2007 Volume 53 Issue 1 Pages 113-120
Metabolic hormones affect ovarian function in the cow. However, the relationship between metabolic factors and ovarian function is not clear in the postpartum primiparous cow because they are still growing. The aim of the present study was to investigate in detail the time-dependent profile of the metabolic hormones, metabolites, and milk yields of ovulatory and anovulatory primiparous cows during the first follicular wave postpartum. We used 16 primiparous Holstein cows and obtained blood samples for the profiles of metabolites (glucose; non-esterified fatty acid, NEFA; ketone body; total cholesterol; and aspartate aminotransferase), metabolic hormones (growth hormone, GH; insulin-like growth factor-I, IGF-1; and insulin), and progesterone every other day from 1 to 21 days postpartum. In addition, all ovaries were observed using ultrasound. Dairy milk yield was recorded during the experimental period. In all cows, the first follicular wave postpartum was observed and 6 of the cows ovulated. The plasma glucose (P<0.0001) and IGF-1 (P<0.001) concentrations were lower and the plasma NEFA (P<0.0001) and ketone bodies (P<0.0001) concentrations and daily milk yield (P<0.0001) were higher in the anovulatory cows compared to the ovulatory cows. However, the GH levels, which enhance lipolysis for milk production, insulin and other metabolites did not differ between the two groups. In conclusion, the present study suggests that anovulation of the dominant follicle during the first follicular wave postpartum in primiparous cows is induced by low IGF-1 levels that are similar to those of multiparous cows. In addition, anovulatory cows are likely to mobilize body fat stores for milk production more easily than ovulatory cows.