Evaluation of a Novel Bacterial 6-Phytase on Growth Efficiency of Broilers at 35 Days of Age

In all vegetable-based diets such as wheat, corn and soybean meal, up to 83% of dietary phosphorus (P) is bound to phytate (Li et al., 2016; Aureli et al., 2017). Phytate is known to contain bound P that is unavailable to the broilers, resulting in the use of inorganic-P sources such as monocalcium phosphate and dicalcium phosphate (NRC, 1994) in order to fulfill the broiler P requirements. However, the use of inorganic-P sources in broilers not only increases the feed cost but results also to an increase of P released resulting in environmental issues. So, nowadays, the most efficient strategy to optimize P utilization in poultry is through supplementation with exogenous phytase. This in turn allows for reductions in the use of expensive inorganic P and increases the utilization of phytate-P. Therefore, three experiments were conducted to evaluate the efficacy of a biosynthetic bacterial 6-phytase produced by Trichoderma reesei on growth performance of broilers from 0 to 35 days of age.

Three broiler performance studies were conducted in three different research facilities. Design was the same for all studies, with three treatments: a positive control (PC) diet formulated to meet or exceed the requirements of birds (starter phase: ME= 12.97 MJ/kg, dig. Lys = 1.22%, Ca =0.90% and avP = 0.41% and grower phase: ME= 13.18 MJ/kg, dig. Lys = 1.01%, Ca =0.60% and avP = 0.32%), negative control (NC) diet reduced by 0.15% units in avP and Ca compared to the PC diet, and the NC diet supplemented with phytase at 500 FTU/kg diet (NC + Phytase) from one to 35 days of age.

The type and nutritional composition of the diets between the 3 studies is quite similar. Experiments 1 and 2 were based on corn-soybean meal diets, whereas the third experiment was based on corn-wheat-soybean meal diets. Same feeding program (starter from d1 to d21 and grower from d22 to d35) was used in the three studies. The 6-phytase (Rovabio PhyPlus, Adisseo France S.A.S, Antony, France) was diluted with water at the rate of one liter per ton feed to spray application in order to provide 500 FTU/ton of feed. Diets without phytase (NC and PC diets) were sprayed with water. Feed and water were provided ad libitum. For each study, a total of 2,160, 1, 296 and 1, 200 one-day-old male Ross 308 chicks were individually weighed and then randomly allocated in 48 (45 birds/pen), 72 (18 birds/pen) and 48 (25 birds/pen) floor pens for trials 1, 2 and 3, respectively.

In each trial, body weight (BW), average daily feed intake (ADFI), average daily feed intake (ADFI), corrected for mortality feed conversion ratio (mFCR), and mortality were measured on a pen basis throughout the experimental period. In addition, BW gain corrected FCR (FCRc) was determined for the global period.

Raw data from growth studies were subjected to ANOVA, with trial, block, and treatment as fixed effects using the ANOVA procedure of XLSTAT to establish differences among diets. In addition, orthogonal contrasts were done to compare NC diet vs. PC diet and NC + Phytase vs. PC diet. Statistical significance was set at P ≤ 0.05.

The P and Ca deficiency in the NC diet resulted in a lower final BW (-7.9%, P< 0.001), ADFI ( -8.0%, P < 0.001) and ADG (-8.0%, P < 0.001) accompanied with higher FCRc (+2.2%, P < 0.001) and mortality (+1.6% unit, P = 0.03) compared with the PC diet (Table 1). These results are in accordance with those reported in several studies showing that dietary reduction in Ca and particularly in avP resulted in a significant decrease of growth performance and an increase in FCRc in broilers (Vieira et al., 2015; Scholey et al., 2018; Jlali et al., 2021). Such findings confirm the essentiality of P and Ca in regulating feed intake and growth performance in broilers (Waldroup, 1999). P and Ca are also essential minerals required for normal muscle and bone development and play vital roles in maintaining osmotic and acid-base balance, energy metabolism, amino acid metabolism, and protein synthesis (Underwood and Suttle, 1999; Proszkowiec-Weglarz and Angel, 2013; Li et al., 2016). The supplementation of NC diet with phytase at 500 FTU/kg diet improved the final BW (+9.9%, P< 0.001), ADG (+10.2%, P< 0.001), ADFI (+10.7%, P< 0.001), and FCRc (-1.8%, P = 0.0003). In addition, it decreased (P = 0.02) the percentage of mortality by 1.9% in comparison with the NC diet. Since phytate is considered as an antinutrient in poultry (Woyengo and Nyachoti, 2013; Dersjant-Li et al., 2015), these improvements on performance as also reported by Amerah et al. (2014) and Dersjant-Li et al. (2020), indicate the effectiveness of the phytase used to improve the P and Ca availability for broilers by acting on its substrate (phytate-P) and by limiting the negative interactions between phytate and other dietary nutrients including Ca within the gastrointestinal tract. The orthogonal contrasts showed that performance parameters were not statistically different in birds fed adequate-nutrient PC diet and those fed NC diet deficient in avP and Ca supplemented with phytase.

In conclusion, this study showed that this novel phytase added at 500 FTU/kg diet allowed birds fed diets reduced in P and Ca to reach a growth performance similar to that of birds fed a diet adequate in all nutrients in a more economically and sustainable way. Thus, avP and Ca can be lowered similarly by 0.15% unit in phytase-supplemented diets without compromising feed efficiency and reducing the production cost of broilers.