# The Effects of Supplemented Conjugated Linoleic Acid on Lipid Metabolism in Cattle

## TL;DR

This paper reviews how adding conjugated linoleic acid (CLA) to cattle diets affects their lipid metabolism, aiming to improve meat and milk quality while managing energy balance.

## Contribution

The paper provides a comprehensive review of CLA supplementation effects in cattle, focusing on t10,c12 CLA and its impact on energy balance and fat distribution.

## Key findings

- CLA supplementation can improve energy balance in dairy cows during the transition period.
- t10,c12 CLA reduces subcutaneous fat while increasing intramuscular fat in beef cattle.
- CLA's effects on lipid metabolism are inconsistent, partly due to differences in study design.

## Abstract

Milk and meat products of cattle are the main source of conjugated linoleic acid (CLA) for human nutrition. Increasing the amount of CLA in milk and meat products may be beneficial for consumers but is associated with changes in lipid metabolism of supplemented animals, which are not completely understood. Currently, CLA is supplemented into diets of high yielding dairy cows to reduce their energy deficit, when they are not able to meet the high energy demand of milk production by increased feed intake. Milk fat depression by CLA can help to avoid negative effects of energy loss and mobilization of body reserves for lactation. Furthermore, CLA was shown to reduce waste fat and to improve marbling fat in ruminants and pigs. Increasing the muscle fat content and improving meat quality without increasing other fat depots and without compromising feed efficiency are important goals in beef production. Additionally, increased CLA in meat makes it a healthier product for human nutrition. However, inconsistent results and higher costs limit the practical application of CLA supplementation. This review summarizes the current knowledge about the effects of supplemented CLA in dairy cows and beef cattle, as well as on individual cells in cell culture models.

Conjugated linoleic acid (CLA) is produced by bacterial biohydrogenation in the rumen of cattle, fulfills various biological functions, and is known for anti-obesity, anti-inflammation, anti-cancer, and other beneficial effects. It has numerous isomers, of which cis-9,trans-11 CLA accounts for 80% of total CLA, followed by trans-10,cis-12 CLA (t10,c12 CLA), with distinct molecular structures, oxidation efficiencies, activities, and functions. Different effects were observed, when isomers were individually supplemented in livestock nutrition. Currently, CLA is supplemented into the diets of dairy cows to improve the energy balance, and avoid negative effects of energy loss during the transition period. Furthermore, t10,c12 CLA was shown to reduce subcutaneous fat and to improve intramuscular fat (IMF) content in the carcasses of ruminants and pigs. Increasing the IMF content without increasing other fat depots and without compromising feed efficiency is an important goal in beef production. However, inconsistent and conflicting results were reported partly based on different study designs. This review aims to summarize studies on CLA supplementation in cattle, focusing on t10,c12 CLA and the effects of the dose, time, and method of supplementation on energy balance, milk yield and body composition, as well as on individual cells in vitro. This may improve our understanding of energy-saving and repartitioning effects of CLA in cattle.