Abstract
This study aims to evaluate the effects of dietary concentrate: forage ratio (C:F) on the development of the gastrointestinal tract in Tibetan lamb. A total of 60 healthy two-month-old weaned black Tibetan sheep (approximately 10.50 kg of initial body weight) were assigned to three treatments and fed C:F of 70:30 (HC group), 50:50 (MC group) and 30:70 (LC group). Using the haematoxylin-eosin (HE) staining, morphological results showed that the increase of dietary roughage level from 30 to 70% exerts a positive effect on the development of the forestomach including rumen, reticulum and omasum, especially in papillae and muscle layer. Both submucosa thickness and muscle layer of abomasum are significantly increased in the LC group when compared with the HC group. Moreover, the mucosal thickness of the small intestine is higher in the LC group than that in the HC group, whereas crypt depth is higher in HC compared to the LC group. These data suggest that increased dietary forage levels promote gastrointestinal tract growth in black Tibetan sheep by changing in papilla, muscle layer and mucosal thickness, and concentrate can be supplemented up to 30% to fulfil the nutrient requirements without restriction on the development of the gastrointestinal tract.