Monocytes-macrophages phagocytosis as a potential marker for disease resistance in generation 1 of dwarf chickens

Monocytes-macrophages play an indispensable role in the immune system. The current study investigated the effect of selection for monocytes-macrophages phagocytosis on disease resistance in generation 1 (G1) of dwarf chickens. Five hundred dwarf chickens of generation 0 (G0) were divided into high and low phagocytic index (PI) groups (HPIG and LPIG, respectively) based on their PI of monocytes-macrophages at 290 d of age. Then, 2 x 2 mating combinations were conducted. Sixty G0 chickens from another dwarf chicken group were used to measure the levels of monocytes-macrophages phagocytosis at different developmental stages. Among a total of 2,500 randomly selected G1 chickens, 2,100 individuals were used for a surviving and growing test under adverse feeding circumstances, and the other 400 individuals were tested for Salmonella Pullorum challenge. The results showed that progenies of HPIG hens (female symbol) were more resistant to Salmonella Pullorum. After challenge, the death rate of progeny from HPIG female symbol (28.9%) was only 58% that of progeny from LPIG female symbol (49.4%, P < 0.001). In addition, the natural infection rate of Salmonella Pullorum before 207 d for offspring from HPIG female symbol (35.0%) was significantly lower than that for offspring from LPIG female symbol (48.3%, P < 0.001). The natural mortality before 56 d in progeny of HPIG female symbol (22.6%) was significantly lower than that in progeny of LPIG female symbol (29.1%) with a P-value of 0.001. The G1 chickens of HPIG G0 female symbol weighed more than those born to LPIG G0 female symbol at 28 and 42 d of age, whereas the difference was not statistically significant at 56 d of age. The heritability of monocytes-macrophages phagocytosis was 0.40, which was moderate. The PI values were at a low level before 126 d and increased dramatically until they declined significantly after 294 d. It could be concluded that phagocytosis of monocytes-macrophages is a marker for breeding excellent progeny with strong disease resistance.