Abstract
The environmental sustainability of beef production is a significant concern within the food production system. Tannins (TANs) can be used to minimize the environmental impact of ruminant production because they can improve ruminal fermentation and ruminants’ lifetime performances and mitigate methane (CH4) emissions. The objective of this study was to evaluate the effects of dietary supplementation with TANs as sustainable natural alternative to reduce the environmental impact on growth performance, rumen fermentation, enteric CH4 emissions, and nitrogen (N) use efficiency of beef cattle through a meta-analysis. A comprehensive search of studies published in scientific journals that investigated the effects of TANs’ supplementation on the variables of interest was performed using the Scopus, Web of Science, and PubMed databases. The data analyzed were extracted from 32 peer-reviewed publications. The effects of TANs were assessed using random-effects statistical models to examine the standardized mean difference (SMD) between TANs’ treatments and control (non-TANs). The heterogeneity was explored by meta-regression and subgroup analysis was performed for the covariates that were significant. TANs’ supplementation did not affect weight gain, feed consumption, feed efficiency, or N use efficiency (p > 0.05). However, it reduced the concentration of ammonia nitrogen in rumen (SMD = −0.508, p < 0.001), CH4 emissions per day (SMD = −0.474, p < 0.01) and per unit dry matter intake (SMD = −0.408, p < 0.01), urinary N excretion (SMD = −0.338, p < 0.05), and dry matter digestibility (SMD = −0.589, p < 0.001). Ruminal propionate (SMD = 0.250) and butyrate (SMD = 0.198) concentrations and fecal N excretion (SMD = 0.860) improved in response to TANs’ supplementation (p < 0.05). In conclusion, it is possible to use TANs as a CH4 mitigation strategy without affecting cattle growth rate. In addition, the shift from urinary to fecal N may be beneficial for environment preservation, as urinary N induces more harmful emissions than fecal N. Therefore, the addition of tannins in the diet of beef cattle could be used as a sustainable natural alternative to reduce the environmental impact of beef production.
Highlights
This article is an open access articleMinimizing enteric methane (CH4 ) emissions from ruminant production while improving feed conversion efficiency and growth rate is a goal for sustainable livestock production [1]
The shift from urinary to fecal N observed in this study may be beneficial for environment preservation, as urinary N induces more harmful emissions than fecal N
One of the most significant findings to emerge from this study is that the environmental impact of beef production systems can be markedly reduced when tannins are included in the diet
Summary
Minimizing enteric methane (CH4 ) emissions from ruminant production while improving feed conversion efficiency and growth rate is a goal for sustainable livestock production [1]. The nitrogen (N) excreted by ruminants is the main source of nitrous oxide (N2 O) emissions in livestock systems [2] and can contribute to air and water pollution [3]. Sustainability 2021, 13, 7410 urinary compounds by diet manipulation could be considered potential options to mitigate urine N2 O emissions and improve sustainability in ruminant production [4]. Among these strategies, dietary tannins’ (TANs’) supplementation has received special attention, in ruminants [5]. TANs are a group of polyphenolic compounds that are present in a wide variety of plants and can have positive effects in animals, such as antimicrobial, antiparasitic, antioxidant, anti-inflammatory, and immunomodulatory [5]
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