Effect of body condition loss in early lactation Holstein cows on plasma IGF-I, prolactin and NEFA during breeding period and its association with some reproductive indices.

The associations between early lactation changes in the body condition score (BCS) and mid-lactation levels of blood insulin-like Growth Factor-I (IGF-1), prolactin, insulin, nonesterified fatty acids (NEFA), milk production and some reproductive indices were investigated. Monthly milk yield and BCS were recorded. Blood samples were collected on days 60, 90, and 120 (±5 days) of lactation. Twelve and 17 cows showed BCS losses ≤0.75 and >0.75 on day 60, respectively. BCS losses ≤0.75 till day 60 after calving enhanced the IGF-I concentration on day 90 (57.8 ± 10.7 vs. 35.6 ± 17.8 ng/mL; p = .001). The differences in blood metabolites were prominent on day 90. Trends of insulin changes between day 60 BCS (p = .04) groups were different. Inverse correlations were detected between IGF-I and NEFA (-0.6, p = .001), IGF-I and milk production (-0.4, p = .05), NEFA and prolactin (-0.8, p < .001) on day 90. Higher percentages of cows with BCS loss >0.75 (day 60) showed their first heat after day 40 postpartum. In conclusion, irrespective of BCS at the time of breeding, the level of BCS loss during the first 60 days of lactation may affect further reproductive performance due to prolonged alterations of IGF-I, NEFA, prolactin and insulin levels. The extent of postpartum BCS loss may be a predictor of the metabolic status of cows during mid-lactation.