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Published on: September 7, 2015
Impact of dietary exogenous feed enzymes on performance, nutrient digestibility, and ruminal fermentation parameters
I M Ferreira1, H C Mantovani2, M Vedovatto3
1Department of Animal Science, Universidade Estadual Paulista "Júlio de Mesquita Filho" (UNESP), Jaboticabal, São Paulo, Brazil; Agência Paulista de Tecnologia dos Agronegócios (APTA), Colina, São Paulo, Brazil; Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, USA.
Abstract:
Exogenous feed enzymes (EFE) are incorporated into beef cattle diets to improve nutrient utilization and animal performance. This meta-analysis estimates the effects of EFE inclusion on beef cattle performance, feed intake, nutrient digestibility, and ruminal fermentation parameters, while also identifying factors influencing these outcomes. We initially screened 94 articles, and 23 studies met the eligibility criteria, contributing data from up to 83 treatment means. The magnitude of the effect (size effect) was determined using weighted mean differences (WMD) between the EFE-treated and control groups (diets without EFE inclusion). Heterogeneity was assessed through meta-regression and subgroup analysis. Results indicated that EFE inclusion did not affect final BW (P ≥ 0.871), DM intake (P ≥ 0.467), average daily gain (P ≥ 0.145), or feed efficiency (P ≥ 0.417). However, a significant increase in hot carcass weight (P = 0.047; WMD = 2.21 kg) was observed. The inclusion of EFE in the diet did not affect the profile of ruminal short-chain fat acid (P ≥ 0.225) or ruminal ammonia nitrogen concentration (N-NH3; P = 0.143). However, EFE inclusion improved the digestibility of DM (P < 0.01; WMD = 16.9 g/kg), CP (P = 0.003; WMD = 20.2 g/kg), and NDF (P = 0.003; WMD = 20.2), with no effect on organic matter or starch digestibility (P ≥ 0.388). Heterogeneity was low (I2 < 25%) for most performance and nutrient digestibility outcomes, indicating consistent effect size estimates. Moderate heterogeneity (P ≤ 0.057; I2 = 25-50%) was noted for DM and NDF digestibility, with EFE application explaining 28.2% of the variability in DM digestibility (P = 0.032), and fully accounting for the heterogeneity in NDF digestibility (P = 0.045). High heterogeneity was found in ruminal fermentation parameters (P < 0.01; I2 > 50%). Funnel plot analysis revealed no publication bias for most variables (P ≥ 0.10). Overall, this meta-analysis demonstrates that EFE inclusion in beef cattle diets increases hot carcass weight, likely due to enhanced digestibility of DM, CP, and NDF, without affecting rumen fermentation parameters.
