Poultry feed and method for breeding 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

Poultry feed and poultry raising method

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

[0002] Eggs are known as a price-performance model, and price increases have been kept in check thanks to the efforts of producers. However, with the sales prices of eggs and chicken meat remaining stagnant for many years, coupled with the recent surge in feed prices, small-scale farmers are going bankrupt, and those that survive are facing extremely difficult financial conditions. While meat chickens are raised and shipped regardless of gender, males raised as egg layers are culled. Currently, approximately 6.5 billion male chicks are culled annually worldwide. However, due to ethical concerns, the culling of male chicks was banned in Germany at the end of 2021 and in France at the end of 2022. Italy has also decided to ban the culling of male chicks by 2026.

[0003] Therefore, the present inventors have begun to develop a technology for sex selection in poultry (Non-Patent Document 1), which describes that "by orally administering a mixture of testosterone and corticosterone, it was possible to change the sex of embryos to 70% male."

[0004] A method for identifying the sex of eggs 8 to 10 days after laying is also known (Non-Patent Document 2). In this method, the air emitted from the eggs is analyzed using gas chromatography and mass spectrometry, and the sex of the embryo inside the fertilized egg is identified by detecting volatile organic compounds diffused through the eggshell.

[0005] Tomohiro Sasanami, "Development of Sex Selection Technology for Poultry," Kieikai Foundation, FY2021 Research Grant List, GrrlScientist (translated by Nobuo Takahashi), "Technology for Smelling Eggs to Determine the Sex of Chickens Before Hatching," Forbes JAPAN, June 10, 2023, 11:30 [Retrieved August 8, 2024], Internet: <https: / / forbesjapan.com / articles / detail / 63644>

[0006] The present disclosure aims to provide a novel feed and method that can bias the sex ratio of fertilized eggs produced by poultry toward females.

[0007] The present inventors have discovered that by feeding certain sex steroid hormones to poultry, the sex ratio of fertilized eggs laid by the poultry can be biased towards females, and have completed the present disclosure.

[0008] The present disclosure relates to, for example, the following: [1] A poultry feed containing 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 birds. [4] The feed according to any of [1] to [3], for biasing the sex ratio of fertilized eggs laid by the poultry towards females. [5] A poultry breeding method comprising a step of feeding poultry at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone. [6] The method according to [5], for biasing the sex ratio of fertilized eggs laid by the poultry towards females. [7] The method according to [5] or [6], wherein the step of administering at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone to the poultry in an amount of 1 to 30 mg / kg body weight / day.

[0009] According to the present 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 problems, such as the need to incubate eggs for eight days, the considerable expense of collecting and analyzing volatile components, and the same number of fertilized eggs produced. According to the present disclosure, the sex ratio of fertilized eggs obtained from poultry can be biased toward females simply by feeding the eggs to the poultry, thereby reducing such labor and costs. Furthermore, according to the present disclosure, the number of females (egg-laying birds) obtained from a single poultry can be increased, thereby increasing the number of table eggs produced compared to conventional methods. These excellent improvements are expected to prevent egg prices from rising. Furthermore, the number of male birds to be culled can be reduced, thereby alleviating ethical issues.

[0011] Figure 1 is a graph showing the effect of administering progesterone to quail on the sex ratio of fertilized eggs. 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 3A is a graph showing the relationship between the sex of fertilized quail eggs and the testosterone concentration contained in the germinal disc. Figure 3B is a graph showing the relationship between the sex of fertilized quail eggs and the corticosterone concentration contained in the germinal disc. Figure 3C is a graph showing the relationship between the sex of fertilized quail eggs and the progesterone concentration contained in the germinal disc. Figure 3D is a graph showing the relationship between the sex of fertilized quail eggs and the estradiol concentration contained in the germinal disc. Figure 4 is a graph showing the effect of administering progesterone to chickens on the sex ratio of fertilized eggs.

