Differential effects of exogenous progesterone administration at different stages of the luteal phase on endogenous oestradiol concentration in cows

Effects of human chorionic gonadotropin and intravaginal progesterone device treatment after artificial inseminations on the reproductive performance of normal and repeat breeder lactating dairy cows

We examined the effects of human chorionic gonadotropin (hCG) treatment on Day 5 (Day 0 = day of artificial insemination: AI) and intravaginal progesterone device (IVPD) treatment from Day 5 to 19 on the conception and detection rates of return to estrus (re-estrus) in lactating dairy cows. A total of 306 cows from a commercial dairy farm were divided into the following three groups on Day 5: non-treatment group (n = 128), untreated; hCG group (n = 71), 3,000 IU hCG was administered (intramuscularly); IVPD group (n = 107), IVPD was inserted into the vagina from Day 5 to 19. Re-estrus detection was performed up to Day 25. Pregnancy was diagnosed by rectal palpation between Day 50 and 60. There was an interaction between treatment and AI number (P < 0.01) on the conception rate of first-AI. For cows with more than three AIs, the IVPD treatment (66.7%) was more effective than the non-treatment (23.1%) (P < 0.05). The re-estrus detection rate was significantly (P < 0.05) higher in the IVPD group (60.7%) than that in the non-treatment group (41.4%) and tended (P < 0.1) to be higher than that in the hCG group (37.8%). Our results suggested that the conception rate can be improved by IVPD treatment, especially in cows with more than three AIs. In addition, IVPD treatment can induce higher estrus expression up to 25 days after AI in non-pregnant cows.

Central genomic regulation of the expression of oestrous behaviour in dairy cows: a review

The expression of oestrous behaviour in Holstein Friesian dairy cows has progressively decreased over the past 50 years. Reduced oestrus expression is one of the factors contributing to the current suboptimal reproductive efficiency in dairy farming. Variation between and within cows in the expression of oestrous behaviour is associated with variation in peripheral blood oestradiol concentrations during oestrus. In addition, there is evidence for a priming role of progesterone for the full display of oestrous behaviour. A higher rate of metabolic clearance of ovarian steroids could be one of the factors leading to lower peripheral blood concentrations of oestradiol and progesterone in high-producing dairy cows. Oestradiol acts on the brain by genomic, non-genomic and growth factor-dependent mechanisms. A firm base of understanding of the ovarian steroid-driven central genomic regulation of female sexual behaviour has been obtained from studies on rodents. These studies have resulted in the definition of five modules of oestradiol-activated genes in the brain, referred to as the GAPPS modules. In a recent series of studies, gene expression in the anterior pituitary and four brain areas (amygdala, hippocampus, dorsal hypothalamus and ventral hypothalamus) in oestrous and luteal phase cows, respectively, has been measured, and the relation with oestrous behaviour of these cows was analysed. These studies identified a number of genes of which the expression was associated with the intensity of oestrous behaviour. These genes could be grouped according to the GAPPS modules, suggesting close similarity of the regulation of oestrous behaviour in cows and female sexual behaviour in rodents. A better understanding of the central genomic regulation of the expression of oestrous behaviour in dairy cows may in due time contribute to improved (genomic) selection strategies for appropriate oestrus expression in high-producing dairy cows.