Zum Einfluss unterschiedlicher Behandlungsverfahren und Zusatzstoffe auf ernährungsphysiologische Parameter und Leistung wachsender Broiler nach Verabreichung weizenbetonter Futtermischungen

Abstract

A 2 x 2 x 4 factorial experimental design was used to investigate the main effects of grinding (hammer mill vs. roller mill), hydrothermal treatment (conditioning 70°C vs. expanding* 100°C) and supplementation of feed additives (antibiotic Zinc-bacitracin 50 mg, NSP-splitting enzyme Roxazyme G2 liquid 150 ppm with cellulase, endo-b-1,3:1,4-glucanase and xylanase activities) and their combination as well as the interaction of these tested factors on broiler performance (feed intake, live weight gain and feed conversion ratio), ileal digestibilities of some amino acids in a growth assay (7. - 28. d) and N-utilisation parameters (N-intake, N-balance, protein utilisation value PNu and efficiency of lysine) as well as N-corrected metabolisable energy (MEn) in a metabolism bioassay (15. - 21. d). The content of CP and energy (MEn) was the same in all tested diets (21,7 % and 12,3 MJ/kg feed). The amino acid lysine was limited of 90 % below the animals daily requirement. The effects of tested factors are mentioned as follow: Grinding: Grinding with roller mill indicated significant improvement on feed intake and feed conversion ratio (-2,8 %) compared to grinding with hammer mill. Nutrient deposition or utilisation levels were not significant different. The ileal digestibility of lysine showed no difference between both grinding types, on the other hand the ileal digestibility of amino acids Thr or Met + Cys was significant increased with roller mill. Grinding with roller mill led to better feed structure and thus led to increased nutrient density in the diets pellet. In the metabolism study, animals with rolled diets increased N-intake, N-balance and the PNu significantly as well as N-corrected metabolisable energy (MEn) compared to tested animals with hammer mill grinded diets. Hydrothermal treatment The application of heat with expander (conditioning/expanding) had no influence on broiler performance, deposition and utilisation of protein and energy compared with conditioning. In the growth trial this processing (conditioning/expanding) led to significant higher ileal digestibility of lysine, on the other hand decreased lysine efficiency in the metabolism bioassay. In general, significantly decreased N-balance, PNu, N-digestibility and metabolisable energy indicated a possible protein damage with expanding in this study. Feed additives: The supplementation of feed additives had a significant effect on daily weight gain and feed conversion ratio (specially inclusion of both supplements antibiotic and enzyme) or only on feed conversion ratio (single supplement of antibiotic or enzyme). The parameters crude protein (CP) utilisation and ileal amino acids digestibility showed a higher significant effect through a single supplement of enzyme compared with control. However, supplementation with antibiotic showed no effect. The content of apparent metabolizable energy was significantly higher by supplementation with enzyme or enzyme plus antibiotic. The results of this study (growth and metabolism trial) indicated a synergistic effect of the inclusion of both supplements. Interaction: The relation between the tested factors has not well appeared in parameters of growth performance. Grinding in combination with thermal treatment led to significant higher feed intake. Hence, the processing combination of hammer milling with conditioning or roller milling with expanding led to significant better daily weight gain and protein and energy deposition. In relation to ileal amino acid digestibility showed the feed additives dependency from thermal treatments, so only the efficiency of enzyme supplementation or in combination with antibiotic was higher under expanding. In the metabolism bioassay the N-utilisation parameters of the combination expanding and hammer mill grinding were negatively correlated. The additives showed dependency from hammer mill grinding with regard to parameter PNu and lysine efficiency.