**Fatty Acid Profile and Conjugated Linoleic Acid Content of Milk from Confined Holstein Cows During the Summer and Winter Seasons**

Araceli Pinelli-Saavedra, Alfonso Martínez-Borraz, Silvia Y. Moya-Camarena, Humberto González-Ríos and Jesús Hernández

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/50774

## **1. Introduction**

102 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

de Agronomía. UCV. Maracay, Venezuela.

Zamora R. 2010. Producción y composición de la leche y queso fresco pasteurizado de cabras suplementadas con grasa sobrepasante con altos niveles de ácidos grasos poliinsaturados. Tesis de grado para obtener el título de Ingeniero Agrónomo. Facultad

> In recent decades, research in dairy cattle has been focused on the evaluation of factors that may cause changes in the lipid composition of milk, due to the fact that unsaturated fatty acids, conjugated linoleic acids (**CLA**) and high monounsaturated fatty acids/saturated fatty acids (MUFA/SFA) and polyunsaturated fatty acids/saturated fatty acids (PUFA/MUFA) ratios in milk have shown beneficial properties, including antiatherogenic and anticarcinogenic effects in humans. The principal factors that determine these effects are the breed (Lawless et al., 1999; Wood et al., 1980) and feeding regime (Cooper et al., 2004) in addition to less-studied factors, such as the parity, days in milk (**DIM)** and extreme temperatures. CLA are a mixture of linoleic acid isomers that contain conjugated double bonds. Studies in experimental animals have demonstrated that CLA has properties that may be beneficial for humans, providing anticarcinogenic, antidiabetic, antiobesity, antiatherogenic and immune stimulatory effects (Huth et al., 2006; Nirvair et al., 2007; Pariza et al., 2001; Parodi., 1999). Milk and dairy products are the primary sources of CLA, and approximately 75 to 90% of the total CLA content in milk fat is represented by *cis*-9, *trans*-11- CLA (Chin et al., 1992; Kay et al., 2004). CLA (9-*cis,* 11-*trans*-CLA) in milk fat is produced in the mammary glands via an endogenous synthesis pathway in which 9-desaturase converts vaccenic acid (*trans*-11 C18:1) to CLA (Bauman et al*.,* 2001; Kay et al., 2005). Under conditions fostered by a certain combination of feed production system, additives, diet, breed, stage of lactation, and season, vaccenic acid is increased in the rumen, which results in a concomitant increase in the 9-*cis*, 11-*trans*-CLA content in milk fat (Griinari et al., 2000; Lock & Bauman, 2004). However, the factors mentioned above have been studied under

© 2012 Martínez-Borraz et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Martínez-Borraz et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Manafiazar et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

controlled conditions. In contrast, our study focused on the evaluation of some of these factors on the fatty acid profile and 9-*cis*, 11-*trans*-CLA content in milk under commercial conditions where extreme temperatures occur. To this end, we evaluated the fatty acid profile and 9-*cis*, 11-*trans*-CLA content in Holstein cow milk during the winter (14 °C) and summer (40 °C) on a commercial dairy farm in Northwestern Mexico (Sonora) by studying the effects of feed composition, parity, stage of lactation (DIM), and milk yield.