F Mirzaei - Department of Animal Science, Faculty of Agronomy and Animal Science, University of Tehran,Karaj-Iran.
M Rezaeian - Department of Animal Health and Nutrition, Faculty of Veterinary Medicine, University of Tehran,Tehran-Iran
A Towhidi - Department of Animal Science, Faculty of Agronomy and Animal Science, University of Tehran,Karaj-Iran
A Nik-khah - Department of Animal Science, Faculty of Agronomy and Animal Science, University of Tehran,Karaj-Iran

Thirty-two lactating Chall ewes were assigned to eight groups and received one of eight dietary treatments for ten weeks as follows: control diet (CON); a fish oil-supplemented diet (20 g/kg dry matter intake (DMI); FO); a safflower oil-supplemented diet (20 g/kg DMI; SO); a monensin-supplemented diet (15 mg/kg DMI; MO); a diet supplemented with fish oil (20 g/kg DMI) and safflower oil (20 g/kg DMI; FS); a diet supplemented with fish oil (20 g/kg DMI) andmonensin (15 mg/kg DM;I FM); a diet that contained safflower oil (20 g/kg DMI) and monensin (15 mg/kg DMI; SM); and a diet that contained fish oil (20 g/kg DMI), safflower oil (20 g/kg DMI) and monensin (15 mg/kg DMI; FSM). During the experimental period, ewes were kept in individual pens and the amounts of feed that were offered to individual ewes were recorded daily. Milk samples were collected weekly and analyzed for their composition. Rumen fluid andplasma samples were obtained from each ewe on the final day of the trial and stored at -20˚C before analysis. Results showed that the SO diet had no significant effect (p< 0.05) on DMI, However, other diets reduced theDMIsignificantly. Milk yield was significantly lower for ewes that were fed diets supplemented with monensin compared to the other groups (p<0.05). The milk fat percentage was relatively low for all treat ments, although only FS, FM and FSM treatments were significantly different from the control group. The yield of milk fat was significantly reduced in the MO, FS, FM, SM and FSM groups. The percentage of protein in milk was significantly reduced in the FS and FSM diets. However, the milk protein yield was reduced significantly as a direct result of the decreased milk yield in ewes that were fed the MO, FS, FM, SM and FSM diets. The MO diet increased significantly the concentration of ureanitrogen in milk. Fish oil and safflower oil-supplemented diets with or without monensin resulted in decreased numbers of infective protozoa, and a decreased acetate-to-propionate ratio in rumen fluid when compared to the CON group. The concentrations of plasma glucose and urea were not affected by any of the treatments, but the plasma concentrations of triglycerides, total cholesterol, and HDL-cholesterol were higher in ewes that consumed the oil-containingdiets than the other groups. It was concluded that dietary supplementation with a combination of fish oil, safflower oil and monensin could alter the composition of milk from ewes and, in particular, cause a reduction in the percentage of fat in the milk. This may make this milk more suitable for human consumption

Milk, ewe, fish oil, safflower oil, monensin