Humic acid and enzymes inclusion in Canola-Based Broiler Diets : effects on physiological and meat quality parameters

Abstract

This study was undertaken to investigate the effects of potassium humate and Axtra XAP enzyme (Xylanase + Amylase + Protease) as dietary additives on growth performance, protein utilisation efficiency, blood parameters, meat quality and tibia bone parameters in broilers fed canola-based diets. Two hundred and twenty broiler chickens were randomly allotted to 5 dietary treatments: control (commercial broiler diet); CM (17.5 % canola meal inclusion); CMEnz (17.5% CM inclusion + 0.3 g/kg Axtra XAP); CMPh (17.5% CM inclusion + 1.5% Potassium Humate, PH) and CMEnzPh (17.5% CM inclusion + 1.5% PH + 0.3 g/kg Axtra XAP). The feeding trial started at the grower phase when the birds were 14 days of age. Intake and weight data were used to calculate average daily feed intake (ADFI), feed conversion ratio (FRC) and average daily gain (ADG). There were no significant (P >0.05) differences on ADFI across all treatments for both grower and finisher phases. However, broilers offered CM had higher ($P$ <0.05) ADG (71 ± 1.08 g/d) compared to birds on all the other diets. Cumulative weight gain of birds fed diet CMEnzPh was the highest throughout the experimental period. Dietary treatment significantly ($P$ <0.05) affected protein utilisation and growth efficiency parameters in both grower and finisher phases apart from the protein consumed (PC) in the finisher phase, specific growth rate was also highest in CM chickens compared to all other treatments. In all instances, the control diet promoted the lowest values for PC, PER, specific growth rate (SGR) and growth efficiency (GE) in the grower phase. Haematological parameters were not influenced ($P$ >0.05) by dietary treatments. The serum biochemistry indices, AST and sodium, were significantly ($P$ <0.05) influenced by dietary treatments but not ALP, ALT, total protein, potassium, albumin, total calcium, cholesterol and magnesium. Diet had no effect on all carcass traits apart from breast weight and breast muscle index of broilers being significantly different. The results on meat quality measurements also showed a lack of significant effect of diet on pH and temperature measurements, drip loss and shear force values of the breast muscle. However, diet had a significant effect on the 3 meat colour coordinates and water-holding capacity (WHC). With regards to meat colour, broiler muscle in the control and CMPh groups (52.94 and 52.91, respectively) had the highest ($P$ <0.05) values for lightness (L*), whilst the meat from broilers fed CMEnzPh had the lowest (47.94). With regards to fatty acid profile, higher values for PUFAs, n-3 fatty acids and n-6 fatty acids were observed in the CM containing diets particularly the CMPh group. The inclusion of CM, enzyme complex and humic acid salt increased the PUFA/SFA ration whilst at the same time reducing the n-6/n-3 ratios. Diet had an effect on latency to lie test with broilers in CMEnz having the highest tendency to lie (2.88 minutes). The highest standing persistency was observed in CMEnzPh (11.19 minutes). Diet had no effect on tibia biomechanics. Diet had an influence (P <0.05) on the macro mineral (calcium, phosphorus, magnesium and potassium) content apart from sodium. Intestinal morphometric parameters demonstrated some differences in the height and width of the intestinal villi and in the width of the intestinal crypts. Gross lesions analysis showed high prevalence of rickets in CMEnz, whilst the inclusion of canola and PH appeared to improve distribution and density of lymphoid tissue in the peripheral and central follicles building tissues of the bursae of fabricius and thymus. Overall, canola meal was shown to have potential as an alternative of soybean meal in broiler diets. Collectively, the findings from the study can be helpful in designing less-expensive feed formulations, physiological and meat quality in poultry farming systems in future.