Production responses of two genetic different types of Merino sheep subjected to different nutritional levels

The primary selection objective in the South African Mutton Merino is meat production, while wool plays a secondary role. The Merino, on the other han d is selected for wool production. Respectively 20 and 23 of each genetic d ifferent type of ewes were used in a 15-week indoor study to quantify the i nfluence of nutrient intake on certain production traits when fed at differ ent levels of their respective requirements during late pregnancy (last 6 w eeks) and lactation (first 6 weeks). Results were used to provide productio n parameters for the two types of ewes and their lambs at different levels of nutrition. Lambing percentage (per ewe lambed) of SA Mutton Merino ewes was 171% compared to 135% for Merino ewes. Live weight gains for meat-wool and wool-type ewes during late pregnancy amounted to 15.9 and 21.9%, with c orresponding live weight losses of -8.3 and -1.1% during the first 6 weeks of lactation. Greasy wool production during the last 9 weeks of pregnancy a nd the first 6 weeks of lactation amounted to 1.57 kg ewe(-1) (meat-wool ty pe ewes) and 2.84 kg ewe(-1) (wool-type ewes). Milk production 17 days post partum was 2.33 kg/day and 1.84 kg/day for the two types of sheep. Lambs o f the meat-wool type ewes had a mean birth weight of 4.1 kg and an average daily gain (ADG) of 270 g/day to 42 days of age. Lambs of the wool-type ewe s had a mean birth weight of 4.9 kg and a 42-day ADG of 192 g/day. There we re clear differences in production traits of the two types of Merino sheep, which were in accordance with their genetic differences. The study gave pr actical production norms for meat-wool and wool-type Merino ewes and their lambs when subjected to different nutritional levels. (C) 2000 Elsevier Sci ence B.V. All rights reserved.