[0012] Although embodiments of the present disclosure will be described below, the present disclosure is not limited to the following embodiments.

[0013] One embodiment of the present disclosure may be a poultry feed containing 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 can 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 may be chemically synthesized. When extracted from naturally occurring sources, the degree of purification may be sufficient to exhibit the effects of the present disclosure, and the extract may be crudely purified and contain impurities to that extent.

[0015] Progesterone may be in the free form or its crystal form. Pregnenolone and medroxyprogesterone may be in the free form, ester form, or their crystal form. Examples of ester forms include acetate ester, hexanoate ester, heptanoate ester, decanoate ester, pentanoate ester, and dodecanoate ester. Crystals may exist in crystalline polymorphism, 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 in a dissolved or suspended state in a solvent. The solvent may be an organic solvent, such as animal fats and oils, or vegetable fats and oils such as sesame oil.

[0016] The content of at least one 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 selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone is within these ranges, the sex ratio of fertilized eggs laid by poultry that have ingested the poultry feed can be biased toward females. The content of at least one 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 selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone is within these ranges, the price of the poultry feed can be kept low, and egg-laying cessation due to the ingestion of progesterone, etc. can be more easily avoided.

[0017] The poultry may be a bird of the Phasianidae or Anatidae families, such as a chicken, quail, turkey, goose, duck, or guinea fowl. The poultry may be a breeding bird for producing egg-laying birds. The poultry may be an adult female chicken. Egg-laying birds are birds for laying eggs, and include so-called egg-laying (e.g., layer) birds as well as meat-producing (e.g., broiler) birds. Among meat-producing birds, females are more tender and tastier than males. According to the present disclosure, it is possible to increase the number of females (meat-producing birds) that can be obtained from a single poultry and that have the above-mentioned advantages in terms of meat taste.

[0018] The feed of one embodiment may contain ingredients contained in known feeds. The feed of one embodiment may contain concentrated feed. Concentrated feed is feed containing a large amount of nutrients such as protein and carbohydrates. The feed of one embodiment may be a compound feed obtained by mixing a plurality of concentrated feeds. The feed of one embodiment may contain grains, brans, lees, animal feed, oligosaccharides, oils and fats, vitamins, minerals, amino acids, organic acids, etc. Examples of grains include corn, rye, barley, rice, etc. Examples of brans include rice bran and wheat bran. Examples of animal feed include fish meal and meat and bone meal. Examples of lees include rapeseed meal, soybean oil cake, brewer's grains, etc. Examples of oils and fats include animal oils and fats and vegetable oils such as sesame oil. Examples of vitamins include vitamin B1 and vitamin E. Examples of minerals include salt, silicic acid, calcium carbonate, tricalcium phosphate, etc.

[0019] The form of the feed according to one embodiment can be appropriately selected depending on the subject to be fed, the rearing 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 mixture thereof.

[0020] The feed according to an embodiment of the present disclosure can be produced by a known method. At least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone may be mixed simultaneously with all of the other feed ingredients, or may be mixed with a mixture obtained by previously 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 toward females. When poultry are fed a feed according to the present disclosure, the ratio of the number of female fertilized eggs to the total number of fertilized eggs obtained from the poultry can be increased to nearly 0.8 by feeding poultry a feed according to the present disclosure. It is believed that, as long as the content or intake amount is within the range described herein, the higher the intake amount of at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, the more likely the sex ratio is to be biased toward females. A feed according to one embodiment may be a feed for biasing the ratio of the number of female fertilized eggs to the total number of fertilized eggs obtained from poultry that have ingested the feed to 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 a step (Step A) of feeding poultry at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone. The poultry raising method according to one embodiment may be a method for biasing the sex ratio of fertilized eggs laid by the poultry toward females. Yet another embodiment of the present disclosure may be a method for biasing the sex ratio of fertilized eggs laid by poultry toward 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 at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, or a feed containing the same, may be fed to the poultry throughout the entire rearing period, or only for a part of the period.

