Abstract
New-born chicks are vulnerable to bacterial infections and not good at regulating body temperature. There is a close relationship between thermal regulation and immunity, however, the underlying mechanism is not well understood. Salmonella Pullorum (SP) is a major concern in developing countries and causes significant economic losses in poultry industry. Early body temperature (EBT) has previously shown to be correlated with host immunity and resistance to pullorum disease. In this study, we challenged three independent chick populations (Beijing You, Dwarf and Rhode Island Red) with SP at 4 days of age, and rectal temperature was measured before and after the SP attack from 2 to 7 days of age. Host defense to SP was evaluated by survival and spleen SP carrier status. The results showed that chicks with higher EBT before SP infection tend to have higher resistance to later SP attack in two populations (Dwarf and Beijing You). The association between EBT before SP attack and SP resistance was non-significant in Rohde Island Red population (P = 0.06), but the trend was consistent with the other two populations. We also found low to moderate heritability in all three populations for EBT before and after the SP attack ranging from 0.14 to 0.20. Genome-wide association studies identified several genomic regions and biological pathways determining EBT before SP attack, which provides candidate functional genes of this trait. Our results reveal the genetic determination of EBT, and the relationship between EBT and SP resistance, providing an alternative strategy for improving SP resistant activities in chicken.
Highlights
Pullorum disease, an acute and systematic chick infectious disease caused by Salmonella Pullorum (SP), occurs frequently and is a major economic concern for chicken farms in developing countries (Barrow et al, 2012)
621 Dwarf Chicken (DW), 586 Rhode Island Red (RIR), and 482 Beijing You (BY) chicks were orally inoculated with 4.8×107 CFU of SP culture at 4 days post-hatch. 40 chicks from each line were randomly selected as control group, which was mock-challenged with the same volume (0.5 mL) of phosphate buffer saline
For RIR, 17.9% of chicks were classed as carriers, compared with 0.6% for BY and 15.8% for DW
Summary
An acute and systematic chick infectious disease caused by Salmonella Pullorum (SP), occurs frequently and is a major economic concern for chicken farms in developing countries (Barrow et al, 2012). Difficulty in measuring disease resistance phenotypes remains a major obstacle in genetic research and breeding. This difficulty arises since it is demanding and costly to do large-scale challenge tests in farm settings. Different infection models have been used in the study of Salmonella resistance, complicating the interpretation of results (Calenge et al, 2010). Despite these problems, it is important to identify traits associated with SP resistance to aid in breeding and selection strategies
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