Animal Molecular Breeding 2024, Vol.14, No.2, 154-164 http://animalscipublisher.com/index.php/amb 159 genotypic data to achieve accurate predictions and significant genetic gains. The use of high-density genotyping and advanced statistical models has proven effective in identifying genetic markers and QTL associated with economically important traits (Bergamaschi et al., 2019; Falker-Gieske et al., 2019). Additionally, the inclusion of genetic marker information, such as the RYR1 locus, has been shown to increase the accuracy and selection response in breeding strategies (Biermann et al., 2015). Looking forward, future perspectives include the continued refinement of genetic models and the incorporation of new technologies such as whole-genome sequencing and gene editing. The development of more precise and efficient selection indexes that include a broader range of traits, such as meat quality and novel carcass traits, will be essential for meeting the growing demand for high-quality pork (Duarte et al., 2017; Willson et al., 2020). Furthermore, the validation and functional characterization of identified QTL and candidate genes will be crucial for translating genetic findings into practical breeding applications (Vidal et al., 2005). 5 Challenges and Limitations 5.1 Genetic diversity and inbreeding concerns One of the primary challenges in using quantitative genetics to improve carcass traits in pigs is maintaining genetic diversity while avoiding inbreeding. Inbreeding can lead to a reduction in genetic diversity, which in turn can result in inbreeding depression, negatively affecting traits such as growth, meat quality, and overall health of the pigs. Studies have shown that while heritability estimates for carcass traits can be moderate to high, the genetic correlations between these traits can vary significantly, indicating the complexity of genetic interactions (Miar et al., 2014a; Miar et al., 2014b). For instance, the heritability estimates for carcass traits ranged from 0.22 to 0.63, suggesting that while genetic improvement is possible, careful management of genetic diversity is crucial to avoid negative consequences (Miar et al., 2014b). Moreover, the genetic correlations between purebred and crossbred pigs can be inconsistent, further complicating breeding programs. The genetic correlations between purebred and crossbred performance (rpc) for various traits have been found to be moderate to high, but with large standard errors, indicating potential issues with the accuracy of selection. This variability underscores the importance of incorporating crossbred performance data into breeding programs to ensure that genetic gains in purebred populations translate effectively to commercial crossbred populations (Esfandyari et al., 2019; Esfandyari et al., 2020). 5.2 Environmental and management factors affecting carcass traits Environmental and management factors play a significant role in the expression of carcass traits, adding another layer of complexity to genetic improvement programs. Factors such as housing conditions, feed quality, and climate can significantly influence the phenotypic expression of genetic traits. For example, genotype by environment interactions (G×E) have been observed, indicating that pigs raised in different environmental conditions (e.g., tropical vs. temperate climates) may exhibit different genetic correlations for carcass traits (Godinho et al., 2019). This suggests that breeding programs need to account for environmental variability to achieve consistent genetic improvements across different production systems. Additionally, management practices such as feeding regimes and housing conditions can impact carcass traits. Studies have shown that significant fixed effects such as company, sex, and slaughter batch, as well as covariates like cold carcass weight and slaughter age, need to be considered in genetic models to accurately estimate genetic parameters (Miar et al., 2014; Miar et al., 2014b). These factors can introduce variability that may mask the true genetic potential of the animals, making it essential to standardize management practices as much as possible to achieve reliable genetic evaluations. 5.3 Ethical considerations in genetic selection Ethical considerations are increasingly important in the context of genetic selection for improved carcass traits in pigs. One major ethical concern is the welfare of the animals. Intensive selection for specific traits, such as increased muscle mass or reduced fat, can lead to unintended negative consequences on animal health and well-being. For instance, selection for increased daily gain and reduced backfat thickness has been associated with
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