Vahel Jaladet Taha, James A. Huntington, Robert R. Wilkinson, Dave Davies

Chestnut tannin supplementation at ensiling: Effects on composition, degradability, and fermentation of forage silages

Introduction

Chestnut tannin supplementation at ensiling: effects on composition, degradability, and fermentation of forage silages. Chestnut tannin supplementation at ensiling improves protein preservation and reduces rumen degradation of forage silages. Enhances composition, degradability, and fermentation for ruminants.

Abstract

Tannins are plant secondary compounds capable of forming pH-dependent reversible bonds with proteins, thereby reducing protein degradation in the silo and rumen. This study evaluated the effect of adding chestnut hydrolysable tannin (HYT) at ensiling on the chemical composition, protein degradability, and rumen fermentation of grass, whole-crop pea, and bean silages. Forages were harvested, wilted (48 h), chopped (5 cm), and ensiled in mini silos (~25 kg) with one of four treatments: 40 g kg-1 FW HYT (HT), 20 g kg-1 HYT (LT), an inoculant (IN), or water (W, control). Tannin addition reduced (p< 0.01) ammonia-N during ensiling by 31% (HT), 19% (LT), and 7% (IN) compared to W. Tannin treatments decreased (p< 0.01) CNCPS fraction A and increased (p< 0.01) fractions B1, B2, and C, as well as undegradable protein at a 0.05 h⁻¹ outflow rate (HT = 282; LT = 273; IN = 222; W = 216 g kg⁻¹ CP). In-situ degradation showed reductions (p< 0.01) in both the immediately soluble fraction “a” and total degradable fraction “a+b” with tannin inclusion. Gas production was also reduced (p< 0.01) with HT (254 ml) and LT (281 ml) compared to IN (310 ml) and W (337 ml). Furthermore, dry matter (DM) and organic matter (OM) disappearance declined (p< 0.01) with tannin treatment (DM: HT = 532, LT = 583; OM: HT = 588, LT = 605 g kg⁻¹ DM) relative to control (DM = 641; OM = 661 g kg⁻¹ DM). In conclusion, ensiling with chestnut tannins improved protein preservation and reduced the rumen degradation and fermentability of protein, suggesting potential benefits for enhancing forage utilization in ruminant diets.

Review

This study critically examines the efficacy of chestnut hydrolysable tannin (HYT) as an additive during the ensiling process, aiming to mitigate protein degradation and optimize rumen fermentation characteristics of various forage silages. The research builds upon the known capacity of tannins to form reversible protein bonds, which can protect proteins from excessive breakdown in the silo and subsequently in the rumen. Utilizing a robust experimental design with grass, whole-crop pea, and bean silages in mini silos, the authors investigated the impact of two tannin concentrations (HT: 40 g kg-1 FW; LT: 20 g kg-1 FW) alongside an inoculant (IN) and a water control (W). This setup effectively allowed for a comparative analysis of tannin's effects against established silage additives and a baseline. The findings presented are compelling and consistently demonstrate the beneficial effects of chestnut tannin supplementation. A key result was the significant reduction in ammonia-N during ensiling, indicating improved protein preservation, with higher tannin levels showing a more pronounced effect. This was further substantiated by favorable shifts in protein fractions (decreased degradable A, increased B1, B2, C, and undegradable protein), alongside reductions in both immediately soluble and total degradable protein fractions observed during in-situ degradation. Moreover, the study revealed a significant decrease in gas production and dry matter and organic matter disappearance in the rumen with tannin treatments, suggesting a controlled and potentially more efficient fermentation profile. These results collectively highlight tannin's dual role in both preserving protein quality during ensiling and modulating its subsequent degradation and fermentation in the rumen. In conclusion, this research provides strong evidence supporting the use of chestnut tannins as an effective silage additive to enhance protein preservation and regulate its ruminal degradation. The consistent and statistically significant improvements across various parameters – from chemical composition to in-situ degradation and gas production – underscore the potential of HYT to positively influence forage quality. The implications for ruminant nutrition are substantial, as reducing protein loss during ensiling and optimizing its release in the rumen can lead to more efficient nitrogen utilization and potentially improved animal performance. This study significantly contributes to the understanding of tannin-forage interactions and offers a promising strategy for enhancing forage utilization in sustainable livestock production systems, warranting further investigation into its practical application and long-term animal performance benefits.

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