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

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.