The present study is conducted at the Animal Farm/ College of Agriculture/ University of Basrah during the period from 2/12/2012 to 2/3/2013. The study include 24 milking Arabi ewes ranged from 2-4 years age, having single lamb, closely lambing date and weighted 42 kg. After giving the ewes preliminary period of 10 days, they are distributed randomly and equally into six feeding groups. The first group is fed 60% concentrate and 40% roughages; soya bean meal is treated by formaldehyde. The second group is fed 60% concentrate and 40% roughages with untreated soya bean meal. The third group is fed 50% concentrate and 50% roughages with treated soya bean meal. The fourth group is fed 50% concentrate and 50% roughages with untreat soya bean meal. The fifth group was fed 40% concentrate and 60% roughages with treated soya bean meal. The sixth group is fed 40% concentrate and 60% roughages with untreated soya bean meal (control). The ration is given as 4% of live body weight. The concentrate consists of 40% barley, 20% corn, 30% wheat bran, 7% soya bean meal, 1% salt and 2% Calcium bicarbonate. Roughage is wheat straw treated with 4% urea and 3kg/ton yeast. Treated soya bean meal reduced degradable protein from 70% to 60% Milk yield of the first and two months for the first, third, fourth and fifth treatments is significantly (P<0.05) higher than that of control treatment. Total milk yield for the first, second, third and fifth treatment is higher (P<0.05) than those of fourth and control groups. The first group is the best in daily milk yield follow by second, third and fifth treatments. Milk composition is the different significantly (P<0.05) among groups except pH. The third treatment showed highest fat and protein%, fourth group in lactose and urea. Third and fourth group showed lowest level of moisture. All feeding groups showed significant (P<0.05) the highest levels of milk content in comparison with control group except moisture. Results revealed that fatty acids% did not influenced by formaldehyde treatments. However, they are significantly (P<0.05) affected by the level of roughage ; the highest value was recorded by second group in comparison with control. Oleic acid is recorded the highest level in the milk (36.3 and 52.61% of first and second groups respectively). The capric acid is rare (1.15 and 3.7% of the second and the fourth groups respectively). All fatty acid percentages are influenced significantly by the treatments except capric acid.