Effect of rice bran oil supplementation on rumen fermentation, milk yield and milk composition in lactating dairy cows

The objective of this study was to determine effects of rice bran oil (RBO) on feed intake, nutrient digestibility, ruminal fermentation, milk yield, and milk composition in lactating dairy cows fed at 0, 2, 4, and 6% in concentrate. Four crossbred (75% Holstein Friesian) lactating dairy cows with an average live weight of 399 ± 59 kg and 64 ± 10 days in milk were randomly assigned according to a 4 × 4 Latin square design. Cows were fed with total mixed ration (TMR), with a concentrate/roughage ratio of 60:40 and urea treated rice straw (5% urea) was used as a roughage source. Cows fed supplemental RBO were linearly decreased in feed intake expressed as kg/d and a percentage of BW. Increased level of RBO in concentrate linearly decreased digestibility of DM, OM, NDF and OM intake, but did not affect those of CP and ADF; however DMI and nutrient digestibility could maintain at 4% RBO supplementation as compared with control (0% RBO). RBO supplementation tended to increased in propionate concentration, which was highest in 4% RBO. Moreover, supplementing RBO linearly decreased in acetate concentration which resulted in a linearly decreased C2:C3 ratio and CH4 production. Although supplementing with RBO had not affected on milk yield and milk composition, while milk fat yield and milk protein yield (kg/d) were linearly decreased. 3.5% FCM and milk fat tended to decrease when increasing level of RBO in the diet. In addition, increased RBO supplementation linearly decreased concentrations of both short- and medium-chain FA, and linearly increased the proportion of long-chain FA in milk fat and cis-9, trans-11 CLA, as well as tended to be increased in total CLA, which was highest in cow fed with 4%RBO. In conclusion, RBO can be used as a good source of additional energy for lactating dairy cows; however adding high level of RBO might have adverse effect on DMI and nutrient digestibility. Based on this study, feeding dairy cow with RBO should not exceed 4% in concentrate to obtain the most beneficial effect on nutrient utilization, rumen fermentation and dairy cow performance.