Exogenous protease supplementation in broiler chicken diets has primarily been attributed to improvements in protein and amino acids digestibility. Therefore, nutritionists can formulate diets with lower levels of dietary protein while maintaining growth performance.
In a typical wheat-soybean meal-based diet, a reduction of 1% in amino acids reduces feed cost by about 3 AUD/Mt.
The use of exogenous phytase in poultry feed is accepted globally, whilst non-starch polysaccharide enzymes (NSPases) such as xylanase and β-glucanase are commonly used in wheat- and barley-based diets, respectively. However, a combination of 3 or more exogenous feed enzymes is less common. A plethora of publications on protease are available, but reports on the effect of protease in diets that include both phytase and NSPases are less frequent. Recently, a deep litter study was conducted by the University of Sydney on wheat/soybean meal-based diets, including phytase, xylanase and protease at stocking densities similar to commercial practice within Australia.
Standard, positive control (PC) diets were formulated to meet or exceed the 2019 Aviagen Ross 308 nutrition specifications and negative control (NC) diets were formulated with a 5% reduction in both crude protein and digestible essential amino acids. A third treatment group consisted of the NC supplemented with the exogenous protease. All diets contained 1000 FTU phytase and 4000 U of xylanase.
Overall broiler growth to 35 days post-hatch exceeded the Ross 2019 male performance objectives by 10.6% for weight gain (2580 versus 2333 g) and was superior by 5.66% in FCR (1.401 versus 1.485). There was a decline in bodyweight gain and inferior FCR when dietary protein was reduced by 5% (2644 versus 2513 g; P = 0.018 and 1.363 versus 1.432; P = 0.005, respectively). However, the addition of protease ameliorated the loss in performance (2583 g bodyweight gain and 1.408 FCR), and results in the finisher period are illustrated in Fig 1. and Fig 2. It is clearly shown that on the basis of phytase and xylanase, adding protease was able to improve amino acids digestibility further and recover 5% reductions in broiler finisher diet essential amino acids and crude protein without an adverse effect on broiler performance.
Fig 1. Bodyweight gain in male Ross 308 broilers from 22-35 days post-hatch (P = 0.061).
Fig 2. Feed conversion ratio in male Ross 308 broilers from 22-35 days post-hatch (P = 0.008).