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

[0025] The feeding method for feeding poultry with at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, or a feed containing the same, may be continuous feeding or restricted feeding throughout the entire rearing period, and these feeding methods may be used depending on the rearing period. In particular, feeding may be performed in accordance with the egg-laying period. For example, in normal feeding, a feed containing no such components is administered, and at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, or a feed containing the same, is administered in accordance with the poultry's ovulation. Furthermore, the feeding method can be selected depending on the egg-laying period, and feeding may be continuous or intermittent.

[0026] Poultry may be fed at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone in an amount of 1.0 mg / day or more, 3.0 mg / day or more, or 10.0 mg / day or more per kg of poultry body weight. When the intake amount of at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone is within these ranges, the sex ratio of fertilized eggs laid by poultry fed the feed can be biased toward females. Poultry may be fed at most 30 mg / day, not more than 25 mg / day, or not more than 20 mg / day of at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone per kg of poultry body weight. When the intake amount of at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone is within these ranges, it is possible to reduce rearing costs and to more easily avoid egg-laying cessation due to the intake of progesterone, etc., because progesterone, pregnenolone, and medroxyprogesterone are expensive. When poultry are fed a feed containing at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone, the feed may be given so that the intake amount of at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone is within these ranges.

[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 Hormones Administration Test Using Quails 1) Experimental Animals: 5-8 week-old quails (Coturnix japonica) purchased from Quail Cosmos were used. Quails were individually housed in bird cages (27 cm wide, 21 cm deep, 23 cm high) placed inside a light-shielded wooden box (140 cm wide, 47.5 cm deep, 45 cm high). Quails were housed at a room temperature of 25°C under a 14-hour light-10-hour dark photoperiod created by artificial lighting. Quails were fed a malt-formulated feed (Uzura Super) purchased from Toyohashi Feed Co., Ltd. ad libitum and provided with tap water ad libitum. The approximate egg-laying time and egg-laying frequency were recorded for each individual quail.

[0029] 2) Collection of fertilized eggs. Females and males that repeatedly laid eggs were mated one-to-one, and fertilized eggs were collected the following day.

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

[0031] 4) Administration experiment: All test substances were dissolved in sesame oil. The test substances dissolved in sesame oil were administered to quails that repeatedly laid eggs. In the progesterone administration experiment, 12 quails were orally administered 150 μl of sesame oil for the first 5 days of the 10-day experimental period, and 150 μl of a progesterone (Wako Co., Ltd.) solution adjusted to 1 mg / ml or 2.5 mg / ml for the last 5 days using a Terumo syringe (Terumo Co., Ltd.) and a Disposable Oral Probe (Fuchigami Kikai Co., Ltd.). In the administration experiments of pregnenolone (Wako Co., Ltd.), 17α-hydroxyprogesterone (Sigma-Aldrich), and medroxyprogesterone (Wako Co., Ltd.), five quails were orally administered 150 μl of sesame oil for the first five days of the 10-day experimental period, 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 every day for 10 days.

[0032] 5) Sexing a. Collection of the blastocyst from fertilized eggs The blunt end of the collected fertilized eggs was cracked, the albumen removed, the position of the blastocyst on the yolk marked with activated charcoal, and the egg was returned to the egg and sealed in plastic wrap. The eggs were boiled for 3 minutes, and the blastocyst was excised with a spoon. The obtained blastocyst was uniformly suspended in 500 μl of PBS and dispensed into tubes in 250 μl portions for sexing 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 nucleolysis solution (100 mM Tris HCl, 0.5 M EDTA, 10% SDS, H ２ 1.0) 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 and 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 Co., Ltd., 25:24:1) was added and stirred until cloudy. Centrifuged at 21,500 × g and 20°C for 5 minutes, and 200 μl of the aqueous layer was recovered. Another 200 μl of phenol / chloroform / isoamyl alcohol was added to the aqueous layer, stirred thoroughly, and centrifuged at 21,500 × g and 20°C for 5 minutes. 120 μl of the aqueous layer was collected, and 12 μl of 3 M sodium acetate (pH 4.8) and 300 μl of 100% ethanol were added, mixed by inversion, and centrifuged at 21,500 × g at 4 ° C for 15 minutes. The aqueous layer was discarded, leaving the precipitate, and 70% ethanol was added, mixed gently by inversion, and centrifuged at 20,000 × g at 4 ° C for 1 minute. The aqueous layer was discarded, and the mixture was dried in an evaporator for 5 minutes, and then 20 μl of H ２ The solution was dissolved in O and the OD values ​​were measured at 260 nm and 280 nm using a spectrophotometer (DeNovix, Wilmington).

