Poultry feed and methods for raising poultry

Abstract

Disclosed are: a poultry feed comprising at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone; and a method for breeding poultry, the method comprising a step for causing poultry to ingest at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone.

Description

Technical Field

[0001] The present disclosure relates to poultry feed and a method for raising poultry.

Background Art

[0002] Chicken eggs are called the优等生 of prices, and price increases have been suppressed by the efforts of production farmers. However, due to the fact that the selling prices of chicken eggs and chicken meat have not increased for many years, and the recent soaring feed prices, small-scale farmers have gone bankrupt, and the operations of the surviving farmers are also in an extremely difficult situation. While male and female broiler chickens are grown and then shipped regardless of gender, there is also a current situation where male chickens that have grown as egg-laying hens are culled. Currently, approximately 6.5 billion male chicks are culled annually worldwide. However, due to ethical issues, the culling of male chicks was prohibited in Germany at the end of 2021 and in France at the end of 2022. In Italy, it has also been decided to prohibit the culling of male chicks by 2026.

[0003] Therefore, the present inventor has started developing a sex-sorting technology for poultry (Non-Patent Document 1). Non-Patent Document 1 describes that "by orally administering a mixture of testosterone and corticosterone, the sex of embryos could be made 70% male."

[0004] A method for discriminating the gender of eggs on the 8th to 10th day after laying is also known (Non-Patent Document 2). In this method, the air generated from the eggs is analyzed using gas chromatography and mass spectrometry, and the volatile organic compounds diffused through the eggshell are detected to identify the gender of the embryos in the fertilized eggs.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

[0006] This disclosure aims to provide a novel feed and method that can bias the sex ratio of fertilized eggs laid by poultry towards females. [Means for solving the problem]

[0007] The inventors have discovered that by administering a certain sex steroid hormone to poultry, the sex ratio of the fertilized eggs produced by the poultry can be biased towards females, and have completed this disclosure.

[0008] This disclosure relates, for example, to the following: [1] A poultry feed comprising at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone. [2] The feed according to [1], wherein the content of at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone is 0.01% by mass or more based on the total mass of the feed. [3] The feed according to [1] or [2], wherein the poultry is a breeding bird for egg-laying. [4] A feed described in any of [1] to [3] for causing the sex ratio of fertilized eggs laid by the above-mentioned poultry to be biased towards females. [5] A method for raising poultry, comprising the step of administering to poultry at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone. [6] The method of [5] for causing the sex ratio of fertilized eggs laid by the above-mentioned poultry to be biased towards females. [7] The method according to [5] or [6], wherein the above step is to administer at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone to the poultry at a dose of 1 to 30 mg per kg of body weight per day. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a novel feed and method that can bias the sex ratio of fertilized eggs laid by poultry towards females.

[0010] The method described in Non-Patent Document 2 had several problems, including the need to incubate the eggs for eight days, the considerable cost of collecting and analyzing volatile components, and the fact that the number of fertilized eggs produced remained unchanged. According to this disclosure, the sex ratio of fertilized eggs obtained from poultry can be biased towards females simply by feeding them to the poultry, thereby reducing such effort and cost. Furthermore, according to this disclosure, the number of females (egg-laying birds) obtained from a single poultry can be increased, making it possible to increase the number of eggs produced for consumption compared to conventional methods. These excellent improvements are expected to suppress the rise in egg prices. In addition, ethical issues can be mitigated by reducing the number of male birds that need to be culled. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a graph showing the effect of progesterone administration on the sex ratio of fertilized eggs in quail. [Figure 2] Figure 2 is a graph showing the effect of administering pregnenolone (Preg), 17α-hydroxyprogesterone (17αP4), or medroxyprogesterone (MP4) to quail on the sex ratio of fertilized eggs. [Figure 3]Figure 3A is a graph showing the relationship between the sex of a quail fertilized egg and the testosterone concentration in the blastodisc. Figure 3B is a graph showing the relationship between the sex of a quail fertilized egg and the corticosterone concentration in the blastodisc. Figure 3C is a graph showing the relationship between the sex of a quail fertilized egg and the progesterone concentration in the blastodisc. Figure 3D is a graph showing the relationship between the sex of a quail fertilized egg and the estradiol concentration in the blastodisc. [Figure 4] Figure 4 is a graph showing the effect of progesterone administration on the sex ratio of fertilized eggs in chickens. [Modes for carrying out the invention]

[0012] The embodiments of this disclosure are described below, but this disclosure is not limited to the embodiments described below.

