1440
Serum apelin concentrations in dairy cows receiving different amounts of concentrate and a nicotinic acid supplement
Apelin, a 77 amino acid preproprotein, which is also known as an adipokine is suggested to play a physiological role in glucose metabolism. It stimulates glucose uptake by adipose tissue in humans and mice, whereas lipolysis in humans is not affected. This might lead to a decreasing lipolysis during the transition period in cattle and may prevent lipid-related disorders. Nicotinic acid (NA), a known antilipolytic agent, might decrease plasma NEFA concentrations and enhances the response to insulin. As plasma apelin concentrations are decreased by a hypochaloric diet, we hypothesized, that different levels of concentrate in the diet combined with NA supplementation would affect the serum apelin concentrations in dairy cows. Thus the objectives of the present study were to quantify apelin in bovine serum samples and to examine the impact of different levels of concentrate in combination with a NA supplementation on apelin serum concentrations. Serum samples were obtained from 20 pluriparous Holstein-Friesian cows at day (d) -42, -14, 1, 7, 14, 21, 42 and d 100 relative to calving. Until d -42 all cows were fed the same silage-based diet. Between d -42 and d -1 10 animals each were assigned to either a high-concentrate (HC, 60:40 concentrate:roughage) or a low concentrate group (LC, 30:70 concentrate:roughage). Both groups were further subdivided into a control and a niacin group (n=5), the latter receiving 24 g/d NA (Lonza, Basel, Switzerland) until d 24. Serum apelin concentrations were measured using a commercially available ELISA kit (Phoenix Pharmaceuticals, Burlingame, CA, USA) validated for bovine samples. Statistical analysis was done using Mixed-Model procedure followed by Bonferroni correction (SPSS 22); d -42 values were considered as covariate. The serum apelin concentrations were not affected by treatment and time (P > 0.05) and remained on a constant concentration (mean 1.21 ± 0.08 ng/ml). The results of this study indicate that serum apelin concentrations are independent of the prepartum feeding regimen as well as of the stage of lactation.
Keywords:
apelin, nicotinic acid, dairy cow