Administration of estradiol benzoate before insemination could skew secondary sex ratio toward males in Holstein dairy cows

作者：Emadi S R; Rezaei A; Bolourchi M; Hovareshti P; Akbarinejad V^*

来源：Domestic Animal Endocrinology, 2014, 48: 110-118.

DOI：10.1016/j.domaniend.2014.03.001

• Dairy cows
• Estradiol
• Secondary sex ratio

The present study was conducted to investigate the effect of estradiol benzoate administration before insemination on secondary sex ratio (proportion of male calves at birth) in Holstein dairy cows. Cows (n = 1,647) were randomly assigned to 2 experimental groups by parity over a 1-yr period. Cows in the control group (n = 827; 232 primiparous and 595 multiparous cows) received 2 administrations of PGF(2 alpha), (500 mu g) 14 d apart, started at 30 to 35 d postpartum. Twelve d after the second PGF(2 alpha) injection, cows received GnRH (100 mu g), followed by administration of PGF(2 alpha) 7 d later. Cows in the treatment group (n = 820; 238 primiparous and 582 multiparous cows) received the same hormonal administrations as the cows in the control group. Additionally, cows in the treatment group received estradiol benzoate (1 mg) I d after the third PGF(2 alpha) injection. Estrus detection by visual observation was started 1 d after the third PGF(2 alpha) injection and after estradiol administration in the control (for 6 d) and treatment (for 36 h) groups, respectively. Artificial insemination was carried out 12 h after observation of standing estrus. Exposure of cows to heat stress at conception was determined based on temperature-humidity index. Estrus detection rate was lower in primiparous than in multiparous cows (P %26lt; 0.05), but conception rate was higher in primiparous vs multiparous cows (P %26lt; 0.05). Estradiol administration improved estrus detection rate and fertility (P %26lt; 0.05); moreover, it increased secondary sex ratio (adjusted odds ratio: 1.645; P = 0.017). Exposure to heat stress diminished heat detection rate and fertility (P %26lt; 0.05), and altered secondary sex ratio toward males (adjusted odds ratio: 2.863; P = 0.012). In conclusion, the present study revealed that estradiol administration before insemination could improve fertility and increase the probability of calves being male in Holstein dairy cows. Moreover, the results showed that cows exposed to heat stress around conception had diminished fertility and increased secondary sex ratio.

• 出版日期2014-7