Effect of supplementation with corn oil on postpartum ovarian activity, pregnancy rate, and serum concentration of progesterone and lipid metabolites in F₁ (Bos taurus × Bos indicus) cows

The aim was to evaluate the effect of corn oil supplementation during postpartum anoestrus on ovarian activity, pregnancy rate, progesterone (P₄), and lipid metabolites (cholesterol, CHO; low and high density lipoproteins; LDL and HDL, respectively) concentrations in blood of F₁ (Bos taurus × Bos indicus) grazing cows. Cows were randomly assigned to an experimental group, fed with a supplement containing 4% corn oil on dry matter basis (OG, n = 11), and a control group with the same supplement without corn oil (CG, n = 12). Both supplements contained equivalent amounts of crude protein and metabolizable energy and were fed for 34 days continuously. All cows were induced to estrous 12 days after beginning of supplementation by using a synthetic progestagen and artificially inseminated 56 h after retiring the implants. Pregnancy diagnosis was performed by transrectal palpation 45 days after insemination, evaluating simultaneously ovarian activity. P₄ and lipid metabolites (CHO, HDL, LDL) concentrations were determined in blood samples collected at 3-day intervals, from the beginning of corn oil supplementation and up to 10 days after artificial insemination. Ovarian activity was affected by treatment (p < 0.05), finding ovarian structures in 72.7% of OG cows and in 50% of CG cows. Concentration of P₄ and CHO was higher for OG with respect to CG (2.52 ± 0.65 vs 1.88 ± 0.62 ng/ml and 117.79 ± 11.57 vs 85.71 ± 12.11 mg/dl, respectively), whereas pregnancy rate and blood concentrations of HDL and LDL were not affected by treatment (p > 0.05). Addition of corn oil to the supplement stimulated ovarian activity and increased serum concentrations of progesterone and cholesterol in grazing B. taurus × B. indicus cows with low body condition score showing postpartum anoestrus.