiles of the tested products in rumen buffer. n=3, ± SD. Fig. 2 shows the pH profile of the tested dolomite in rumen buffer. n=3, ± SD.ExamplesExample 1: In vitro rumen buffer experiment1. MaterialsRumen Buffer Rumen Buffer was prepared based on Zamarreňo et al., A new methodology for studying theperformance of products against ruminal acidosis; Journal of Science of Food and Agriculture, 1607- 1612, 2003 as follows: ^Sodium acetate ≥ 99.0 % LOT # BCBV8909, S8750, PCode: 101971843 ofSigma-Aldrich ^Sodium propionate ≥ 99.0 % LOT # SLBQ2286V, P1880, PCode: 102007437 ofSigma-Aldrich ^Sodium phosphate dibasic ≥ 99.0 % LOT # STBH2634, 71640, PCode: 102034835of Sigma-Aldrich ^Maleic acid ≥ 99.0 % LOT # SLBV7407, M0375, PCode: 101993859 ofSigma-Aldrich ^Butyric acid ≥ 99.0 % LOT # STBG6728, B103500, PCode: 101982732 ofAlfa Aesar ^Deionized H2O^ Sodium hydroxide (1M) of Sigma-Aldrich for final pH adjustmentBuffer solution was prepared the day before the experiment and stored in closed containers at 4° C. Before the experiment was started, buffer was heated to 39°C in a water bath and, the pH was adjusted to 5.5 with NaOH (1M). After adjusting the pH, the volume was filled up to 1000ml with water.Table 1 shows the composition of the rumen buffer that was used for all experiments.Table 1: Composition of the rumen buffer. Sodium Hydroxide was used to adjust the pH to 5.5 if needed. Recipe for 1 L of buffer. Chemicals Concentration [mmol / L] Weight [g]Sodium Acetate 65 5.33Sodium propionate 30 2.88Sodium phosphate dibasic (anhydrous) 20 2.84Maleic acid 40 4.64Butyric acid 10 0.88Deionized water Ad.1000 mlTested Products^ HBD1, obtained by calcining dolomite at 850°C and grinding via 2 passes with a pin millto d50 and d98 as indicated in Table 2^ HBD2, obtained by calcining dolomite at 850°C and grinding via 2 passes with a pin millto d50 and d98 as indicated in Table 2 ^Red calcareous algae 1^ Red calcareous algae 2, which is based on red calcareous algae 1 being ground to d50and d98 as indicated in Table 2 ^Red calcareous algae 3^ MgO mixed in equimolar ratio with ground CaCO3 ** 10g of MgO was mixed with 24.83g of ground calcium carbonate, d50 = 6.5 µm of Omya^ Dolomite obtained by milling a commercial dolomite having a d50 of 900 µm on aplanetary ball mill (including wolfram carbide crucible (50 ml) and 10 mm milling balls) for 10 min at a speed of 250 rpm to a d50 and d98 as indicated in Table 2 Table 2 summarizes the characteristics and composition of the tested products. Table 2: Characteristics and composition of the tested products Name Composition CaCO3MgO d50 in d98 in (%) (%) µm µm HBD1 Half-burned dolomite 69.9 25.2 17.1 57.5HBD2 Half-burned dolomite 69.9 25.2 28.4 117Red calcareousCommercial product based on marine algae 62-75 130 441algae 1 Red calcareous Commercial product based on marine algae62-75 12.1 567algae 2 with similar d50 and d98 as HBD1 and HBD2 Red calcareousCommercial product based on marine algae 80-91 108 566algae 3 MgO / CaCO3 mix 10g of MgO was mixed with 24.83g of CaCO3 69.9 25.2to achieve same MgO / CaCO3 ratio as HBD1 and HBD2 MgO MgO 88 25 339Ground CaCO3 Ground CaCO3 98 6.5 32Dolomite Dolomite -- 20.1 25.1 108.5In Tables 3 and 4, the BET specific surface area and particle size distribution of the differenttested products are summarized. Table 3: Specific surface area of the different products, measured by BET. n=1. Sample / Product BET [m2 / g]HBD1 5.8817HBD2 5.9104Red calcareous algae 1 6.9607Red calcareous algae 2 9.8687Red calcareous algae 3 2.2142MgO 5.9748Ground CaCO3 1.5937 Dolomite 0.8633Table 4: Particle size distribution of the HBD products and dolomite, measured on theMastersizer 3000 with the Aero S attachment. Samples HBD1HBD2 Dolomite [µm] [µm] [µm] Dx (10) 3.7 5.14 1.74Dx (50) 17.1 28.4 25.1Dx (60) 21 35.5 --Dx (90) 40.1 71.8 77.6Dx (98) 57.5 117 108.5The mineralogical and chemical analysis of HBD1 and HBD2 are given in the following table 5.Table 5: Mineralogical and chemical analysis of HBD1 and HBD2 and dolomiteSample HBD1 HBD2 Dolomite HBD1 HBD2 DolomiteMineralogical analysis Chemical analysisMgO 25.2 % 25.2 % -- 27.5 % 27.5 % 20.1 %CaCO3 69.9 % 69.9 % -- -- -- --CaO < 1.0 % < 1.0 % -- 39.2 % 39.2 % 31.3 %MgCO3 4.7 % 4.7 % -- -- -- --Dolomite -- -- 94.8 % -- -- --Calcite -- 3.9 % -- -- --Remainings 0.1 % 0.1 % 1.3 % < 0.08 % < 0.08 % < 1.8 %Loss of33.2 % 33.2 % 46.8 %ignition 2. Equipment^ Balance (PG6002-S+XP404S, Mettler Toledo)^ Dissolution apparatus (AT7, Sotax)^ Ph meter (S40 B149520840, Mettler Toledo)^ Heating bath (Julabo SW23)3. MethodspH profile For the pH profile, a standard USP 2 dissolution-apparatus (AT7, Sotax) was used. Temperature of the bath was 39°C, stirring speed of the paddles was 30 rpm, and buffer volume was 300 ml. The pH was measured manually after 0, 30, 60, 120, 240, 360, 480 minutes using a standard pH meter. Sample weight was 360 mg. Measurements were started at T=0, pH=5.5, by dropping the samples into the vessels. Every sample was measured in triplicates (n=3). Results are presented as average ± standard deviation. Specific surface area (BET) The specific surface area was measured via the BET method according to ISO 9277:2010using nitrogen as adsorbing gas on a Micromeritics ASAP 2460 instrument from Micromeritics. The samples were pretreated in vacuum (10-5bar) by heating at 150 °C for a period of 60 min prior to measurement. Particle size distribution (PSD) Volume determined median particle size d50(vol) and the volume determined top cut particle size d98(vol) as well as the volume particle sizes d90(vol) and d10(vol) were evaluated using a Malvern Mastersizer 3000 Laser Diffraction System (Malvern Instruments Plc., Great Britain) with Aero Sattachment. The d50(vol) or d98(vol) value indicates a diameter value such that 50 % or 98 % byvolume, respectively, of the particles have a diameter of less than this value. The raw data obtained by the measurement was analyzed using the Mie theory, with a particle refractive index of 1.57 and an absorption index of 0.005. The methods and instruments are known to the skilled person and are commonly used to determine particle size distributions of fillers and pigments. The sample was measured in dry condition without any prior treatment. If not otherwise indicated herein, the particle sizes were evaluated using a Malvern Mastersizer 3000 Laser Diffraction System (Malvern Instruments Plc., Great Britain) with Aero S attachment. 4. ResultsFig. 1 shows the pH profiles of the different products over a period of 8 hours. None of thetested products reaches a stable pH after 8 hours. This indicates that the pH would most likely furtherincrease if the experiment was continued. The inventive products HBD1 and HBD2 show a fast onsetand reach the highest pH value after 8 hours. Red calcareous algae 3 shows a slow onset andreaches the lowest pH value after 8 hours. Fig. 2 shows the pH profile of dolomite over a period of 8hours. In said period no significant change in pH was observed. Furthermore, the pH value wassignificantly less than for the other samples and especially the inventive products HBD1 and HBD2.During the first 30 minutes, the pH of the pure buffer (blank) slightly increases, which isprobably due to volatile components of the buffer (Butyric Acid) evaporating resulting in a pH increase. Both tested HBD samples behave similar with respect to kinetics and endpoint (pH after 8h),respectively, showing the fastest and highest increase of pH over time. An as fast but overall lower pHincrease is seen for the MgO / CaCO3 mix and red calcareous algae 2, which have a finer PSDcomparable to the tested HBDs. A slower and overall lower pH increase was observed for calcareousalgae 1 and 3 compared to the other tested materials. This data shows that the HBD increases rumen pH faster and to a higher pH, meaning thatthey have a better buffering capacity then the other tested products. It could be seen that both of theinventive HBDs perform better than commercially available buffering products based on redcalcareous algae as well as dolomite. Moreover, it could be observed that the inventive HBDs have abetter buffering performance than commercially available MgO and CaCO3 mixed at the sameCaCO3:MgO ratio or dolomite then HBD and with comparable PSD, demonstrating the superiority ofHBD for this application.

