RESUMO
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.