Effects of phytase supplementation and increased nutrient density on growth performance, carcass characteristics, and hypothalamic appetitive hormone expression and catecholamine concentrations in broilers from 1 to 43 days of age

Effect of 25-hydroxycholecalciferol and high phytase doses on performance, vitamin D status, bone mineralization, and mechanistic target of rapamycin gene expression of broilers

The use of exogenous phytase and vitamin D3 metabolites such as 25-hydroxycholecalciferol (25-OH-D3) for poultry is well consolidated, but the potential for additive effects when supplementing both requires further investigation. This study investigated possible interactions between supplementation of 25-OH-D3 and high doses of phytase for broilers fed Ca- and P-deficient diets. A total of 1 200 one-d-old male broiler chicks were randomly allocated from one of four dietary treatments in a 2 × 2 factorial arrangement: 600 or 2 000 phytase units (FYT)/kg and with or without the inclusion of 25-OH-D3 at 69 µg/kg, with 12 replicates of 25 broilers each. Two feeding phases were stablished (1-to-21 and 22-to-42 d) and all diets contained commercial levels of vitamin D3 (100 µg/kg) with total Ca and available P respectively set to 0.6 and 0.3%. Supplementation with 25-OH-D3 increased body weight gain (BWG) and reduced feed conversion ratio (FCR) from 1 to 21 d (P < 0.05), as well as increased BWG from 1 to 42 d (P < 0.05). Serum 25-OH-D3 levels at 21 and 42 d were increased with 25-OH-D3 (P < 0.001). Phytase did not affect growth performance from 1 to 21 d, but a higher dose (2 000 FYT/kg) reduced feed intake and FCR from 22 to 42 d compared to 600 FYT/kg, also reducing FCR in the total period (P < 0.05). The mRNA expression of mechanistic target of rapamycin in breast muscle assessed at 42 d was enhanced with 2 000 FYT/kg (P < 0.001). Bone weight, bone contents of ash, Ca, and P, and bone breaking strength of tibia bone measured at 42 d were not affected by any dietary treatment. Although both additives are known to improve dietary Ca and P utilization, there were no detected additive or synergic effects. The results suggested that the inclusion of 25-OH-D3 and phytase combined with regular vitamin D3 levels can help minimize losses of performance and bone mineralization of broilers fed Ca- and P-deficient diets. Furthermore, vitamin D status is refined with dietary 25-OH-D3 and potential improvements on breast meat yield can be obtained with a high phytase dose of 2 000 FYT/kg.

A novel consensus bacterial 6-phytase variant supplemented to an all-vegetable broiler diet totally replaced added trace minerals including zinc, iron, copper and manganese in two experiments

Two experiments tested the effect of a bacterial 6-phytase (PhyG) supplemented to a vegetable broiler diet without or with added trace minerals (TM), on growth performance and TM utilization. Each tested 12 treatments in a 2 × 6 factorial arrangement with 3,360 Ross 308 males (35 birds/pen, 8 pens/treatment) in a randomized complete block design. Phytase levels comprised no PhyG or PhyG at 2,000, 1,500 and 1,000 FTU/kg during 0 to 10, 10 to 20 and (Experiment 2) 20 to 35 d of age, respectively; TM diets comprised: no added TM (diet 1); 10, 15, 3 and 10, or 20, 30, 6 and 20 mg/kg of Zn, Fe, Cu and Mn as sulphate (diets 2 and 3); 15, 3 and 10 mg/kg of Zn, Cu and Mn as oxide and 15 mg/kg Fe as sulphate, or 30, 6 and 20 mg/kg of Zn, Cu and Mn as oxide and 30 mg/kg Fe as sulphate (diets 4 and 5), and; 10, 3, 15 and 10 mg/kg of organic Zn, Cu, Fe and Mn (diet 6). Apart from no added TM, basal diets were nutritionally adequate; phytase-supplemented diets were reduced in Ca and retainable P. All diets were pelleted and fed ad libitum. In both experiments during all phases there were interactions (P < 0.05) between phytase and TM on BW, BW gain (BWG), feed intake (FI), FCR (experiment 2 only) and tibia Zn. Without phytase, TM improved (P < 0.05) these measures. Phytase without TM increased (P < 0.05) d 35 BW, overall BWG and FI, equivalent to or beyond the level achieved by TM without phytase. Tibia Zn at d 10 and 20 in Experiment 2 was increased by phytase beyond the level achieved by TM without phytase (P < 0.05). Phytase also increased (P < 0.05) liver Zn, Fe, and Mn at d 10 and 20 and plasma Zn at d 20 d. There was no consistent effect of TM source or dose on bird responses. In conclusion, PhyG phytase replaced the effect of added TM on performance during 0 to 35 d of age and could support a reduction in commercial dose levels of added TM in all-vegetable broiler diets.