Selection for litter size at day five to improve litter size at weaning and piglet survival rate1

Abstract

Selection for total number of piglets born (TNB) since 1992 has led to a significant increase in this trait in Danish Landrace and Danish Yorkshire but has also been accompanied by an increase in piglet mortality. The objective of this study was to estimate the genetic and phenotypic parameters for litter size and survival to find alternative selection criteria to improve litter size at weaning. Data from Landrace (9,300 litters) and Yorkshire (6,861 litters) were analyzed using REML based on a linear model including genetic effects of sow and service-sire. The estimates of heritability (based on the sow component) for TNB, number born alive (NBA), and number alive at d 5 after birth (N5D) and at weaning (about 3 wk, N3W) ranged from 0.066 to 0.090 in Landrace and 0.050 to 0.070 in Yorkshire. Genetic correlations between TNB and N3W were 0.289 in Landrace and 0.561 in Yorkshire, but between N5D and N3W the estimated genetic correlation was 0.995 in both populations. The approximate estimates of heritability for survival rate per litter at birth (SVB = NBA/TNB), from birth to d 5 (SV5 = N5D/NBA), and from d 5 to weaning (SVW = N3W/N5D) were 0.130, 0.131, and 0.023, respectively, in Landrace, and 0.095, 0.043, and 0.009, respectively, in Yorkshire. Genetic correlations between TNB and survival rates at different stages were negative. On the other hand, genetic correlations between N5D and survival rates and between N3W and survival rates were strongly or moderately positive, except for the correlations with SVW in Yorkshire. The results suggest that selection for N5D could be an interesting alternative to improve litter size at weaning and piglet survival for Danish Landrace and Danish Yorkshire.

Variance and covariance components for liability of piglet survival during different periods

“…Further, the estimates of genetic correlations for survival between different periods were low or moderate, and most were not significantly different from zero. The results agree with those of previous studies based on litter records Su et al, 2007) or on piglet records (Arango et al, 2006). Serenius et al (2004) obtained an estimate of the genetic correlation between the proportion of stillbirth and piglet mortality from birth to weaning close to zero.…”

“…Arango et al (2005) reported estimates of heritability for number of piglets born dead of 0.09, 0.10 and 0.11 in parity 1, 2 and 3, respectively. Su et al (2007) reported estimates of heritabilities for survival rate at farrowing and during early suckling ranging from 0.042 to 0.129, and near to zero for survival rate during late suckling period, based on sow genetic component at the litter level. Several studies have included the direct additive genetic effect of the piglet in the analysis on piglet survival.…”

“…At the litter level, Lund et al (2002) reported a direct heritability of 0.01 for survival at birth and 0.04 for survival from birth to weaning in Landrace, while the respective estimates were 0.05 and 0.02 in Yorkshire. Based on litter records using a linear Gaussian model, Su et al (2007) estimated direct heritability at the litter level to be 0.108, 0.136 and 0.024 in Landrace and 0.008, 0.064 and 0.024 in Yorkshire for SVB, SV5 and SVW, respectively.…”

“…The rate of piglet survival till weaning is about 80% on average (Meat and Livestock Commission, 2000;Le Dividich, 2002;Knol et al, 2002b). Lower piglet survival rate was observed in the lines submitted to selection for total number of piglets born (Johnson et al, 1999;Arango et al, 2006;Su et al, 2007). The high piglet mortality results in large economic losses in pig production, and has a detrimental impact on animal welfare.…”

Avaliação genética do tamanho de leitegada em suínos das raças Landrace e Large White

“…2). Irgang et al (1994) Por fim, por meio da correlação de Spearman (correlação de posto) entre os valores genéticos do NLNV e NLV5, período que considera a capacidade de criação da fêmea, e menor mortalidade dos leitões (Su et al, 2007), foram obtidos valores, tanto para o primeiro parto quanto para o segundo, próximos da unidade (0,99), sugerindo que o registro do NLV5 poderia ser dispensado.…”