Phytase expressed from Saccharomyces pombe ameliorates footpad lesions in cage‐reared broiler chicks

Abstract Background/aim The condition of footpad is an important aspect of poultry welfare. This is a problem that plagues the poultry industry because it occurs whether birds are reared in the cage or on the floor. It is reported that feeding phytase to floor‐reared broiler chicks could ameliorate footpad lesions, which is related to the reduction of litter moisture. However, some studies reported that phytase supplementation could ameliorate footpad lesions, but did not affect litter quality. Therefore, phytase supplementation may have other potential mechanisms to improve the footpad lesions. Cage‐reared broiler chicks were used in this study because they had no access to litter. Material and methods A total of 234 1‐day‐old broiler chicks were randomly assigned to three groups based on the initial body weight (42.22 ± 0.18 g) with six replicate cages and 13 birds (mixed sex) per cage. The experimental period was 45 days. Dietary treatments were based on a corn–soybean meal‐basal diet and supplemented with 500 and 750 FTU/kg Saccharomyces pombe expressed phytase. The unit of phytase (FTU) was defined as the amount of enzyme that catalyzes the release of one micromole phosphate from phytate per minute at 37°C and pH 5.5. Result and conclusion We found that dietary supplementation of S. pombe expressed phytase could improve calcium and phosphorus digestibility and subsequent improvement in toe ash, thus ameliorating footpad lesions in broiler chicks with no access to litter.


INTRODUCTION
Footpad quality is an important aspect of poultry welfare. When the lesion situation is serious, it will cause pain in birds, thus impairing the feed intake and growth performance. In addition, chicken paw prices have escalated due to an insatiable demand for high-quality paws in export markets. The lesions are a concern to the poultry industry as a cause of product downgrade issues (Shepherd & Fairchild, 2010). The event of footpad lesions occurs in both cage-reared or floor-reared broiler chicks (Roenchen et al., 2007). It has been reported that dietary supplementation of phytase was a way to ameliorate the footpad dermatitis in floor-reared broiler chicks, which was related to the prevention of wet litter (Shepherd & Fairchild, 2010). However, Delezie et al. (2015) noted that the mechanisms of footpad lesions amelioration by supplementing phytase may have other aspects besides improving litter quality. Since the cage-reared broiler chicks had no access to litter, we want to understand better whether dietary supplementation of phytase improves footpad lesions when the factor of litter quality is eliminated.
In addition, the digestibility of phosphorus and calcium, growth performance, and bone ash are commonly used parameters to evaluate the efficacy of phytase (Dersjant-Li et al., 2015). We tested the efficacy of phytase by investigating the apparent ileal digestibility, growth performance, and toe ash, so as to reveal the relationship between phytase supplementation and footpad lesions amelioration. We hypothesized that dietary supplementation of Saccharomyces pombe expressed phytase could improve the apparent ileal digestibility and subsequent improvement in toe ash and growth performance, thus improving footpad lesions in cage-reared broiler chicks. , the stability of this phytase is over 95% after storage in 20 • C environment for 6 months. The optimal pH is 4.5.

Information of phytase
One phytase unit (FTU) was defined as the amount of enzyme that catalyzes the release of one micromole phosphate from phytate per minute at 37 • C and pH 5.5 (EFSA, 2019).

Animals and housing
A total of 234 1-day-old Ross 308 broiler chicks were randomly assigned to three groups based on the initial body weight (

Treatments and diets
The experiment lasted for 45 days and was divided into four phases: Co., Moline, IL, USA). Phytate-P in raw materials and diets was determined using the method described by Reichwald and Hatzack (2008).
Absorbance was determined using a Media spectrophotometer (Mar-  IF is the indigestible-marker concentration in ileal digesta; and AD is the nutrient concentration in diet.

Toe ash
The left and right middle toes were excised from the above eutha-

Footpad lesions score
Lesions score of footpad dermatitis was measured on day 44 for all birds. Footpad dermatitis was scored on a four-point scale: score 0, no lesions on the footpads; score 1, small lesions of the footpad epithelium (< 1 cm); score 2, larger lesions (>1 cm); and score 3, dorsal swelling visible.

Statistical analysis
All data were statistically analyzed using the General Linear Model procedure (SAS Inst. Inc., Cary, NC, USA) in a completely randomized block design. The replicate cage was used as the experimental unit. Orthogonal contrasts were used to examine the linear and quadratic effects in response to increasing the dietary supplementation of phytase. Variability in the data was expressed as the standard error of means (SEM), and p < 0.05 was considered statistically significant.

RESULTS AND DISCUSSION
In the present study, dietary supplementation of S. pombe expressed phytase did not affect the growth performance of broiler chicks ( The mechanism of improving nutrient digestibility by phytase supplementation is generally accepted (Dang & Kim, 2021). Phytase could hydrolyze phytate and release phytate-bound nutrient ingredients, thus improving the utilization of nutrients in animals feed ingredients (Delezie et al., 2015). In this study, broiler chicks fed the diet supplemented with S. pombe expressed phytase increased the AID of calcium (p = 0.036) and phosphorus (p = 0.045), but did not affect the crude protein (Table 3), which was affirmed by the study of Hajimohammadi et al. (2020). In brief, dietary supplementation of 250 and 500 FTU/kg S. pombe expressed phytase could degrade phytate, which was manifested in the increase of the AID of phosphorus and calcium.
Toe ash is one of the sensitive parameters for the utilization of phosphorus and calcium (Garcia & Dale, 2006). In this study, dietary supplementation of S. pombe expressed phytase resulted in an increase of toe ash (p = 0.023; Table 4), which was affirmed by the study of Selle et al. (2009). Therefore, we considered that dietary supplementation of S. pombe expressed phytase could increase the utilization of calcium and phosphorus, which was manifested in the improvement of toe ash.
Footpad quality is an important aspect of poultry welfare. It occurs in both floor-reared or cage-reared birds. It is reported that dietary supplementation of phytase could ameliorate the footpad lesions in floor-reared broiler chicks, which was related to the prevention of wet litter (Shepherd & Fairchild, 2010). However, Delezie et al. (2015) reported that feeding floor-reared broiler chicks with Pichia pastoris expressed phytase did not improve the litter quality, but ameliorate the footpad lesions. In this study, phytase supplementation also ameliorated the footpad lesions in cage-reared broiler chicks (p = 0.044;  Therefore, we considered that the mechanism of improving footpad lesions by phytase supplementation has other aspects instead of the litter quality improvement. Mukovozov et al. (2021) noted that atopic dermatitis in humans was related to poor bone health. In addition, poor absorption of certain minerals could also cause dermatitis in domestic animals (Soetan et al., 2010). The footpad lesions ameliorated by phytase supplementation have been reported to correspond to the improvement of bone quality and phosphorus and calcium digestibility (Shepherd & Fairchild, 2010). Therefore, we considered that the footpad lesions improved by S. pombe expressed phytase supplementation were related to the improvement of phosphorus and calcium digestibility and toe ash.
Therefore, S. pombe expressed phytase supplementation has great significance for ameliorating footpad lesions in cage-reared broiler chicks, which was related to the increase of phosphorus and calcium utilization, manifested in the increase of phosphorus and calcium digestibility and subsequent improvement in toe ash.