Validation of the model for prediction of improvement of metabolizable energy by xyla in maize-based diets for broiler chickens

Introduction

For years, many nutritionists around the world thought that NSP enzymes and, more specifically, xylanases, provided little or no benefit when used in diets based on maize-soy.

During the past 10 years, however, a large number of trials with xylanase Nutrase Xyla in maize-soy diets, both in experimental centers as in field, have shown that the product has special features. Research on fattening broilers fed with maize-soy diets with the inclusion of Nutrase Xyla achieved an ME increase that varies from 90 to 120 kcal / kg, depending on the exact composition of the feed.

Based on these investigations, a prediction model was developed to estimate the effect expected from Nutrase Xyla on ME, submitted by Mombaers & Van de Mierop (2009). The model uses the information on the content of water-soluble and -extractable arabinoxylanes (WE-AX) and insoluble/non-extractable (WU-AX) present in the raw materials as a tool for prediction of ME improvement achieved by Nutrase Xyla.

Although the model is based on a large number of studies with animals in separate facilities, using a wide variety of diets and raw materials, nutritionists often want to see the effectiveness of the product confirmed in local conditions. This is mainly due to their own experience and to publications that show a variation of the effect of the enzyme, resulting from interactions with the nutritional level, type of use of fat, by-products, factors of handling, etc. The present study was conducted to test the response of Nutrase Xyla, a pure endo-1, 4-β-xylanase, in broiler chicken production conditions and with the raw materials used in the United States. Other two commercial NSP enzymes, enzyme (h) and (f) enzyme were included as market references.

The H enzyme is a mannanase, mainly aimed at the degradation of the components of soy. The F enzyme is an enzyme cocktail including xylanase and β-glucanase as main activities..

Materials & Methods

The experiment was carried out in pens, with 35 pens with 60 broilers each, in a 50:50 male/female ratio. The five treatments were replicated in 7 blocks with all treatments, randomly, within each block. Southern Poultry Research, Inc. (SPR) performed a randomization procedure for the assignment of treatments and blocks on each pen.

One-day old Cobb Cobb chicks from Pilgrim's Pride, Athens, GA (USA) were used. Batch and vaccination history was recorded by hatchery. The birds were not vaccinated in the trial house; weight was measured by pen and sex on days 0 and 49.

Diets

Southern Poultry Research, Inc. (SPR) supplied all the feed. All basal feed (Table 1) was produced at the feed factory of Georgia University, Athens, GA. All the diets included poultry subproduct flour, DDGS and phytase. Coban (90 g / t) + DMO (50 g / TM) was added to all diets. Once the food was received at SPR, the enzymes were applied post pelletization/extrusion. The amounts of each of the basal feed and trial enzymes used to prepare the batches of feed for the trial were recorded. The enzymes were diluted with water until 1000 ppm were included, to ensure a uniform distribution. Each batch of feed was mixed and packaged separately.

Feed for the initial stage was supplied from day 0 to 21. On day 21, initiation feed that had not been consumed was weighed and discarded. Feed for the growth stage was supplied up to day 35. On day 35, growth feed that had not been consumed was weighed by pen and discarded. Feed for the growth stage was supplied up to day 49. On day 49, growth feed that had not been consumed was weighed by pen and discarded.

