Comparative Study Of Growth Performance And Parameters Of Digestive Physiology Between Small-Tailed Han Sheep And Tan Sheep

This study was conducted to determine the differences of growth performance, diet digestibility, nitrogen use and digestive physiology between Small-tailed Han sheep and Tan sheep.Twenty 80-day-old lambs, equally representing the Small-tailed Han sheep and Tan sheep, were paired by breed, placed in 2 enclosed pens, and offered TMR (13.03% CP, 22.37% CF, 43.23% NDF, 9.85 MJ/kg DM) ad libitum. Lambs were allowed a 10-d adaptation period, and remained on trial for 80 d. Starting body weight (BW) was not different (P>0.05) between Small-tailed Han sheep (15.96 kg) and Tan sheep (14.08 kg). Daily gain of Small-tailed Han sheep (72 g/d) were greater (P<0.01) than that of Tan sheep (44 g/d). Daily dry matter intake of Small-tailed Han sheep (682 g/d) were higher (P<0.01) than that of Tan sheep (514 g/d), and feed to gain ratio ranged from 10.94 in Small-tailed Han sheep and 12.16 in Tan sheep, but was not different (P>0.05) between breeds.Four Small-tailed Han sheep and Tan sheep of each breed were selected for the metabolism trial. All animals were allowed 15 d adaptation period before the beginning of experiment, were offered TMR (13.03% CP, 22.37% CF, 43.23% NDF, 9.85 MJ/kg DM), followed by 5 d of total collection of ort, feces and urine. Blood samples were collected via jugular venipuncture at the end of trial period. Lambs body weight (BW) was not different (P>0.05) between Small-tailed Han sheep (21.13 kg) and Tan sheep (20.25 kg). There was not significant difference in feed intake between Small-tailed Han sheep and Tan sheep. Digestible feed intake was greater in Tan sheep than Small-tail sheep (P<0.05 or P<0.01). Coefficients of apparent digestibility of DM (P<0.01), OM (P<0.05), NDF (P=0.072), ADF (P=0.057), NFE (P<0.01) and gross energy (P<0.01) were greater in Tan sheep compared to Small-tailed Han sheep, however, no significant (P>0.05) differences were observed in crude ether extract, CP, absorbed nitrogen. Retained nitrogen % of N intake were different between Small-tailed Han sheep and Tan sheep (21.86% vs 15.44%, P=0.055). Serum glucose was greater (P<0.01) in Tan sheep than Small-tailed Han sheep, but serum urea-N and creatinine were not different (P>0.05) between Small-tailed Han sheep and Tan sheep.Four lambs per breed were slaughtered after metabolism trial for digestive enzyme activity and gastroenteric morphology. The relative activity of protease in caecum content (P<0.01), trypsin in colon content (P<0.05), trypsin in jejunum content (P<0.05), trypsin in caecum content (P<0.01) and cellulase in rumen content (P<0.05) of Tan sheep were significantly higher than those of Small-tailed Han sheep; however, the relative activity of amylase in rumen (P<0.05) and caecum content (P<0.01) in Small-tailed Han sheep was significantly higher than that of Tan sheep; Relative weight and absolute weight of rumen, reticulum, omasum, abomasums and small intestine were not different (P>0.05) between Small-tailed Han sheep and Tan sheep, however, length of jejunum, alimentary tract and small intestine was greater (P<0.05) in Small-tailed Han sheep than those of Tan sheep, villus height of jejunum, crypt depth of duodenum and ileum was also greater (P<0.05) for Small-tailed Han sheep than Tan sheep.Based on results of the present research, it is concluded that growth performance of Small-tailed Han sheep was greater than that of Tan sheep because of the higher intake of digestive nutrients and nitrogen availability for Small-tailed Han sheep.