Genetic Correlations Between Juvenile Insulin-like Growth Factor-I (IGF-I) and Measures of Sow Reproductive Performance Are Low

Sow reproductive data (N=9 652 sows) and records on juvenile insulin-like growth factor I (IGF-I: N=23 730 records) were used to estimate genetic correlations between IGF-I and age at first farrowing (AFF), the total number of litters produced prior to culling (TNL), weaning to conception interval between the first and second parity (WCI₁₂), and number born alive (NBA₁-₃) or average piglet birth weights (ABWT₁-₃) recorded in parities one to three. Heritability estimates (h₂±S.E.) were moderate (0.26±0.02) for IGF-I, but considerably lower (range:0.03±0.01 to 0.15±0.04) for sow reproductive traits. Estimates of genetic correlations between IGF-I and most sow reproductive traits were generally low (range: -0.08 to +0.08), did not differ significantly from zero, and were accompanied by negligible phenotypic correlations. The exceptions were either unfavourable genetic (rg) and/or phenotypic (rp) correlations between IGF-I and AFF (rg: -0.15±0.10, rp: -0.06±0.02) or WCI₁₂ (rg: -0.45±0.15, rp: 0.01±0.03). Genetic correlations between IGF-I and NBA or ABWT were low and favourable in parities one and two, unfavourable in parity three, but not significantly different from zero in all cases. In a multiple trait context, selection for improved efficiency of lean meat production using information provided by juvenile IGF-I is unlikely to result in significant unfavourable correlated responses in sow reproductive performance.