Estimation of variance components, genetic parameters and genetic trends for litter size of swines

Abstract

-Records of Large White breed animals were used to estimate variance components, genetic parameters and trends for the character total number of born piglets (TNBP) as measure of litter size. For obtaining variance components and genetic parameters, it was used the Restricted Maximum Likelihood Method using MTDFREML software. Two mixed models (additive and repeatability) were evaluated. The additive model contained fixed effect of the contemporary group and the following random effects: direct additive genetic and residual effect for the first parturition. Repeatability model had the same effects of the additive model plus parturition order fixed effect and non-correlated animal permanent environment random effect for the second, third and forth parturition. Direct additive heritability estimates for TNBP were 0.15 and 0.20 for the additive and repeatability models, respectively. The estimate of the ration among variance of the non-correlated effect of animal permanent environment effect and the phenotypic variance, expressed as total variance proportion (c2) was 0.09. The estimates of yearly genetic trends obtained in the additive and repeatability models have similar behaviors (0.02 piglets/sow/year).

Multi-trait and repeatability models for genetic evaluation of litter traits in pigs considering different farrowings

“…According to these authors, this observation may be related to the overestimation of genetic variance in the second farrowing. A study focusing on the multi-trait model for the NBA trait in Large White pigs showed an increasing pattern of heritability up to the third farrowing, which differs from our findings (BARBOSA et al, 2010). Noguera et al (2002) found the same systematic increasing trend and this tendency was observed until the sixth farrowing.…”

“…Although Damgaard et al (2003) did not analyze litter traits' heritability according to the order of farrowing, they reported that MW0 was also the trait with the highest heritability (0.39). Similarly to other studies, the first farrowing presented the lowest heritability in all studied traits (ROEHE & KENNEDY, 1995;BARBOSA et al, 2010). The genetic correlations between NBA, NP3, and LW3 did not present a regular pattern among farrowings.…”

“…On the other hand, the traits LWO, MW0, and MW3 presented high genetic correlations among different farrowings, albeit not equal to one. According to Barbosa et al (2010), knowing the magnitude of correlations between farrowings is important to define the best evaluation process for breeding programs. High genetic correlation suggests that these traits are controlled by the same genes or gene combinations, implying in selection for a given trait in the first farrowing results in genetic gains for this trait in subsequent farrowings.…”

Estimation of litter size variability phenotypes in Large White sows

“…However, the differences between those two models and BM were small. This result, together with a very similar proportion of genetic variance to phenotypic variance estimated via the three models, leads to practically the same heritability, which was within the range known from the literature (Barbosa et al, 2010; Felleki et al, 2012; Lopez, Kim, Makumbe, Song, & Seo, 2017; Putz, Tiezzi, Maltecca, Gray, & Knauer, 2015) and similar to that previously reported by Sell‐Kubiak et al (2015) for the same data set.…”

Acompanhamento Da Mortalidade Em Leitões Em Relação À Ordem De Expulsão Durante O Parto Até O Período Da Desmama

“…O melhoramento genético de suínos encontra-se num patamar onde a prolificidade já é uma realidade, porém buscam-se melhorar os índices de sobrevivência da leitegada através do manejo de homogeneidade de lotes, controle local da temperatura, dietas balanceadas de acordo com o estágio de gestação (BARBOSA et al, 2010). Cuidados com a sanidade, melhoria nas dimensões e tipo de instalações zootécnicas, socialização de fêmeas até o momento do parto, visando o bem estar dos animais na fase de prenhes e qualificação da mão de obra.…”