The objective of this study was to evaluate the microbial production, production, composition and fatty acids profile of milk from dairy cows fed rations with growing levels of sunflower cake. Eight Girolando cows were used, averaging 515 kg of body weight. The experimental design was a 4 x 4 Latin square, in duplicate, where the factors consisted of the rates of sunflower cake inclusion in the concentrate portion (0, 7, 14 and 21%). A decreasing linear effect was observed for protein and fat production in milk and N urea content. Allantoin rates (mmol day-1) were influenced by the levels of sunflower cake inclusion, with quadratic effect (p < 0.05). Uric acid, total purines, absorbed purines, microbial nitrogen and microbial synthesis were not affected (p > 0.05) by the levels of sunflower cake inclusion. A decreasing linear effect was observed with the levels of sunflower cake inclusion for palmitic acid (C16:0); no statistical differences were observed (p > 0.05) for the other fatty acids. The use of sunflower cake may represent an alternative feed for dairy cows, but does not alter the efficiency of microbial protein synthesis and fatty acids profile of milk.
co-product; non-protein nitrogen; microbial synthesis