Meta-analysis of performance responses of broiler fed diets containing β-mannanase

The β-mannans are commonly present in a wide variety of feedstuffs, including soybean
meal, and have been described as one of the major anti-nutritional factors for non-ruminant
animals. These substances can activate nonspecific responses of the innate immune system
and, thus, may interfere on animal performance by nonproductive energy expenditure. Using
β-mannanase may be an alternative to deal with the problem. In this context, the current study
was developed using meta-analytic techniques to evaluate the effect of β-mannanase on
broiler performance. Thirty-three published papers describing performance of 31,869 broilers
fed diets supplemented with β-mannanase were selected. After the papers selection, the
information related to the proposed theoretical model and other additional variables were
copied from the materials and methods and the results sections in the original publication,
and transferred to an electronic spreadsheet. Codes were used to consider the variability
among the compiled experiments and as qualitative grouping criteria in the analytical models.
Under this later item, the main codes were applied for the supplementation (control
treatments, BM-; or β-mannanase supplemented treatments, BM+). The meta-analysis
followed three sequential analyses: graphic (to evaluate the database quality), correlation (to
identify the factors that should be considered in the statistical models), and variancecovariance
(to compare groups and to generate prediction equations). Dietary
supplementation with β-mannanase did not influence (P > 0.05) feed intake, weight gain, and
final body weight of the broilers. However, β-mannanase improved feed conversion (BM-:
1.77 x BM+: 1.69 g/g; P = 0.03), viability (BM-: 96.9 x BM+: 97.6%; P = 0.06), and the ratio
villus height : crypt depth (BM-: 11.4 x BM+: 11.9 µm/µm; P = 0.01) compared to the
control group. According to the estimated relationship between weight gain and energy
intake, β-mannanase saved 2.7% of metabolizable energy expenditure for growth, which
represented a saving of 187 kcal for each kg of broilers weight gain. Current results indicate
that β-mannanase supplementation may be considered an important tool for poultry
nutritionists searching for improvement in performance indexes.