Conservation genetics of traditional and commercial pig breeds, and evaluation of their crossbreeding potential for productivity improvement

The Food and Agriculture Organization have emphasised the importance of farm animal genetic diversity for the assurance of future global food security. Modern pig production has concentrated on a small number of commercialised breeds. This has significantly contributed to genetic erosion and loss of native breeds, deemed productively inefficient. It has been recommended to conserve the unique traits of traditional breeds as genetic insurance against future challenges. In order to ascertain the commercial viability of traditional breeds, genetic and productivity analyses were completed, using the Large White (LW) and Landrace (LR) as the commercial comparison. Genetic diversity was assessed using a D-loop fragment of mitochondrial DNA for comparison between three purebred traditional breeds: Gloucester Old Spot (GOS), British Lop (BL) and Welsh (W), and commercial LW x LR. The traditional breeds greatly differed from the commercial hybrid, and possessed high variability at this genetic region. The BL and W demonstrated the greatest potential for crossbreeding to increase the diversity of commercial populations. The crossing of LW x LR dams with GOS, BL and W terminal sires produced traditional crossbreds for comparison with LW sired crossbreds. Nuclear DNA diversity was assessed using a region of the iodothyronine deiodinase type 3 (DIO3) gene. This demonstrated that crossbreeding could improve future productivity, by utilising traditional variation to maximise heterozygosity in the progeny. The productivity assessment established that the traditional and commercial crossbreds performed comparably for most of the growth variables measured, however there were highly significant differences for birth weight, weaning weight, back fat and production length. The traditional crossbreds have shown potential for future application, with the W most suited for commercial production, due to the equivalence with the LW. To conclude, the crossbreeding of traditional and commercial pig breeds is a viable genetic management strategy to conserve and genetically improve both groups.