The objective of this research was to evaluate two levels of lipids (3 and 7%) in the diet of milking cows, and to evaluate in the 7% lipids two lipid sources (crushed soybean and soybean oil), on milk production and composition, ruminal parameters, ammonia production by mixed ruminal bacteria and dry matter intake. Six mature Holstein cows, purebred or crossbred, 500 kg of live weight, 30 days after calving and milk production of 20 l/day, were assigned to a two 3x3 latin square. Each experimental period last 23 days, in which 16 was for adaptation and seven days for data and sampling collection. Milk production was measured twice daily, from the 15th to the 23rd day of each experimental period, and sampled for protein and fat analysis. Ruminal samples were collected by esophageal catheter and squeezed in cheesecloth. Milk and 4% corrected milk, protein, fat, lactose, total solids, non fatty solids and density were not affected by lipids level and source in the diet. There was a negative effect of lipids on butyrate and dry matter intake, in which soybean oil caused the major effect. The pH increased in the crushed soybean diet only. Acetate, propionate, acetate:propionate, isobutyrate, isovalerate, ammonia and specific activity of ammonia production were not affected by the diets.
intake; rumen; pH; volatile fatty acids