Table 1. Basal feed types - Compositions, nutrients (%) and energy levels

	Initial stage feed	Growth stage feed	Final stage feed
	Positive	Negative	Positive	Negative	Positive	Negative
Maize	60.09	56.63	64.19	62.42	70.98	65.92
Soy flour	28.46	27.20	24.04	23.09	18.40	16.95
Wheat bran	-	5.51	-	3.72	-	6.9
DDGS	5.00	5.00	5.00	5.00	5.00	5.00
Subprod.poultry slaughterhouse	3.00	3.00	3.00	3.00	3.00	3.00
Fat	0.87	-	1.14	-	0.53	-
Mineral calcite	0.79	0.89	0.91	1.07	1.03	1.21
DL-Methionine	0.16	0.16	0.18	0.18	0.06	0.06
Lysine	0.11	0.13	0.20	0.22	0.01	0.03
Fitase	0.02	0.02	0.02	0.02	0.02	0.02
Coban	0.09	0.09	0.09	0.09	0.09	0.09
DMO	0.05	0.05	0.05	0.05	0.05	0.05
Premix	1.36	1.32	1.18	1.14	0.83	0.77
Gross protein	21.50	21.50	19.75	19.75	17.50	17.50

Gross fat	3.82	3.05	4.16	3.10	3.68	3.27
Dig. Lysine	1.07	1.04	1.03	1.01	0.74	0.71
Available P	0.45	0.45	0.40	0.40	0.35	0.35
Metabolizable Energy (ME_birds), (kcal/kg)	3029	2930	3084	2987	3128	3029

Treatments (Table 2)

The positive control diets (treatment 1) were formulated to be similar to the standards of the commercial sector and included none of the NSP enzymes.

The negative control diets (treatment 2), and the diets supplemented with enzymes (treatments 3-5) were formulated to be of lower energy content by approximately 100 kcal / kg, without affecting the pattern of amino acids.

In this trial, the reduction of energy was carried out by the substitution of corn, soybeans and fat by bran and wheat sharps (see table 2 for the compositions of diets).

Table 2. Treatments

	Basal feed types	Enzyme	Inclusion
1	Positive control	-	-
2	Negative control (- 100 kcal/kg)	-	-
3	Negative control (- 100 kcal/kg)	Nutrase Xyla	100 g/ton
4	Negative control (- 100 kcal/kg)	Enzyme H	100 g/ton
5	Negative control (- 100 kcal/kg)	Enzyme F	100 g/ton

Results and Discussion

The results in Table 3 and Figure 1 confirm the substantial decrease in performance as result of the decrease of ME in the diets of treatment 2 (negative control) in comparison with treatment 1 (positive control).

The reduction of nutrient values in treatment 2 led to an increase in FCR and significantly lower weight gain.

The statistically significant differences in weight gain and FCR between, treatment 2, on one hand, and treatments 3-5 on the other hand, confirm that the NSP enzymes have an important effect on the performance of fattening broiler chicken fed with a maize-soy diet.

Table 3. Zootechnical parameters (49 days)

	Treatments	Weight (g)	FCR	FCR_corr	Mortality (%)
1	Positive control	2586ª	1.902^c	1.684	6.19ª
2	Negative control	2432^b	2.003^a	1.846	5.24^ab
3	Nutrase Xyla	2586ª	1.913^c	1.695	2.38^b
4	Enzyme H	2549ª	1.955^b	1.747	5.95^ab
5	Enzyme F	2525ª	1.946^b	1.752	4.29^ab

^{Means with unequal letters differ significantly (p < 0.05).}

Figure 1: Zootechnical parameters (49 days)

The performance of birds of the Nutrase Xyla group was identical to the positive control diet, meaning that the estimated nutrient uplift was fulfilled. Enzyme H and enzyme F were also able to improve performance significantly compared to the negative control group. Nevertheless FCR were significantly higher than the positive control and Nutrase Xyla group, which indicates that ME energy upgrading was significantly lower compared to Nutrase Xyla.

Conclusions

Based on the identical weight gain, compared to the positive control group and the almost identical Food Conversion Rate, Nutrase Xyla was the only enzyme that compensated the decrease of 100 kcal / kg of Metabolizable energy in the negative control diets.

The lower weight gains, combined with (statistically significant) food conversion rates for both the H enzyme and the F enzyme, show that the effect of these enzymes on ME in a maize-soy diet for fattening broiler chickens is significantly lower. None of the 2 enzymes was able to overcome the ME reduction of 100 kcal / kg in the diet of the negative control.

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.