Responses of Lactation, Rumen Fermentation and Blood Biochemical Parameters with Increasing Dietary Inulin Supplementation in Mid-Lactation Dairy Cows

Effects of dietary supplementation of inulin in dairy cows were investigated in this study. Thirty-six mid-lactation Holstein dairy cows were randomly divided into six groups with six cows per group and offered a total mixed ration supplemented with 0 (control), 50, 150, 200, 250 and 350 g/d inulin per head, respectively. The animals were pre-fed for 2 weeks before rumen fluid, milk and blood samples were collected weekly for 3 weeks. With increasing inulin doses, milk yield ( p < 0.01) and milk fat concentration ( p = 0.04) were linearly increased, while milk urea nitrogen ( p < 0.01) and somatic cell count ( p = 0.04) were linearly decreased. Linear increases were also detected in the proportions of milk saturated fatty acids ( p < 0.01) and polyunsaturated fatty acids ( p = 0.04); however, milk monounsaturated fatty acids were linearly decreased ( p = 0.04). The ruminal concentrations of acetate, propionate and butyrate increased, while the ruminal pH and the concentration of NH 3 -N reduced at a decreasing rate with increasing inulin doses ( p < 0.01). Moreover, the concentrations of lactic acid ( p = 0.03) and total volatile fatty acids ( p < 0.01) were linearly upregulated. There were linear increases in the serum concentrations of superoxide dismutase ( p = 0.02), immunoglobin G ( p < 0.01), immunoglobin M ( p = 0.04), interleukin-2 ( p < 0.01) and interleukin-10 ( p = 0.04); quadratic increases in serum total protein ( p < 0.01) and albumin ( p = 0.02) and linear decreases in serum total cholesterol ( p = 0.02), triglyceride ( p < 0.01) and malondialdehyde ( p < 0.01). The results indicated that inulin increased milk production, shifted milk fatty acid profile, upregulated rumen volatile fatty acid concentration, and enhanced antioxidant and immunity function in dairy cows in a dose-dependent manner.