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Table 4: Influence of Phytase Superdose on the Incidence of White Striping and Wooden Breast in Broilers Phytase, FTU/kg None


Trial 1 500


1,500


Trial 2 500


1,500


Trial 3 500


1,500


Average of all 3 trials 500


1,500


23.2 27.8


1.6 0.0


40.2 44.6


21.7 24.1


White Striping Incidence, % Mild


34.5 33.0


84.3 84.3


46.4 46.4


55.1 54.6


utilization become important when considering the increasing costs of poultry feed, the future of mineral supplementation in poultry diets and excretion into the environment, specifically of Zn and Cu, and the use of these micro-minerals to aid in an antibiotic-free production system (EFSA, 2014, 2015).


Poultry Products Increasing incidences of abnormalities in chicken breast muscle have become apparent in recent years. The main myopathies of interest include wooden breast (WB), which is characterized by pale, hard areas on the muscle, and white striping (WS), which is defined by superficial white striations (Sihvo et al., 2013). These abnormalities have been linked to improvements in genetic selection for improved growth rate, carcass yield and feed conversion, attributes that are also associated with dietary phytase supplementation. It is therefore of interest to understand what effect superdosing of phytase might have on breast muscle myopathies. To this effect, three trials were conducted to evaluate superdoses of phytase and the incidence of WS and WB in broilers. The results indicate that the incidence of WS and WB were not significantly influenced by superdoses of phytase, and while the incidence of WB was less prevalent than WS, superdoses of phytase reduced the most severe cases of WB by approximately 25% (Table 4; T. York and C. Walk, unpublished) and this could be as high as 50% in field conditions. The etiology of WS and WB is yet to be determined but most likely


multifactorial, predominantly associated with fast growth of the breast muscle (Russo et al., 2015) and a lack of nutrients to the area, which results in necrosis and an infiltration of immune cells (Sihvo et al., 2013). Eventually muscle fibers are replaced with granulation tissue or collagen-rich connective tissue, which results in the white striations, WB lesions and a higher fat content of the muscle (Sihvo et al., 2013). Due to the improvements in Zn and Fe utilization from superdoses of


PAGE 44 MAY/JUNE 2017 FEED COMPOUNDER Severe


43.2 39.2


14.2 15.7


13.4 8.9


23.6 21.3


None


35.9 38.5


41.7 44.1


66.1 65.2


47.9 49.3


Wooden Breast Incidence, % Mild


49.6 51.1


48.8 48.8


25.0 25.0


41.1 41.6


Severe


14.5 10.4


9.5 6.4


4.5 4.9


9.5 7.2


phytase, it could be hypothesized that the reduction in the incidence of severe WB may be due to the provision of minerals associated with oxygen and antioxidant capacity within the tissues. Previous authors have reported phytase supplementation at levels >1,000 FTU/ kg increased free Fe in vitro and increased hemoglobin (Stahl et al., 1999) or hematocrit concentration (S. Mansbridge, I. Wellock, and C. Walk, unpublished) in the blood of pigs. Other authors reported high levels of phytase (12,000 FTU/kg) enhanced the antioxidant status of


broilers by increasing the concentration of vitamin E, conenzyme Q10 and free retinol in the liver (Karadas et al., 2009). These effects have yet to be determined in the breast muscle of birds fed superdoses of phytase. Regardless, the incidence of WS and WB appears to be related to a multitude of unknown factors, most often cited is fast growth. Therefore, from the current work, it can be concluded that the use of superdoses of phytase will allow for improvements in feed efficiency or further reductions in dietary available P without negatively influencing the incidence of WS or WB and in some cases possibly reducing the most severe forms of WB.


Conclusions In conclusion, superdoses of phytase result in near complete destruction of IP6 as well as a reduction in IP4 and an increase in inositol. This removal of IP6 and phytate esters has been previously associated with improvements in feed efficiency. New data indicate that superdoses of phytase allow for additional improvements in mineral utilization, particularly P, Zn and Fe. These improvements could allow for: 1. reduction in inorganic P in the diet, 2. result in an increase in oxygen capacity or antioxidant status of the bird and a reduction in the incidence of severe breast meat myopathies, or 3. improve the utilization of environmentally interesting minerals, such as Zn or Cu and thereby allow for more precise recommendations of these nutrients in the diet.


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