Effects of varying diet nutrient density and enzyme inclusion strategy for Ross 708 male broilers under a natural disease challenge

Authors: BROWN, ANDREW - Mississippi State University; CANTLEY, STACI - Huvepharma Inc; GUTIERREZ, OMAR - Huvepharma Inc; LEMONS, MARK - Mississippi State University; WAMSLEY, KELLEY - Mississippi State University

Submitted to: Journal of Applied Poultry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2020
Publication Date: N/A
Citation: N/A
DOI: https://doi.org/10.1016/j.japr.2020.09.005

Interpretive Summary: Nutrients within ingredients used for commercial broiler diet formulation are not 100% digestible; to enhance their digestibility, enzymes are commonly added into the feed. Two common enzymes are phytases (enhance calcium and phosphorus) and xylanases (enhance energy use from plant cell wall - fibrous component). These enzymes can work differently depending upon the diet composition. Additionally, certain diets increase a bird's risk of developing unfavorable characteristics such as woody breast (gives breast meat chewy texture), foot pad dermatitis (sores on bird foot caused by excess litter moisture), as well as disease (excess nutrients can feed undesirable bacteria in the bird's gastrointestinal tract). Therefore, the goal of this research was to test varying inclusions of a commercially available phytase and xylanase in diets that varied in ingredient/nutrient composition. Bird performance (feed intake, weight gain, feed utilization) and processing characteristics (breast yield, foot pad dermatitis, woody breast incidence, etc.) were recorded after a 60 day grow-out. Overall, optimal enzyme inclusion strategy differed, depending upon the nutrient density of the diet; however, using the consistent inclusion of phytase and lower tested level of xylanase improved overall breast yield, while only increasing the chance of woody breast slightly. These data can be used by commercial nutritionists to determine an optimal broiler diet formulation, depending upon the ingredient cost and availability.

Technical Abstract: Phytase and xylanase are routinely used to reduce indigestible components and improve broiler performance; however, more research is needed to determine combined enzyme inclusion strategies (EIS) to maximize performance within diets varying in nutrient density (ND). It is also of interest to explore the potential for EIS to assist with disease mitigation. Therefore, a 2 ND (low density [LD]: 5% decrease in energy and digestible lysine; or high density [HD]: 2% increase in energy and 3% increase in digestible lysine) and 3 EIS (EIS1: no enzyme, EIS2:1,500 phytase units [FTU]/kg + 1,500 endopentosanase units [EPU]/kg, or EIS3:1,500 FTU/kg + 1,500 EPU/kg from 0–14 d and 1,500 FTU/kg + 3,000 EPU/kg from 14–60 d) factorial arrangement was used to determine the effects on broiler performance, footpad dermatitis (FPD), woody breast severity (WBS), and breast yield (BY) under a natural disease challenge. The ND specifications were all relative to Ross 708 recommendations. From 0 to 59 d, HD-fed broilers consumed 64 g less feed/bird and had an 18-point reduction in the feed conversion ratio (FCR) compared with those fed LD. In addition, broilers fed EIS2 had an improved FCR by 4 pts vs. EIS1. For BY, a ND × EIS interaction demonstrated that broilers fed HD + EIS3 had the lowest BY and all other treatments were higher, but similar. For FPD, feeding HD diets resulted in increased incidence of “0” scores and decreased “2” scores. Broilers receiving HD demonstrated lower incidences of “1” and “3” scores for WBS than birds receiving LD. Birds fed EIS3 exhibited the lowest WBS score percentage of “1” scores vs. all other EIS. In general, EIS2 improved live performance throughout the experimental periods, but this effect was lost during overall performance; BY was also improved; however, it also increased “1” score incidence for WBS.