Effect of feeding Atriplex browse to lactating ewes on milk yield and growth rate of their lambs

The study was conducted to determine the effect of feeding a diet containing saltbush (Atriplex) on the milk yield of Awassi ewes and BW gain of their lambs. Fifty-four adult Awassi ewes (4 +/- 1-year-old, 58.1 +/- 2 kg BW, with parities ranging from 1 to 3) in late gestation were randomly selected and distributed into nine equal groups, six animals each. The selected ewes were fed with the dietary treatments for 3 weeks before the projected lambing date and continued until the end of the study, which lasted for 143 days. Three dietary treatments were assigned to the nine groups; each treatment was applied to three groups (pens) of ewes, and each pen contained six ewes fed as a group in the same pen. Each group received a concentrate ration (4.5 kg) and was supplemented with either tibin (shredded barley straws) (6.0 kg); or tibin (3.0 kg) and dried Atriplex browse (3.0 kg); or dried Atriplex browse (6.0 kg). The dietary treatments had a significant (P < 0.01) effect on the overall DMI of ewes. The ewes receiving diets containing the saltbush increased feed intake significantly compared with intake levels of control animals fed with concentrate ration and tibin. The treatments had a significant (P < 0.01) effect on DMI of ewes during the different physiological stages: late gestation, suckling and after weaning. The ewes' BW averaged 58.4 kg at lambing, declined to 53.2 kg at weaning and then increased to 56.9 kg at the end of the experiment. The dietary treatments had no significant effect either on the final BW or on the overall BW changes of ewes (the difference between initial and final BW). The control animals showed a positive change in BW (1.5 kg per ewe) whereas the ewes receiving the diets containing saltbush at 50 and 100% lost 0.7 and 4.5 kg in BW, respectively. There was no significant effect of the proportion of saltbush foliage in diet on milk production. Means of daily milk production were 0.27, 0.33 and 0.35 kg per ewe for the diets containing 0, 50 and 100% saltbush, respectively. Milk production of ewes lambing single was higher (0.37 kg per ewe) than the ewes lambing twins (0.27 kg per ewe). The treatments had no significant effect on birth weight, weaning weight and growth rate of lambs. Feeding Atriplex browse with concentrate ration to lactating Awassi ewes did not present any significant problems on milk yield or growth rate of lambs; the most important sources of income for stockmen. Substituting saltbush browse for tibin in diets of sheep will reduce the cost of roughage component by US$ 0.022 per head per day. (c) 2005 Elsevier B.V. All rights reserved.