Influence of selection for improved growth rate on pork quality.

摘要

It is hypothesized that selection for improved growth rate has the potential to result in a loss of desirable fresh pork quality. The objective of this study was to investigate if genetic selection of sires for improved growth rate is associated with changes in fresh pork quality. A sample derived from the cross between a commercial line of Duroc sires and white line dams was subdivided according to the sires' estimated breeding value (EBV) for age at 125 kg. Differences in age at 125 kg were achieved by assigning pigs sired by High EBV growth boars (n=48), Low EBV growth boars (n=48) or a control group (n =32). Loin pH and temperature decline were monitored on each carcass. Fresh pork quality characteristics and water holding capacity were monitored at 2 d postmortem. Sensory traits (juiciness, tenderness, chewiness, flavor, and off-flavor) and star probe texture were measured 10 d postmortem. Proteolysis was estimated by desmin degradation and micro-calpain autolysis at 2 d postmortem. Progeny were separated according to the sire EBV group into a Fast Growth EBV group and a Slow Growth EBV group. Selection for improved growth rate resulted in Fast Growth EBV progeny being significantly younger at 125 kg than Slow Growth EBV progeny (153 d vs. 177 d). Sire EBV group did not affect pH decline in the longissimus dorsi. Loin color and drip loss were not affected by growth rate. Loins from carcasses in the fast growth group had higher subjective marbling scores and higher lipid content than loins from carcasses in the slow growth group. EBV did not affect star probe or sensory quality of fresh pork loins. Selection for improved growth rate resulted in significant differences in proteolysis measurements between the Fast Growth and Slow Growth EBV groups. Correlation analysis of growth, quality and biochemical variables was executed within each EBV group. Measures of tenderness and WHC correlations differed between the two groups, as evidenced by differing correlations of significance for pH measurements and strength of sensory trait correlations. Also, the High EBV group was more correlated with measurements of postmortem proteolysis than the Low EBV group. The results show that variation in pork quality could not be attributed to lower pH but could be due to proteolysis differences associated with growth. They also show that selection for rapid growth by improving days of age at 125 kg did not significantly affect the quality of fresh pork loin. Therefore this method of selection can be used without compromising fresh pork quality. It also provides insights into the potential differences associated with selecting for growth rate, especially when looking at the correlations among the two sire EBV groups. The results also demonstrate the importance of accounting for genetic background of the animal in addition to selection practice application when accounting for variations in pork quality. Selection for improved growth rate can be used as a successful selection practice without compromising fresh pork quality.