High doses of phytase on growth performance and apparent ileal amino acid digestibility of broilers fed diets with graded concentrations of digestible lysine

Abstract

Two experiments of the same design were conducted to determine the influence of phytase on performance and apparent ileal digestibility (AID) of amino acids in broilers fed graded concentrations of digestible lysine (dgLys). Cobb 400, male broilers were allocated to 1 of 16 diets consisting of 4 basal diets formulated at 80, 88, 96, or 104% of the Cobb 400 dgLys requirements for each feeding phase. Phytase was included in each basal diet at 0, 750, 1,500, or 3,000 phytase units (FTU)/kg. In Exp. 1, 33 birds/pen from hatch to day 42 were fed a 2-phase feeding program with 12 replicate pens/diet. In Exp. 2, there were 25 birds/pen from hatch to day 21 and 8 replicate pens/diet. Data were analyzed as a 4 × 4 factorial and means separated using orthogonal contrasts. In Exp. 1, feed intake (FI) increased (quadratic, P < 0.05) as dgLys increased in the diet. Body weight gain (BWG) increased (quadratic, P < 0.05) as dgLys concentration or phytase dose increased in the diet. As phytase dose increased in the diet, feed conversion ratio (FCR) was improved in a linear or quadratic (P < 0.05) manner depending on the dgLys concentration of the diet (dgLys × phytase, P<0.05). In Exp. 2, FI linearly (P < 0.05) increased as dgLys increased in the diet. Increasing the concentration of dgLys or phytase in the diet increased (quadratic, P < 0.05) BWG and improved (quadratic, P < 0.05) FCR. The AID of most amino acids was influenced by a dgLys × phytase interaction (P < 0.05), except threonine, valine, tryptophan, serine, cysteine, or leucine (linear or quadratic effect of phytase, P < 0.05), where phytase improved the AID in birds fed diets containing 80, 88, or 96% of the dgLys requirement, but not birds fed 104%. The predicted dgLys requirement to maximize performance, carcass, and digestible lysine intake was 97.6 to ≥ 104%. The predicted dose of phytase to maximize BWG or FCR was between 1,990 and 2,308 FTU/kg, regardless of the dgLys concentration in the diet. The predicted dose of phytase to maximize carcass weight was between 1,527 and 2,658 FTU/kg of diet and to maximize breast weight was 0 to ≥ 3,000 FTU/kg diet, depending on the dgLys concentration in the diet. In conclusion, optimal performance in the absence of phytase could be achieved at much lower levels of lysine in the presence of phytase.

Comparative aspects of phytase and xylanase effects on performance, mineral digestibility, and ileal phytate degradation in broilers and turkeys

“…There is now considerable interest in understanding the role of higher levels of phytase supplementation than traditionally employed ( Walk et al., 2013 , Kim et al., 2018 , Skřivan et al., 2018 ). This will have implications of wider scope than enhancing P utilization but also on more complete destruction of phytate, the release of lower inositol phosphate esters ( InsPs ), and production of myo -inositol ( MI ) in the digestive tract ( Beeson et al., 2017 , Sommerfeld et al., 2018 , Walk and Rao, 2019 ). In addition, the use of other enzymes, for example xylanase, under such conditions of high levels of phytase supplementation is not clear.…”

Large-scale genomic and transcriptomic analyses elucidate the genetic basis of high meat yield in chickens

“…However, these characteristics are a severe disadvantage in modern aviculture. After decades of directional breeding, the BrP of modern broilers can reach 25% (breast weight to dressed weight) [73] , [74] . This produces a plump carcass, the appearance of which is preferred over that of local breeds in the chicken market.…”

Effect of different phytases derived from E. coli AppA gene on the performance, bone mineralisation and nutrient digestibility of broiler chicken

“…The effect of supplementing microbial phytase does, however, depend on its inclusion rate, form of the diet, bird age and genotype, and nutrient content of the diet (Singh, 2008). However, it has been acknowledged that the source and level of the phytase in feed can influence the magnitude of responses in poultry, both on performance and bone development (Walk et al, 2018;Leyva-Jimenez et al, 2019;Walk et al, 2019). However, the effect of level, source and granulometry of Ca sources has been shown to have a negative impact on phytase activity (Amerah et al, 2014;Delezie et al, 2015;Dersjant-Li et al, 2018;Kim et al, 2018).…”