Analysis of Variation in cis-9, trans-11 Conjugated Linoleic Acid (CLA) in Milk Fat of Dairy Cows

Abstract

Conjugated linoleic acid (CLA) is a fatty acid with numerous putative health benefits and is a natural component of ruminant-derived food products. An intermediate in rumen biohydrogenation is cis-9, trans-11 CLA, the major CLA isomer in milk fat. However, the major source of cis-9, trans-11 CLA in milk is endogenous synthesis by delta 9-desaturase conversion of trans-11 C18:1, another rumen biohydrogenation intermediate. The desaturase indices serve as a proxy for delta 9-desaturase activity and are calculated from the ratios of fatty acid pairs that represent product/substrate for this enzyme. This study analyzed individual animal variation in milk fat content of cis-9, trans-11 CLA and in desaturase indices in milk fat. Thirty lactating Holstein cows were allocated to one of three treatment groups: one received a standard total mixed ration, one received a diet that produced an elevated milk fat content of CLA, and a third treatment group was alternated between these diets at 3-wk intervals over the 12-wk study. There was a two- to threefold variation among individuals on the same diet for both milk fat content of CLA and desaturase indices in milk fat. This hierarchy was maintained to a large extent over the 12-wk study even in the variable treatment group that alternated between the two diets. Within the variable diet treatment, some animals consistently had a substantial response in milk fat content of CLA to dietary shifts, whereas other cows had little or no response. We conclude that while diet is a major determinant of the CLA content in milk fat, individual animal differences also have a substantial effect. The variation among individuals includes differences related to both rumen biohydrogenation and delta 9-desaturase activity in the mammary gland.

Variation in Fatty Acid Contents of Milk and Milk Fat Within and Across Breeds

“…Similarly, Royal and Garnsworthy (2005) reported heritability values of 0.30 and 0.19 for the ratios of 14:1 to (14:0 + 14:1) and 18:1 to (18:0 + 18:1), respectively. Lock et al (2005) and Peterson et al (2002) confirmed that nutritional and individual variation in ∆ 9 -desaturase activity were the major factors contributing to the concentration of rumenic acid in milk.…”

“…The ∆ 9 -desaturase activity can be studied by analyzing the ratio of product to substrate (14:1 cis-9 to 14:0, 16:1 cis-9 to 16:0, 18:1 cis-9 to 18:0, and 18:1 trans-11 to CLA). Through this methodology, Lock and Garnsworthy (2003) studied the seasonal variation in the activity of this enzyme and Peterson et al (2002) showed individual animal differences in ∆ 9 -desaturase activity. Studying the genetics of the nutritional quality of milk requires a large amount of data.…”

Alimentation animale et valeur nutritionnelle induite sur les produits dérivés consommés par l’homme : Les lipides sont-ils principalement concernés ?

“…Le contenu en CLA augmente dans l'équivalent indien du yaourt (dahi), quand il est laissé après une nuit à température ambiante [108]. Les variations individuelles en biohydrogénation dans le rumen et en activité de delta-9-désaturase expliquent les variabilités de teneurs en CLA selon les animaux [109]. Par conséquent [107], les réactions métaboliques microbiennes sont responsables de la relation positive entre le contenu en CLA et celui des isomères de l'acide oléique.…”

Effect of Fat-Mineral Preparation from Fish Oil on Fatty Acid Content on Cow Milk

“…breed, age, stage of lactation. Yet the strongest effects belongs to food factors [1,7,8,21,23,27,36] . Supplementation of food rations for cows with monoand poly-unsaturated fatty acids in the form of seeds, extruded crushed meal, calcium oils and salts influences PUFA biohydrogenation in rumen content, modifying milk composition [2,3,9,26] .…”

“…Cis-9,trans-11 CLA present in milk fat is synthesized in 64-78% in milk gland with VA by ? 9 -desaturase (stearoyl-CoA desaturase) [6,10,11,17,27] . Cis-9, trans-11 CLA synthesis in milk gland can range up to 91% of total CLA milk fat content [19] .…”