In evaluating feed additive supplementation of poultry, growth performance and energy metabolism were essential parameters that were determined. The phytase enzyme is one of the most extensively utilized feed additives in the commercial poultry business. The enzyme phytase was responsible for hydrolyzing the phytate found in poultry feed components. Phytase's ability to improve growth performance and nutrient digestibility in poultry was dependent on the feed composition, mineral content, endogenous microbiota that affects pH range in the gastrointestinal tract, source of phytase, species of birds, and age of the birds (El-Hack et al., 2018; EL Enshasy et al., 2018).
According to numerous publications, the use of phytase improves growth performance, particularly BWG and FCR (Amiri et al., 2021; Babatunde et al., 2020b; Beeson et al., 2017; Y. Dersjant-Li et al., 2018; Khan et al., 2019; Pieniazek et al., 2017). According to the growth performance data, this study confirmed Amiri et al. (2021), who stated that adding phytase (500 FTU/Kg) to experimental diets during the trial period increased broiler body weight gain and improved feed efficiency compared to the control group. Following that, Khan et al. (2019) found that administration of broilers basal diets with phytase (500, 1000, and 1500 FTU/kg) for three weeks (1-21 days old) improved live body weight and feed efficiency (1.4) compared with control treatment without phytase addition.
Phytase activity was pH-dependent, all phytases have a pH optimum that is microbial source dependant, and it affects the capacity of phytase to perform within the GI tracts of animals (El-Hack et al., 2018). Some yeast strains have high viability (more than 50%) at pH 2-3 in vitro assays (Chen et al., 2010; Lohith & Appaiah, 2014), high microbial phytase viability under acidic conditions allows for maximum phytase hydrolysis activity (Yueming Dersjant-Li et al., 2015). Sommerfeld et al. (2018) report that the presence of phytase in the proventriculus (pH 2,5-3,5) and distal ileum (pH 6,5-7,5) improves phytate hydrolysis and the appearance of myo-inositol (Svihus, 2014). The presence of phytase in digesta of the proventriculus and ventriculus suggests that phytase has begun hydrolyzing phytate and releasing nutrients for use by poultry. Therefore, phytase administration may promote weight gain and feed efficiency (Babatunde et al., 2020a). In line with our study, C. tropicalis TKd-3 phytase allowed to improve phytate hydrolysis in the proximal segment of the gastrointestinal tract, particularly in the proventriculus segment, to promote weight gain and feed efficiency performance index.
Metabolic energy was affected by the amount of energy-protein intake and excreted, and also the ability of animals to feed metabolize in the body (Sibbald & Wolynetz, 1986). These results show a positive correlation with the results of the growth performance parameters. The better growth performance associated with the addition of phytase may be related to the increased energy released from the diet due to nutrient digestibility improvement via the release of nutrients bound to phytic acid and increased phosphorus utilization efficiency (El-Hack et al., 2018). He et al. (2017) report that phytase administration in the diet increased daily body weight gain (BWG), serum Ca levels and P tibia level, and apparent digestion of energy in the starter period of broiler. Babatunde et al., (2020a), in their research result, stated that broiler chickens with microbial phytase administration were able to increase their productivity in terms of growth performance, energy and nutrient utilization, and bone mineralization. Santos et al. (2008) found that adding a phytase enhanced ME value by 65–195 kcal/kg in 21-day broilers fed meals containing 500–1000 FTU/kg, and only by about 195 kcal/kg in 22–42-day broilers fed diets containing 750 and 1000 FTU/kg phytase.
The energy improvements mechanism associated with phytase addition may result from the enhancement in protein absorption or increased carbohydrate and fat digestibility due to the dissolution of the phytate complexes (Humer et al., 2015). The ability to counteract endogenous losses by phytase administration may also enhance metabolizable energy by lowering the energy required for maintenance, thereby allowing significantly more energy for growth (D. Wu et al., 2015).
In broiler chickens, adding phytase enzymes to the diet improves the VH and the ratio of VH to CD (Amiri et al., 2021). The capacity for nutritional absorption is highly influenced by the morphology of the small intestine tissue structures, one of which is the villus height structure. The higher the villi structure of the intestine, it is mean the more comprehensive the area of absorption of nutrients (Adil et al., 2010; Brudnicki et al., 2017). Numerous studies have demonstrated that phytase addition supplementation in diet improved the intestinal morphometric indices of broiler chickens (Y. B. Wu et al., 2004; Zaefarian et al., 2013). This experiment confirmed the resulting study of Sajadi Hezaveh et al. (2020), who demonstrated a rise in VH in the small intestine of broiler chickens following feed treatment with phytase.
