Effect of different doses of phytase and protein content of soybean meal on growth performance, nutrient digestibility, and bone characteristics of broilers

Abstract

This study evaluated the effects of high phytase doses and soybean meal ( SBM ) with different CP content on growth performance, ileal nutrient digestibility, digestible energy, plasmatic myo -inositol, phosphate release in vitro, and bone composition of broiler chickens. One thousand two hundred 1-day-old broilers were distributed in a 2 × 2 completely randomized factorial arrangement, with 2 phytase doses (1,000 and 2,500 phytase units [ FYT ]/kg of feed) and 2 SBM with different CP concentrations (45 and 47%), totaling 4 treatments with 12 replicates of 25 birds each. The chickens received feed and water ad libitum. Diets were based on corn and SBM, with different inclusions of soybean hull used to dilute the CP content of SBM according to each treatment. The inclusion of 2,500 FYT increased weight gain from 0 to 21 d ( P < 0.05), whereas growth performance from 22 to 42 d was not affected, and SBM had no effect on growth performance. At day 21, ileal digestibility of dry matter, ash, and P, and digestible energy were greater in diets with 2,500 FYT/kg ( P < 0.05), as well as phosphate in vitro release ( P < 0.01) compared to the lower dose. At day 42, diets with SBM 47% CP and 2,500 FYT/kg promoted greater digestibility of dry matter, ash, CP, Ca, P, and digestible energy ( P < 0.001), and greater phosphate release ( P < 0.05) in comparison to other treatments. myo -inositol level in the plasma at 21 and 42 d was higher with the use of 2,500 FYT compared to 1,000 FYT ( P < 0.05). The higher phytase dose increased tibia ash, toe ash, and Seedor Index ( P < 0.05) at day 21, and the Ca content in tibia was higher with 2,500 FYT and SBM 47% CP at day 42. In conclusion, higher phytase doses for broilers improve weight gain, myo -inositol provision, and bone mineral composition. Nutrient ileal digestibility can be enhanced by higher phytase doses when in combination with SBM of greater nutritional quality.

The Duration of the Trial Influences the Effects of Mineral Deficiency and the Effective Phytase Dose in Broilers’ Diets

“…As birds’ feed intake is based on the dietary energy level, the higher availability of some nutrients (including energy) in diets with added phytase could explain the reduced intake and improved conversion rate of animals fed with added phytases. Moreover, an age effect on phytase efficacy, according to which this effect is more evident in young animals due to the immaturity of the digestive enzymes and acids, has been reported by other studies in broilers [ 19 , 20 , 33 ] and in pigs [ 29 ].…”

Effect of Phytase Level and Form on Broiler Performance, Tibia Characteristics, and Residual Fecal Phytate Phosphorus in Broilers from 1 to 21 Days of Age

“…In two of their experiments, they observed higher day-21 BW for birds fed diets with 1000 FTU of an uncoated phytase, compared to birds fed diets with the same inclusion of a coated phytase and a negative control with no phytase inclusion. Several studies have obtained similar results of increased body weight and feed intake with phytase supplementation at low and high inclusion levels [ 40 , 41 ]. This may be caused by the activity of phytase in the gastrointestinal tract, which contributes to the breakdown of IP 6 and lesser phytate esters, therefore increasing the availability of phytate-bound nutrients [ 41 , 42 ].…”

“…Several studies have obtained similar results of increased body weight and feed intake with phytase supplementation at low and high inclusion levels [ 40 , 41 ]. This may be caused by the activity of phytase in the gastrointestinal tract, which contributes to the breakdown of IP 6 and lesser phytate esters, therefore increasing the availability of phytate-bound nutrients [ 41 , 42 ]. Additionally, these data indicate that apart from improving nutrient utilization, phytase also stimulates a feed intake response and, consequently, improves BW.…”

“…The results for FCR that were obtained in this study suggest that phytase inclusion in diets with reduced Ca and aP is able to prevent the P deficiency effects on growth performance parameters, thus allowing birds to match the performance of birds fed nutrient-adequate diets [ 41 ]. Dersjant-Li et al [ 45 ] obtained similar results when using a dose of 1000 FTU/kg of a coated phytase in diets with different reduced Ca levels.…”

“…In addition, Walk et al [ 20 ] and several other authors have observed that tibia ash and other bone parameters improve with phytase addition [ 36 , 39 , 52 ]. This indicates a positive effect of phytase in bone mineralization, which is associated with an increase in the amount of aP [ 41 ]. Moreover, these results suggest that phytase supplementation is beneficial for bone mineralization and is in accordance with the data obtained for growth performance measurements.…”