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

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.