Evaluation of a carbohydrolase in corn/soybean-based diets for broilers

The search of alternatives for more efficient, lower cost feed formulations is an ongoing effort among nutritionists. In this context, exogenous enzymes have emerged as one of the most important discoveries in the nutrition biotechnology arena. The benefits of using enzymes cannot be denied, and they are now broadly recognized. The use of enzymes in monogastric feeding can be related with the supplementation of enzymes that the body synthesizes only in insufficient amounts, or that it does not synthesize at all. In addition, reduced nutrient excretion, increased nutrient availability, minimum levels of antinutritional factors, intestinal health maintenance, and improved economic viability are additional benefits of using enzyme-based feed additives (Sheppy, 2001; Dallmann et al., 2008). Until recently, carbohydrolases were only added to diets based mainly on alternative ingredients. Nevertheless, it is now recognized that also in feeds formulated with corn and soybean meal as energy and protein sources, respectively, nutrients that in the past were not utilized by birds can now be made available by the addition of these enzymes, due to the presence of up to 14.5% non starch polysaccharides (NSP) in soybean meal (Huisman et al., 1998). NSP exist in nature in various forms, prevailing in plant cell walls. NSP content is reversely related with metabolizable energy (ME) in cereals (Ott, 2005). More recently, enzyme supplementation has allowed nutritionists to decrease nutrient levels in corn/soybean meal-based diets. This is particularly important at times when the cost of feedstuffs raise, resulting in higher formulation costs (Caires et al., 2008). With the above in mind, the purpose of this research was to study the use of an exogenous carbohydrolase in broiler diets, and to evaluate its effects on broiler performance and carcass yield.

The study was undertaken in the experimental farm, College of Veterinary Medicine and Animal Husbandry, University of São Paulo, Brazil. For this purpose, 504 commercial Cobb broilers were distributed using a completely-at-random experimental design with 3 treatments and 14 12-bird repetitions. Treatments included: T1, control diet; T2, diets with reduced nutrient levels, and no enzyme supplementation; T3,  T2 + 50g enzyme/ton. The enzyme consisted of a carbohydrolase, at the above-mentioned dose rates. The nutrient-reduced feed included decreases of 100 kcal ME and 1.5% amino acid and protein levels. Performance parameters studied were body weight (BW), feed intake (FI) and feed conversion rate (FCR) at both 21 and 42 days of age. Diets were formulated based on corn and soybean meal, and birds received water and feed ad libitum (Table 1). In order to evaluate carcass yield, 2 birds per repetition were killed at experiment completion for  carcass yield evaluation in terms of total carcass/breast/leg yields. Data was subjected to analysis of variance using the GLM procedure by SAS (2002). Whenever significant differences were found, Tukey´s test was applied (<0.05).

Table 1. Experimental diet composition

Broiler performance results at 21 days of age showed decreased FI and decreased FCR in the animals receiving the carbohydrolase-supplemented diet (Table 2). At 42 days of age FI was not affected by the experimental treatments, but diets supplemented with 50 g/Ton carbohydrolase gave improved WG and FCR (Table 3). Zanella et al. (1999) observed improved performance in broilers fed carbohydrolase-containing feeds. As far as carcass yield is concerned, birds supplemented with 50g/Ton enzyme showed higher carcass yields (P<0.05) than all other treatments. These results match those obtained by Ahmadauli et al. (2008), who found improved breast yields in animals fed a carbohydrolase. Enzyme-improvement of the parameters evaluated can be the result of increased nutrient availability.

Table 2. Performance of broilers fed carbohydrolase-supplemented feeds (1 - 21 days)

Table 3. Performance of broilers fed carbohydrolase-supplemented diets (1-42 days)

Table 4. Carcass yield in broilers fed carbohydrolase-supplemented diets

Broilers are sensitive to reduced nutrient densities beyond dietary specifications, resulting mainly in decreased weight gain. Feed supplementation with a product effective in breaking down non starch polysaccharides can result in the full recovery of broiler performance when fed low nutrient diets, as compared with the positive controls. This study demonstrated that carbohydrolase, at an inclusion level of 5 kg/Ton, does work in corn/soybean-based diets for high yield broiler strains, and it can contribute 100 kcal metabolizable energy/kg plus 1.5% amino acids.

Ahmadauli O, Eslami, M, Fayazi J. 2008. The effects of using the multi carbohydrase preparation in diets containing canola meal on performance of broiler chickens. Intern. J. Poult. Sci. 7:919-924.

Caires CM, Fagundes NS, Fernandes EA. 2008. Rev Elet Nut. 5:491-497.

Dallmann HM, Dallmann PR, Maier JC, et al. 2008. In: Congresso Brasileiro de Medicina Veterinária, Conbravet, 2008, Anais.., Gramado: Conbravet, 2008, CD-Room

Huisman MMH, Schols HA, Voragen AGJ. 1998. Cell wall polysaccharides from soybean (Glycine max) meal. Isolation and characterization. Carbohydr Polym. 37:87-95.

Ott RP. 2005. Utilização de carboidrases em dietas para frangos de corte. Dissertação de Mestrado. Universidade Federal do Rio Grande do Sul. 83p.

SAS Institute, 2002. SAS User´s Guide: Statistics, SAS Institute Inc, Cary, NC.

Sheppy, C. 2001. Farm Animal Nutrition, CABI, New York.

Zanella I, Sakomura NK, Silversides FG, et al. 1999. Effect of enzyme supplementation of broiler diets based on corn and soybeans. Poult. Sci. 78:561-568.