Effect of incremental levels of crude degummed canola oil on milk progesterone, plasma luteinizing and follicle stimulating hormones of primiparous Holstein–Friesian cows in a pasture-based system

Dietary supplementation of lactating cows with fat can alter the profiles of key reproductive hormones and boost postpartum energy balance. However, published data under Australian pasture-based dairy production conditions are scanty and inconsistent. Therefore, the objective of this study was to determine whether dietary inclusion of crude degummed canola oil (CDCO) at incremental levels for eight-weeks will have significant influence on progesterone (P4), luteinizing hormone (LH) and follicle stimulating hormone (FSH) of primiparous Holstein–Friesian cows grazing pastures. We tested the hypothesis that postpartum supplementation of primiparous Holstein–Friesian cows with dietary CDCO in a pasture-based system will alter the concentrations of P4, LH and FSH reproductive hormones. A random allocation of twenty primiparous Holstein–Friesian cows into four treatment groups that consisted of a wheat-based pelleted basal diet with no supplemental CDCO (control), or a wheat-based pelleted basal diet with CDCO added at 25 ml/kg (low), 35 ml/kg (medium) and 50 ml/kg (high) was employed in an eight-week feeding trial after two weeks of adjustment. Supplementation levels of CDCO and week of data collection were significant sources of variation (P < 0.05) that influenced FSH and P4 concentrations. However, there was no significant effect of supplementation on LH concentration (P > 0.05). It was apparent that cows in the high (0.459 ng/ml), medium (0.367 ng/ml) and low (0.251 ng/ml) levels of oil treatments had higher mean plasma FSH concentrations compared to the control (0.172 ng/ml) cows. It was concluded that the current levels of CDCO can be used in pasture-based dairy systems to increase FSH, but not LH and P4.