Abstract
Abstract Exogenous fibrolytic enzymes (EFE) added to the ruminant diet can increase fiber digestibility and production efficiency. A systematic review was conducted to understand the interactions between EFE and diet on digestibility and animal performance. The database included variables from 384 experiments with EFE and 264 controls from 85 papers published since 2000 (classification criteria: 1) type of study (in vitro, in situ, in vivo), 2) type of ruminants (sheep, buffaloes, goats, beef and dairy cattle), 3) primary EFE activity (cellulases (Cel) or xylanases (Xyl)), 4) forage proportion (FP), 5) type of plant (TP: legumes or grasses), 6) number of ingredients in diets, and 7) application time (AT)). In over 52.85% of cases, EFE improved the degradability of dry matter (DMD), neutral and acid detergent fiber (NDFD and ADFD), in vitro gas production (GP), volatile fatty acids (VFA), the acetate: propionate ratio (A:P ratio), protein and fat milk, milk yield and average daily gain (ADG) (by 7.78–21.85%). Cel improved organic matter degradability (OMD), GP, VFA, milk yield, and milk protein and fat content. EFE in FP≥40% diets enhanced the ADG, and in grassbased diets increased the dry matter intake (DMI). The AT of EFE affected the DMD, NDFD, and ADFD. Significant correlations were found between the improvements of NDFD or ADFD with DMD (r>0.59), milk yield (r=0.64), and ADG (r=0.59). In conclusion, many factors interact with EFE supplementation effects, but EFE consistently enhanced the DMD, NDFD, and ADFD of ruminant diets, which are related to improvements in productive performance.
Highlights
MethodsSampling method A database was generated by extracting information from a non-recurring list of peer-reviewed articles published between 2000 to 2013, obtained by a literature search of Google Scholar (http://www.scholar.google.com/) and CAB Abstracts (http://www.cabi.org/) using the following combinations of words: 1) “fibrolytic enzymes”; 2) “cellulases xylanases ruminant”; 3) “exogenous fibrolytic enzymes ruminant”; 4) “exogenous fibrolytic enzymes”; and 5) “exogenous enzymes ruminant”, according to the procedures of Arriola et al (2017) and Tirado-González et al (2018)
Studies were excluded from the list of 226 articles if it was not possible to separate the EFE effect from other factors, or if they did not address variables related to fermentation patterns, in vivo, in situ, or in vitro digestibility, or productive animal performance
Consistent with recent studies where Xyl and Cel improved the degradability of organic matter (OM), DM, CP, NDF, and acid detergent fiber (ADF), and the proportion of volatile fatty acids (VFA) (López-Aguirre et al, 2016 a; Vallejo et al, 2016 a; Vallejo-Hernández et al, 2018), the present analysis shows how in the majority of experiments, the use of EFE had positive effects on the digestibility of the diet components (DM, NDF, and ADF), the gas production (GP), VFA and A:P ratio, and the productive characteristics of the animals
Summary
Sampling method A database was generated by extracting information from a non-recurring list of peer-reviewed articles published between 2000 to 2013, obtained by a literature search of Google Scholar (http://www.scholar.google.com/) and CAB Abstracts (http://www.cabi.org/) using the following combinations of words: 1) “fibrolytic enzymes”; 2) “cellulases xylanases ruminant”; 3) “exogenous fibrolytic enzymes ruminant”; 4) “exogenous fibrolytic enzymes”; and 5) “exogenous enzymes ruminant”, according to the procedures of Arriola et al (2017) and Tirado-González et al (2018). Articles included The search procedure identified 423 non-recurring items from Google Scholar, and 226 articles from CAB Abstracts. 50 articles published from 2013 to 2019 were selected from a random searching in Google Scholar and were included for comparison. Exclusion criteria The 226 articles from CAB Abstracts gave a representative sample of all articles published from 2000 to 2013 presented in Google Scholar. Statistical analysis was performed in 85 non-recurrent items from the original list of articles (see Appendix A1), discussion was made using additional 44 articles
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