Karami et al. (2020) also demonstrated consistent results with those obtained in the study. They stated that phytase addition into the diet with a dose of 500 FTU/kg significantly raised VH (P<0.01) of broiler chickens at 28 days of age and significantly increased the value of VH to CD ratio (P<0.01). According to Mohammadagheri et al. (2016), phytase raised VH, lowered CD, and significantly increased VH/CD ratio in broilers. A high VH/CD ratio indicates that broiler chickens have optimally mature enterocytes at the tips of the villi, resulting in increased surface area and absorption. Shallower crypts and longer villi are related to an increased enterocyte lifespan, decreased cell turnover, faster repair of damaged enterocytes, and enhanced intestinal function (Awad et al., 2009). Increased surface area and absorption in the villi of the ileum indicate that the primary function of the ileum in mineral absorption is functioning correctly (Svihus, 2014). According to the present study, addition in broiler chicken diets with L. plantarum A1-E phytase increased the ileal villi surface area, which means that mineral and other nutrient absorption occurred optimally.
This investigation revealed that the highest mineral content in breast meat was detected in samples of meat from FB treated with L. plantarum A1-E phytase. Particularly in kinds of the mineral P, Mg, and Fe. Moreover, the treatment with C. tropicalis Tkd-3 phytase resulted in the highest mineral content in thigh meat, particularly for the minerals Ca, P, Mg, Zn, and Fe. The results showed that the mineral content of the breast meat positively related to the results obtained on the performance of the ileal villi. The high surface area in the FB treatment allowed the optimum mineral absorption, so that the mineral content in the breast meat was higher than the control group. Numerous studies have demonstrated that phytase administration can increase myo-inositol concentrations in the gut and blood (Babatunde et al., 2019; Schmeisser et al., 2017; Sommerfeld et al., 2018; Walk et al., 2019), thereby increasing this molecule availability for peripheral tissue metabolism. Due to the presence of myo-inositol in the blood, the chelate-mineral release effect is enhanced, resulting in the greater availability of minerals that can be absorbed.
According to Ali et al. (2019), the mineral composition of meat was affected by various factors, including species, breeding conditions, age, and nutrient supplementation. Geldenhuys et al. (2015) also stated that the main determinants that affect the mineral content of meat are genetic, gender, environmental, and nutritional factors. In this study, the treatment of different types of phytase gave different responses to the affected broiler meat. An important result in this study was the highest concentration of Fe minerals in the breast meat of the broiler group that received L. plantarum A1-E phytase and thigh meat from the broiler group that received C. tropicalis TKd-3 phytase. These two mineral elements play an essential role in the body of broiler chickens. In this role, Fe contributes to hemoglobin synthesis, oxidation-reduction processes, Fe collaborates with zinc in bone formation, nucleic acid metabolism and protein synthesis, and eggshell formation (Wang et al., 2015).
The result of the tibia mineral content parameter indicated a linear relationship with the highest surface area of an ileal villus in broiler from FB treatment that gave L. plantarum A1-E phytase. In this study, phytase administration at a dose 500 FTU/kg significantly increased tibia mineral content, particularly for minerals P, Mg, and Fe. Bone development depends on the function of the digestive tract, the availability of digestive enzymes, and the number of nutrients absorbed (Palander et al., 2006). In addition, heat stress and hydration (electrolyte balance) also affect health performance and bone structure in poultry. According to Cruvinel et al. (2021), heat stress and electrolyte imbalance affect the bone mineral density of birds (Japanese quail). Antinutritive factors such as phytates found in untreated raw seeds decrease nutrient digestibility and reduce calcium, phosphorus, or iron absorption (Hassan et al., 2003; Muszyński et al., 2018).
Phosphorus is an essential component in broiler diets for proper growth and development. It is the second most of the body prevalent mineral, and a lack of it can lead to rickets, growth retardation, and other skeletal abnormalities. In addition to increasing feed costs, excessive P administration in feed was not used by animals and will be released so that it can damage the environment (Gautier et al., 2017). Rao et al. (2013) stated that the group fed an organic trace mineral supplement diet had higher concentrations of Ca, P, and other trace minerals in their tibia than the group fed an inorganic trace mineral supplement diet. In addition, they also stated that phytase supplementation at the level of 500 FTU/kg in broiler chicken feed would improve the performance of the ileal villi and increase the number of organic trace minerals that could be absorbed.
The results of this study accordance with research from Broch et al.(2021) which states that broilers fed phytase has higher tibia Ca and P content than controls. In line with that, Nourmohammadi et al. (2012) found that there was a 6 percent increase in Mg digestibility in broiler chickens fed phytase supplementation in the diet. The increase in tibia mineral content in the treatment group with phytase supplementation could be caused by the increased availability of Ca, P, Fe, and other minerals released from the complex phytate minerals (Gautier et al., 2018).
Based on the result, it can be concluded that administration of microbial phytase both L. plantarum A1-E and C. tropicalis TKd-3 as a feed additive was able to improve body weight gain, performance index, and tend to increase metabolic energy of broilers. In addition, administration of L. plantarum A1-E as a feed additive improved the morphology of the ileal villus that caused the enhancement of mineral absorption of the ileum, followed by enhancement of mineral deposits tibia.