Growth Rate and Backfat. Genetic evaluation models were applied to different breeds and to small closed herds. Parameter estimates were made and genetic trends were computed. A program (MTPIGEBV) was written in 1998. Concern about connectedness or data structure on swine evaluations was also important. Different measures of connectedness were compared both theoretically and empirically. A study on breeding systems and how exchanges could improve accuracy of genetic evaluations was also conducted.
Other studies. Sow reproductive traits were also studied and a genetic evaluation system developed and put into place as a service for Ontario. The effects of direct and maternal genetics on litter size were studied. At one time there were quarterly across-herd evaluations for sow reproduction and monthly within-herd interim evaluations. Procedures for combining the across-herd evaluations into the interim within-herd evaluations was developed.
A live animal experiment with the Guelph research herd was started in which animals were selected for high and low EBVs for immune response levels.
Carcass traits and the effects of the PSS genotype on carcass quality have been important. More work will be done on looking for QTLs in swine in the future.
Much biochemical work has been done on the causes of boar taint, in the hopes of finding genetic markers or QTLs which might suppress boar taint. Boar taint is caused by high levels of skatole and/or androstenone in carcasses. Androstenone is synthesized in the testis, while skatole is produced by the bacterial degradation of skatole in the gut. Both products enter the blood stream and are either metabolized in the liver or they accumulate in the fat. The accumulation of these products in carcasses are controlled by a balance between the processes that produce these compounds and by the processes that are involved in degrading and removing the compounds. Work on the synthesis of androstenone has been done at the protein level and at the DNA level. The cytochrome b5 protein and cytochrome P450C17 are involved in the synthesis of androstenone in the testis. Polymorphisms are being identified in the hopes of finding a genetic marker for low androstenone pigs.
The metabolism and clearance of skatole has also been studied to identify the metabolites of skatole which are associated with skatole levels in fat. The key enzymes in the metabolims of skatole have also been identified. Hopefully genetic markers for these enzymes can be found so that low skatole pigs could be produced.