[0034] c. Embryo sex determination by PCR reaction: Embryo sex was determined by amplifying the chromohelicase DNA binding gene (CHD gene) (Fridolfsson AK & Ellegren H, 1999). A mixture containing a forward primer (2550F), a reverse primer (2718R), TaKaRa EX Taq (registered trademark) (Takara Bio Inc.), and dNTPs was prepared, and 9.5 μl of the mixture was mixed with 0.5 μl of the extracted DNA. For PCR, DNA was amplified by performing pre-denaturation at 94°C for 90 seconds, followed by 5 cycles of 94°C for 20 seconds (denaturation), 60°C for 20 seconds (annealing), and 72°C for 40 seconds (extension reaction), 5 cycles of 94°C for 20 seconds (denaturation), 55°C for 20 seconds (annealing), and 72°C for 40 seconds (extension reaction), 5 cycles of 94°C for 20 seconds (denaturation), 51°C for 20 seconds (annealing), and 72°C for 40 seconds (extension reaction), and 25 cycles of 94°C for 20 seconds (denaturation), 50°C for 20 seconds (annealing), and 72°C for 40 seconds (extension reaction). After the PCR reaction, electrophoresis was performed at 100V using a 1% agarose gel and TAE. After electrophoresis, the bands were confirmed using an LAS 500 (GE Healthcare Bio-Sciences AB, Uppsala) and sexing was performed. The CHD gene is a gene on the sex chromosome 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 sexing results are shown in Figures 1 and 2. In Figures 1 and 2, the solid bars represent the ratio of the number of male fertilized eggs to the total number of fertilized eggs obtained from poultry, and the shaded bars represent the ratio of the number of female fertilized eggs to the total number of fertilized eggs obtained from poultry.

[0035] 6) Measurement of Egg Yolk Steroid Hormone Concentrations: Egg yolk collected from the scutellum precipitate was suspended in 250 μl of PBS and the entire volume was applied to an Extrelute NT3 column (Merck, Kenilworth) and allowed to stand for 5–10 minutes. Three aliquots of a 7:3 mixture of diethyl ether and petroleum ether (6 ml, 6 ml, and 3 ml) were added, and the eluate was collected. All eluates were pooled, and the solvent was removed using nitrogen (JET AIR VAPORIZER, Ishii Shoten Co., Ltd.). The eluate was then dissolved in 250 μl of ELISA buffer (1% BSA, 4 M sodium chloride, 10 mM EDTA, 0.1% sodium azide) to prepare the sample. The extracted samples were subjected to colorimetric quantification using the Testosterone ELISA Kit, Corticosterone ELISA Kit, Progesterone ELISA Kit, and Estradiol ELISA Kit (Cayman Chemical, Ann Arbor). 50 μl of B0 (ELISA buffer), standards (S1-S8), or samples was added to a plate with immobilized secondary antibody (Mouse Anti-Rabbit IgG), and 50 μl of AChE-labeled test substance and antisera specific to each steroid hormone was added to each well and 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 left to stand for 60-90 minutes. After standing, measurements were made using a microplate reader (TECAN, Mannedorf). The results are shown in Figure 3. Figure 3 shows the relationship between the sex of the fertilized eggs and the concentrations of steroid hormones (testosterone, corticosterone, progesterone, and estradiol) contained in the germinal disc. The horizontal axis of the graph represents the concentration of steroid hormones. Males are plotted above the vertical axis of the graph, and females below.

