Protease supplementation reduced the heat increment of feed and improved energy and nitrogen partitioning in broilers fed maize-based diets with supplemental phytase and xylanase

Authors: McCafferty, Klint; CHOCT, MINGAN - University Of New England; MUSIGWA, SOSTHENE - University Of New England; MORGAN, NATALIE - University Of New England; COWIESON, AARON - Dsm Nutritional Products, Ltd; MOSS, AMY - University Of New England

Submitted to: Animal Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2021
Publication Date: 1/21/2022
Citation: Mccafferty, K.W., Choct, M., Musigwa, S., Morgan, N., Cowieson, A., Moss, A. 2022. Protease supplementation reduced the heat increment of feed and improved energy and nitrogen partitioning in broilers fed maize-based diets with supplemental phytase and xylanase. Animal Nutrition. 10:2022, 19-25. https://doi.org/10.1016/j.aninu.2021.10.011.
DOI: https://doi.org/10.1016/j.aninu.2021.10.011

Interpretive Summary: Mono-component feed enzymes, such as protease, may be included in commercial broiler diets due to their positive effects on crude protein and amino acid digestibility. Improvements in broiler energy utilization have also been reported with protease supplementation. However, the source and magnitude of these energy-sparing effects have not been well defined. This study was conducted to evaluate the effects of supplemental protease and digestible amino acid concentrations on energy and nitrogen partitioning and live performance of broilers from 1 to 35 d of age. These results demonstrated protease and digestible amino acid concentrations interacted to affected feed conversion (29 to 35 d of age), energy partitioning, and utilization efficiency, with protease responses being most apparent in diets formulated with reduced digestible amino acids concentrations. Protease supplementation did not affect apparent metabolizable or net energy of diets, but significantly decreased heat increment of feed, demonstrating that mode of action of protease extends beyond direct digestibility to net effects, which may have altered maintenance energy requirements. This information is important for nutritionists at broiler production facilities, universities, and feed companies for determining the value of supplemental protease on broiler growth performance and dietary energy utilization.

Technical Abstract: An experiment was conducted to explore the effects of digestible amino acid (dAA) concentrations and supplemental protease on live performance and energy partitioning in broilers. Ross 308 male broilers (n = 288) were distributed into 24 floor pens and offered 1 of 4 dietary treatments with 6 replicates from 1 to 35 d of age. Dietary treatments consisted of a 2 × 2 factorial arrangement with dAA concentrations (standard and reduced; 34 g/kg below standard) and supplemental protease (without or with) as the main factors. At 1, 15, 28, and 35 d of age, feed and broilers were weighed to determine live performance. From 20 to 23 d of age, a total of 32 birds (2 birds/ chamber; 4 replicates) were placed in closed-calorimeter chambers to determine respiratory exchange (heat production; HP), apparent metabolisable energy (AME), retained energy (RE), and net energy (NE). From 29 to 35 d of age, supplemental protease in the reduced-dAA diet decreased broiler FCR by 5.6 points, whereas protease supplementation in the standard-dAA diet increased FCR by 5.8 points. The indirect calorimetry assay revealed that supplemental protease decreased (P < 0.05) the heat increment of feed (HIF) by 0.22 MJ/kg. Also, from 20 to 23 d of age, broilers offered the reduced-dAA diet with supplemental protease had a higher daily BWG (+10.4%), N intake (+7.1%), and N retention (+8.2%) than those offered the standard-dAA with supplemental protease. Broilers offered the reduced-dAA without supplemental protease exhibited a 3.6% higher AME: crude protein (CP) than those offered other treatments. Protease supplementation in the standard- and reduced-dAA diets resulted in 2.7 and 5.6%, lower AME intake: N retention ratios, respectively, compared with the unsupplemented controls. Reduced-dAA increased (P < 0.05) AME intake (+4.8%), RE (+9.8%), NE intake (+5.8%), NE intake: CP (+3.0%), and RE fat: RE (+8.6%). Protease supplementation increased (P < 0.05) respiratory quotient (+1.2%) and N retention: N intake (+2.2%), NE: AME (+1.9%), and reduced HP (-3.6%), heat increment (-7.4%), and NE intake: N retention (-2.5%). In conclusion, protease positively affected FCR and energy partitioning in broilers; responses were most apparent in diets with reduced-dAA concentrations.