Genetic parameters of natural antibody isotypes and survival analysis in beak-trimmed and non-beak-trimmed crossbred laying hens

Natural antibodies (NAb) are important humoral components of innate immunity. As the first line of defense, NAb provide protection against infection and support adaptive immunity. An earlier study indicated that serum levels of NAb isotypes IgM and IgG at a young age were predictive for survival in non-beak-trimmed purebred laying hens during the laying period. In the present study, genetic parameters of NAb isotypes were estimated and relationships between survival and NAb isotypes levels in crossbred laying hens were investigated. In total, 1,555 beak-trimmed and 1,169 non-beak-trimmed crossbred laying hens were used. Genetic parameters of IgM and IgG titers binding keyhole limpet hemocyanin at 24 wk of age were estimated with a linear animal model. The heritabilities of NAb isotypes IgG and IgM were 0.21 (SE = 0.04) and 0.26 (SE = 0.04), respectively. The genetic correlation between IgG and IgM isotypes was 0.43 (SE = 0.11). These results indicated that NAb isotype titers were heritable traits in the crossbred laying hens. Both NAb isotypes can be selected for simultaneously because the detected positive genetic correlation (0.43, SE = 0.11) between them is positive. Both row and level of the cage were indicated to be associated environmental factors for NAb isotype titers. Different from an earlier study with purebred hens, survival analysis showed no significant associations of survival with NAb isotype titers in beak-trimmed or non-beak-trimmed crossbred hens. Non-health-related causes of mortality, especially in birds with intact beaks, overruled the anticipated relationships between NAb isotype titers and survival