Effect of feeding calcium soaps to early postpartum dairy cows on plasma prostaglandin F2 alpha, luteinizing hormone, and follicular growth.

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.