The effect of pre-slaughter factors on meat quality varies between muscle cuts

The Australian pork industry has focused on developing an eating quality pathway (Channon et al. 2016) to improve quality and consistency of pork; however, this has focused on conventional housed pigs with an average HCW of 74.9 kg. This study investigated the effect of housing type (H), carcass weight (W) and sex (S) on objective pork quality. The hypothesis tested was that housing type, carcass weight and sex, as individual and additive factors, does not affect objective quality of several pork cuts. A total of 384 Large White × Landrace commercial pigs (PrimeGro Genetics™, Corowa, NSW, Australia) were selected over eight replicates in a 2 × 2 × 3 factorial experiment with the main treatments being: (1) Housing: Conventional (CON) and deep-litter (DL); (2) Sex: Female or castrated pigs (IM); and (3) Carcass weight: Light 60–70 kg (L), Medium 70.1–80 kg (M) or Heavy 80.1–91 kg (HV). Methods are previously described by Lealiifano et al. (2017) with objective meat quality measurements (shearforce, pH, drip loss, L*, a* and b*) conducted 24 h post-slaughter on Musculus longissimus thoracis et lumborum (loin), M. biceps femoris (silverside) and M. gluteus medius (rump) from the carcass’s left side. Data was analysed using ANOVA (Genstat 16, VSN International, Hemel Hempstead, UK).

There was a significant main effect of H on the shear force values, such that overall meat cuts from DL were lower than meat cuts from CON pigs (Table 1). There was no effect of carcass weight on the objective meat quality measures of the loin. Shear force in the rump decreased as carcass weight increased (4.22 kg v. 4.02 kg v. 3.97 kg, SE 0.09 for L, M and HV, respectively, P = 0.012). The increase in carcass P2 with increasing weight could have affected the increased tenderness associated with heavier carcasses. The silverside drip loss increased with an increase in slaughter weight (3.19%, 3.41%, 3.64%, SE 0.002, P = 0.024 for L, M and HV carcass weights, respectively). The increased drip loss in the silverside could be due to increased muscle size and a slower chilling rate for the heavier carcasses. Loin objective quality was not significantly affected by S differences. IM had lower drip loss, higher pH in the rump and silverside (SS) compared to females (Rump Drip loss: 3.46% v. 3.96%, SE 0.01, P = 0.025; SS Drip loss: 3.12% v. 3.70%, SE 0.01, P = 0.005; Rump pH: 5.47 v. 5.44, SE 0.01, P = 0.005; SS pH: 5.53 v. 5.49, SE 0.01, P = 0.01 respectively). There were no significant interactions of shear force by cut type due to S, W, or interactions with H. Deep litter carcasses had an increased drip loss level in the silverside over the three carcass weights (L: 3.26% v. 3.12%, SE 0.27; M: 3.63% v. 3.18%, SE 0.27; HV: 4.10% v. 3.18%, SE 0.27 DL v. CON housed respectively P = 0.049). There were also significant H × W interactions (L: 44.99 v. 47.05, SE 0.42; M: 45.08 v. 45.83, SE 0.42; HV: 44.81 v. 46.32, SE 0.42 DL v. CON housed respectively P = 0.049) and S × H × W interactions (L IM: 45.62 v. 46.95, SE 0.59 respectively; L Female: 44.37 v. 47.15, SE 0.59 respectively; M IM: 45.30 v. 45.92, SE 0.59 respectively; M Female: 44.86 v. 45.74, SE 0.59 respectively; HV IM: 44.45 v. 46.84, SE 0.59 respectively; HV Female: 45.18 v. 45.80, SE 0.59 respectively P = 0.010) for L* value in the silverside.

Table 1.  Means and standard error of the difference (SED) for the effect of housing on pH, Minolta L*, drip loss (%) and shearforce (kg) in the loin, rump and silverside (SS)

The hypothesis was rejected as these results show that housing had a significant effect on key objective meat quality measures, with carcass weight and to a lesser extent sex impacting meat quality. The effects however were varied between meat cuts.