Milk Fatty Acids II: Prediction of the Production of Individual Fatty Acids in Bovine Milk

Abstract

Previously observed relationships between dietary composition and production of a small number of indi- vidual milk fatty acids were the motivation to examine whetherequationscouldbedevelopedtopredictproduc- tion of all the major individual milk fatty acids. Such equations could be incorporated into ration formulation programs and used to examine factors that influence milk fat composition. Data from 29 published experi- ments onHolstein cows thatprovided 120dietary treat- mentswereenteredintoCPM-Dairytoobtainestimates of amounts of individual long-chain fatty acids (LCFA) absorbed from the intestines. These derived data and other dietary and animal data including the reported fatty acid composition of milk fat were entered into a spreadsheet. Descriptors of dietincluded daily intake of dry matter, total fermentable carbohydrate, total fatty acids,andprofileofdietaryfattyacids,intakeofneutral detergent fiber, supplemental fish-oil, buffer, and mag- nesium oxide. Cow data included body weight and days in milk (DIM). Multiple linear regression was used to develop equations to predict the production (g/d) of each of 26 major LCFA. The equations developed generally hadR2valuesinexcessof0.5.Production(g/d)oftotalde novo fatty acids (C4:0 to C15:0) (PTdenovo) was found to be positively related to the intake of fermentable carbohydrate, and negatively related to the intake of fish oil fatty acids and the estimated total amount of unsaturated fatty acids absorbed from the intestines. The PTdenovo was greater in pasture-fed cows than total mixed ration-fed cows and was negatively related to the square root of DIM. Production of each individual de novo fatty acid was described by a fixed proportion of PTdenovo. These proportions were 0.12 ± 0.006 (C4:0), 0.083 ± 0.0039 (C6:0), 0.0516 ± 0.0025 (C8:0), 0.111 ± 0.003 (C10:0), 0.134 ± 0.0037 (C12:0), 0.441 ± 0.007 (C14:0), 0.046 ± 0.0024 (C14:1), and 0.0432 ± 0.0017