Abstract:

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 twenty four crossbred weaned male lambs of Poll Dorset (♂)×(Tansheep × Small Tailed Han sheep) (♀) weighing (25.83±6.14) kg at the age of 3–5 months were divided similarly into three groups. They were fed on the diets with concentrateroughage ratio of 65∶35（A）,50∶50（B）and 35∶65（C）（digestible energy and crude protein were at 1.0, 0.9 and 0.8 times of NRC recommendation） respectively during the 40 days of regular experimental periods. Six lambs from each group were slaughtered for sampling at the end of regular feeding periods. The results showed that: (1) Concentration of total VFA (TVFA) in rumen liquid of lambs from group A was obviously higher than those from group B and C (P<0.05). (2) The pH of rumen liquid, homogenates of mucosa (7.03, 7.31 and 7.35) and contents (7.19, 7.30 and 7.58) in behindjejunum，and of contents in ileum(7.16, 7.33, 7.57) were affected significantly by the concentrateroughage ratio of diets（P<0.05）. (3)Molar proportions of acetic acid and propionic acid were ranged from 0.612 to 0.654 and from 0.185 to 0.190 respectively, the acetic / propionic ratios varied ranging from 3.38 to 3.57. (4) There were nonuniform pattern ranked of activities of various digestive enzyme along small intestine with concentrateroughage ratio of the diets. (5)The highest activities of chymotrypsin in content and those of lipase in mucosa homogenate and content occurred in the middlejejunum, activity of trypsinase in contents of behindjejunum was the highest, and the highest activities of αamylase were noted in content of duodenum and behind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 behind section of small intestine were affected by the concentrateroughage ratio of the diets; there was also higher activity of αamylase in duodenum.

Key words: concentrateroughage ratio, nutritional level, fattening lamb, pH of alimentary canal, VFA, digestive enzymes