Genome-wide identification of quantitative trait loci in a cross between Hampshire and Landrace I: carcass traits.

We report the identification of quantitative trait loci (QTL) affecting carcass composition, carcass length, fat deposition and lean meat content using a genome scan across 462 animals from a combined intercross and backcross between Hampshire and Landrace pigs. Data were analysed using multiple linear regression fitting additive and dominance effects. This model was compared with a model including a parent-of-origin effect to spot evidence of imprinting. Several precisely defined muscle phenotypes were measured in order to dissect body composition in more detail. Three significant QTL were detected in the study at the 1% genome-wide level, and twelve significant QTL were detected at the 5% genome-wide level. These QTL comprise loci affecting fat deposition and lean meat content on SSC1, 4, 9, 10, 13 and 16, a locus on SSC2 affecting the ratio between weight of meat and bone in back and weight of meat and bone in ham and two loci affecting carcass length on SSC12 and 17. The well-defined phenotypes in this study enabled us to detect QTL for sizes of individual muscles and to obtain information of relevance for the description of the complexity underlying other carcass traits.

Effect of stunning conditions on occurence of PSE defects in hams of rn+/RN(-) pigs.

Pigs of the same genetic type at the RN and HAL loci, i.e. rn(+)RN(-)/NN were reared in similar conditions of feeding and housing. They were slaughtered in two abattoirs (referred to as A1 and A2) using a mixture of air (30%) and CO(2) (70%), at a rate of 300 pigs per hour per slaughterline. One hundred and thirty-two pigs from 11 farms were slaughtered in A1 using a corusinga restrainer and 127 pigs from 5 farms were slaughtered in A2 with the backloading technique. pH at 40 min, 2.5 h and 24 h after slaughter and colour (L*, a*, b*) at 24 h after slaughter were measured in the semimembranosus muscle. Meat quality of the ham was scored as follows: 1, no PSE-zone; 2, doubtful; 3, PSE-zones in the semimembranosus and sometimes on the internal flexor muscles; 4, PSE-zones in all the flexor muscles. The muscle pH value was higher in A2 than in A1 at 40 min post mortem (P<0.01), but not at 2.5 and 24 h. L* (P<0.001) and b* (P<0.05) were higher in A1 than in A2. There was a remarkable difference in meat quality scores, with 50% of the hams scoring 3 or 4 in A1, vs 13% in A2. Lairage time before slaughter affected (P<0.01) the pH value at 2.5 h (5.69 vs 5.93). The values of pH1 and pH2.5 decreased with increasing the meat quality score. The values of L* and b* increased markedly with the score. The results of the present study indicate that the method of bringing the slaughter pigs to the stunning device affects the frequency and importance of PSE meat in the ham. The automated driving of groups of animals to the stunning machine combined with the backloading of a nacelle, compared to a traditional system driving pigs in single file using electrical goads and a restrainer was beneficial with respect to both meat quality and animal welfare.

Determination of RN(-) phenotype in pigs at slaughter-line using visual and near-infrared spectroscopy.

The specific characteristics of meat from the Hampshire breed of pig, including high glycogen content and low ultimate pH and technological yield, have been associated with the dominant RN gene. In Sweden, purebred Hampshire or Hampshire x Yorkshire is often used as terminal sire in the three-way crosses used for pig meat production. For the industry producing cured and cooked hams there is a need to detect the RN(-) carriers of the pigs early post mortem in order to select non-carriers for ham production. In the present study, the possibility of separating RN(-) carriers from non-carriers using a combination of visual and near-infrared (NIR) spectroscopic measurements in reflectance mode through a fibre-optic probe has been studied on commercial pigs in a slaughterhouse. The NIR measurements were performed 30 min post-mortem. Sixty-three animals were considered to be carriers and 33 animals non-carriers based on their glycolytic potential in M. semimembranosus (above 200 µmol/g for RN(-)rn(+) and below 180 µmol/g for rn(+)rn(+)). By using NIR together with classification with neural networks, RN(-) carriers could be separated from non-carriers. None of the carriers and only four non-carriers of the RN gene were misclassified as carriers of the RN gene. The ultimate pH could be predicted using linear partial least squares regression with a correlation coefficient of 0.57 and an accuracy of 0.074 root mean square error of prediction.