Influence of energy balance on postpartum reproduction in dairy cattle

Kathie A Berghorn, Purdue University

Abstract

This study was undertaken to determine the influence of energy balance on ovarian activity and estrous behavior in postpartum dairy cows. At parturition, 39 Holstein cows and 19 Holstein first-calf heifers were allotted at random to 1 of 3 total mixed rations for 90 (Trial 1) or 60 d (Trial 2) postpartum. Rations, fed ad libitum, contained the following forage:concentrate ratios: (1) 30:70, (2) 50:50 and (3) 70:30. Animals were checked 2x daily for estrus and bled frequently for subsequent analysis of serum progesterone (P4) and cortisol. Ration did not influence (P $>$.05) days to first (DFO) or second (DSO) postpartum ovulations in Trials 1 or 2. In Trial 1, as the 14 d cumulative energy balance became more negative, DFO increased (P $<$.05; R$\sp2$ =.28). Days to zero energy balance were negatively associated with DFO (P $<$.05; R$\sp2$ =.21). Similarly, as the cumulative energy balance associated with days to zero energy balance became more negative, DFO increased (P $<$.05; R$\sp2$ =.28). In Trial 2, as 60 d cumulative milk yield increased, DFO increased (P $<$.05). A low proportion of cattle (17/58) were detected in estrus at the first postpartum ovulation; however, a higher proportion of animals (29/43) exhibited estrus at the second postpartum ovulation. Serum concentrations of P4 were higher during the second luteal phase than during the first luteal phase. In conclusion, energy balance negatively influenced DFO while the proportion of cows detected in estrus did not change. An in vitro superfusion system was developed to evaluate basal and hCG-induced release of P4 and estradiol-17$\beta$ (E2) by isolated, bovine preovulatory follicles. Effluent was collected during successive 10 min intervals for 480 min. Mean steroid production between 120 and 180 min of superfusion was defined as basal release. To stimulate steroid release, Medium 199 containing 3.9 IU hCG/ml, was delivered to each chamber for 20 min after 180 min of superfusion. Basal P4 production was 776 $\pm$ 237 pg/ml and increased (p $<$.01) to 1664 $\pm$ 560 pg/ml 120 min after hCG stimulation. During the basal release period, E2 production was 3853 $\pm$ 1085 pg/ml and increased to 4476 $\pm$ 1238 pg/ml by 300 min of superfusion. Thus, the superfusion system can be effectively used to investigate the dynamics of steroid production by bovine preovulatory follicles.

Degree

Ph.D.

Advisors

Allrich, Purdue University.

Subject Area

Livestock

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