A retrospective analysis of allele frequency changes of major genes during 20 years of selection in the Italian Large White pig breed
JOURNAL OF ANIMAL BREEDING AND GENETICS
Authors: Fontanesi, L.; Schiavo, G.; Scotti, E.; Galimberti, G.; Calo, D. G.; Samore, A. B.; Gallo, M.; Russo, V.; Buttazzoni, L.
Abstract
In this study, we investigated whether a selection programme based on boar genetic evaluation obtained with a classical BLUP animal model can change allele frequencies in a pig population. All Italian Large White boars born from 1992 to 2012 with estimated breeding value reliability >0.85 (n=200) were selected among all boars of this breed. Boars were genotyped with markers in major genes (IGF2 intron3-g.3072G>A,MC4R p.D298N, VRTNPRE1 insertion, PRKAG3 p.I199V and FTO g.276T>G). Genotyping data were analysed grouping boars in eight classes according to their year of birth. To evaluate the influence of time on allele frequencies of the genotyped markers, multinomial logistic regression models were computed. Four of five polymorphic sites (IGF2,MC4R, VRTN and FTO) showed significant (p<0.01) changes in allele frequencies over time due to a progressive and continuous increase of one allele (associated with higher lean meat content, higher average daily gain and favourable feed: gain ratio) and, consequently, decrease of the other one, following the directional selection of the selection programme of this pig breed. The retrospective analysis that was carried out in Italian Large White boars suggests that selection based on methodologies assuming the infinitesimal model is able to modify in a quite short period of time allele frequencies in major genes, increasing the frequency of alleles explaining a relevant (non-infinitesimal) fraction of the overall genetic variability for production traits.
Association of swine vertnin (VRTN) gene with production traits in Duroc pigs improved using a closed nucleus breeding system
ANIMAL SCIENCE JOURNAL
Authors: Hirose, Kensuke; Mikawa, Satoshi; Okumura, Naohiko; Noguchi, Go; Fukawa, Kazuo; Kanaya, Naoe; Mikawa, Ayumi; Arakawa, Aisaku; Ito, Tetsuya; Hayashi, Yoichi; Tachibana, Fumio; Awata, Takashi
Abstract
Vertnin (VRTN) is involved in the variation of vertebral number in pigs and it is located on Sus scrofa chromosome 7. Vertebral number is related to body size in pigs, and many reports have suggested presence of an association between body length (BL) and meat production traits. Therefore, we analyzed the relationship between the VRTN genotype and the production and body composition traits in purebred Duroc pigs. Intramuscular fat content (IMF) in the Longissimus muscle was significantly associated with the VRTN genotype. The mean IMF of individuals with the wild-type genotype (Wt/Wt) (5.22%) was greater than that of individuals with the Wt/Q (4.99%) and Q/Q genotypes (4.79%). In addition, a best linear unbiased predictor of multiple traits animal model showed that the Wt allele had a positive effect on the IMF breeding value. No associations were observed between the VRTN genotype and other production traits. The VRTN genotype was related to BL. The Q/Q genotype individuals (100.0cm) were longer than individuals with the Wt/Q (99.5cm) and Wt/Wt genotypes (98.9cm). These results suggest that in addition to the maintenance of an appropriate backfat thickness value, VRTN has the potential to act as a genetic marker of IMF.