Variation in sow health affects the information provided by lactation feed intake data

Using data from two maternal lines of pigs (N~2200), medication events were used as proxy indicators of sow health, to examine changes in associations between lactation feed intake and other traits that occur with changes to sow health status. Estimates of heritability for total born, average piglet birth weight, litter gain until day 10 (LG10), average sow feed intake during lactation (LFI), total sow feed intake during the first three days of lactation, lactation length and the underlying liability for a shortened lactation (SL) or surviving to farrow in parity 2 (FP2) were 0.14±0.01, 0.33±0.03, 0.09±0.04, 0.18±0.04, 0.06±0.04, 0.06±0.03, 0.15±0.09 and 0.06±0.07. Genetic (ra) and phenotypic (rp) correlations indicate that high lactation feed intake was favourably associated with SL and FP2 (ra: -0.78±0.19 and 0.42±0.41; rp: -0.49±0.01 and 0.31±0.01). Compared to estimates obtained using only subsets of data from sows that met lactation length targets or unmedicated sows, heritabilities for LFI were higher in the medicated data set and phenotypic correlations with LG10, SL or FP2 were of increasingly larger magnitude across these data subsets. Sow health status affects the information content of lactation feed intake data, but larger studies will be required to confirm if significant changes also occur in genetic parameters because of health status. Knowledge of health status could be important for other studies which examine associations between feed intake, recorded in any physiological state, and other production traits.