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Abstract
Technological meat quality is a significant economic factor in pork production, and numerous publications have shown that it is strongly influenced both by genetic status and by rearing and slaughter conditions. The quality of meat is often described by meat pH at different times postmortem, as well as by color and drip loss, whereas carcass quality is often characterized by lean percentage. A meta-analysis of findings relating to 3,530 pigs reported in 23 publications was carried out to assess the effects of the halothane gene, sex, breed, and slaughter weight of animals on 7 selected variables: pH at 45 min postmortem, ultimate pH, reflectance (L*-value), redness (a*-value), yellowness (b*-value), drip loss, and lean percentage. Two statistical methods were used in the meta-analysis: the method of effect size and the better known random effects model. The method of effect size was associated with Markov chain Monte Carlo techniques for implementing Bayesian hierarchical models to avoid the problems of limited data and publication bias. The results of our meta-analysis showed that the halothane genotype had a significant effect on all analyzed pork quality variables. Between-study variance was evaluated with the Cochran (1954) Q-test of heterogeneity. Meta-regression was used to explain this variance, with covariates such as breed, sex, slaughter weight, and fasting duration being integrated into different regression models. The halothane gene effect was associated with the breed effect only for the following variables: L*-value, b*-value, and drip loss. Slaughter weight contributed significantly only to the explanation of differences in ultimate pH between homozygous genotypes. In response to inconsistencies reported in the literature regarding the difference between the genotypes NN and Nn, results of the meta-analysis showed that the difference between these 2 genotypes was significant for all the analyzed variables except the a*-value.
Highlights
Pork quality depends on genetic factors, environmental factors, and their interactions
The regression method showed that the effect of the halothane gene on pH measured 45 min (pH45) was significantly influenced by sex (P = 0.0002), which explained almost 78% of the variability between the combined studies (Table 2)
2 meta-analytic methods were used to quantify the effect of the halothane gene on a range of key attributes of pork quality in pig populations
Summary
Pork quality depends on genetic factors, environmental factors, and their interactions. The mutated halothane “n” allele is considered fully recessive, there is conflicting information regarding the meat quality of heterozygous animals (Monin et al, 1999; Channon et al, 2000; Miller et al, 2000) Another unresolved debate concerns the effect of the halothane gene on ultimate pH in LM (Larzul et al, 1997; Fisher et al, 2000). In response to these gaps in the scientific literature, we chose to combine existing results in a meta-analysis (i.e., an analysis combining published results in a statistically sound way; DuMouchel, 1990). This method is useful when results from independent studies are contradictory because it increases statistical power (Cucherat et al, 2002)
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