Abstract
The present study investigates the effect of Capsicum oleoresin (CAP) supplementation on the dry matter intake, milk performance, plasma metabolites, and nutrient digestibility of dairy cows during the summer. Thirty-two lactating Holstein dairy cows (n = 32) were randomly divided into four groups. The CAP was dissolved in water and added to the total mixed ration with graded levels of CAP (0, 20, 40, and 80 mg/kg of dry matter). The trial period consisted of seven days for adaptation and thirty days for sampling. Data were analyzed using the MIXED and GLM procedure SAS. The linear and quadratic effects were tested. The milk yield, milk fat, and milk urea nitrogen increased linearly with the dietary addition of CAP (p < 0.05). The dry matter intake increased linearly in the 20CAP group (p < 0.05). Additionally, the 4% fat-corrected milk, energy-corrected milk, milk fat yield, and milk fat to milk protein ratio increased quadratically (p < 0.05), while the rectal temperature decreased quadratically (p < 0.05). Serum total cholesterol and non-esterified fatty acids increased linearly (p < 0.05); glucose and β-hydroxybutyrate tended to increase quadratically with the dietary addition of CAP (p = 0.05). Meanwhile, CAP supplementation did not affect the milk protein yield, blood concentration of triglyceride, insulin, lipopolysaccharide, immunoglobulin G, or heat shock protein 70 expression level (p > 0.05). In addition, nutrient digestibility was comparable among groups (p > 0.05). These findings indicated that CAP supplementation could enhance the lactation performance of dairy cows during the summer.