221 Effect of varying growth rates on early and aged pork loin and chop quality

Abstract The pork industry has observed an upward trend in ending live weights, resulting in heavier hot carcass weights (HCW). Heavier HCW positively affects loin tenderness; however, the mechanism of this effect is unclear. One possibility is increased growth rate, associated with greater HCW, resulting in more tender loins. The objective was to determine the effect of growth rate on early and aged pork quality. Pigs (N=634) were divided into three groups based on average daily gain (kg/d) from 12-26wk of age; slow (< 0.96kg/d, n=96), intermediate (0.96-1.16kg/d, n=452), and fast (≥ 1.17kg/d, n=86). The MIXED procedure of SAS was used to evaluate the main effects of growth rate, breed, sex, and their interactions on loin quality. Birth and weaning weight did not differ between growth rate (P≥0.15) but, overall ADG was increased (P<0.001) in fast growing pigs by 0.15 kg/d. Fast and intermediate growing pigs had darker loins (P=0.03) by 0.23 units. Intermediate growing pigs had firmer loins (P=0.04) by 0.07 units. Ventral a* increased as growth rate increased (P=0.04) indicating fast growing pigs had the reddest loins (9.77 vs. 9.26 vs. 8.99). Aged ventral marbling, ultimate pH, purge loss, cook loss, instrumental tenderness, and chop moisture and extractable lipid did not differ (P≥0.32) between growth rate groups. Duroc-sired pigs had increased tenth rib back fat amongst all growth rate groups, but the magnitude of difference was much greater in the slow and intermediate groups. Between all growth rate groups, slow growing Pietrain-sired Pigs had the smallest loineye areas (LEA). Carcass yield, bone-in carcass cutting yield, and boneless carcass cutting yield did not differ (P≥0.37) between growth rate groups. While fast growth rates improved aged ventral visual color, instrumental tenderness did not differ between growth rate groups.