Effect of Feed on the Composition of Milk Fat

Abstract

Researchers attending the Wisconsin Milk Board 1988 Milk Fat Roundtable indicated that the ideal nutritional milk fat would contain 10% polyunsaturated fatty acids, 8% saturated fatty acids, and 82% monounsaturated fatty acids. This cannot be accomplished by modifying diets of lactating cows. Monounsaturated fatty acid (C18:1) content can be increased by 50 to 80% and may approach 50% of milk fatty acids by feeding lipids rich in 18-carbon fatty acids. Because of ruminal hydrogenation and intestinal and mammary desaturase activity, degree of unsaturation of dietary 18-carbon fatty acids is not critical in influencing milk fat C18:1. Feeding low roughage diets increases the proportion of C18:1 in milk fat, and effects of feeding low roughage diets and lipid may be additive. Palmitic acid (C16:0) content of milk fat can be reduced by 20 to 40% unless the supplemented lipid is rich in C16:0. Milk fat alteration is dependent on the level of lipid supplementation. Limited evidence indicates frequency of lipid feeding and physical form of oil (free oil vs. oilseed), and heat treatment of oilseeds has relatively little influence on modification of milk fat. Significant changes in milk fat composition can be achieved on farm via nutritional modifications.

Effects of dietary sources of vegetable fats on performance of dairy ewes and conjugated linoleic acid (CLA) in milk

“…Our results concur with those of Wu et al (1993) and Bu et al (2007) in cows. Other studies, using saturated or protected fats (Grummer, 1991;Palmquist and Beaulieu, 1993, in cows;Pérez Alba et al, 1997;Gargouri et al, 2006, in sheep), report an increase in the percentage of milk fat. Results of dietary supplementation with unprotected oils rich in PUFA are quite varied.…”

“…Grummer (1991) indicates that it is easier to increase the C18:0 content of the fat in milk with supplements rich in mono and polyunsaturated fatty acids than with supplements that provide stearic acid per se. The higher levels of oleic acid (cis-9 C18:l) observed in the milk of ewes given the SO diet compared with those in the milk of ewes given the HPO diet may be partly due to the action of A 9 -desaturase enzyme in the mammary gland over a portion of the C18:0 generated in the rumen, and partly to the fact that SO contains higher concentrations of oleic acid than HPO (Table 2).…”

Efeito da condição corporal ao parto sobre a produção e composição do leite, a curva de lactação e a mobilização de reservas corporais em vacas da raça Holandesa

“…O comportamento cúbico das equações ajustadas possivelmente reflete ajustes de manejo ou fatores dietéticos que influenciaram a síntese de gordura do leite nas multíparas de ambas as classes, como alterações da proporção volumoso:concentrado nas rações fornecidas aos animais durante a lactação (Grummer et al, 1991).…”

Recent advances in the regulation of milk fat synthesis

“…Davis and Brown (1970) categorized two types of diets that induce MFD: (1) those that contained high levels of fermentable carbohydrate and low levels of fiber and (2) those that contained high concentrations of unsaturated oils. The extent of MFD with such diets is modified by many factors including associative dietary effects, feed management practices and animal physiological state (see reviews by Sutton, 1989;Grummer, 1991;Palmquist et al, 1993;Chilliard et al, 2000;Lock et al, 2006a). Researchers quickly realized that many diets that caused MFD also resulted in alterations in ruminal environment and fermentation, most notably a decrease in pH and a decrease in the acetate to propionate molar ratio ).…”