[0013] One embodiment of the present disclosure may be a poultry feed comprising at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone. In the poultry feed according to the present disclosure, progesterone, pregnenolone, and medroxyprogesterone may also be referred to as poultry feed additives.

[0014] Progesterone, pregnenolone, and medroxyprogesterone may be extracted from naturally occurring sources such as plants and microorganisms, or they may be chemically synthesized. When extracted from naturally occurring sources, the degree of purification only needs to be sufficient to demonstrate the effects of this disclosure, and to that extent, the extract may be a crude extract containing impurities.

[0015] Progesterone may be in free form or crystalline form. Pregnenolone and medroxyprogesterone may be in free form, esterified form or crystalline form. Examples of esterified forms include acetate, hexanoic acid, heptanoic acid, decanoic acid, pentanoic acid, and dodecanoic acid. Crystals may exist in polymorphic form, but are not limited to any of these, and may be any single crystalline form or a mixture thereof. Progesterone, pregnenolone, and medroxyprogesterone may be used dissolved or suspended in a solvent. The solvent may be an organic solvent, animal fats and oils, or vegetable oils such as sesame oil.

[0016] The content of at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone may be 0.01% by mass or more, 0.03% by mass or more, or 0.1% by mass or more based on the total mass of the poultry feed. When the content of at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone is within these ranges, the sex ratio of fertilized eggs laid by poultry that consume the feed can be biased towards females. The content of at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone may be 0.3% by mass or less, 0.25% by mass or less, or 0.2% by mass or less based on the total mass of the poultry feed. When the content of at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone is within these ranges, the price of the poultry feed can be kept down, and it becomes easier to avoid egg-laying cessation due to the intake of progesterone, etc.

[0017] Poultry may be birds of the pheasant or duck family, such as chickens, quails, turkeys, geese, ducks or guinea fowls. The poultry may be breeding birds for producing egg - laying birds. The poultry may be female adult chickens. An egg - laying bird is a bird for laying eggs, including not only so - called egg - laying (e.g., layer) birds, but also meat - type (e.g., broiler) birds. In meat - type birds, the meat of females is softer and more flavorful than that of males. According to the present disclosure, the number of females (meat - type birds) having the above advantages in terms of meat taste obtained from one poultry can be increased.

[0018] The feed according to one embodiment may contain components included in known feeds. The feed according to one embodiment may contain concentrated feed. Concentrated feed is feed rich in nutrients such as protein and carbohydrates. The feed according to one embodiment may be a formulated feed obtained by mixing a plurality of concentrated feeds. The feed according to one embodiment may contain grains, bran, oil cakes, animal feeds, oligosaccharides, oils and fats, vitamins, minerals, amino acids, organic acids, etc. Examples of grains include corn, rye, barley, rice, etc. Examples of bran include rice bran, wheat bran, etc. Examples of animal feeds include fish meal, meat and bone meal, etc. Examples of oil cakes include rapeseed cake, soybean oil cake, beer cake, etc. Examples of oils and fats include animal fats and vegetable oils such as sesame oil. Examples of vitamins include vitamin B1, vitamin E, etc. Examples of minerals include table salt, silicic acid, calcium carbonate, tricalcium phosphate, etc.

[0019] The form of the feed according to one embodiment can be appropriately selected according to the object to be fed, the breeding period, etc. The feed according to one embodiment may be solid or liquid. The feed according to one embodiment may be mash feed, pellet feed, crumble feed, expander feed, flake feed or a mixed feed thereof.

[0020] A feed according to one embodiment of this disclosure can be manufactured by known methods. At least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone may be mixed simultaneously with all the other feed ingredients, or it may be mixed with a mixture obtained by pre-mixing the other feed ingredients.

