Protected (encapsulated or calcium salts) lipids in dairy cow diets. Effects on production and milk composition

Abstract

A limitation to an extensive use of fat in ruminant diets is the subsequent disturbance of carbohydrate ruminal digestion. In order to overcome this problem, different kinds of protection of lipids have been proposed. This paper summarizes the effects of the addition of encapsulated animal fats (941 g/day on average) and vegetable oils (693 g/day), as well as calcium salts (593 g/day) in dairy cow diets, on feed intake, milk production and composition. Addition of protected fats decreases food intake, less for calcium salts (0.55 kg DM/day) than for encapsulated animal fats (1.1 kg DM/day) or vegetable oils (1.3 kg DM/day). These decreases are comparable to those observed with non protected fat. Encapsulated animal fats or calcium salts increase milk yield by approximately 1 kg/day, when encapsulated vegetable oils do not modify it. Addition of encapsulated animal fats or calcium salts decreases milk protein content by 1.8 and 1.2 g/kg, respectively, when encapsulated vegetable fat does not modify it. This difference is a consequence of variations in milk yield : total protein output does not vary with any of the three supplements. An important increase in milk butterfat is observed with encapsulated animal fat (4.0 g/kg) and vegetable oils (6.4 g/kg). The increase in long-chain fatty acids is higher than the decrease in de novo synthesis of short- and medium-chain fatty acids. Increase in the polyunsaturated fatty acid output is a criterion of the extent of protection of lipids against ruminal hydrogenation. Addition of calcium salts does not modify milk butterfat. According to the experiments, inhibition of de novo synthesis is compensated for by an increase in secretion either of palmitic acid, or of oleic acid.