LAUSR

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.