Relationships between Pork Quality Traits and Growth Factor Concentrations in Serum and Longissimus dorsi Muscle before and at Slaughter in Female Market Pigs

The present study was conducted to test a hypothesis that pork quality traits would be influenced by the systemic and/or local bioavailability of insulin-like growth factor-I (IGF-I), transforming growth factor-${\beta}1$ (TGF-${\beta}1$), or epidermal growth factor (EGF) before or at slaughter. To this end, 60 cross-bred female market pigs weighing approximately 110 kg were slaughtered, after which Longissimus dorsi muscle (LM) samples taken at slaughter (D 0) and blood samples taken at D -7 and D 0 were analyzed. The 60 carcasses rendered 36 RFN (reddish-pink, firm, and non-exudative), 16 RSE (reddish-pink, soft, and exudative), and 6 PSE (pale, soft, and exudative); 2 DFD (dark, firm, and dry) also were found but were excluded in subsequent experiments. The $L^*$ and drip loss were greater in PSE vs. RFN and RSE and in PSE and RSE vs. RFN, respectively, as they should (P<0.05). The $pH_{45min}$ was less in PSE vs. RFN (P<0.05); $pH_{24h}$ tended to be less in the former (P=0.09). The LM IGF-I and TGF-${\beta}1$ as well as serum EGF concentrations were less in PSE than in RFN. None of the other LM and serum concentrations of the three growth factors differed across the three pork quality categories. The LM IGF-I and TGF-${\beta}1$ concentrations and serum EGF concentration at D 0 were negatively correlated with drip loss [r = -0.36(P<0.01), -0.44 (P<0.01), and -0.32 (P<0.05), respectively]. However, none of the serum and LM growth factor variables was correlated with $L^*$ or $a^*$ (redness) of LM. Taken together, results suggest that locally expressed IGF-I and TGF-${\beta}1$ and blood-borne EGF may have a beneficial effect on postmortem water holding capacity of the muscle and that pork quality traits could be predicted to some extent from concentrations of IGF-I and TGF-${\beta}1$ in muscle and EGF in serum at slaughter.