Effects of including a ruminally protected lipid supplement in the diet on the fatty acid composition of beef muscle

Enhancing the polyunsaturated fatty acid (PUFA) and decreasing the saturated fatty acid content of beef is an important target in terms of improving the nutritional value of this food for the consumer. The present study examined the effects of feeding a ruminally protected lipid supplement (PLS) rich in PUFA on the fatty acid composition of longissimus thoracis muscle and associated subcutaneous adipose tissue. Animals were fed ad libitum on grass silage plus one of three concentrate treatments in which the lipid source was either Megalac (rich in palmitic acid; 16:0) or PLS (soyabean, linseed and sunflower-seed oils resulting in an 18:2n−6:18:3n−3 value of 2·4:1). Treatment 1 contained 100g Megalac/kg (Mega, control); treatment 2 (PLS1) contained 54g Megalac/kg with 500g PLS/d fed separately; treatment 3 (PLS2) contained no Megalac and 1000g PLS/d fed separately. The PLS was considered as part of the overall concentrate allocation per d in maintaining an overall forage:concentrate value of 60:40 on a DM basis. Total dietary fat was formulated to be 0·07 of DM of which 0·04 was the test oil. Total intramuscular fatty acids (mg/100g muscle) were decreased by 0·31 when feeding PLS2 compared with Mega (P