Changes in triglyceride fatty acid composition of mammary secretions during involution.

Changes in fatty acid composition were determined for fat triglycerides from mammary secretions of 5 Holstein cows during the first 31 d of the nonlactating period. Proportions of short-chain (4:0 to 8:0) and medium-chain (10:0 to 14:0) fatty acids declined by about 50% during the first 3 d of involution, whereas proportions of stearic (18:0) and oleic acids (18:1) increased during the same period. Little change in proportions of those fatty acids occurred after d 3 of involution. Palmitic acid (16:0) was unchanged in proportion during involution. Fatty acid composition of mammary secretion triglycerides changed rapidly in the early nonlactating period, which may reflect a specific decline in de novo fatty acid synthesis in the involuting gland.