Genetic analysis of age at first service, return rate, litter size, and weaning-to-first service interval of gilts and sows1

Abstract

The aim of this study was to estimate genetic parameters of seven traits related to sow reproductive performance. Data on all Norwegian Landrace pigs (NL) born in nucleus herds and raised in nucleus or multiplying herds from 1990 to 2000 were extracted from the Norwegian national recording scheme. Reproductive traits investigated were age at first service (AFS), return rate in gilts (RRg), age at first farrowing (AFF), live-born piglets in the first litter (NBA1), interval from weaning to first service after first litter (WTS1), return rate after first litter (RR1), live-born piglets in the second litter (NBA2), and interval from weaning to first service after second litter (WTS2). After editing, the data set comprised 12,583 to 56,042 records, depending on the trait. A mixed linear and a joint linear threshold animal model were used to estimate (co)variance components. A full Bayesian approach via Gibbs sampling was adopted. The statistical model used for analysis included contemporary groups of herd-year (-season), purebred or crossbred litter, single or double insemination, mating type, parity in which the animal was born, a regression on lactation length, and an additive genetic effect. Neither the estimated heritabilities nor the genetic correlations differed much between the two approaches, but there was a tendency for higher genetic correlations using the joint linear threshold model approach. Average heritabilities were as follows: AFS = 0.31; RRg = 0.03; RR1 = 0.02; NBA1 = 0.12; NBA2 = 0.14; WTS1 = 0.08; and WTS2 = 0.03. The highest genetic correlations were estimated between NBA1 and NBA2 (r(g) = 0.95), RR1 and WTS1 (r(g) = 0.93), and between WTS1 and WTS2 (r(g) = 0.78). The estimated genetic correlation between NBA and WTS were close to zero. Selection for increased NBA will slightly increase AFS and reduce the probability of a return. Selection for decreased AFS will have a favorable effect on WTS intervals; however, selection for decreased AFS seems to have an unfavorable effect on return rate both on gilts and sows. Conversely, selection for decreased WTS intervals will reduce the probability of a return. Potential selection candidates to include in a multivariate fertility index are AFS, NBA, and WTS1. Due to the low heritability and low, but favorable, genetic correlations to NBA and WTS, RR is not recommended as a selection candidate.

The effect of scope of analyzed data on the value of the heritability coefficient of litter size traits in pigs

“…The presented data show that the heritability of LBP calculated based on fertility realized in the first partus/farrowing ranged from 5.6 to 16.4 %. These values, with the exception of value recorded for farm 2 ( = 0.056), are in concordance with the results obtained by Logar (2000), Čechova and Tvrdon (2002), Radojković et al (2005), Holm et al (2005) and Luković (2006). Value obtained on farm 2 is in concordance with values presented by Petrović et al (1998), Kim (2001) and Vuković (2003).…”

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

“…These results are similar to those found in the present study. However, Roehe & Kennedy (1995) and Holm et al (2005) reported heritability estimates for number of piglets born of about 0.10 when using a model that only included first parity records of Landrace pigs.…”

Impact of wean to standing reflex interval on litter size of sows (Short Communication)

“…Although statistically significant difference between three and four inseminations in case of W-SR within 108 h was observed, its incidence was restricted only to this specific W-SR interval. Holm et al 2005 in their study show that genetic variance for interval from weaning to first service, which correspond to W-SR, after first litter exist and selection for this trait is therefore possible. Nevertheless, the potential selection for W-SR is being complicated by low heritability found by Sterning et al 1998 which found the heritability of weaning to oestrus interval which corresponds to SR is 0.24.…”