Multiple trait model combining random regressions for daily feed intake with single measured performance traits of growing pigs

Abstract

-A random regression model for daily feed intake and a conventional multiple trait animal model for the four traits average daily gain on test (ADG), feed conversion ratio (FCR), carcass lean content and meat quality index were combined to analyse data from 1 449 castrated male Large White pigs performance tested in two French central testing stations in 1997. Group housed pigs fed ad libitum with electronic feed dispensers were tested from 35 to 100 kg live body weight. A quadratic polynomial in days on test was used as a regression function for weekly means of daily feed intake and to describe its residual variance. The same fixed (batch) and random (additive genetic, pen and individual permanent environmental) effects were used for regression coefficients of feed intake and single measured traits. Variance components were estimated by means of a Bayesian analysis using Gibbs sampling. Four Gibbs chains were run for 550 000 rounds each, from which 50 000 rounds were discarded from the burn-in period. Estimates of posterior means of covariance matrices were calculated from the remaining two million samples. Low heritabilities of linear and quadratic regression coefficients and their unfavourable genetic correlations with other performance traits reveal that altering the shape of the feed intake curve by direct or indirect selection is difficult. random regression / variance component / Gibbs sampling / feed intake / pig

Use of serial pig body weights for genetic evaluation of daily gain

“…In the literature, heritability estimates vary according to breed, feeding regime and stage of growth. Heritability estimates for lifetime daily gain were around 20% (Lutaaya et al 2001;McPhee et al 2001), while estimates for daily gain during the fattening period (from around 30 to about 100 kg) were generally higher with 35-45% (Schnyder et al 2002;Gilbert et al 2007;Hoque et al 2007). However, also lower estimates were reported (Hermesch et al 1999).…”

Recording strategies and selection potential of feed intake measured using the X-ray method in rainbow trout

“…In farm animals, average daily feed intake is typically recorded during each day of a long testing period, in some cases over the whole production time (e.g., in pigs). For instance, the testing period has been 35-100 days for pigs [33,35], 70-119 days for cattle [1,2], 42-56 for lambs [4,11,37], and 23-182 days for chicken [5,34]. In comparison, in the present study feed intake was recorded at each age only during three days, yet over a 21-day testing period.…”

“…Accordingly, the aim of genetically changing feed intake is not always to reduce it. In farm animals, random regression methods have been applied to simultaneously analyse all separate feed intake records over the whole life span, in order to control the genetic changes occurring at different ages [33,35]. Applying the random regression method for individual daily records appears difficult in salmonids.…”

Up hill, down dale: quantitative genetics of curvaceous traits

“…In a REML framework of estimation, this is readily done by fitting an equivalent model that incorporates permanent environmental effects in the residual; see Meyer (2001b) for details. For Bayesian analyses via Gibbs sampling, constraints on parameters have been used for this purpose (Schnyder et al 2002).…”