Influence of a Mixture of a Patented Activated Clay and Vegetal Extracts on Performance of Broilers Exposed to a Low or High Challenge

Most of published trials are conducted in experimental farms, under good conditions, and generally give better performance than average field ones. We can then question about the practical use of these results in field conditions.

In order to evaluate the influence of the conditions under which a product evaluation is done on the conclusion of the test, a 2x2 factorial study was conducted with broilers from 1 to 42 days of age : animals were submitted or not to a natural challenge based on a combination of stocking density and feed viscosity and received or not a mixture of patented activated clay and vegetal extracts named B-Safe.

Bodyweight and feed intake were recorded. Litter quality, foot-pad and breast skin lesions were scored.

Challenging the chicks significantly decreased weight gain and FCR. B-Safe had a tendency to improve FCR (2.4% in challenging conditions). Challenge had a negative effect on litter score, foot-pad lesions and breast skin scores. B-Safe tended to reduce the adverse effects of the challenge on foot-pad and breast skin lesions (-8.3%).

This trial clearly demonstrated that the conclusion on the efficacy of a feed additive are depending on environmental conditions. Challenging conditions, which are more representative of field conditions, are necessary to evaluate the effects of alternative products on the performance and welfare of poultry.

INTRODUCTION

The ban of antibiotics growth promoters in European countries resulted in many trials to evaluate promising natural alternatives. Most of these studies were carried out under perfect husbandry conditions within experimental research farms, with low stocking density, no restriction of access to feeding and drinking equipment, controlled environmental conditions and low sanitary pressure. However, field conditions are typified by a diversity of production conditions and most of the time, less favorable conditions than in experimental farms (higher sanitary pressure, more competition to feeders and drinkers, ...). Therefore, there is major concern about the validity of extrapolating results from trials conducted under standard experimental conditions to commercial practice, as suggested by Rosen (2003).

Therefore, testing of growth promoting products in non challenging conditions can lead to very limited or lack of response, which would lead to conclude than the product has no efficiency. To illustrate this assertion, Guyonvarch (2007) showed that the average improvement in performance of broilers with avilamycin was about 1% for both growth rate and FCR in 8 trials conducted under standard experimental farm conditions whereas Wellenreiter (2000) and Bories (1998) suggested that avilamycin generally improves growth rate between 2 to 5% and FCR from 0 to 5% in field conditions.

The ideal way to avoid false positive or false negative results would then be to screen the products directly in the field. However, it is logistically impossible in most cases to obtain objective field comparisons of products while using contemporary positive and negative controls. As a consequence, an objective evaluation of products has to resort to using experimental farm trials but they have to be conducted under challenging conditions to ensure results have the maximum practical relevance.

Many challenge protocols have already been proposed in the literature but most the time, performance is significantly reduced due to the influence of one single factor ; as a consequence, this create a bias by selecting products that have a specific action on this factor. For example, challenges based on bacterial inoculation will only help in selection of antibacterial products, but will not help in selection of products that promote growth by another way than bacteria control.

The aim of the current study was first to evaluate the ability of an innovative challenge protocol combining several factors to affect broiler performance, and secondly to compare the response of an alternative growth promoter product in standard experimental farm conditions and in challenging conditions.

MATERIALS AND METHODS

2940 day old Ross 308 chicks as hatched were obtained from 42 weeks of age parent stock.

At arrival, the birds were housed in a close, environmentally controlled barn of experimental farm containing 24 floor pens of 8.2 m² covered by 3 cm of wood shavings.
Temperature and lighting program were similar to field practice.

Feed was provided via a 3-phases feeding program. The nutrient level was as in commercial diets. No feed additive other than phytase and tested additive B-Safe was included in any of the diets. The starter diets contained 100 ppm of monensin and the grower diets 70 ppm of salinomycin. The finisher diet did not contain any coccidiostatic product.

The experiment was set up as a 2x2 factorial design (Challenge x Feed additive B-Safe), with 6 replicates per treatment : (T1) Low challenge x No additive, (T2) Low challenge x B-Safe, (T3) High challenge x No additive, (T4) High challenge x B-Safe.

Low challenge was a combination of low stocking density (12.8 birds/m²) and low viscosity diet (12.1 mPa/s according to Bedford (1993)). High challenge was a combination of high stocking density (17.1 birds/m²) and high viscosity diet (15.1 mPa/s) created by inclusion of rye and barley (Table 1). Low and high viscosity diets had similar nutritional values.

