A study was conducted to investigate the hypothesis that over-processing (OP) of meat and bone meal (MBM) exacerbates infection with necrotic enteritis in normal and high phytase diets. A total of 768 Ross 308 male chicks were randomly assigned to 8 treatments with 6 replicate floor pens each housing 16 chicks using a 2 × 2 × 2 factorial arrangement of treatments for 42 d. Factors were: NE challenge, no or yes; phytase* level, 500 or 5000 FTU/kg (both using 500 matrix values for Ca, P and Na of 1.6, 1.5 and 0.35 g/kg respectively); and MBM, Normal (as received) or OP (by autoclaving for 90 mins at 128⁰C at 2 bars). Challenged birds were given three field strains of Eimeria spp. (Eimeria Pty Ltd) on d 9, and 108 CFU per mL of Clostridium perfringens strain EHE-NE18 (known to express NetB toxin, CSIRO) per os on d 14 and d 15. Challenge × MBM interactions were detected for body weight (BW), FCR and feed intake (FI) at d 14, 21 and 28 (P < 0.05) indicating that OP of MBM depressed BW and FI and increased FCR in challenged birds only. Phytase × NE interactions were detected on d 21 for BW (P < 0.048) and FI (P < 0.034) indicating the superdose of phytase increased BW and FI in unchallenged birds but decreased in challenged birds. On d 42 no 2-way or 3-way interactions were detected for BW, FCR, FI or livability. NE challenge decreased BW and FI and increased FCR (P < 0.001). Effects of phytase dose or OP MBM were not detectable on 42 d. These findings confirm the hypothesis that OP of MBM negatively impacts performance and increases the severity of NE incidence. A superdose of phytase was beneficial in unchallenged birds on d 21 but did not carry through to d 42. These results concur with those of Apajalahti and Vienola (2016) indicating undigested MBM protein accumulates in the hind gut where it may interact with NE infection.
Table 1 - Effect of necrotic enteritis, phytase and meat and bone meal on the performance of broilers, d 21.
ACKNOWLEDGEMENTS: This study was funded by AB Vista Feed Ingredients (UK).
Presented at the 31th Annual Australian Poultry Science Symposium 2020. For information on the next edition, click here.