[0021] A feed according to one embodiment may be a feed for biasing the sex ratio of fertilized eggs laid by poultry towards females. When poultry are fed the feed according to this disclosure, the ratio of female fertilized eggs to the total number of fertilized eggs obtained from the poultry can be increased to 0.6 or more, 0.65 or more, 0.7 or more, or 0.75 or more. When poultry are fed the feed according to this disclosure, the ratio of female fertilized eggs to the total number of fertilized eggs obtained from the poultry can be increased to nearly 0.8, and within the range of content or intake described herein, it is considered that the higher the intake of at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, the more likely the sex ratio is to be biased towards females. A feed according to one embodiment may be a feed for making the ratio of female fertilized eggs to the total number of fertilized eggs obtained from poultry that have ingested the feed 0.6 or more, 0.65 or more, 0.7 or more, or 0.75 or more.

[0022] Another embodiment of the present disclosure may be a method for raising poultry, comprising the step (step A) of administering to poultry at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone. A method for raising poultry according to one embodiment may be a method for raising poultry to bias the sex ratio of fertilized eggs laid by the poultry towards females. Yet another embodiment of the present disclosure may be a method for biasing the sex ratio of fertilized eggs laid by poultry towards females, comprising step A.

[0023] Step A may be a step of feeding poultry a feed containing at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone. In Step A, the feed containing at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone may be fed to the poultry over the entire rearing period or only for a part of the period.

[0024] Poultry may be raised under general rearing conditions. If the poultry is chicken, feed containing at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, or a feed containing such substance, can be given to chickens from 150 days of age until they stop laying eggs. If the poultry is quail, feed containing at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, or a feed containing such substance, can be given to quail from 5 weeks of age until they stop laying eggs. If the poultry is turkey, feed containing at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, or a feed containing such substance, can be given to turkeys from 150 days of age until they stop laying eggs.

[0025] The feeding method for poultry to ingest at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, or a feed containing such substances, may be continuous feeding or restricted feeding throughout the entire rearing period, and these feeding methods may be used differently depending on the rearing period. In particular, feeding should be timed to coincide with the egg-laying period. For example, in normal feeding, feed that does not contain these components can be administered, and at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, or a feed containing such substances, can be ingested in conjunction with the poultry's ovulation. Furthermore, the feeding method can be selected depending on the egg-laying period, and feeding can be continuous or intermittent.

[0026] Poultry may be fed at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone at a rate of 1.0 mg / day or more, 3.0 mg / day or more, or 10.0 mg / day or more per kg of body weight. When the intake of at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone falls within these ranges, the sex ratio of fertilized eggs produced by poultry that consume this feed can be biased towards females. Poultry may be fed at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone at a rate of 30 mg / day or less, 25 mg / day or less, or 20 mg / day or less per kg of body weight. When the intake of at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone falls within these ranges, the cost of raising livestock can be reduced because progesterone, pregnenolone, and medroxyprogesterone are expensive, and it becomes easier to avoid egg-laying cessation due to the intake of progesterone, etc. When feeding poultry a diet containing at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, the feed may be provided so that the intake of at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone falls within these ranges. [Examples]

[0027] The present disclosure will be described in more detail below using examples, but the present disclosure is not limited to the following examples.

[0028] <Example 1: Sex steroid hormone administration test using quail> 1) Laboratory animals Quail (Coturnix japonica) aged 5-8 weeks were purchased from Quail Cosmos. The quail were individually housed in bird cages (27cm wide, 21cm deep, 23cm high) placed inside wooden boxes (140cm wide, 47.5cm deep, 45cm high) that blocked out external light. The quail were raised at a room temperature of 25°C under a photoperiod of 14 hours of light and 10 hours of dark created by artificial lighting. The quail were continuously fed malt-based feed (Quail Super) purchased from Toyohashi Feed Co., Ltd., and continuously supplied with tap water. The approximate time and frequency of egg-laying were recorded for each individual quail.

