Effect Of Different Sources Of Starch On Rumen Fermentation, Digestion And Metabolism Of Nutrients In Yaks

This study was conducted to investigate the effect of different sources of starch on rumen fermentation, digestion and metabolism of nutrients in Yaks. First, the effect of different sources of starch supplementation on growth performance, digestion and metabolism of nutrients in Yaks was investigated, and then studied the effects of ruminal infusion of different starch sources on ruminal fermentation and serum biochemical indexes.In experiment1, the effect of different sources of starch supplementation on growth performance, digestion and metabolism of nutrients in Yaks was investigated.Sixteen healthy and age-mached yaks with body weight of (91.65±9.59) kg were assigned to4groups with4replicates each by body weight and each yak was fed in an individual pen. The experiment included four kinds of treated diets [a oat hay basic diet (control group), oat hay+300g/d corn starch (CS group), oat hay+300g/d resistant starch (RS group) and oat hay+300g/d barley, respectively].The experiment lasted for45days. The results showed as follows:1) Resistant starch, corn starch and total starch content of barley were70.62%,98.08%and61.85%; resistant starch, corn starch and barley amylose/amylopectin ratio, respectively3.95,0.31and0.27.average daily gain of control group was significantly lower than that of other two starch groups (P<0.05).The apparent digestibility of nutrients(starch、CP、OM) in total tract were no significant differences among four groups (P>0.05) There were no significant affect of supplementation of the corn starch, resistant starch and barley on fecal energy and fecal nitrogen (P>0.05). serum urea nitrogen content、triglyceride content of control group was significantly higher than that of other two starch groups (P<0.05).In experiment2, This experiment was conducted to investigate the effects of ruminal infusion of different starch sources on ruminal fermentation and serum biochemical indexes in yaks. According to a3×3Latin square design, three yaks with permanent rumen cannulas and similar body weight of (244±15) kg were fed oat hay (1.2time of maintenance energy feeding level).The experiment included three periods and three kinds of treated diets [a oat hay basic diet (control group), oat hay+900g/d corn starch (CS group), oat hay+900g/d resistant starch (RS group), respectively].Yaks were fed18days in each period. The results showed as follows:the pH value of control group was significantly higher than that of other two groups (P<0.05), the ammonia nitrogen (NH3-N) content of control group was significantly higher than that of other two groups (P<0.01). The microbial crud protein (MCP) and volatile fatty acids (VFA) contents of control group were significantly lower than those of other two groups (P<0.05). In post-prandial4and6h, the blood glucose contents of control group was significantly lower than that of other two groups (P<0.05), serum insulin, glucagon and triglyceride contents of yaks were no significant differences among three groups (P>0.05), and serum urea nitrogen content was significantly higher than that of other two groups (P<0.05),. In conclusion, the supplementation of corn starch and resistant starch can reduce the NH3-N and urea nitrogen contents, increase the ruminal MCP synthesis and VFA content, and raise the blood glucose content; yaks are able to utilize different source starchs effectively.In summary, those three different sources of starch can affect ruminal fermentation and the digestion and metabolism of nutrients significantly. The composition of two kinds of starch had lots of difference. The corn starch has76.18%of amylopectin, but the content of amylopectin in resistant starch was only20.19%. Starch supplementation is able to enhance digestion and metabolism of nutrients and increase average daily gain significantly. Then, the supplementation of corn starch and resistant starch can reduce the NH3-N and urea nitrogen contents, increase the ruminal MCP synthesis and VFA content, and raise the blood glucose content. In conclusion, yaks are able to utilize different source starchs effectively,therefore, Starch supplementation is able to increase growth performance of yaks.