Salmonella Pullorum resistance in dwarf chickens selected for high macrophage phagocytosis

SUMMARY This experiment was conducted to investigate the differences in disease resistance, production traits, and molecular mechanisms in 2 chicken lines with continuing breeding to generation 2 (G2) and generation 3 (G3) according to macrophage phagocytosis. Chickens were divided into high- and low-phagocytic groups according to macrophage phagocytosis. The natural infection rate of Salmonella Pullorum of progeny from different phagocytic groups was detected by slide agglutination. Production traits were calculated upon hatching. Pro-inflammatory cytokine and MHC mRNA expression of different phagocytic chickens in G2 and G3 were tested by quantitative real-time PCR (qPCR). Nitric oxide (NO) was tested by the Griess reaction assay. The results showed that 1) natural infection rate of Salmonella Pullorum of progeny from high phagocytosis product group (HPPG) hens was 6.4% ± 0.92%, which was significantly lower than that of progeny from low phagocytosis product group (LPPG) hens (19.7% ± 2.66%) in G3. 2) For production traits, fertilization, hatchability of fertilized eggs and rate of healthy chicks of high phagocytic index group (HPIG) hens were significantly higher than those of low phagocytic index group (LPIG) hens in G0. Rate of healthy chicks of HPPG hens was 0.96 ± 0.16, which was significantly higher than that of LPPG hens (0.91 ± 0.14) in G1. 3) Heritability of macrophage phagocytosis was 0.31 based on data from 2,666 chickens from 3 generations. 4) When stimulated with LPS, an analogue of Salmonella, macrophages cultured in vitro from high phagocytic chickens had higher levels of pro-inflammatory cytokine mRNA expression, MHC mRNA expression and NO than those from low-phagocytic chickens. Overall, macrophage phagocytosis was a useful marker in breeding of Salmonella Pullorum resistant lines of dwarf chickens.