Multiparous Holstein cows (n = 52) were fed one of six diets consisting of a totally mixed ration (corn silage, corn grain, soybean meal, dried distillers grains, and whole cottonseed) plus either alfalfa hay, alfalfa cubes, or bermuda-grass hay fed chopped as a component in the mixed ration or separate as long hay. Predicted energy balance was calculated from DM intake, milk yield and composition, and BW. On d 25 postpartum, ovarian status was programmed by injecting 25 mg of prostaglandin F2 alpha and treating cows for 15 d with an intravaginal device containing 1.9 g progesterone. Before d 25, number of class 1 follicles (3 to 5 mm; detected by ultrasonography) decreased with increasing days postpartum, and number of class 3 (10 to 15 mm) and class 4 (greater than 15 mm) follicles increased. The number of class 1 and 2 follicles (6 to 9 mm) decreased with increasing energy balance, and number of class 3 follicles increased with energy balance. Before d 25, predicted energy balance explained treatment differences in the number of follicles within each size class. After d 25, energy balance did not affect the average number of follicles per cow, but diet affected the number of follicles within each class. Predicted energy balance and dietary treatments influenced number of follicles at different times after calving. These results identify the importance of diet and energy balance to follicular and ovarian function in postpartum lactating dairy cows.

Multiparous Holstein cows (n = 18) were fed a total mixed ration containing corn silage, corn grain, whole cottonseed, soybean meal, dried distillers grains, and chopped bermudagrass hay (control) or same diet plus Ca salts of long-chain fatty acids (2.2% of diet DM) for the first 60 d postpartum. Predicted energy balance was calculated from DM intake, milk yield and composition, and BW. On d 25 postpartum, cows were injected with 25 mg of prostaglandin F2 alpha and treated for 15 d with an intravaginal device containing 1.9 g progesterone. Profiles of 15-keto-13,14-dihydro-prostaglandin F2 alpha (d 1 to 21) and plasma triglycerides (d 7 to 60) were similar between groups. Average number of follicles, determined by ultrasonography prior to d 25, tended to differ between groups; controls had more 3- to 5-mm and fewer 6- to 9-mm follicles than the group of fat-fed cows. Basal, smoothed mean concentration, and average luteinizing hormone amplitude, determined by 10-min samples for 8 h on d 10, were not significantly different between groups. Increasing predicted energy balance was associated with increased pulse amplitude and diameter of the largest follicle on d 10. During the progesterone treatment period and the postprogesterone treatment estrous cycle, cows fed fat had greater numbers of 3- to 5-mm and greater than 15-mm follicles. In conclusion, feeding fat did not influence 15-keto-13,14-dihydro-prostaglandin F2 alpha or luteinizing hormone dynamics but did alter the average number of follicles within different size classes and the diameter of largest and second largest follicle after progesterone treatment.

Nonlactating dairy cows were used to examine effects of bovine somatotropin (bST) on components of the insulin-like growth factor (IGF) system. Estrus was synchronized in cows with a Presynch + Ovsynch protocol and timed AI (TAI; n = 55) or not TAI (cycling, C; n = 23) on d 0 (time of synchronized ovulation). On d 0 and 11, cows received bST (500 mg) or no bST, and were sacrificed on d 17. Pregnancy rates were less in bST cows (27.2%, 9 of 33) than in controls (63.6%; 14 of 22). In contrast, conceptuses were larger in bST-treated cows (39.2 +/- 4.8 cm) than in controls (20 +/- 4.3 cm). Total interferon-tau in uterine luminal flushings (ULF) was greater in bST-treated cows (7.15 > 2.36 microg). Number of class 2 follicles (6 to 9 mm) was less in bST-C cows on d 7 and 16. On d 17, corpus luteum (CL) weight tended to be greater in bST-treated cows. Concentrations of progesterone were greater after d 10 in C than in pregnant (P) cows. In the ULF, IGF-binding protein-3 was greater in bST-P cows than in pregnant cows. A tendency for an increase in IGF-I hormone concentrations in the ULF was detected on d 17 in bST-treated and cyclic cows. Endometrial mRNA for IGF-I, IGF-II, IGFBP-2, and IGFBP-3 increased in bST-C, but not in bST-P cows. Treatment with bST increased plasma concentrations of insulin, IGF-I, and growth hormone (GH). In conclusion, bST may have hyperstimulated plasma IGF-I and insulin to cause asynchrony between conceptus and uterus that was detrimental to pregnancy.