APSS 2013 Proceedings - The University of Sydney

Aust. Poult. Sci. Symp. 2013.....24
CARBOHYDRASES IMPROVE PERFORMANCE OF BROILERS FED BOTH
NUTRITIONALLY ADEQUATE AND DOWNSPEC WHEAT DIETS
D. WU 1 , R.A. SWICK 1 , Y.G. LIU 2 , S.B. WU 1 and M. CHOCT 3
Although the main non-starch polysaccharides (NSPs) in wheat are arabinoxylans,
considerable amounts of β-glucan and cellulose are also present. In soybean meal (SBM) and
canola meal, the major polysaccharides are pectins and cellulose. Since more plant
ingredients containing different forms of NSPs are being used for diet formulations, an
enzyme combination with additional activities each differing in substrate preference may
further enhance nutrient utilization. A study was conducted to investigate the use of Rovabio
Excel LC (liquid), an enzyme complex containing 19 carbohydrase activities on broilers fed a
nutritionally adequate or downspec diet. The positive control (PC) was a nutrient adequate
wheat-SBM based diet with its specifications varying according to starter, grower and
finisher stages. Nutrient levels in the negative control (NC) were 0.366 MJ/kg ME and 1.5%
digestible amino acids (DAA) lower compared to PC. A total of 1008 day-old Ross broiler
chicks were randomly allocated to four treatments with seven replicates of 36 birds each and
reared until d 42. It was a 2 x 2 factorial design where PC and NC either contained Rovabio
Excel (200ml/tonne) or did not. On d 27 and d 42, ileal digesta samples from each pen were
collected for the analysis of nutrient digestibility and viscosity.
Birds fed the downspec diet had 2.3% poorer FCR (P < 0.01) at the end of the
experiment. Inclusion of Rovabio Excel improved body weight by 3.2% (P < 0.05) and FCR
by 3.1% (P < 0.01) from 0 to 42 days. Ileal viscosity was reduced in birds consuming feed
treated with Rovabio Excel on day 42 (P < 0.05) with a trend for reduced viscosity from
Rovabio Excel on day 27 (P = 0.07). From 0 to 27 days, Rovabio Excel significantly
improved apparent ileal digestibility of crude protein (P < 0.01) regardless of the diet type.
The addition of Rovabio Excel possibly improved protein digestion by depolymerizing
viscous NSPs thus allowing endogenous proteases to better access the substrate. The
breakdown of physical entrapment of protein in plant cell wall architecture may be another
essential mechanism through which the enzyme complex exerted its action. Overall, the
inclusion of a multi-carbohydrase enzyme complex reduced the ileal digesta viscosity and
enhanced the crude protein digestibility, leading to a complete offset of the performance loss
of birds fed the downspec diet.
Table 1 - Performance of broilers fed Rovabio Excel from 0 to 42 days
Treatment
means
Weight
kg/bird
Intake
kg/bird FCR
Livability
%
PC 3.246 5.227 1.633 b 92.6
PC + RB XL 3.343 5.212 1.580 a 93.1
NC 3.235 5.320 1.669 c 96.6
NC + RBXL
3.345 5.336 1.617 b 93.1
Main effects and interactions
Diet NS NS < 0.01 NS
RBXL