Relationship between sire estimated breeding values and the meat and eating quality of meat from their progeny grown on two planes of nutrition

Abstract

The meat of 140 female lambs was examined. These lambs were sired by 9 Poll Dorset sires (3 selected for growth, 3 for muscling and 3 control) and fed either a low or high plane of nutrition from birth to slaughter. All carcasses were electrically stimulated and portions of 'M. longissimus thoracis et lumborum' (loin) aged for 5 days before freezing. Subsequently, 10 consumers tested each portion for eating quality traits. A portion of the same muscle from the opposing side of the carcass was divided into 3 sections and aged for either 1, 3 or 5 days and then used to measure shear force (objective tenderness). Portions of the 'M. semimembranosus' (topside) were also aged for 3 or 5 days and subjected to shear testing. Low plane animals produced tougher loins (based on shear force). As ultimate pH increased, shear force of the loin increased for low plane animals, while for high plane animals there was no such effect. This latter group had significantly lower ultimate pH values in all 3 muscles tested. Plane of nutrition had the greatest effect on topside shear force with low plane lambs producing tougher topsides. As ultimate pH increased, the topsides became tougher and as expected ageing improved the tenderness. There was no effect of sire EBVs (estimated breeding values) on shear force or objective meat quality traits apart from loin lightness which increased as the EBV for post-weaning weight (PWWT) increased and intramuscular fat in the loin which decreased as sire EBV for post-weaning muscle depth (PEMD) increased. Plane of nutrition did not have a significant effect on eating quality attributes as assessed by consumers. There was, however, an effect of sire EBV for muscling (PEMD) on tenderness, juiciness, flavour and overall liking, such that increased EBV led to decreased scores for the sensory traits. The findings suggest selection of sires for increasing PEMD will have a detrimental affect on the eating quality of their progeny, but this will not be reflected in shear force values or other objective meat quality traits apart from intramuscular fat. The effects of a low plane of nutrition on eating quality were minimal and largely controlled by the use of best practice processing, but were evident for a number of meat quality traits.