Over-processed meat and bone meal and phytase effects on broilers challenged with subclinical necrotic enteritis:Part 1.Performance,intestinal lesions and pH,bacterial counts and apparent ileal digestibility

This feeding study investigated the hypothesis that over-processing of meat and bone meal(MBM) would impair the performance,gut health and ileal digestibility of nutrients in birds challenged with necrotic enteritis(NE).The effect of phytase(500 vs.5,000 FTU/kg) was also examined using manufacturers recommended matrix values for 500 FTU for both levels.Ross 308 male broilers(n=768) were assigned to 8 diets,with 6 replicate pens per diet and 16 birds per replicate pen using a randomized design with a factorial arrangement of treatments.Factors were NE challenge(no or yes),MBM(as received or overprocessed),and phytase level(500 or 5,000 FTU/kg).Half of the birds were challenged with 5,000 oocysts of field strains of Eimeria acervulina and Eimeria brunetti,and 2,500 oocysts of Eimeria maxima on d 9 and 10~8 CFU/mL of Clostridium perfringens strain EHE-NE18 on d 14 and 15 post-hatch.Challenge × MBM interactions were detected for weight gain(WG),feed conversion ratio(FCR) and feed intake(FI) at d 14,21 and 28,showing that challenged birds fed over-processed MBM had decreased WG(P <0.05) and FI(P <0.05) at d 14,increased FCR(P <0.05) at d 21 and decreased WG(P <0.05) and FI(P> 0.05) at d 28.Birds fed low phytase had increased livability(P <0.05) at d 42.The challenge increased the prevalence and severity of NE induced lesions in the jejunum(P <0.05) and ileum(P <0.05).The birds fed over-processed MBM had decreased pH in the jejunum(P <0.05) and ileum(P <0.05) at d 16.High phytase increased apparent ileal digestibility(AID) of Ca(P <0.05) and P(P <0.05),and over-processed MBM increased AID of carbon(C;P <0.05) and Ca(P <0.05) at d 29.The challenge increased the caecal counts of Lactobacillus spp.(P<0.05) and C. perfringens(P <0.05) at d 16.The results indicated that supplementation of diets with high phytase reduces the negative impact on performance from over-processed MBM during NE as a result of increased nutrient digestibility.