Effects of Feeding Whole Cottonseed on Composition of Milk

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Abstract
Complete mixed diets containing O, 10, 15 or 20% whole cottonseed were fed to 12 cows in a 4 .times. 4 Latin square design. Cows were assigned to the Latin square by production status resultin in 1 square each for cows in early 1st lactation and older cows in early or late lactation. Diets were fed for ad lib intake, and periods were 21 days. Percentages of milk fat and total solids increased, and protein percentage decreased with cottonseed feeding. Milk casein N decreased from 0.387 to 0.375 with cottonseed feeding. N in whey remained unchanged, and nonprotein N increased. Proportion of total N in casein and whey fractions was not altered, but proportion of nonprotein N increased. Cottonseed decreased proportions of short-chain fatty acids (C-6-C-16) in milk and increased stearic and oleic acids. Actual yield of milk was not affected by cottonseed feeding, but yields of fat-corrected milk and milk fat were increased. Production status affected milk composition with older cows in early lactation producing milk of lower fat, total solids and protein content compared with cows in other groups. Casein N was highest for 1st lactation and lowest for older, high-producing cows. Whey N was highest for older, low-producing cows. First lactation cows had the highest proportion of N in the casein fraction, and older, low-producing cows had the lowest. Milk fatty acids composition changed little with status.