Abstract #306

# 306
Ovarian follicular dynamics, endocrinology, and estrous behaviour in repeat breeder cattle.
P. Sood*1, H. D. Sarma2, P. K. Dogra1, V. Kadwad3, S. S. Sachdev3, 1DR G C Negi College of Veterinary and Animal Sciences, Palampur, Himachal Pradesh, India, 2Bhabha Atomic Research Centre, Mumbai, Maharashtra, India, 3Board of Radiation and Isotope Technology, Mumbai, Maharashtra, India.

Repeat breeding (RB) in cattle is a global and multifactorial problem causing reproductive wastage and economic losses. We investigated follicular dynamics, certain reproductive hormones (FSH, E2, LH and P4) and estrous duration as well as estrous behavior score (intensity) in PGF induced estrous cycles in repeat breeding (RB) and normal (C) cows. Depending on the number of follicular waves, the cows were categorized as 2 – wave (RB-2; n = 10 and C-2; n = 10) or 3 – wave (RB-3; n = 6 and C-3; n = 10). The results were analyzed (separately for 2 – and 3 – wave patterns) by ANOVA for repeated measures using the mixed procedure of the SAS and Student’s t-tests. The RB versus C with either wave pattern differed (P < 0.05 at least) in terms of (1) shorter interovulatory interval, (2) greater number of recruited follicles, (3) delayed selection of the dominant follicles, and (4) greater count of small and medium follicles. A treatment-by-day interaction of P < 0.12 and P < 0.08 was observed for FSH in RB-2 and RB-3, respectively; the plasma FSH remained greater, especially around selection of dominant follicles, and failed to exhibit a precipitous drop in peak as observed in the corresponding C-2 and C-3. Except for greater E2 (pg/mL) in RB-2 than C-2 at estrus (15.6 ± 1.1 versus 9.4 ± 0.5), its concentrations were similar at different stages of estrous cycle in RB and C. The plasma LH concentrations did not differ for the RB and C. Progression of P4 toward peak was slower in RB, in spite of which its concentrations at different days of estrous cycle and area under curve did not differ from C. There was no difference in estrous duration (h) (16.5 ± 5.1 in RB-2 versus 17.4 ± 4.5 in C-2 and 18.2 ± 5.8 in RB-3 versus 16.1 ± 3.9 in C-3) and estrous behavior score (1065.6 ± 146.1 in RB-2 versus 615.3 ± 149.1 in C-2 and 951.3 ± 278.4 in RB-3 versus 650.8 ± 110.9 in C-3) between the RB and C. In conclusion, while exogenous P4 can suffice its slow increase in RB, the cause – effect relation between greater FSH and altered follicular dynamics needs to be corrected in RB, which may restore normal reproduction in infertile cows.

Key Words: repeat breeder cows, follicular dynamics, endocrinology