Diet selection and n-3 polyunsaturated fatty acid deposition in lambs as affected by restricted time at pasture

X Q Zhang,W B Badgery,Tana Tana,Y M Jin

doi:10.1038/s41598-017-15875-8

Abstract

This study investigates the effects of restricted grazing time on forage selectivity and meat fatty acid deposition of lambs compared to a traditional grazing system. Results showed that the animals preferred to graze pasture species that were more palatable and lower in fibre, while demonstrating a partial preference for species with high protein levels. Leymus chinensis was more preferentially selected by lambs grazing pasture for shorter periods than longer periods. Lambs that grazed for 4 h per day had a high LNA (α-linolenic acid) intake. The accumulation of LNA and its elongation products in tissue was closely related to the LNA level in diet. Therefore, allowing lambs to graze for at least 4 h per day resulted in a meat fatty acid profile that is richer in health-promoting fatty acids. In particular, the highest DHA (docosahexaenoic acid) was observed in meat from lambs which grazed pasture for 4-h versus 8- and 12-h. It can be concluded that, in grassland systems, a healthier meat fatty acid profile for humans and the potential for better pasture management is achieved by limiting the grazing of lambs to 4 h per day rather than grazing over longer time periods.

Highlights

Long-chain n-3 polyunsaturated fatty acids (PUFA), including eicosapentaenoic acid (EPA, C20:5 n-3) and docosahexaenoic acid (DHA, C22:6 n-3), have been shown to enhance human health[1]
The highest (P < 0.001) metabolizable energy (ME) was found in concentrate; among-pasture species, it was higher (P < 0.001) in Stipa krylovii and L. chinensis compared to Cleistogenes squarrosa and Allium ramosum
C20:3 n-3 and EPA were found in A. ramosum but they were not measured in other forage species

Summary

Introduction

Long-chain n-3 polyunsaturated fatty acids (PUFA), including eicosapentaenoic acid (EPA, C20:5 n-3) and docosahexaenoic acid (DHA, C22:6 n-3), have been shown to enhance human health[1]. Meat has lower concentrations of these fatty acids compared to oily fish, it is a significant source for many people with low levels of fish in their diet. Compared to meat from animals fed concentrates indoors, grazing pasture, even for restricted periods of time each day, improves the FA properties of lamb’s meat[4,5] and cow’s milk[6]. The diurnal variation in the LNA (α-linolenic acid, C18:3 n-3) content of ryegrass (Lolium Perenne) in the sward and the time of day animals were given access to grazing was a factor influencing the FA composition of meat and milk. Restriction of grazing and that this will result in subsequent increases in healthier FAs of EPA and DHA in the diet and muscle composition

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Discussion

Conclusion