Abstract
A total of 420 day-old male Ross chicks were weighed at d 1 of life and assigned to test diets to assess the efficacy of a new Buttiauxella spp. phytase expressed in Trichoderma reesei. Diets were: positive control (PC) adequate in nutrients and negative control (NC) diet (40% and 17% less available phosphorous (P) and calcium (Ca), respectively) supplemented with 6 levels of phytase 0, 250, 500, 750, 1,000, and 2,000 phytase units (FTU)/kg of diet. All diets had titanium dioxide as digestibility marker and each diet was allocated to ten cages (6 birds/cage). Diets were fed for 3 wk to measure growth performance, apparent retention (AR) on d 17 to 21 and bone ash and ileal digestibility (AID) on d 22. Growth performance and nutrient utilization was lower (p<0.05) for NC vs PC birds. Phytase response in NC birds was linear (p<0.05) with 2,000 FTU showing the greatest improvement on body weight gain (20%), feed conversion (7.4%), tibia ash (18%), AR of Ca (38%), AR of P (51%) and apparent metabolizable energy corrected for nitrogen (5.1%) relative to NC. Furthermore, phytase at ≥750 FTU resulted in AID of total AA commensurate to that of PC fed birds and at ≥1,000 FTU improved (p<0.05) AR of P, dry matter, and N beyond that of the lower doses of phytase and PC diet. In conclusion, the result from this study showed that in addition to increased P and Ca utilization, the new Buttiauxella phytase enhanced growth performance and utilization of other nutrients in broiler chickens in a dose-dependent manner.
Highlights
Amongst the biotechnological feed enzyme additives, microbial phytases have made the most progress and impact in feed industry
The objective of the study was to assess the efficacy of Buttiauxella phytase expressed in Trichoderma reesei over a range of doses on growth performance, nutrient retention and bone mineralisation in young broiler chicken
Apparent ileal digestibility (AID) and apparent retention (AR) of nutrients and apparent metabolizable energy corrected for nitrogen (AMEn) were calculated as described by Woyengo et al (2010)
Summary
Amongst the biotechnological feed enzyme additives, microbial phytases (myo-inositol [1,2,3,4,5,6] hexakisphosphate phosphohydrolases) have made the most progress and impact in feed industry. Rapid penetration of phytase in poultry nutrition has been associated with the acceptance as a replacement for inorganic phosphates and concomitant considerable investment in application research, leading to strategic development of highly efficacious microbial phytases (Selle and Ravindran 2007; Adeola and Cowieson, 2011; Kiarie et al, 2013). Data demonstrating consistent effects of microbial phytases on utilization of other nutrients than release of phytate-bound P has been very variable. For amino acids (AA), Ravindran et al (1999) and Rutherfurd et al (2002) reported that exogenous phytases increased the ileal digestibility of AA, whereas Rutherfurd et al (2004) and Zhang et al (1999) observed no such effect. A review of several independent studies showed that the improvement of phytase supplementation on energy utilization in broiler chickens ranged from –0.7% to 5.2% (Selle and Ravindran, 2007)
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