Fatty Acid Composition of Milk. III. Variation with Stage of Lactation

Abstract Variations in component fatty acids in milk of four Holstein cows were measured during their entire lactation (43-50 wk). Least-squares fits of the measured values were then made to a succession of polynomials and the added contribution to reducing the unexplained variation calculated to determine the best-fitting function. Linear regression equations best describe the proportions of 6:0, 8:0, 16:0, and 16:1, with only 16:0 having a negative slope. The proportion of 10:0, 12:0, 16:iso, 17:0, 18:0, 18:iso, 18:1, and 18:2 were best described by quadratic regression equations. There were wide variations throughout the progress of lactation in the slopes of the curves in these latter cases. Cubic regression equations adequately described the proportions of 10:1, 12:1, 14:0, 14:1, 15:0, and 18:3 fatty acids.

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