Effects Of Chitosan On Milking Performance, Digestion Of Nutrients And Related Serum Biochemical Parameters In Dairy Cows

The objective of this study was to determine the effects of different levels of chitosan on ruminal fermentation, milking performance, nutrient digestibility, gut microflora and the related serum biochemical parameters in dairy cows through in vitro and in vivo experiments, so as to provide a theoretical reference for chitosan application in dairy cows.The in vitro trial was conducted to explore the effects of chitosan on in vitro ruminal fermentation and production of greenhouse gases. Five treatments were designed to contain 0.5 g substrate with 0,0.3%、0.6%、1.2% and 2.4% of chitosan, respectively, and each treatment included 6 replicates. Every artificial rumen vessel with a rubber plug was injected with 60 mL artificial rumen fluid and 0.5 g substrate. Then, the fermentation liquid was cultured under suitable conditions in vitro for 24 h. At the end of the trial, samples were collected to determine artificial rumen fermentation indexes and the production of greenhouse gas. The results indicated that ruminal pH increased linearly (P<0.001) or quadratically (P<0.001) as chitosan inclusion in the substrate increased. Then, ruminal ammonia nitrogen concentration also increased linearly (P=0.041) or quadratically (P=0.037). Chitosan treatment quadratically affect dry matter digestibility (P=0.004). The gas production in 6,12,18 and 24 h, respectively, increased quadratically (P=0.015, P= 0.014, P=0.025, P=0.025) as the proportion of chitosan in the substrate increased. And supplementation of chitosan linearly (P=0.050) decreased methane generation.Forty Holstein cows at mid-lactation with similar milk yield, calving date and parity were randomly divided into five groups with 8 cows in each. The control group was fed the basal diet without adding chitosan. The other four experimental diets were the basal diet supplemented with 500,1000,1500, and 2000 mg/kg chitosan, respectively. Feeding trial lasted for 60 days during which the effects of chitosan on the milking yield, milking composition, somatic cell count (SCC), nutrient digestibility, serum biochemical parameters and gut microflora were determined. The results indicated that milk yield showed a linear (P=0.023) and quadratic (P=0.014) response to supplementation of dietary chitosan during days 30-60. Milk composition was not affected by dietary treatments, although there was a linear decline in SCC of milk on days 30 (P=0.053) and 60 (P=0.032) as the proportion of chitosan in the diets increased. Dietary supplementation of chitosan quadratically improved the digestibility of dry matter (DM) (P=0.005), neutral detergent fiber (NDF) (P=0.052) and phosphorus (P) (P=0.039) on day 60, but linearly decreased ether extract (EE) digestibility on days 30 (P=0.031) and 60 (P=0.028). Moreover, the counts of Lactobacillus in hinder gut quadratically increased. In addition, supplementation of chitosan resulted in a linear (P= 0.038) and quadratic (P=0.044) response in serum insulin-like growth factor I (IGF-I) concentration on day 30, and also resulted in a quadratic (P= 0.049) response in serum prolactin (PRL) concentration on day 60. High density lipoprotein cholesterol (HDL-C) concentration showed a quadratic change on day 60 (P= 0.020). However, the contents of triglyceride (TG) (P= 0.003), total cholesterol (TC) (P= 0.006) and low density lipoprotein cholesterol (LDL-C) (P= 0.027) had a linear decline response on day 60. In addition, consumption of chitosan increased linearly P concentration in serum on day 60.In conclusion, the appropriate supplementation of chitosan in diets could improve the milking performance of dairy cows. And the promoting action was achieved mainly by improved ruminal fermentation, increased DM, NDF and P digestibility, increased IGF-I, PRL, HDL-C and P, declined TG, TC and LDL-C concentration in serum, as well as improved microflora in the hinder gut.