Validation trial for the prediction model for metabolizable energy upgrading of raw materials by nutrase Xyla in broilers

Introduction

An accurate estimation of the energy value of NSP enzymes and a flexible way to incorporate this in least cost optimalisation was a subject in many broiler studies. The NSP level and NSP characteristics determine the antinutritional effect of a broiler diet and therefore these parameters are important to estimate the energy value of NSP-enzymes. Arabinoxylan (AX), quantitatively the most important NSP structure, is abundantly present in raw materials for broiler diets and can be divided into a WE-AX (water-extractable) and WU-AX (water-unextractable) fraction, each contributing to the overall anti-nutrtional effect in a different way. Nutrase Xyla proved to be effective in hydrolysing both, WE-AX as well as WU-AX. Broiler trials, using feeds with varying WE-AX and WU-AX levels (wheat and/or corn based) showed that the energy uplift obtained by Nutrase Xyla was correlated with the level of WE-AX and WU-AX, as presented by Mombaerts & Van de Mierop (2009).

Enzyme energy factors were calculated to be used in following formula:
ME_poultry+NX = ME_poultry + 100 * WE-AX (%) + 25 * WU-AX (%)

To validate the prediction model, diets with extremely low and high AX levels were composed by using respectively sorghum or rye as main cereal sources. So 4 treatments were included: sorghum control, sorghum + Nutrase Xyla, rye control and rye + Nutrase Xyla were tested.

Materials & Methods

Each treatment had 12 floor pens (6 males / 6 females) of 15 Ross 308 broilers. Feed intake, body weight and mortality were measured on day 11 and day 46, weight adjusted feed conversion (WAFC) was calculated.

Experimental house description and management
The experimental house is divided into pens of equal size, arranged along a central aisle. The birds were kept in 48 floor pens, each an area of 0.8 m², with built up wood ss as bedding. The diets were provided ad libitum in one feeding trough per pen. Water was provided ad libitum with two drinking nipples per pen. Standard floor pen management practices were used throughout the experiment.

Birds
Day of hatch straight run Ross 308 chickens were obtained from Belgabroed, Belgium. The breeder flock history and vaccination record at the hatchery were recorded. The broilers were vaccinated at the farm on day 14 against Gumboro and Newcastle Disease via drinking water. Broiler weights by pen by sex were recorded on days 0, 11 and 46. Feed intake was measured immediately after weighing on day 11 and day 46.

Diets (Table 1)
The rye and sorghum based basal diets were manufactured by Ilvo Merelbeke and Huys feed mill, Belgium, respectively. Once the feed was received at the Zootecnical center of the Catholic University of Leuven, the enzymes were included. All feeds were fed as mash. Quantities of all basal feed and test enzymes used to prepare treatment batches were documented. Each batch of feed was mixed and bagged separately.

Starter feed was fed from day 0 to 11. On day 11, non-consumed starter was weighed by pen and discarded. Grower + finisher feed was issued and fed until day 46. On day 46, non-consumed grower + finisher was weighed by pen and discarded.

Table 1. Diets - basal compositions, nutrient and energy levels (%)

Ingredients	FEED 1 (sorghum)	FEED 2 (rye)
Sorghum	55.30	-
Rye	-	40.00
Soy bean meal 50	30.50	-
Soy bean meal 46		22.70
Full fat soy beans	-	12.00
Wheat	-	9.20
Corn	5.00	5.00
Fat	3.00	6.30
Soy oil	1.50	1.00
Limestone	1.20	0.63
MCP	0.53	1.06
Na-Bicarbonate	0.10	-
L-Threonine	0.09	0.10
DL-Methionine	0.30	0.27
Salt	0.23	0.31
Premix	1.90	1.00
L-Lysine HCl	0.24	0.24
Phytase	+	+
Crude protein	20.3	20.6
Crude fat	6.7	10.9
Digestible Lys	1.04	1.07
ME_broilers (kcal/kg)	2900	2750
ME_poultry (kcal/kg)	3094	3010

Treatments (table 2)

To validate this prediction model, 4 treatments were included. Two groups were included for the very low AX level diets, based on sorghum : sorghum control, sorghum + Nutrase Xyla. Two groups were also included for the very high AX level diets : rye control and rye + Nutrase Xyla.

Table 2. Treatments

	Diets	Enzyme	Inclusion level
1	Feed1: sorghum based	-	-
2	Feed1: sorghum based	Nutrase Xyla	100 ppm
3	Feed 2: rye based	-	-
4	Feed 2: rye based	Nutrase Xyla	100 ppm

Results & Discussion

Results from sorghum groups
The sorghum diet contained 0.1 % WE-AX and 2.5 % WU-AX, giving an expected enzyme ME-effect of 73 kcal. Adding Nutrase Xyla improved body weight gain by 6.7% and FC_C by 2.4 %. This equals an energy liberation of 76 kcal/kg and confirms the estimations based on the enzyme coefficients and the AX profile.

Figure 1. Growth and feed conversion performance in the sorghum diets

Validation trial for the prediction model for metabolizable energy upgrading of raw materials by nutrase Xyla in broilers - Image 1

Results from rye groups
For the rye diets the WE-AX and WU-AX levels were resp. 1.4 % and 3.2 % and so and increase of energy of 220 kcal is expected. Zootechnical results improved by 19.6 % and 9.7 % for resp. body weight and FCC. Energy liberation that correspond with these zootechnical data is 325 kcal/kg. These results demonstrate that the energy uplift, calculated according to the prediction model, even underestimated the actual energy liberation of Nutrase Xyla.

Figure 2. Growth and feed conversion performance in the rye diets

Validation trial for the prediction model for metabolizable energy upgrading of raw materials by nutrase Xyla in broilers - Image 2

Conclusions

It was concluded that the model derived from wheat and corn trials is also valid without overestimation for estimating energy upgrading in diets with other raw materials, even when using extreme AX levels.

Bibliography

Mombaerts R & Van de Mierop K. 2009. Water-extractable (WE-AX) and water-unextractable (WU-AX) arabinoxylans as a prediction tool for AME-upgrading of raw materials with a bacterial endo-xylanase. International Poultry Scientific Forum, Atlanta, GA, USA.