Sixty crossbred (Large White × Landrace × Duroc) pigs were used to compare the growth performance, carcass and pork quality characteristics of entire, surgically castrated and immunologically castrated male pigs from two Western Australian commercial genotypes (genotype A : ‘lean’ genotype and genotype B : propensity for increased subcutaneous fat deposition). Pigs from genotype B had a higher average daily gain and a superior food conversion ratio compared with pigs from genotype A. Entire males had lower backfat compared with surgically and immunologically castrated male pigs. Pork from entire males was drier, tougher and had lower overall acceptability scores compared with surgically or immunologically castrated male pigs. Pork from genotype A pigs had a lower m. longissimus thoracis (LT) ultimate pH and higher drip loss compared with pork from genotype B pigs. However, consumer taste panel assessment indicated that pork from genotype A pigs was more tender, had higher juiciness and overall acceptability scores compared with pork from genotype B pigs. Within genotype A, the consumer taste panel preferred pork from surgically castrated pigs compared with either entire or immunologically castrated pigs. Within genotype B, the consumer taste panel preferred pork from immunologically castrated pigs compared with either entire or surgically castrated male pigs. These results indicate that interactions between genotype and castration method can significantly influence eating quality of pork.

This investigation was designed to evaluate the effects of the dietary inclusion of vegetable oil and its composition on fatty acid composition and lipid oxidation in pig muscle. Pigs were given the following diets from 50 kg to slaughter (90 kg): a control diet with no added fat (NF) or diets containing 20 g/kg of sunflower (SUN), olive (OL) or sunflower + linseed (SUN + LIN) oils. Meat from pigs given the SUN + LIN diet showed the highest thiobarbituric acid reactive substances (TBARS) from day 3 of refrigerated storage to the end of the experiment (P < 0·05). The OL group showed the lowest TBARS after 9 days of storage (P < 0·05). Pigs on NF showed intermediate values that were generally closer to those recorded for pigs given the SUN + LIN than the OL diet. By day 9, there was no statistical difference between the NF and the SUN + LIN group. The SUN group also showed intermediate TBARS throughout storage, with no statistical differences compared with the NF group. After 9 days of storage the lowest CIELAB a* value, corresponded to the SUN + LIN group and the highest to the OL group. These results indicate similar behaviour to that of lipid oxidation. Meat samples from pigs given the diet not enriched with fat showed greater drip loss than those given the remaining diets (P < 0·05) while there was no significant effect of dietary fat source on water-holding capacity. The inclusion of oils rich in linoleic fatty acids in pig diets modifies muscle fatty acid composition but susceptibility to lipid oxidation does not appear to be increased with respect to that occurring in pigs given diets with no added fat.

The relationships between reflectance values measured with an EEL reflectometer, and C1ELAB L* a* b* coordinates measured with a tristimulus meter, were determined using 572 samples of pork m. longissimus dorsi. These samples covered the muscle colour/condition range from extreme pale, soft, exudative (PSE) to extreme dark, firm, dry (DFD). There was a good (r = 0·91) and slightly curvilinear relationship between L* value and reflectance, the other relationships being significantly poorer. Based on these findings, pork loins with L* values between 49 and 60 would on average have consistently good visual appeal using criteria in the Meat and Livestock Commission blueprint for quality pork.