Selection for lean growth rate and correlated responses in litter traits in a synthetic line of Yorkshire-Meishan pigs

Abstract

[205][206][207][208][209][210][211][212][213][214]. Selection for lean growth rate (LGR) was conducted for four generations in a synthetic line of Yorkshire-Meishan pigs to study the effectiveness of selection for LGR and correlated responses in litter traits. Lean growth rate was estimated from ultrasound measurements of 10th-rib backfat thickness and longissimus muscle area. In the selection line, 7 boars and 20 gilts with the highest LGR were selected to produce the next generation. The generation interval was 13 mo and the average selection differential per generation was 1.1 phenotypic standard deviation units. A contemporaneous control line was maintained by randomly selecting 5 boars and 15 gilts. Data from a total of 1057 pigs sired by 58 boars and out of 133 sows were available from the two lines. Selection responses were estimated from deviations of the selection line from the control line using least squares (LS) and by multiple trait derivative-free restricted maximum likelihood analysis using an animal model (AM). The estimate of response to selection per generation using LS was 9.4 ± 0.95 g d -1 for LGR. The corresponding estimate from the AM was 9.8 ± 0.51 g d -1 . Correlated responses in litter traits were regressed on generation. For the LS method, regression coefficients were negative but not significant (P > 0.05) for total number born, number born alive, and number at 21 d and at 42 d. Significant, positive correlated responses occurred in 42-d litter weight and 21-d piglet weight (P < 0.05). For the AM method, the regression coefficients were also negative, but were not significant (P > 0.05) for number alive at birth, at 21 d, and at 42 d. A significant positive correlated response occurred only for 42-d litter weight (P < 0.05). Although results are based on a population of limited size, it can be concluded that selection for LGR in a synthetic line is effective and should have little effect on litter traits. LGR ont été sélectionnés pour produire la génération suivante. L'intervalle entre les générations était de 13 mois et le différentiel de sélection moyen par génération s'établissait à 1,1 unité d'écart-type phénotypique. Parallèlement, on a élevé une lignée témoin de contemporains en sélectionnant au hasard 5 verrats et 15 truies nullipares. Les deux lignées ont permis de recueillir des données sur 1 057 porcs venant de l'accouplement de 58 verrats avec 133 truies. On a estimé les effets de la sélection en appliquant la méthode des moindres carrés (LS) et un modèle animal reposant sur la méthode du maximum de vraisemblance restreint sans dérivée pour les caractères multiples aux écarts entre la lignée sélectionnée et la lignée témoin. La réaction à la sélection estimative était de 9,4 ± 0,95 g par jour par génération selon la LS et de 9,8 ± 0,51 g par jour pour le modèle animal. La variation des caractères de la portée qui présentent une corrélation avec la réaction de la sélection a fait l'objet d'une analyse de régression pour la génération. Les coefficients de régression était nég...

Parameters of genetic and phenotypic type in pigs mating in pure breed and crossbreeding on litter size

“…From the data in Table 5, we can see that, the genetic and phenotypic correlation between the traits is great and highly statistically significant (P<0.01). The results are in agreement with most researchers (Choi et al, 1995;Chen et al, 2001Chen et al, , 2003Vidović et al, 2011a,b) Figure 1 is used to present the effect of parity on reproductive traits. From data in the figure, it is clearly evident that, the number of piglets born alive is gradually increased till the fourth farrowing, and then gradually decreased till thirteen farrowing.…”

Genetic variation and responses in reproductive performance of sows in lines selected for growth rate under restricted feeding

“…favourable) with backfat by Tholen et al (1996), Cameron (1996a), andHermesch et al (2000). However, correlated responses in litter birth (or weaning) weights to selection for high lean growth in other studies have been either negative (DeNise et al, 1983;Fredeen and Mikami 1986) or non-significant (Cleveland et al, 1988;Chen et al, 2001;Gibson et al, 2001). Differences between selection response and genetic parameter estimates of correlations between reproductive and performance traits are to be expected due to the notoriously high errors to which they are subject.…”

“…Correlated responses in reproduction traits have been measured in experiments in which selection has been carried out for growth rate or backfat (Kuhlers and Jungst, 1992;1993) or an index combining increased growth rate and decreased backfat (Vangen, 1980;DeNise et al, 1983;Fredeen and Mikami, 1986;Cleveland et al, 1988;Zhang et al, 2000;Chen et al, 2001;Gibson et al, 2001). Reproductive traits have not been shown to be significantly influenced by selection based on growth rate alone.…”

Economic values for traits of pigs in Hungary

“…The genetic correlation near zero was estimated between the trait of the number of piglets born alive or litter weight at day 21 on the one hand, and the growth and carcass traits on the other (Chen et al, 2001). Therefore, when developing an economic selection index, the breeding values can be directly multiplied by the marginal economic values to obtain the appropriate weights for the index traits.…”