LAUSR

Abstract Background High‐yielding dairy cows develop insulin resistance during late gestation associated with disruption of the growth hormone (GH)–insulin‐like growth factor (IGF)‐I axis and cause metabolic and reproductive disorders. Objective This study aimed to determine the effects of dietary pioglitazone (PIO) supplementation as an insulin sensitizer agent on milk yield, plasma metabolite status and GH–IGF‐I axis in transition Holstein dairy cows. Methods Twenty multiparous cows were randomly assigned into two experimental groups (n = 10 animals per group) and either fed with a basal diet (control) or the basal diet supplemented with 6 mg PIO/kg body weight (BW) from day 14 before parturition to day 21 postpartum. The BW and body condition score (BCS), non‐esterified fatty acids, beta‐hydroxybutyrate (BHBA), insulin, glucose, GH and IGF‐I concentrations, milk production and composition were measured weekly. Results BW and BCS losses were lower in PIO than in control cows (p < 0.05). The percentage and amount of milk fat were decreased, and the amount of protein increased only in the first post‐calving week in the PIO‐treated cows compared to the control (p < 0.05). Dietary PIO supplementation increased glucose concentration at calving, but insulin concentration was increased at calving and in the first post‐calving week (p < 0.05). Plasma concentrations of IGF‐I and the ratio of IGF to GH were increased in the PIO group (p < 0.05). The mean revised quantitative insulin sensitivity check index with BHBA, as an insulin sensitivity index, was greater in PIO‐supplemented cows (p < 0.05). Conclusions Our results showed beneficial effects of PIO supplementation on improving insulin sensitivity and the GH–IGF‐I axis that may cause lower negative energy balance and better metabolic and health status in transition dairy cows.