B-Safe is a mixture of patented activated clay and vegetal extracts that had previously shown growth promoting effects (Neovia unpublished trials). The product was included at 2 kg/t of complete feed in starter and grower feeds and at 1 kg/t of complete feed in finisher diet.
Average birds body weight and feed intake per pen were measured at 1, 10, 28 and 42 days of age. Litter quality was visually evaluated on a scale from 1 (very good) to 5 (very bad). 10 male birds per pen (60 birds per treatment) were visually scored at 41 days of age for foot-pad lesions according to Mirabito (2007) and for breast skin lesions on a 0 (no lesion) to 2 scale.

Data were checked with the Dixon-test for outliers before data analysis. Results were analyzed according the following model by using Anova of the statistical package Genstat v.8.2. The body weight at 1 day of age was included as covariate in the model. Mortality, breast skin and foot-pad lesions were analysed by using a binomial general linear model. p<0.05 was retained as significance threshold.

RESULTS

Birds growth in finisher and on the global raising period was significantly affected by the challenge (Table 2) : average daily gain on the control diet was reduced by 13.9% on finisher and by 6.6% on global period due to the challenge. The addition of B-Safe to the diet had no effect on the growth of the animals.

The challenge had also a significant effect on FCR since 10 days of age (Table 3). B-Safe significantly improved FCR on grower and global period (1.5% on grower, 1.9% on global) whatever the challenge condition. The interaction between challenge and feed additive utilisation was not significant but effect of B-Safe on FCR was numerically higher in high challenge condition (2.4% FCR improvement) than in low challenge condition (1.3% FCR improvement).

High challenge conditions significantly degraded litter quality and proportion of animals with severe foot-pad lesions (Table 4) : proportion of animals with foot-pad scores higher than 2 switched from 50% on the low challenge control to 86% in the high challenge control. Interaction between challenge and addition of B-Safe was significant : when the challenge was low, B-Safe tended to degrade quality of litter and foot-pad, but when challenge was high, B-Safe improved the litter and foot-pad quality (- 0.3 points on litter score, 6% less animals with foot-pad lesions higher than 2, and 19% less animals with score 4 than the control). The same observation were done on breast skin lesions.

DISCUSSION AND CONCLUSION

Animals conducted in low challenge conditions obtained at 42 days of age the body weight and FCR expected at 39 days according to the genetic potential of Ross 308, which is quite uncommon in the field. When conducted in high challenge conditions, animals reach at 42 days the body weight expected at 37 days. FCR was also 10% higher than the one enabled at 37 days by the genetic potential, which is more commonly observed in field conditions. So the tested challenge have made experimental farm performance closer from field performance.

The impact on performance and litter quality of the tested feed additive was different according to the challenge condition under which it was tested ; in low challenge condition, B-Safe had no effect on growth, a limited impact on FCR, and little effect on litter quality. In high challenge conditions, B-Safe numerically improved growth (1.6%), improved FCR (2.4%) and improved litter quality and foot-pad lesions (6% less animals with severe lesions than in control).

According to these data, it can be concluded that B-Safe can improve animal performance and welfare when stocking conditions are similar to field conditions. These data also well demonstrate that testing this feed additive only in non challenging conditions would have conducted to a false negative conclusion on the product efficiency.

REFERENCES

Bedford, M.R., and H.L. Classen. 1993. An in vitro assay for prediction of broiler intestinal viscosity and growth when fed rye-based diets in the presence of exogenous enzymes. Poultry Science 72 : 137-143.
Bories G., and P. Louisot. 1998. Rapport concernant l'utilisation d'antibiotiques comme facteurs de croissance en alimentation animale. 30 Mai 1997, 20 pp.
Guyonvarch, A., J. Michard, and G. Benzoni. 2007. Practical selection of alternatives to antibiotic growth promoters. Proceedings of the 16th European Symposium on Poultry Nutrition.
Mirabito, L., M. Colas, C. Arnould, V. Allain, and V. Michel. 2007. Analyse des relations entre differentes lesions indicatrices du bien-etre chez le poulet de chair. Proceedings des 7eme Journées de la recherche avicole : 64-68.
Rosen, G, D. 2003. Setting and Meeting Standards for the Replacement of Pronutrient Antibiotics in Poultry. Proceedings of the 30th Annual Carolina Poulrty Nutrition Conference, Carolina Feed Industry Association, Research Triangle Park : 69-79.
Wellenreiter R.H., D.H. Mowrey, L.A. Stobbs and J.A. d'Assonville. 2000. Effects of avilamycin on performance of broiler chickens. Veterinary Therapeutics 1: 118-124.