[0029] 2) Collection of fertilized eggs Female and male fish that were repeatedly laying eggs were mated one-on-one, and fertilized eggs were collected starting the following day.

[0030] 3) Artificial lighting used for breeding White fluorescent lamps (National, Indonesia, 18 watts) were used as artificial lighting.

[0031] 4) Dosage experiment All test substances were dissolved in sesame oil before use. The test substances dissolved in sesame oil were administered to quail that were repeatedly laying eggs. In the progesterone administration experiment, 12 quail were orally administered 150 μl of sesame oil for the first 5 days of the 10-day experimental period, and 150 μl of progesterone (Wako Co., Ltd.) solution prepared at 1 mg / ml or 2.5 mg / ml for the last 5 days, using a Terumo syringe (Terumo Corporation) and a disposable oral tube (Fuchigami Kikai Co., Ltd.). In the administration experiments with pregnenolone (Wako Inc.), 17α-hydroxyprogesterone (Sigma Aldrich), and medroxyprogesterone (Wako Inc.), five quail were orally administered 150 μl of sesame oil for the first five days of the 10-day experiment, and 150 μl of a 2.5 mg / ml test substance solution for the last five days. Mating with males was performed immediately after administration on the first day and immediately after administration on the sixth day. Fertilized eggs were collected daily for 10 days.

[0032] 5) Sexing a. Collection of the blastocyst from the fertilized egg. The blunt end of the recovered fertilized egg was broken open, the egg white was removed, the position of the blastocyst on the yolk was marked with activated charcoal, and the egg was returned to the yolk and sealed with plastic wrap. The eggs were boiled in boiling water for 3 minutes, and the blastocyst was scooped out with a spatula. The obtained blastocysts were uniformly suspended in 500 μl of PBS and dispensed into 250 μl tubes for sex determination and steroid hormone measurement. Each tube was centrifuged at 2,500 × g and 25°C for 3 minutes, the supernatant was removed, and the precipitate was collected.

[0033] b. DNA extraction 300 μl of nuclear decomposition solution (100 mM Tris HCl, 0.5 M EDTA, 10% SDS, H2O) and 1.2 μl of Proteinase K (Takara Bio Inc.) were added to the tube containing the precipitate and incubated at 56°C for 1 hour. After incubation, the tube was centrifuged at 21,500 × g at 20°C for 3 minutes, and 300 μl of the supernatant was transferred to a 1.5 ml tube. 300 μl of phenol / chloroform / isoamyl alcohol (Nippon Gene Inc., 25:24:1) was added and stirred until turbidity was achieved. The mixture was centrifuged at 21,500 × g at 20°C for 5 minutes, and 200 μl of the aqueous layer was collected. Another 200 μl of phenol / chloroform / isoamyl alcohol was added to the aqueous layer and stirred well, then centrifuged at 21,500 × g at 20°C for 5 minutes. 120 μl of the aqueous layer was collected, 12 μl of 3M sodium acetate (pH 4.8) and 300 μl of 100% ethanol were added, and the mixture was turned. The mixture was then centrifuged at 21,500 × g for 15 minutes at 4°C. The aqueous layer was discarded, leaving the precipitate, and 70% ethanol was added and gently turned. The mixture was then centrifuged at 20,000 × g at 4°C for 1 minute. The aqueous layer was discarded, dried in an evaporator for 5 minutes, dissolved in 20 μl of H2O, and the OD values ​​were measured at 260 nm and 280 nm using a spectrophotometer (DeNovix, Wilmington).

