Teores de caroço de algodão em dietas contendo silagem de milho para vacas em lactação

Abstract

Five canulated (rumen and proximal duodenum) mature Holstein cows, averaging 200 days in milk, were used in a 5x5 Latin square design to evaluate: dry matter intake, nutrient digestibility and ruminal parameters of diets containing cottonseed. The treatments were T0, T6, T12, T18 e T24 corresponding to 0%, 6%, 12%, 18%, 24% of cottonseed in the diet (Dry Matter basis). The cows were fed 40% concentrate and 60% corn silage. Milk production (kg/day) and milk protein (g/day) had a quadratic response while fat corrected milk production had a quadratic tendency. There was a tendency to reduce dry matter and organic matter intake. Dry matter apparent digestibility was reduced (P < 0.05) linearly. Ether extract apparent digestibility was increased (P < 0.05) linearly. Apparent digestibility of crude protein, neutral detergent fiber and crude energy were not altered. Acid detergent fiber apparent digestibility was reduced (P < 0.05) linearly. Ruminal pH and total volatile fatty acids did not differ among treatments. Acetate and propionate concentration and acetate propionate ratio had a quadratic response while butyrate was reduced (P < 0.05) linearly. The effective degradability of dry matter in the passage rates of 2%, 5% and 8%/h, as well as soluble fraction and insoluble in water were not changed, although the degradability of insoluble fraction decreased linearly and the potential degradability increased linearly.