Claims

Claims 1. Animal feed composition comprising half-burned dolomite in an amount of at least 10wt.-%, based on the total weight of the composition.

2. The animal feed composition according to claim 1, wherein the half-burned dolomitehas a magnesium oxide (MgO) content of ≥ 15 wt.-%, preferably from 15 to 50 wt.-%, more preferably from 20 to 35 wt.-% and most preferably from 20 to 30 wt.-%, based on the total weight of the half- burned dolomite.

3. The animal feed composition according to claim 1 or 2, wherein the half-burneddolomite has a calcium carbonate (CaCO3) content of ≥ 39 wt.-%, preferably from 39 to 85 wt.-%, more preferably from 50 to 80 wt.-% and most preferably from 65 to 75 wt.-%, based on the total weight of the half-burned dolomite.

4. The animal feed composition according to any one of claims 1 to 3, wherein the half-burned dolomite has a calcium oxide (CaO) content of ≤ 5 wt.-%, preferably ≤ 4 wt.-%, and most preferably ≤ 3.5 wt.-%, based on the total weight of the half-burned dolomite.

5. The animal feed composition according to any one of claims 1 to 4, wherein the half-burned dolomite has a weight median particle size d50 in the range from 1 to 200 µm, preferably from 1to 150 µm, more preferably from 1 to 100 µm, and most preferably from 5 to 50 µm, as determined bylaser diffraction, and / or the half-burned dolomite has a BET specific surface area in the range from 1to 20 m2 / g, preferably from 1 to 15 m2 / g, and most preferably from 2 to 10 m2 / g, measured usingnitrogen and the BET method according to ISO 9277:2010.

6. The animal feed composition according to any one of claims 1 to 5, wherein the half-burned dolomite is present in an amount ranging from 10 to 100 wt.-%, preferably from 20 to 100 wt.- %, more preferably from 40 to 100 wt.-% and most preferably from 65 to 100 wt.-%, based on the total weight of the composition.

7. The animal feed composition according to any one of claims 1 to 6, wherein thecomposition further comprises one or more agent(s) comprising anions selected from the group comprising oxides, hydroxides, carbonates, hydrogen carbonates, sulfates, chlorides and the like, and / or cations selected from the group comprising magnesium, calcium, sodium, potassium and mixtures thereof.

8. The animal feed composition according to claim 7, wherein the composition comprisesthe one or more agent(s) in a total amount ranging from 0 to 90 wt.-%, preferably from 0 to 80 wt.-% and most preferably from 0 to 35 wt.-%, based on the total weight of the composition.

9. The animal feed composition according to any one of claims 1 to 8, wherein thecomposition further comprises a binder, such as molasses, clays, lignosulfonates, sodium alginate, in an amount ranging from 1 to 10 wt.-%, preferably from 1 to 5 wt.-% and most preferably from 1 to 3 wt.-%, based on the total weight of the composition.

10. The animal feed composition according to any one of claims 1 to 9, wherein thecomposition is in form of a compacted composition such as granules, preferably granules having an average particle size of 0.5 to 10 mm, more preferably 2 to 6 mm.

11. Animal feed formulation comprising the animal feed composition according to any oneof claims 1 to 10.

12. The animal feed formulation according to claim 11, further comprising ingredients suchas vitamins, minerals, trace elements, roughage, sugar, amino acids, proteins, bentonite, zeolite, yeasts, flavorings, colorants, preservatives, oils, probiotics, prebiotics, antioxidants, emulsifiers,regulators, digestability enhancers and mixtures thereof.

13. The animal feed formulation according to claim 11 or 12, wherein the formulation hasa content of half-burned dolomite ranging from 0.1 to 10 wt.-%, preferably from 0.1 to 5 wt.-%, morepreferably from 0.25 to 3 wt.-%, and most preferably from 0.5 to 2 wt.-%, based on the total weight of the formulation.

14. Use of half-burned dolomite in a feed formulation for animals, preferably poultry,ruminants, polygastric and monogastric animals such as cows, horses, sheeps, goats, swines and the like, and fish.

15. The use according to claim 14, wherein the half-burned dolomite is used asmagnesium and calcium ion source and / or pH control agent.