[0034] c. Sex determination of embryos by PCR reaction The sex of the embryos was determined by amplifying the Chromo Helicase DNA binding gene (CHD gene) (Fridolfsson AK & Ellegren H, 1999). A mixture containing a forward primer (2550F), a reverse primer (2718R), TaKaRa EX Taq® (Takara Bio Inc.), and dNTPs was prepared, and 9.5 μl of this mixture was mixed with 0.5 μl of extracted DNA. In PCR, DNA was amplified by pre-denaturing at 94°C for 90 seconds, followed by 5 cycles of 20 seconds at 94°C (denaturation), 20 seconds at 60°C (annealing), and 40 seconds at 72°C (extension reaction); 5 cycles of 20 seconds at 94°C (denaturation), 20 seconds at 55°C (annealing), and 40 seconds at 72°C (extension reaction); 5 cycles of 20 seconds at 94°C (denaturation), 20 seconds at 51°C (annealing), and 40 seconds at 72°C (extension reaction); and 25 cycles of 20 seconds at 94°C (denaturation), 20 seconds at 50°C (annealing), and 40 seconds at 72°C (extension reaction). After the PCR reaction, electrophoresis was performed at 100V using a 1% agarose gel and TAE. After electrophoresis, the bands were identified using LAS 500 (GE Healthcare Bio-Sciences AB, Uppsala) to determine the sex of the birds. The CHD gene is located on the sex chromosomes of birds, and it is known that one band is observed in males (ZZ) and two bands are observed in females (ZW) (Fridolfsson & Ellegren, 1999). The sex ratios obtained from the sex determination are shown in Figures 1 and 2. In Figures 1 and 2, solid bars represent the ratio of male fertilized eggs to the total number of fertilized eggs obtained from poultry, and diagonal bars represent the ratio of female fertilized eggs to the total number of fertilized eggs obtained from poultry.

[0035] 6) Measurement of yolk steroid hormone concentration Egg yolk collected from the blastodisc precipitate was suspended in 250 μl of PBS and added entirely to an Extrelute NT3 column (Merck, Kenilworth), where it was allowed to stand for 5-10 minutes. A mixture of diethyl ether and petroleum ether (7:3) was added in three separate additions of 6 ml, 6 ml, and 3 ml, and the eluate was collected. All of the eluate was pooled, the solvent was evaporated with nitrogen (JET AIR VAPORIZER, Ishii Shoten Co., Ltd.), and then dissolved in 250 μl of ELISA buffer (1% BSA, 4M sodium chloride, 10 mM EDTA, 0.1% sodium azide) to prepare the sample. The extracted samples were colorimetrically quantified using Testosterone ELISA Kit, Corticosterone ELISA Kit, Progesterone ELISA Kit, and Estradiol ELISA Kit (Cayman Chemical, Ann Arbor). A plate immobilized with secondary antibody (Mouse Anti-Rabbit IgG) was treated with B0 (ELISA buffer), 50 μl of standard (S1-S8), or sample. 50 μl of AChE-labeled analyte and antiserum specific to each steroid hormone were added to each well, and the plate was incubated at room temperature for 1 hour. After 1 hour, the solution was discarded, and the plate was washed five times with 200 μl of wash buffer. After washing, 200 μl of substrate was added, and the plate was allowed to stand for 60-90 minutes. After standing, the plate was measured using a microplate reader (TECAN, Mannedorf). The results are shown in Figure 3. Figure 3 shows the relationship between the sex of the fertilized egg and the concentrations of steroid hormones (testosterone, corticosterone, progesterone, and estradiol) contained in the blastodisc. The horizontal axis of the graph represents the concentration of steroid hormones. Males are plotted above the vertical axis, and females below.

[0036] 7) Statistical analysis Microsoft Excel 2019 was used for data analysis. The sex ratio was analyzed using a binomial test. For the comparison of steroid hormone concentrations between males and females, the F-test was used to confirm equal variances, followed by a t-test. The statistical analysis software R (http: / / cran.r-project.org / ) was used to create the linear model and likelihood ratio test. The results are shown in Tables 1 and 2.

[0037] [Table 1]

[0038] [Table 2]

[0039] According to Example 1 (particularly "6) Measurement of Egg Yolk Steroid Hormone Concentration" and Figure 3), it was found that progesterone ingested by poultry accumulates in the blastodisc of eggs laid by the ingested poultry. A very significant correlation was also shown between the progesterone concentration in the blastodisc and the sex ratio (Figure 3C). It was suggested that the accumulation of progesterone in the egg blastodisc preferentially releases the Z chromosome during meiosis. As a result, the W chromosome is more likely to remain in the nucleus, and a higher proportion of female fertilized eggs are thought to be obtained. This idea can also be applied to medroxyprogesterone, a progesterone analog. Furthermore, it is thought that a similar mechanism naturally operates in other poultry species besides quail, as they are also birds, and that by ingesting at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, the sex ratio of fertilized eggs obtained from those poultry species can be biased towards females.

