Levels of cottonseed in diets containing corn silage for lactating cows

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.