BOARD-INVITED REVIEW: Opportunities and challenges in using exogenous enzymes to improve ruminant production

Abstract

The ability of ruminants to convert plant biomass unsuitable for human consumption into meat and milk is of great societal and agricultural importance. However, the efficiency of this process is largely dependent on the digestibility of plant cell walls. Supplementing ruminant diets with exogenous enzymes has the potential to improve plant cell wall digestibility and thus the efficiency of feed utilization. Understanding the complexity of the rumen microbial ecosystem and the nature of its interactions with plant cell walls is the key to using exogenous enzymes to improve feed utilization in ruminants. The variability currently observed in production responses can be attributed to the array of enzyme formulations available, their variable activities, the level of supplementation, mode of delivery, and the diet to which they are applied as well as the productivity level of the host. Although progress on enzyme technologies for ruminants has been made, considerable research is still required if successful formulations are to be developed. Advances in DNA and RNA sequencing and bioinformatic analysis have provided novel insight into the structure and function of rumen microbial populations. Knowledge of the rumen microbial ecosystem and its associated carbohydrases could enhance the likelihood of achieving positive responses to enzyme supplementation. The ability to sequence microbial genomes represents a valuable source of information in terms of the physiology and function of both culturable and unculturable rumen microbial species. The advent of metagenomic, metatranscriptomic, and proteomic techniques will further enhance our understanding of the enzymatic machinery involved in cell wall degradation and provide a holistic view of the microbial community and the complexities of plant cell wall digestion. These technologies should provide new insight into the identification of exogenous enzymes that act synergistically with the rumen microbial populations that ultimately dictate the efficiency of feed digestion.

Effect of fibrolytic enzymes added to a Andropogon gayanus grass silage-concentrate diet on rumen fermentation in batch cultures and the artificial rumen (Rusitec)

“…The enzyme-mediated increase in NDF and ADF disappearance after 24 h of incubation in our batch culture study also supports the contention that applying enzymes 2 h before feeding provides sufficient time for the hydrolysis of sugars from plant cell walls. Supplementing ruminant diets with EFE has been reported to increase the rate, but seldom the extent of feed digestion (Meale et al, 2014). The lack of an effect of EFE on daily NH 3 -N, VFA and CH 4 production in this study agrees with the lack of an effect of this additive on DM and fibre digestibility.…”

“…However, this hydrolysis is not complete due to the complexity of cell wall architecture and the limited residence time of chopped forages in the rumen (Wang and McAllister, 2002). Enzymes have been included in ruminant diets with the aim of increasing plant cell wall digestibility, but responses have been variable (Meale et al, 2014). Factors such as formulation, dosage, method of application and the nature of the substrate to which they are applied contribute to this variability .…”

In vitro gas production kinetics and degradability of a diet for growing lambs: effect of fibrolytic enzyme products at different dose levels

“…There is a renewed interest in the use of fibrolytic exogenous enzymes for ruminants due to the increase in feeding costs and access to high quality enzymes (Adesogan et al 2014;He et al 2014). However, the effectiveness of enzyme products is highly variable (Colombatto et al 2003a(Colombatto et al , 2003bMeale et al 2014;Mendoza et al 2014). …”

<b>Xylanase - complex efficacy in high-energy diet for bulls finished in feedlot

“…However, during the other phases, ENZ did not show a favorable effect (p > 0.05) on ADG, DMI in kg day Oliveira et al, 2015), with the exception of adaptation period. Meale et al (2014) consider that to obtain results in performance using enzymes, the type and amount of substrate, amount of enzymes, and enzymesubstrate relationship must be adequate. First of all, in these energy-dense diets, substrate for enzymatic action and enzyme-substrate relationship were not the limiting factors.…”

“…Nevertheless, results obtained in the literature are inconsistent regarding the enzymes use on performance of the animals in these dietary conditions (Beauchemin, Rode, & Sewalt, 1995;DiLorenzo et al, 2011;Hristov, McAllister, & Cheng, 2000;Oliveira et al, 2015). This inconsistency of results can be attributed in part to differences in activity and characteristics of the enzymes used in each study, as well as physical and chemical properties of the diet, since enzymes performance are related with substrate specificity (Meale, Beauchemin, Hristov, Chaves, & McAllister, 2014).…”