1685
EFFECT OF CHITOSAN AND SOYBEAN OIL COMBINATION ON RUMINAL FERMENTATION AND MILK YIELD AND COMPOSITION OF DAIRY COWS
The aim of this study was to evaluate the effects of chitosan addition in mid-lactating dairy diet without or with soybean oil on ruminal fermentation and milk composition. Twenty-four Holstein cows (4 ruminally cannulated), averaging 174.7 ± 53.1 DIM, were randomly assigned in six Latin Square design with a two by two factorial arrangement of treatments. The diets contained Chitosan (150mg/kg of body weight) and soybean oil (3.3% of the diet DM). Each experiment period had a 14 d adaptation period and an seven for collection data. Sampling of milk was done on days 16, 17 and 18 of each period to evaluate the composition. On the 21th day of each period rumen fluid samples were collected from cannulated cows in seven times to evaluate the effect of the diets on ruminal fermentation. The results of milk composition were subjected to analysis of variance, while fermentation data were analyzed as repeated measures, both by PROC MIXED of SAS. There was no interaction effect (P>0.05) of factors and the time on ruminal fermentation. The addition of soybean oil in the diet increased the concentration of propionate and decreased acetate and the total concentration of short chain fatty acids (SCFA) in mmol.L-1, however the ratio acetate:propionate was decreased. Those diets decreased (P<0.05) the levels of milk fat in 5g/kg on average. The addition of chitosan in the diet reduced the total concentration of SCFA, although ruminal fermentation and milk composition was not altered significantly. The protein contents in milk were on average 3.06% and were not affected by diets. There was interaction (P<0.05) of the factors for milk yield. Milk yield was same in control and chitosan diets and was higher in diet with soybean oil than diet with chitosan and soybean oil, with averages of 33.87, 32.85, 32.86 and 31.26, respectively. In conclusion, the use of chitosan as a feed additive for dairy cattle was positive in increasing the milk production, when in diet of low lipids level, not altering, however, ruminal fermentation and milk composition.
Keywords: additive, milk fat, rumen.