Strain differences in effects of dietary supplementation with

Abstract

Context Concerns about feed costs and environmental pollution in the poultry industry may be alleviated through use of Aspergillus spp. for prebiotic supplementation in reduced-protein diets. Aim We studied different A. niger cultures as supplements in protein-reduced diets for effects on performance, organ weights, plasma biochemistry, ileal microflora and meat lipid oxidation of young broilers. Methods Two strains of A. niger from a fungi collection were cultured in wheat bran by solid-state fermentation. Male broilers (Ross 308, 1 day old, n = 192) were randomly assigned to 24 cages in a completely randomised design with four treatments in six replicates of eight birds. Diets were formulated for starter (Days 1–10) and grower (Days 11–24) phases to meet nutrient requirements (control) or to contain 95% of recommended crude protein (reduced protein). For two treatments, uncultured wheat bran (1.5 g/kg) was added to control or reduced-protein diets. The other treatments comprised wheat bran cultured by one of the two A. niger strains in reduced-protein diets. Key results Body weight gain was higher (P < 0.05) in groups supplemented with A. niger, and feed intake was generally higher with Strain 1 supplementation than other treatments. Feed conversion ratio was generally highest in broilers fed reduced protein with uncultured wheat bran. Relative weights of proventriculus and small intestine were lowest with A. niger 2 supplementation, and abdominal fat was lowest in both A. niger groups. Serum triglyceride, cholesterol and uric acid decreased with A. niger 1 supplementation, and high-density lipoprotein, total protein and globulin increased with A. niger 2 supplementation (P < 0.05). Meat malondialdehyde content was decreased (P < 0.05) in both A. niger groups. Broilers receiving Strain 2 showed higher ileal counts of lactic acid bacteria and total aerobic bacteria, and all reduced-protein groups showed lower coliform count, than the control (P < 0.05). Conclusion Use of A. niger culture in wheat bran to supplement a lower protein broiler diet improves some parameters, including growth performance and lipid oxidative stability of meat. Some strain differences are evident. Implication Addition of fermentation products such as produced by A. niger to low-protein diets can reduce production costs while maintaining quality.