Effects of a corn straw or mixed forage diet on Bovine Milk Fatty Acid Biosynthesis

Abstract Text: The study was designed to investigate the effects of different forage types on milk fatty acid (FA) profile. Thirty two dairy cows were divided into group MF (alfalfa and corn silage as forage source) and group CS (corn stover as forage source). The whole experiment lasted for 15 wk (2-wk adaptation and 13-wk experimental period) following 2-wk covariate period (a total of 17-wk). Milk fat content and fatty acid profile were measured. Statistical analysis was performed using the PROC MIXED procedure of SAS 9.0. The results showed that milk fat content in group MF was higher than group CS, but no difference was observed (4.46 vs 4.38 %, P>0.05). The proportion of milk saturated fatty acid (SFA) was significantly higher in group MF (74.77 vs 69.93 %). However, unsaturated fatty acid (UFA) in group CS was higher than group MF (25.23 vs 30.07 %). Unlike polysaturated fatty acid (PUFA), proportion of monounsaturated fatty acid (MUFA) in group CS exhibited significantly higher level mainly due to the large proportion of cis-9 C18:1 (MUFA, 21.62 vs 26.51 %). Feeding the MF diet significantly increased short- and medium-chain fatty acid (SMCFA) proportion but decreased long-chain fatty acid proportion in group MF (SMCFA, 47.38 vs 41.02 %; LCFA, 52.62 vs 58.98 %). Therefore, corn stover as forage source in the diet could increase the proportion of UFA but decrease the proportion of SMCFA in milk.

Keywords: alfalfa, corn silage, corn stover