Influences of Total Mixed Diets with Different Concentrate-Roughage Ratio on pH and Activity of Digestive Enzymes in Alimentary Canal of Fattening Lambs at Tibetan Plateau

摘要

This study was conducted to investigate the effects of concentrate-roughage ratio in diets on concentration of VFA in rumen liquid, pH and digestive enzyme activities in different sections of alimentary canal. The 48 weaned male lambs of Ganjia sheep weighing (23.18±2.16) kg at the age of 3-5 months were divided similarly into three groups which each group included 16 lambs. Lambs were fed diets with a concentrate-roughage ratio of 40:60 (A), 50:50 (B) and 60:40 (C). Digestible energy and crude protein levels were 0.8, 0.9 and 1.0 times the NRC-recommended levels during the 60 days experimental period. About 12 lambs from each group were slaughtered for sampling at the end of the regular feeding period. The results showed that concentration of Total VFA (TVFA) in rumen liquid of lambs from Group C was obviously higher than those from Group A and B (p<0.05); the pH of rumen liquid, homogenates of mucosa and contents in posterior segment-jejunum and of contents in ileum were affected significantly by the concentrate-roughage ratio of diets (p<0.05); there were non-uniform pattern ranked of activities of various digestive enzyme along small intestine with concentrate-roughage ratio of the diets; the highest activities of chymotrypsin in content and those of lipase in mucosa homogenate and content occurred in the middle piece-jejunum, activity of trypsinase in contents of posterior segment-jejunum was the highest and the highest activities of α-amylase were noted in content of duodenum and posterior segment-jejunum. It was concluded that still acetic acid pattern of rumen fermentation was kept in lambs fed total mixed diet with higher concentrate-roughage ratio; the pH of contents in rumen and abomasums of mucosa and contents in posterior segment section of small intestine were affected by the concentrate-roughage ratio of the diets; there was also higher activity of α-amylase in duodenum.