Abstract
Twenty young Maremmana bulls were randomly allotted to two dietary groups during a finishing period (~90 days): C diet (without lipid supplementation), and L diet (with linseed supplementation, 20% concentrate feed). The aim was to investigate the effects of dietary linseed supplementation on the intramuscular fat composition, and the shelf-life of minced beef. The L diet did not alter the dressing rate and daily weight gain, whereas the C18:3n-3 content in the intramuscular fat significantly increased (from 0.85 to 1.78 g/100 g of total fatty acid, +109%), leading to a reduction in a n-6/n-3 ratio below four and an increase in the overall proportion of long chain n-3 fatty acids in beef lipids. These effects were principally related to differences in the distribution of fatty acids between the neutral and polar lipids. The results demonstrated that linseed supplementation modified the lipid composition of beef, without negatively impacting overall productivity, in the period from weaning the bull until its slaughter. However, the total amount of n-3 fatty acids in the beef of young bulls on the L diet, was not sufficient for the aliquot of humans′ n-3 fatty acid requirements. This was mainly related to the low levels of fat in the beef. Comparing beef samples from animals on the L diet, with samples from animals on the C diet, the higher levels of n-3 polyunsaturated fatty acids led to a significant reduction of shelf-life starting after 2 days of storage at 4°C, because of fatty acid and cholesterol oxidation. The L diet group samples showed a higher level of TBARS (+80%) and COPs (+73%), two important parameters to estimate the oxidation level of beef. This suggests that enriching beef with n-3 fatty acids should be coupled with packaging techniques that consider the higher susceptibility to lipid oxidation. In conclusion, dietary linseed supplementation led to a higher proportion of n-3 fatty acids in beef lipids, however, the natural content of antioxidant substances was not able to protect intramuscular fat from oxidation during storage at 4°C.
Highlights
An adequate dietary intake of n-3 fatty acids (FAs) can protect one against the risks of cardiovascular disease, diabetes, and obesity as well as some types of cancer [1]
It is important to consider that when treatments are applied during the finishing phase, differences due to energy supplementation were observed in terms of fat deposition, which could reduce treatment differences in average daily weight gain
Data from this study showed that linseed supplementation induced a higher concentration of t11,c13CLA, c11,t13CLA, and t12,t14CLA in intramuscular fat
Summary
An adequate dietary intake of n-3 fatty acids (FAs) can protect one against the risks of cardiovascular disease, diabetes, and obesity as well as some types of cancer [1]. There is interest in increasing the content of n-3 FAs and other potentially bioactive FAs (i.e., conjugated linoleic acid isomers) in the food chain, including in animal-derived food such as beef [2]. Feeding strategies have been applied in beef cattle to promote the muscle tissue deposition of n-3 polyunsaturated FA (PUFA) and conjugated linoleic acid (CLA) isomers and to lower the n-6/n-3 PUFA ratio [3]. The inclusion of α-linolenic acid (C18:3 n-3) sources in the diet of beef cattle, such as wellpreserved forage [4], pasture [5], linseed [6], or linseed oil [7] has been found to increase the concentration of some of the long chain n-3 PUFA in intramuscular fat. Higher levels of n-3 FA enrichment may be achieved by supplementing grazing heifers with linseed oil-enriched concentrates [8]
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