[0036] 7) Statistical analysis: Microsoft Excel 2019 was used to analyze the data. Sex ratios were analyzed using a binomial test. For comparisons of steroid hormone concentrations between males and females, homogeneity of variance was confirmed using the F test, and a t test was used. The statistical analysis software R (http: / / cran.r-project.org / ) was used to create linear models and likelihood ratio tests. The results are shown in Tables 1 and 2.

[0037]

[0038]

[0039] According to this Example 1 (particularly "6) Measurement of Egg Yolk Steroid Hormone Concentrations" and Figure 3), progesterone ingested by poultry was found to accumulate in the germinal disc of eggs laid by the ingested poultry. A highly significant correlation between progesterone concentration in the germinal disc and sex ratio was also shown (Figure 3C). It was suggested that progesterone accumulation in the germinal disc of eggs preferentially releases the Z chromosome during meiosis. As a result, it is believed that the W chromosome is more likely to remain in the nucleus, resulting in a higher proportion of female fertilized eggs. This concept can also be applied to medroxyprogesterone, a progesterone analog. Furthermore, since poultry other than quail are also birds, it is likely that a similar mechanism operates. Therefore, it is believed that feeding at least one selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone can bias the sex ratio of fertilized eggs obtained from the poultry toward females.

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

[0041] 2) Collection of fertilized eggs Females that repeatedly laid eggs were artificially inseminated with 100 μL of chicken semen diluted 4-fold with Lake's solution, and fertilized eggs were collected the following day.

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

[0043] 4) Administration Experiment: Progesterone dissolved in sesame oil was administered to four recurrently laying hens. During the 14-day experimental period, 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. In the oral administration group, progesterone was administered at a dose of 3.125 mg / kg (body weight) using a Terumo syringe (Terumo Co., Ltd.) and a Disposable Oral Probe (Fuchigami Instruments Co., Ltd.). In the subcutaneous administration group, progesterone was administered at a dose of 2 mg / 0.5 ml using a Terumo syringe (Terumo Co., Ltd.) and a 25G needle (Terumo Co., Ltd.). Artificial insemination was performed 2 days prior to administration, 2 days prior to administration, 6 days prior to administration, and 9 days prior to administration. Fertilized eggs were collected daily for 14 days.

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

[0045] 6) Calculation of egg laying 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 value obtained by multiplying the number of days to lay by the number of test hens. The collected eggs were incubated for 3 days, cracked, and fertilization was confirmed by the presence or absence of embryos. The fertilization rate was calculated by 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]

[0047] 7) Statistical analysis Data was analyzed using Microsoft Excel 2019. The proportion of female chicks was analyzed using a binomial test.

[0048] As shown in Table 3, subcutaneous administration of progesterone significantly reduced egg production, whereas oral administration did not. 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 demonstrate that oral administration of progesterone can significantly bias the sex ratio of fertilized eggs toward females in chickens without negatively affecting egg production and fertilization.

Claims

1. A poultry feed containing at least one member 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 breeder of egg-laying birds.

4. The feed according to any one of claims 1 to 3, for biasing the sex ratio of fertilized eggs laid by the poultry towards females.

5. A method for raising poultry, comprising a step of feeding poultry at least one member selected from the group consisting of progesterone, pregnenolone, and medroxyprogesterone.

6. The method of claim 5 for biasing the sex ratio of fertilized eggs laid by said poultry towards females.

7. The method according to claim 5 or 6, wherein the step comprises feeding the poultry 1 to 30 mg / kg body weight / day of at least one member selected from the group consisting of progesterone, pregnenolone and medroxyprogesterone.