Published online by Cambridge University Press: 09 March 2007
1. The fatty acid composition of milk fat of Coopworth sheep offered varying pasture allowances has been determined after 1, 14 and 35 d of lactation. Differences in fatty acids occurred, particularly between 1 and 14 d, with a major increase in C18:0 whilst C16:0, C14:0 and C18:3 showed decreases.
2. When pasture allowances were restricted there were decreases in the short-chain fatty acids from C6 to C14 and an increase in C18:1 as has been observed previously for cattle. The C18:1:C10 value is a convenient measure of these changes and can be determined more rapidly than determining all the lower fatty acids.
3. The increased demand for milk resulting from suckling twin lambs caused an increase in C18:1 and decreases in C10 and C12 due to an increased utilization of body reserves.
4. The level of linoleic acid was much greater than has been previously observed in sheep given hay and contributes to the rapid rise in linoleic acid levels in lambs born under grazing conditions.