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Intake, digestibility and ruminal fermentation in dairy cows fed with different fat sources

Grant number: 12/04879-4
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): August 01, 2012
Effective date (End): January 31, 2013
Field of knowledge:Agronomical Sciences - Animal Husbandry - Animal Nutrition and Feeding
Principal Investigator:Francisco Palma Rennó
Grantee:Natasha Crippa
Home Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The use of different additional fat sources in dairy cows diets has been common practiced in feed, mainly to allow improvement the energy status of these animals. However, when evaluate the supplementation of diets for ruminants with fat sources, all physiological processes should be taken into consideration, because the rumen metabolism, intestinal absorption, transport and systemic metabolism, secretion and deposition of fat in the body are aspects directly related to lipid metabolism and may influence the physiological responses of animals receiving fat in the diet. The biohydrogenation is an important step in the rumen metabolism of fatty acids and can be considered self-defense process of rumen microorganisms that convert unsaturated fatty acids into saturated fatty acids, less toxic to the rumen microbial population. Additionally, this process reduces the intestinal flow of polyunsaturated fatty acids to the duodenum and contributes to the accumulation of CLA isomers, cis and trans in products derived from ruminants depending on the fat source used. These CLA isomers have been evaluated and found in products derived from ruminants raised on pasture or fed diets rich in linoleic and linolenic acids, usually from oilseeds such as soybeans, and soybean and sunflower oils. While most of the fatty acids may be influenced by ruminal metabolism, the biohydrogenation is usually not complete, resulting in a variety of fatty acids. When there is incomplete biohydrogenation of polyunsaturated fatty acids, an increase of the duodenal flow of trans fatty acids - C18:1 and conjugated linoleic acid cis-9, trans-11-CLA and trans-10, cis-12-CLA, the first isomer shown a nutraceutical effect and the last isomer shown to affect milk fat synthesis during lactation, by reducing the expression of lipogenic genes. Thus, besides being an energy source, the fatty acids are also suitable and used as moderators metabolism and physiology. However, the hypothesis to be evaluated in this experiment is that depending on the source of fat used, there may be changes in rumen fermentation, dry matter intake and digestibility. This experiment will be conducted to study the effects of different fat sources on intake, digestibility and ruminal fermentation in dairy cows during the dry period. (AU)