Β-Mannan in soybean meal is one of the main antinational factors to decrease the efficiency of nutrient use. It has been found to be deleterious to broiler chicken performance, depressing chicken body weight gain and feed conversion ratio (FCR), as well as glucose and water absorption. Adding the exogenous mannanase has been demonstrated to improve chicken performance, significantly reduce coccidial lesion sores and increase egg production.
Recently, the University of Sydney conducted a broiler chicken trial to investigate the effect of the exogenous mannanase on broiler chicken performance and meat quality in reduced protein diets.
Standard, positive control (PC) diets were formulated to meet or exceed the 2019 Aviagen Ross 308 nutrition specifications and negative control (NC) diets were formulated with a 0.18 MJ in the starter and 0.21 MJ in grower and finisher phases. Another six treatments consisted of the PC and NC supplemented with the exogenous mannanase 100, 200 and 300 mg/kg, respectively. All eight diets contained 1000 FTU phytase.
Overall broiler growth to 35 days post-hatch exceeded the Ross 2019 male performance objectives by 23.6% for weight gain (2884 versus 2333 g) and was superior by 10.71% in FCR (1.326 versus 1.485). Adding 200 mg/kg β-Mannanase in low energy diets obtained better body weight gain and FCR compared with that in the normal standard diets. Interestingly, in the finishing period, adding β-mannanase to low density diets did not significantly increase feed intake but supported heavier breast meat (Figure 1); However, adding β-Mannanase to standard normal energy density diets significantly increased feed intake and consequent body weight gain but tended to reduced abdominal fat (Figure 2), indicating the dietary energy was efficiently used to produce chicken meat but not fat accumulation. Therefore, β-Mannanase supplementation could save both energy (50 kcal/kg) and amino acids (1% of all essential amino acids reduction).
Fig 1. Breast meat in male Ross 308 broilers from 0-35 days post-hatch (P = 0.111).
Fig 2. Abdominal fat contents in male Ross 308 broilers from 0-35 days post-hatch (P =0.117).