Abstract
This study was conducted to understand the relationship between the peripartum nutritional status, as reflected in the levels of some blood and milk constituents and changes in body weight, and postpartum return to normal ovarian activity in dairy Holstein cattle. The time from parturition to resumption of a normal estrous cycle, estimated from changes in milk P4 levels, was 43.7±2.2 (mean±SE) days for this dairy herd. Animals with low values of milk protein (<3.0%) and solids-not-fat (SNF) (<8.5%) showed a significant delay (50.5±3.8 days and 56.2±5.8 days vs. 43.7±2.2 days, p<0.05), and the animals with low values of milk fat, P/F ratio and milk sugar displayed a tendency to delay the resumption of the estrous cycle. Furthermore, the groups with the most highest and a higher rate of peripartum body weight loss displayed a significant delay (59.1±7.4 days, p<0.01 and 41.5±2.4 days, p<0.05) in postpartum resumption of the estrous cycle when compared with groups that had less body weight loss (35.9±3.5 days).
