Abstract
Simple SummaryTannin has been extensively assessed for its potential and utilisation as a ruminant feed additive in recent years and is becoming important due to its beneficial effects on modulating ruminant performance and health and mitigating methane emissions. However, evidence concerning the effect of tannin in extracted forms on ruminants appears to be inconclusive on whether it can genuinely provide either beneficial or detrimental effects for ruminants. Moreover, the effects of various sources, types of tannin extract, or appropriate levels of supplementation on ruminants remain unclear. Therefore, there is a need for a systematic evaluation concerning the effects of tannin extract on rumen fermentation, digestibility, performance, methane emissions, and metabolism of ruminants.The objective of this meta-analysis was to elucidate whether there are general underlying effects of dietary tannin extract supplementation on rumen fermentation, digestibility, methane production, performance, as well as N utilisation in ruminants. A total of 70 papers comprised of 348 dietary treatments (from both in vivo and in situ studies) were included in the study. The database was then statistically analysed by the mixed model methodology, in which different experiments were considered as random effects and tannin-related factors were treated as fixed effects. The results revealed that an increased level of tannin extract inclusion in the diet lowered ruminant intake, digestibility, and production performance. Furthermore, the evidence also showed that an increased level of tannin extract decreased animal N utilisation where most of rumen by-pass protein was not absorbed well in the small intestine and directly excreted in the faeces. Due to the type of tannin extract, HT is more favourable to maintain nutrient intake, digestibility, and production performance and to mitigate methane production instead of CT, particularly when supplemented at low (<1%) to moderate (~3%) levels.
Highlights
Tannin is known for its anti-nutritional properties due to its detrimental effects on feed intake, rumen microorganisms, nutrient utilisation, and production performance of ruminant livestock, when present at a high concentration in the diet [1].when present at a low to moderate level, tannin may provide beneficial effects to modulate ruminant performance, health, and environmental sustainability [2]
Another beneficial effect is the toxic effect of tannin that could diminish undesirable ruminal microorganisms involved in methane formation, resulting in lower methane production [7]
The present meta-analysis study evaluated experimental evidence concerning the effects of tannin extract in a beneficial perspective on methane emission reduction and providing higher rumen by-pass protein with the appropriate level of tannin extract
Summary
Tannin is known for its anti-nutritional properties due to its detrimental effects on feed intake, rumen microorganisms, nutrient utilisation, and production performance of ruminant livestock, when present at a high concentration in the diet [1]. When present at a low to moderate level, tannin may provide beneficial effects to modulate ruminant performance, health, and environmental sustainability [2]. Its molecular structure enables it to modulate ruminal fermentation by binding to protein through hydrogen bonds and forming a tannin–protein complex, influencing protein degradation in the rumen [3]. Tannin supplementation commits to lowering the amount of protein that is degraded in the rumen and increases the flow of by-pass protein to the small intestine. Tannin may alleviate the toxic effect of high rumen ammonia concentration and improve nitrogen efficiency [5,6]
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