Dietary effects on immune response of fast-growing chicks to inoculation of sheep erythrocytes and Escherichia coli

Responses to SRBC and Escherichia coli inoculations were measured during the early posthatch period in broiler cockerels fed diets differing in nutrient density. Diet A consisted of 20% protein and 2,685 kcal ME/kg and Diet B consisted of 24% protein and 3,146 kcal ME/kg. There was no effect of diet on antibody response of chicks inoculated at 10 d of age with 0.25, 2.50, 5.00, or 25.00% suspensions of SRBC. A significantly larger proportion of chicks, however, produced antibody at the 25.00% than at the 0.25% dosage of SRBC. When inoculated at 15 d of age with 10(-6), 10(-4), or 10(-2) dosage of E. coli, there were no significant diet by dosage interactions for lesion scores, or relative change in BW 24, 48, and 120 h after inoculation. There were differences among E. coli dosages for severity of lesions and mortality, with rankings being 10(-2) > 10(-4) > 10(-6). Lesion scores and mortality were higher for the chicks fed Diet B than those fed Diet A. Also, deleterious effects of E. coli on BW 24, 48, and 120 h after inoculation were greater for chicks fed Diet B than for chicks fed Diet A. Responses to inoculations of SRBC and E. coli of broilers fed a diet with a lower nutrient density were equal or superior to those of broilers fed a diet with a higher nutrient density.