Changes in the fatty acid composition of goat milk fat after a 48-hour fast.

Abstract

Five lactating goats were milked twice daily. After a control period of 3 days, they were fasted for 48 hr. The milk was collected at each milking. At the end of the fasting period, milk yield fell to 28% and milk fat to 55% of the original yield. The percentage of milk fat increased. Generally, the relative concentrations of fatty acids with less than or equal to 16 carbons, containing even and odd-numbered straight-chain as well as monomethyl-substituted fatty acids of the milk fat, decreased significantly 24 hr after food was withheld. The decrease was most pronounced for the fatty acids with the shortest chain lengths. Longer-chain acids increased or did not change. Iso and anteiso-acids seemed to follow the same, although less pronounced trend, the effect being obvious after 48 hr of fasting. It is suggested that the decline in the proportions of fatty acids with less than or equal to 16 carbons was due to the inhibition of mammary gland synthesis. The increase in the proportions of longer-chain fatty acids was ascribed to adipose tissue lipolysis.