Effects of whole cottonseeds on milk yield, milk composition, and blood components of dairy cows in hot weather

Abstract

Sixteen multiparous Friesian cows, 70–140 days post partum, were allotted to two groups of eight cows, according to calving date, lactation number and daily yield, and assigned randomly to one of two diets in a crossover design experiment. The two experimental diets were concentrate, containing either 20% whole cottonseeds and 13% soya bean meal or 14% cottonseed meal and 18.5% soya bean meal, plus a mixture of maize silage and straw in the proportions 8:1 (fresh weight) ad libitum. The concentrate was offered individually, in two equal meals daily at 0.4 kg kg −1 of milk produced, and the mixture of maize silage and straw was offered ad libitum once daily on a group basis. The experimental period lasted from 10 June to 4 August 1993, and the cows were housed in an open lot. Dry matter intake, milk protein content and yield, as well as content of milk lactose, total solids and solids not fat were not significantly affected by the diet. In contrast, whole cottonseeds supplementation increased actual milk yield (25.1 vs. 23.1 kg day −1; P < 0.05), 4% fat-corrected milk yield (25.0 vs. 21.5 kg day −1; P < 0.05), milk fat content (3.98 vs. 3.56%; P < 0.05) and milk fat yield (1.0 vs. 0.82 kg day −1; P < 0.05). No significant differences were observed in blood plasma concentrations of glucose, total protein, urea, sodium, potassium, calcium, phosphorus and magnesium. In contrast, increased concentrations in plasma of triglycerides (18.8 vs. 15.9 mg (100 ml) −1; P < 0.05), cholesterol (225.1 vs. 173.2 mg (100 ml) −1; P < 0.001) and phospholipids (225.6 vs. 169.6 mg (100 ml) −1; P < 0.001) were obtained when the cows were fed on the diet containing whole cottonseeds.