The growth and development of Oula-type Tibetan sheep in an alpine meadow area at the eastern margin of the Qinghai-Tibet Plateau

This study shows measurements from 30 ewes and 30 rams of Oula-type Tibetan sheep that were born within 72 hours of each other at two representative grasslands in Maqu County, Tibetan Autonomous Prefecture of Gannan, Gansu. We measured their weight, height at withers, body length, chest girth, chest width, chest depth, and hip width, and analysed their growth and development from birth to 18 months old (March 2013 to September 2014). The stage from birth to 6 months old is the most important time for significant weight increase (P<0.05). Weight gain increase is fastest when sheep are 2 months to 4 months old, while weight gain from 8 months to 12 months old significantly slower (P<0.05). The stage from birth to 6 months old is the main growing time, so it appropriate to slaughter lambs at this time. The body indices of this type of sheep increase mainly from birth to 6 months old, then increase more slowly from 6 months to 14 months old. Although there is a continuing growing trend from 14 months to 18 months old, it is smaller than that from birth to 6 months old. This type of sheep basically completes its development by 6 months old. Therefore, the lambs can be slaughtered when they are 6 months old. There are no significant differences in early growth and development between the ewes and rams, but differences appear with continued growth.