Humic acid and enzymes in canola-based broiler diets: Effects on bone development, intestinal histomorphology and immune development
The objective of the study was to investigate the effects of dietary inclusion of humic acid and enzymes on bone development, histomorphology of internal organs and the incidence of rickets in broiler chickens fed canola-based diets. In the study, Cobb 500 broiler chicks were used and the following five dietary treatments were administered: control (commercial diet); CM (17.5% canola meal inclusion); CMEnz (17.5% CM inclusion + 0.3g/kg Axtra XAP); CMPh (17.5% CM inclusion + 1.5% potassium humate (PH)); and CMEnzPh (17.5% CM inclusion + 1.5% PH + 0.3g/kg Axtra XAP). These diets were formulated and randomly allocated to 20 pens (experimental units), each housing 11 birds. The birds were phase fed, with the starter diet being given to all birds from day 1 to day 14. During the grower (days 15–28) and finisher phases (days 29–42) birds were fed the experimental diets. Diet differed significantly across all treatments on latency-to-lie (LTL) test. Broilers fed CMEnz had the lowest standing persistence (2.88 ± 2.69 min) and those on CMEnzPh had the highest (11.19 ± 2.69 min), followed by those offered the control diet (9.05 ± 2.69 min). Gross lesion analysis displayed high prevalence of rickets in boilers fed CMEnz diet compared with all other dietary treatments. Intestinal morphometric parameters demonstrated some dietary differences in the height and width of the intestinal villi and intestinal crypts. In conclusion, inclusion of humic acid in canola-based diets appeared to positively influence digestion and assimilation dynamics that were consequential to the improvement in bone and immune development in broilers.
Keywords: Bursae of Fabricius, latency-to-lie, poultry, thymus, tibia biomechanics, tibia gross lesions