Lamb performance, milk production and composition from ewes supplemented with soybean oil partially replaced by fish oil blend

The objectives of these experiment were to evaluate the effects of small amounts of fish oil blend supply in partial replacement of soybean oil on dry matter intake (DMI), lactation performance and milk fatty acid composition of ewes and also on performance of their lambs. Fifty Santa Inês lactating ewes (63±6 kg of initial BW; mean±SD) were penned individually and used in a randomized complete block design with 10 blocks and 5 treatments. The oils were added to a basal diet that contained 700 g/kg DM of concentrate and 300 g/kg DM of forage (fresh sugarcane bagasse). The treatments were as follows: (1) basal diet without added oil (CONT); (2) 40 g/kg DM of soybean oil (0FO); (3) 2.5 g/kg DM of fish oil blend+37.5 g/kg DM of soybean oil (25FO); (4) 5 g/kg DM of fish oil blend+35 g/kg DM of soybean oil (50FO); and (5) 7.5 g/kg DM of fish oil blend+32.5 g/kg DM of soybean oil (75FO). All diets were isonitrogen (140±4 g/kg DM of CP). Once a week, from the second to the eighth week of lactation (weaning time), ewes were separated from their lambs, stimulated by a 6-IU intravenous oxytocin injection, and milked to empty the udder. After 3 h, milk production was obtained after the same procedure. DMI (kg/d; % of BW and g/kg BW0.75) was higher for ewes fed the control diets vs. fat-supplemented. However, no effect was observed on DMI when fish oil blend inclusion in the diets increased. Nevertheless, milk production increased linearly when fish oil blend replaced soybean oil. As a consequence, the preweaning average daily gain (ADG) of lambs increased linearly. Milk fat concentration was similar for all diets. Milk protein and total solids concentrations decreased linearly when fish oil blend addition increased. Lactose milk concentration was higher for ewes fed the fat-supplemented diets vs. the control. Stearic acid, oleic acid, vaccenic acid, linoleic acid, linolenic acid and CLA cis-9, trans-11 showed higher concentrations in milk of animals fed diets containing soybean oil and fish oil blend compared to the control diet. Vaccenic acid, CLA trans-10, cis-12, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased linearly with fish oil blend inclusion. Small amounts of fish oil supplementation does not exert an additional effect on the concentration of CLA C18:2 cis-9, trans-11 as compered to exclusive use of soybean oil. However, the addition of 7.5 g/kg DM of fish oil blend mixed with 32.5 g/kg DM of soybean oil is recommended, because it increased the concentration of EPA, DHA and C18:1 trans-11 in the milk, as well increasing the performance of the ewes and their lambs.