The influence of meat-and-bone meal and exogenous phytase on growth performance, bone mineralisation and digestibility coefficients of protein(N),amino acids and starch in broiler chickens

The objective of this study was to examine the influence of meat-and-bone meal(MBM) and phytase inclusion on growth performance, bone mineralisation and apparent digestibility coefficients of nutrients in broiler chickens offered wheat-based diets. The feeding study comprised 7 dietary treatments: positive control(PC, 9.0% Ca and 4.5% available phosphorous [AvP] in starter, 7.0% Ca and 3.5% AvP in finisher); negative control(NC, 7.2% Ca and 3.0% AvP in starter, 5.2% Ca and 2.0% AvP in finisher) diets incorporating a 3 × 2 factorial array of 3 MBM inclusions(0, 60, 120 g/kg) and 2 levels of phytase supplementation(0 and 1,000 FYT/kg). Each treatment was allocated to 6 replicated pens with 30 birds per pen in an environmentally-controlled deep litter facility. A total of 1,260 one-day-old male Ross 308 chicks were offered starter diets from 1 to 14 days post-hatch and finisher diets from 15 to 36 days posthatch. There were significant(P < 0.05) interactions between MBM inclusions and phytase supplementation on weight gain and feed intake in starter diets. Phytase significantly increased weight gain in diets without MBM and did not influence weight gain in diets with 60 and 120 g/kg MBM. Collectively,increasing MBM inclusion significantly reduced weight gain in starter diets(P < 0.0001). There were dietary interactions(P < 0.01) on toe ash where phytase significantly improved toe ash in diet without MBM and did not influence toe ash in the other two groups of negative control diets. There were no dietary treatment interactions on apparent ileal digestibility coefficients of starch and protein except that diets without MBM had significantly(P < 0.01) lower ileal starch digestibility and diets with 120 g/kg MBM had significantly(P < 0.0001) lower ileal protein digestibility. No dietary influence on ileal fat digestibility was observed. There were dietary interactions on ileal digestibilities of isoleucine, valine and glycine. Phytase significantly increased glycine digestibility in diets with 60 and 120 g/kg MBM but not in diets without MBM, Including 120 g/kg MBM significantly(P < 0.01) depressed apparent digestibility coefficients of 13 ex 16 amino acids in the distal ileum. This study demonstrated the negative impacts of MBM on amino acid digestibility and growth performance. Also, responses to phytase were more pronounced in diets without MBM, which may have been due to their relatively lower available P and higher phytate concentrations in comparison to diets containing MBM.