Association of peripartum plasma insulin concentration with milk production, colostrum insulin levels, and plasma metabolites of Holstein cows.

The main objective of this study was to assess associations between plasma insulin concentration around parturition and production in Holstein cows. Primiparous and multiparous cows (n = 267) were enrolled. Blood samples were collected within 12 h after parturition (d 0), and on d 3 and 10 after calving. In addition, blood samples were collected 7 d before (-7 d) the expected date of parturition and colostrum samples were collected within 8 h after parturition from a subset of cows to measure insulin concentration (n = 47). All samples were harvested from 0630 to 1100 h and were used to quantify insulin, nonesterified fatty acids (NEFA), and β-hydroxybutyrate. The plasma concentrations of insulin on d -7 and 0 were not correlated with insulin levels in colostrum. Cows were grouped according to plasma insulin concentration based on the median as low insulin (L-INS) or high insulin (H-INS) on d 0 (median = 0.35 ng/mL; range 0.2 to 1.2), 3 (median = 0.32 ng/mL; range 0.2 to 1.6), and 10 (median = 0.30 ng/mL; range 0.2 to 0.8). We detected that cows in the L-INS group on d 0 (L-INS = 0.57 ± 0.02; H-INS = 0.49 ± 0.02 mmol/L), d 3 (L-INS = 0.56 ± 0.02; H-INS = 0.49 ± 0.02 mmol/L), and d 10 (L-INS = 0.61 ± 0.03; H-INS = 0.55 ± 0.03 mmol/L) had higher NEFA concentrations compared with cows in the H-INS group. Compared with H-INS cows, milk yield was higher for cows classified as L-INS on d 0 (L-INS = 40.75 ± 0.69; H-INS = 38.41 ± 0.64 kg) and d 10 (L-INS = 40.95 ± 0.74; H-INS = 38.66 ± 0.64 kg). Moreover, fat-corrected milk was higher for cows classified as L-INS on d 0 (L-INS = 40.59 ± 2.36; H-INS = 37.73 ± 2.31 kg) and d 10 (L-INS = 41.00 ± 2.42; H-INS = 38.65 ± 2.28 kg) compared with H-INS cows, and energy-corrected milk was higher for L-INS cows compared with H-INS cows regardless of the day (d 0, L-INS = 44.50 ± 0.70 vs. H-INS = 41.67 ± 0.64 kg; d 3, L-INS = 43.65 ± 0.74 vs. H-INS = 40.88 ± 0.72 kg; d 10, L-INS = 44.09 ± 0.73 vs. H-INS = 40.55 ± 0.68 kg). We conclude that low plasma insulin concentration during early lactation is associated with higher milk yield in the long term.