title: Immunological responses as affected by dietary protein and arginine concentrations in starting broiler chicks.
abstract: The study presented here aimed to investigate the effect of dietary protein content on Arg needs and immunological responses of broiler chicks during the starter period. A total of 715 one-day-old male Ross broiler chicks were randomly assigned to 5 replicate pens for each of 11 experimental diets during a 21-d feeding trial. The dietary treatments included a corn-soybean meal control diet or experimental diets (corn-soybean meal-corn gluten meal) containing 5 dietary Arg levels of 80, 90, 100, 110, or 120% of NRC recommendations and 2 dietary protein levels of 19 and 22.35% of diet. Increasing dietary CP content significantly (P<0.001) increased daily feed consumption and weight gain. Also, feeding diets deficient in Arg to the chicks led to a noticeable decline in feed intake, and dietary Arg supplementation overcame decreased feed consumption and weight gain observed in Arg-deficient chicks. Feed efficiency was affected only by dietary Arg concentration so that chicks on Arg-deficient diets markedly (P<0.001) increased feed conversion ratio. Contrast comparisons showed that the highly variable responses of chicks to dietary Arg level were mainly attributed to dietary protein concentration: more dietary protein content and higher Arg demands. Among lymphoid organs, thymus (P<0.001) and spleen (P<0.05) were affected by dietary Arg deficiency, whereas diets low in CP content decreased (P<0.001) relative weights of thymus and bursa of Fabricius. Increase in dietary CP level from 19 to 22.35% caused an increase (P<0.001) in the proportion of lymphocytes and consequently lower (P<0.05) heterophil-to-lymphocyte ratio. Broiler chicks on Arg-deficient diets decreased the proportion of heterophils in peripheral blood. Furthermore, skin reaction to phytohemagglutinin P was impaired when the diets were low in CP and Arg contents. Similarly, a decrease in dietary CP and Arg levels diminished the antibody production response to Newcastle disease virus. The broken-line analysis indicate that the Arg requirements of starting broiler chicks for optimal immune functions (107% of NRC values) are higher than those for maximum growth performance (101%) or feed efficiency (103%) and are dependent on dietary protein concentration.
authors.affiliation: Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan 84156, Iran. r.jahanian@gmail.com
authors.forename: R
authors.initials: R
authors.lastname: Jahanian
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D000906:Antibodies / Q000097:blood; D001120:Arginine / Q000494:pharmacology*; D001772:Blood Cell Count / Q000662:veterinary; D002645:Chickens / Q000097:blood / Q000276:immunology*; D004032:Diet / Q000662:veterinary; D004044:Dietary Proteins / Q000494:pharmacology*; D008297:Male
chemical_list: D000906:Antibodies; D004044:Dietary Proteins; D001120:Arginine