Abstract: To select an optimal cross-combination in lamb production in natural plateau pasture ecosystem of China, and search for a more beneficial way for using Gansu Alpine Merino germplasm resource in the plateau habitats, a cross experiment was conducted, taking the introduced breeds (Texel, Australian Merino, White Suffolk, and Bond) as the rams, and Gansu Alpine Merino as the ewes. By the method of artificial insemination, mating was conducted in November, while lambing was in next April. The birth weight, weaning weight, 6-month-old weight, and 12-month-old weight of the crossbred lambs were measured, and the slaughter trials were conducted when the lambs were weaned, 6-month old, and 12-month old. The results showed that the average birth weight, weaning weight, and 6-month-old weight of Texel F1 were 5.53, 27.86 and 31.24 kg, respectively, being significantly higher than those of the other cross combinations (P<0.05). The growth of the crossbred lambs became slow from 6-month-old to 12-month-old. When the lambs were weaned and 6-month old, the carcass weight of Texel F1 was 14.25 kg and 14.55 kg, respectively, significantly higher than those of the other cross combinations (P<0.01). The dressing percentage and carcass meat percentage of the weaned and 6-month-old Texel F1 were higher than those of the other crossbred lambs (except the dressing percentage of Australian Merino crossbred lambs when weaned), but the ratio of meat to bone was lower than that of the other crossbred lambs. From the analysis of the growth and slaughter performance, the Gansu Alpine Merino-Texel crossing model was the ideal combination for the lamb production in the natural plateau pasture ecosystem.

Key words: Citrus grandis, Phosphorus supply, Doubled CO₂ partial pressure, Photosynthetic parameter