Abstract: This study aimed to assess the effects of different pelleted diets on growth performance, nutrient apparent digestibility and serum biochemical indexes in fattening sheep. A total of 60 wether lambs at ages of 70±10 days of Tan sheep with similar weights were selected and randomly divided into control group （n=15）, experimental group Ⅰ （n=15）, experimental group Ⅱ （n=15） and experimental group Ⅲ （n=15）. The control group fed 100% self-prepared total mixed ration （40% self-prepared concentrate + 60% self-prepared forage）, experimental group Ⅰ fed 50% self-prepared total mixed ration （20% self-prepared concentrate + 30% self-prepared forage） + 50% commercially available total mixed pelleted diet for fattening sheep, experimental group Ⅱ fed 100% commercially available total mixed pelleted diet for fattening sheep, and experimental group Ⅲ fed 45% pelleted concentrate supplement + 55% pelleted forage. The feeding experiment included a 16 days pre-test period and an 87 days formal test period. The experimental fattening sheep in different groups were weighed at the beginning and end of the experiment, and the average daily gains during the feeding experiment were calculated. The feed intakes were observed and recorded, and the average daily feed intakes and feed/gain were calculated. At the end of the feeding experiment, the apparent digestibility of dry matter, organic matter, crude protein and neutral detergent fiber as well as the serum biochemical indexes were determined using routine methods. The indictors associated with growth performance, nutrient apparent digestibility and serum biochemical indexes among different groups were statistically compared. The results showed that the highest average daily gain was observed in experimental group Ⅱ, which was significantly （P<0.05） higher than those of experimental group Ⅰ and experimental group Ⅲ, and was extremely significantly （P<0.01） higher than that of control group; the average daily feed intake of experimental group Ⅱ was significantly （P<0.05） lower than those of experimental group Ⅰ and control group; the experimental group Ⅱ had the lowest feed/gain, which was decreased by 60.63%, 35.69% and 9.41% compared to control group, experimental group Ⅰ and experimental group Ⅲ, respectively. The apparent digestibility of dry matter, organic matter, crude protein and neutral detergent fiber of experimental group Ⅱ were higher than those of the other three groups, and significant （P<0.05） difference was observed in apparent digestibility of crude protein. There were no significant （P>0.05） differences in serum biochemical indexes among different groups. In summary, feeding total mixed pelleted diet improves the growth performance and increases the nutrient apparent digestibility of the fattening Tan sheep, and has no obvious affection on their health.

Key words: Tan sheep, pelleted diet, growth performance, nutrient apparent digestibility, serum biochemical indexes