The aim of study was to investigate the effects of different sources with or without plant essential oils on efficiency of milk and colostrum production as well as modifying the fatty acid composition of ewes' milk. For this purpose, 40 ewes were used in a completely randomized design with 2×2 factorial method and four experimental groups. Experimental groups were: 1) diet containing calcified soybean oil, 2) diet containing calcified fish oil, 3) diet containing calcified soybean oil and a mixture of plant essential oils and 4) diet containing calcified fish oil and a mixture of plant essential oils. The ewes were kept in individual pens from one month before lambing until the lambs are weaned. The rations in different treatments were isonitrogenous and isocaloric rations before and after lambing. The ewes are fed with a mixture of alfalfa hay, wheat straw and concentrate twice a day. After lambing, the volume of the first colostrum was determined and a sample of it was taken. Milk production was also assessed weekly. The main copositions and fatty acids profile were eva‎luated in milk and colostrum smaples. Volatile fatty acids in ruminal fluid were examined. At the beginning of study, lambing day, and days 30 and 60 after parturition, blood samples were taken from the jugular vein. Birth weight, growth rate and weight gain of lambs were determined up to 2 months of age. Results showed that adding plant essential oils in ewes' feed, increased (P<0.05) their feed intake (1.61 vs. 1.58 kg/d) and the digestibility of DM and NDF. Essential oils increased (P<0.05) acetate production in the rumenal pH. Consumption of of fish oil (omega-3 source), increased (P<0.05) colostrum production and also increased (P<0.05) its protein level. Feeding fish oil decreased (P<0.05) milk fat percentage and increased (P<0.05) milk protein percentage. The fatty acids profile of ewes' milk was improved by using fish oil in rations and the ratio of omega-6 to omega-3 fatty acids was reduced (P<0.05) from about 13.5:1 to 1.2:1. In groups fed plant essential oils, the level of plasma urea and triglyceride decreased (P<0.05) and the levels of total plasma antioxidant capacity increased (P<0.05). Consumption of fish oil reduces (P<0.05) the level of aspartate aminotransferase enzyme and on the other hand, consumption of essential oils reduces (P<0.05) the level of alanine aminotransferase enzyme in ewes' blood. The average of lambs' daily growth was higher (P <0.05) in group consuming fish oil with plant essential oils (453g/d) compared to the other groups. It was concluded that the feeding fish oil with plant essential oils in transition rations of Shall ewes improved their feed intake, milk quality, blood metabolites and rumen pH.

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رسول كوثر ، امير حسين گلي