Growth, efficiency and the fatty acid composition of blood and muscle from previously grazed late-maturing bulls fed rumen protected fish oil in a high concentrate finishing ration

摘要

In bulls, with a genetic predisposition for leanness and reared in a grass-based production system dietary fish oil may further enhance the nutritional value of beef by increasing the concentration of the omega 3 polyunsaturated fatty acids (PUFA) eicosapentanoic acid (EPA) and docosahexanoic acid (DHA). The impact of including rumen protected fish oil in the finishing diet of late maturing breed bulls on their growth, feed efficiency, carcass fat classification, aspects of ultimate meat quality and the fatty acid composition of the M. Longissimus thoracis muscle (LT) was examined. Twelve month old bulls were supplemented with a barleybased concentrate (500g/kg dietary dry matter) from turn-out to pasture in spring until housing 94 days later. Bulls were housed indoors and offered ad libitum, either the same concentrate or a concentrate containing rumen protected fish oil (PFO) at a ration fat concentration of 50g/kg dry matter, along with grass silage to appetite, for 88 days pre-slaughter. Inclusion of PFO increased (P<0.05) concentrate consumption, but this was not reflected in carcass growth, classification or fat colour or in LT colour or tenderness. Concentrations of 18:2, EPA, DHA, total PUFA and the PUFA: saturated fatty acid ratio (0.19 v 0.14) were higher (P<0.05) in LT from PFO compared to control bulls. The increase in EPA + DHA, associated with PFO inclusion, from 7 to 12 mg/100g muscle is below the concentration required by European Commission regulations (40 mg/100g) to allow this beef to be labelled a "source of EPA + DHA. Nevertheless, consuming beef from PFO bulls would make a greater contribution to the daily consumer requirement for omega-3 PUFA than beef from the control bulls. This has potential to add value to beef from the PFO production system.