Genetic parameters were estimated for haemoglobin (Hb) levels in sows and piglets as well as sow reproductive performance and piglet survival. Reproductive traits were available between 2005 and 2014 for 7857 litters from 1029 Large White and 858 Landrace sows. In 2012 and 2013, Hb levels, sow BW and sow back fat depth were measured on 348 sows with 529 litters 5 days prior to farrowing. In addition, Hb levels were available for 1127 one-day-old piglets from 383 litters (a maximum of three piglets per litter) of 277 sows with Hb levels. The average Hb levels in sows (sow Hb), their litters (litter Hb, based on average Hb of three piglets) and individual piglets (piglet Hb) were 112 ± 12.6 g/l, 103 ± 15.3 g/l and 105 ± 21.7 g/l, respectively. Heritabilities for Hb levels were 0.09 ± 0.07 for sow Hb, 0.19 ± 0.11 for litter Hb and 0.08 ± 0.05 for piglet Hb. Estimates for the permanent environment effect of sows were 0.09 ± 0.09 for sow Hb, 0.11 ± 0.12 for litter Hb and 0.12 ± 0.03 for piglet Hb. In comparison, heritabilities for both number of stillborn piglets and pre-weaning survival were lower (0.05 ± 0.01 and 0.04 ± 0.01). Sow BW had no significant heritability, while sow back fat depth was lowly heritable (0.10 ± 0.08). Positive genetic correlations were found between sow Hb and litter Hb (0.64 ± 0.47) and between litter Hb and sow back fat depth (0.71 ± 0.53). Higher litter Hb was genetically associated with lower number of stillborn piglets (−0.78 ± 0.35) and higher pre-weaning survival (0.28 ± 0.33). Negative genetic correlations between sow Hb and average piglet birth weight of the litter (−0.60 ± 0.34) and between piglet Hb and birth weight of individual piglets (−0.37 ± 0.32) indicate that selection for heavier piglets may reduce Hb levels in sows and piglets. Similarly, selection for larger litter size will reduce average piglet birth weight (rg: −0.40 ± 0.12) and pre-weaning survival (−0.57 ± 0.13) and may lead to lower litter Hb (−0.48 ± 0.27). This study shows promising first results for the use of Hb levels as a selection criterion in pig breeding programs, and selection for higher Hb levels may improve piglet survival and limit further reduction in Hb levels in sows and piglets due to selection for larger and heavier litters.

The objective of this study was to explore the sensitivity of breeding values for growth rate and worm egg count (WEC, cube root transformed) to environmental worm burden, measured as the average WEC for each contemporary group (CGWEC). Growth rate and WEC were measured on 7,818 naturally infected Merino lambs in eight flocks across Australia, linked through common use of AI sires. Through bivariate analysis, genetic correlations of 0.55 ± 0.23 and 0.30 ± 0.16 were found for growth rate and WEC between low and high CGWEC, respectively. In a second analysis, breeding values for growth rate and WEC were regressed on CGWEC with a random regression model. The heritability for growth rate varied from 0.23 to 0.16 from low to high CGWEC, and the heritability for WEC varied from 0.25 to 0.36. Results suggest that breeding values for both growth rate and WEC are sensitive to environmental worm burden. Animals expressed less genetic variation for growth rate and more genetic variation for WEC in high CGWEC than in low CGWEC. This form of genotype-by-environment interaction should therefore be considered in genetic evaluation of both growth rate and WEC, to increase the efficiency of selection for animals that are more parasite resistant and more resilient to environmental worm challenge.

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