[0040] <Example 2: Sex steroid hormone administration test using chickens> 1) Laboratory animals Chickens (Gallus gallus domesticus) aged 31-33 weeks, purchased from Akita Foods Co., Ltd., were used. The chickens were raised individually in single-fed cages designed for laying hens. They were raised at a room temperature of 25°C under a 14-hour light-10-hour dark period created by artificial lighting. The chickens were continuously fed adult chicken feed purchased from JA Zen-Noh Kumiai Feed Co., Ltd., and continuously supplied with tap water. The approximate laying time and laying frequency were recorded for each individual chicken.

[0041] 2) Collection of fertilized eggs Female chickens that were repeatedly laying eggs were artificially inseminated with 100 μL of chicken semen diluted four times with Lake's solution, and fertilized eggs were collected starting the following day.

[0042] 3) Artificial lighting used for breeding White fluorescent lamps (National, Indonesia, 18 watts) were used as artificial lighting.

[0043] 4) Dosage experiment Four chickens that were repeatedly laying eggs were administered progesterone dissolved in sesame oil. During the 14-day experiment, 1000 μl of sesame oil was administered orally or subcutaneously for the first 7 days, and progesterone (Wako Co., Ltd.) solution was administered orally or subcutaneously for the last 7 days. The oral administration group received progesterone at a dose of 3.125 mg / kg (body weight) using a Terumo syringe (Terumo Corporation) and a disposable oral tube (Fuchigami Kikai Co., Ltd.). The subcutaneous administration group received progesterone at a dose of 2 mg / 0.5 ml using a Terumo syringe (Terumo Corporation) and a 25G injection needle (Terumo Corporation). Artificial insemination was performed 2 days before administration, before administration on day 2, before administration on day 6, and before administration on day 9. Fertilized eggs were collected daily for 14 days.

[0044] 5) Sexing The procedure was carried out under the same conditions as in Example 1. The percentage of female chicks obtained from the sex determination results is shown in Figure 4.

[0045] 6) Calculation of spawning rate and fertilization rate The egg-laying rate and fertilization rate were calculated for the collected fertilized eggs. The egg-laying rate was calculated by dividing the number of eggs laid by the number of chickens involved in the experiment (number of days of laying). The fertilization rate was calculated by incubating the collected eggs for 3 days, then breaking them open to confirm fertilization by checking for development, and finally dividing the number of fertilized eggs by the number of collected eggs. The egg-laying rate and fertilization rate are shown in Table 3.

[0046] [Table 3]

[0047] 7) Statistical analysis Microsoft Excel 2019 was used for data analysis. A binomial test was used to analyze the proportion of female chicks.

[0048] As shown in Table 3, subcutaneous administration of progesterone significantly reduced the egg-laying rate, while oral administration did not reduce either the egg-laying rate or the fertilization rate. Furthermore, as shown in Figure 4, the proportion of female chicks in the oral administration group was significantly higher than in the control group (p=0.014). These results indicate that in chickens, oral administration of progesterone can significantly shift the sex ratio of fertilized eggs toward females without negatively affecting the egg-laying rate or the fertilization rate.

Claims

1. A poultry feed for causing the sex ratio of fertilized eggs laid by poultry to be biased toward females, comprising at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone.

2. The feed according to claim 1, wherein the content of at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone is 0.01% by mass or more based on the total mass of the feed.

3. The feed according to claim 1, wherein the poultry is a breeding bird of an egg-laying bird.

4. A method for raising poultry to bias the sex ratio of fertilized eggs laid by poultry towards females, comprising the step of administering to poultry at least one substance selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone.

5. The method according to claim 4, wherein the step is to administer at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone to the poultry at a dose of 1 to 30 mg per kg of body weight per day.

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