@conference {41137,
	title = {Marker-assisted Selection for Meat Quality and the Ovine Calpastatin Gene},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {59},
	year = {1999},
	month = {Jan},
	pages = {266-268},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The calpain-calpastatin system (CCS) comprises a family of calcium-dependent neutral proteases, the calpains, and calpastatin, a specific inhibitor of the calpains that regulates their activity in vivo. The CCS is found in most animal tissues and influences many important processes including muscle development and degeneration, meat tenderisation postmortem, cataract formation and fertility. The calpains have been shown to play the major role in postmortem tenderisation in beef, lamb and pork by degrading specific muscle structural proteins. The level of calpastatin immediately postmortem appears critical in determining the ultimate tenderness of aging muscles. Tenderness has been shown in consumer surveys and tasting panel tests to be the most important characteristic determining the overall eating quality of meat. In using a molecular genetic approach to studying meat quality in sheep we have chosen the ovine calpastatin gene (CAST) as a candidate gene for meat quality. We have described a three allele system of polymorphic variants (CAST a, b and c) in a region of the ovine CAST. Since 1995 we have carried out slaughter trials on small groups of Dorset Down hoggets and Dorset Down x Coopworth lambs to ascertain any association between meat quality traits and the molecular markers in CAST. Sheep with the genotypes of CAST aa, ab and ac were compared. These trials indicate an association of the CAST genotype ac with increased liveweight gain (+12-17\%,p >0.05), increased age-corrected carcass weight (+15-18\%, p>0.05), but also increased longissimus dorsi shear force (+4-12\%, nonsignificant) compared to sheep with the CAST genotype aa. },
	issn = {1176-5283},
	author = {Palmer BR and Morton JD and Roberts N and Ilian MA and Bickerstaffe R}
}
@conference {40965,
	title = {A candidate gene approach to animal quality traits.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {57},
	year = {1997},
	month = {Jan},
	pages = {294-296},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {A variety of animal quality traits, particularly those associated with meat and wool production and disease resistance, have been the subject of sophisticated genetic analyses. Investigation of the biochemistry and physiology underlying disease or production traits has implicated particular proteins and hence genes as "candidates" for having major phenotypic effects. This makes the candidate gene approach a useful complement to animal genome mapping of markers and QTLs. We have applied the candidate gene approach for the sheep quality traits of meat tenderness and footrot resistance. A three allele system detected by polymerase chain reaction - single strand conformational polymorphism (PCR-SSCP) has been observed for the ovine calpastatin gene. Calpastatin is the specific inhibitor of the ubiquitous calcium-dependent proteases u-calpain and m-calpain. There is very strong population genetic and protein assay data in cattle to inversely correlate post-mortem calpastatin levels with meat tenderness. Assay of post-mortem calpastatin levels in aging lamb confirms an important regulatory role for calpastatin in sheep meat aging. Data sets from preliminary experiments testing the association of the three allele ovine calpastatin system with meat tenderness values and other meat quality characteristics show significantly different fillet tenderness, early post-mortem calpastatin and u-calpain levels between ewes with different calpastatin genotypes. The early post-mortem calpastatin levels and the longissimus dorsi pH at 24 hr post-mortem of sheep representing two different genotypes was also significantly different. The major histocompatibility (MHC) proteins of vertebrates have a role in presenting peptide fragments from pathogenic organisms to the systemic immune system. It is hypothesised that a component of resistance in sheep to footrot is based on an effective systemic immune response and hence controlled by MHC presentation. Sixteen alleles have been identified at the ovine MHC class II DQA2 locus and 8 at the DQA1 locus. A significant (p=0.001) association between footrot status and DQA2 genotype was observed in a halfsib family challenged with the disease under standardised field conditions. },
	issn = {1176-5283},
	author = {Palmer BR and Hickford JGH and Bickerstaffe R}
}
