Abstract: 【Objective】This study was conducted to investigate the effects of restricted access time to pasture combined with indoor feeding on growth performance and feed intake of Ujumuqin lambs. 【Method】Thirty castrated male Ujumuqin lambs were randomly assigned into five equal groups with similar metabolic energy diet: (i) alone feeding indoor (0H; control), (ii) 2-h access to pasture (2H), (iii) 4-h access to pasture (4H), (iv) 8-h access to pasture (8H), and (v) full-time access to pasture (12H). Lambs were raised for 102 days, coinciding with a 15-d feed adaptation period and 87-d experimental periods. Body weight, height and length, and heart girth of the lambs were measured before eating in the morning (about 06:00 am) from last of July to September, once a month. The pasture intake was estimated using the n-alkane method in the middle of each month from July to September. 【Result】The restrictions at pasture did not significantly (P＞0.05) affect the amounts of body length and height, and heart girth of the lambs, but had significant (P＜0.05) effects on the ratios of length/height and chest/length. The ratios of length/height in the 8H and 12H groups were higher (P=0.05) compared to the 0H group. The ratios of chest/length in 0H, 2H and 4H groups were higher (P＜0.05) than the 12H group, respectively. No differences were found in final body weight, total weight gain, average daily weight gain (ADG), and total feed intake of lambs among the five groups (P＞0.05). In July, the weight gain significantly decreased (P＜0.01) as the grazing time increased. The gain of lambs of 12H group decreased by 101, 84, 69, and 38 g•d-1 (P＜0.01) as compared to the lambs of 0H, 2H, 4H, and 8H groups, respectively. The gain of grazing 2 and 4 h groups did not differ (P＞0.05) from the 0H group. In August, the maximum gain of lambs was observed in all groups. The lambs imposed with limited pasture access time of 4, 8, and 12 h had much higher weight gain (P=0.045) than the lambs fed indoor or allocated 2 h access to pasture. In September, the gain of lambs in the 0H group was significantly higher (P＜0.05) than in the other groups, and there was no significant difference (P＞0.05) between the latter four groups. As the time at pasture increased, the pasture intake was significantly increased (P＜0.001), but the supplementation intake had a decline tendency. Total feed and pasture intakes respectively decreased by 0.44 and 0.78 kg per day for each one kilogram increase in supplementation. The amount of concentrate consumed in addition to hay/grazing on pasture per unit weigh gain of the 4H group was slightly superior to that of the 2H and 8H groups. 【Conclusion】Thereby, the restriction of 4 h at pasture is sufficient for optimizing growth performance. With a combination of grasslands protection and feeding cost, it can be concluded that lambs offered 4 h access to pasture combined with 0.52 kg supplements of concentrate and grass hay (at a ratio of 1﹕1) is an optimum grazing management method.

Key words: grazing , time-limited , lamb , growth , weigh gain , feed intake