Estimates of genetic parameters associated with lactation feed intake and reproductive performance in purebred and F1...

Daily feed intake during lactation was recorded in parity records from purebred Yorkshire (n = 1587), Landrace (n = 2197) and reciprocal cross F1 (n = 6932) females, and lactation feed intake (LFI) curves were predicted using a mixed model. Evaluation of the difference in feed intake between two consecutive days of lactation resulted in the following classifications: three periods for purebreds, days 1-6, days 7-10 and days 11-18, and two periods for F1 sows, days 1-5 and days 6-18. Average rate of change in intake (ARC), average daily intake (ADI) and variation from predicted LFI values (VAR) were computed for each period of lactation. Gibbs sampling was used to estimate genetic (co)variance components for LFI metrics and reproductive performance traits. Genetic variance estimates for each LFI metric were obtained with univariate animal models, and covariance estimates were estimated with bivariate models. Heritability estimates for ADI, ARC and VAR metrics computed over the duration of lactation were 0.37, 0.24, and 0.16, respectively. Heritability estimates were highly variable across periods of lactation for ARC (0.03-0.17), ADI (0.09-0.36) and VAR (0.04-0.18) metrics in purebred and F1 populations. Genetic correlations between LFI metrics and reproductive traits were relatively low, although LFI metrics later in lactation were more highly correlated with reproductive performance.