Composition of Goat's Milk: Changes Within Milking and Effects of a High Concentrate Diet

Abstract In Experiment 1, 14 lactation goats of various breeds were used to measure changes of milk fat content during the milking process. Milking was divided into quarterly intervals with equal amounts of milk. There was an increase of fat percent of quarterly fractions through milking. In Experiment 2, 11 lactating goats were used to determine the effect of a high concentrate, low roughage diet on milk yield, fat yield, milk composition, and ruminal volatile fatty acid concentration. High concentrate diet caused an 18% decrease of milk yield and a 7 to 20% depression of milk fat percent. Proportions of long chain unsaturated and short chain fatty acids were increased, and long chain saturated fatty acids were decreased by the diet depressing milk fat. No changes of either milk protein or total solids were observed. Feeding the high concentrate diet caused an increase of molar percent of propionic acid and decreases of molar percent of acetic acid and ratio of acetate to propionate compared with the high roughage diet. The response of milk fat depression in goats with a high concentrate diet was similar to that for dairy cattle.