Effects of replacing roasted soybean seeds with roasted canola seeds in diet of lactating cows on milk production and milk fatty acid composition

Oil seeds are commonly used in the diet of lactating cows to meet energy and protein requirements. Exploring new type of oil seeds is beneficial for achieving nutrient needs more appropriately; also sometimes present types are not readily accessible. The study was conducted to evaluate the replacement of roasted soybean seeds with roasted canola seeds in diet of dairy cows on milk production and fatty acid composition in milk fat.
One hundred and four multiparous (2.35±1.39) early lactation (20 ± 0) dairy cows with average milk production of 47±7.8 kg/d were used from 20 to 80 days after calving in a randomized complete block design (n=26 per treatment). The experimental treatments were varied with ratios of roasted soybean seeds to roasted canola seeds in the diets (dry matter basis) as fallow: 1) 100:0, 2) 66:33, 3) 33:66, and 4) 0:100. The diets were formulated with forage to concentrate ratio at 60:40 (dry matter basis) and fed ad libitum TMR twice daily in the morning and afternoon during 8 weeks (2 weeks for adaptation and 6 weeks for sampling).
the result of this experiment showed that milk and protein production quadartically affected by increasing the level of roasted canola seed in the diet in which the diets that consisted of either soybean or canola seeds were more productive than the mixture of two ingredients (P= 0.002). Also, production 3.5 % fat corrected milk and lactose tended to be affected in the same way. However, production of milk fat and percentage of milk components were not affected by the treatment. Body condition score of cows increased linearly with increasing the level of roasted canola seeds in the diet. The concentration of palmitic acid in milk fat linearly decreased while the concentration of oleic acid linearly increased with increasing the level of roasted canola seeds in the diet. The concentration of linoleic acid and linolenic acid in the milk fat of cows that fed with roasted canola seed was decreased especially in cows fed with canola seed as only oil seeds. Whereas, concentration of conjugated linoleic acid were not affected by the treatments.
it could be concluded that roasted soybean can be replaced by roasted canola seed in the diet of dairy cows but the milk production or milk fat composition varied with the ratio of soybean to canola seeds in the diets.