Methane Production of Fresh Sainfoin, with or without PEG, and Fresh Alfalfa at Different Stages of Maturity is Similar but the Fermentation End Products Vary.

Pablo José Rufino-Moya,Margalida Joy,Mireia Blanco,Juan Ramón Bertolín

doi:10.3390/ani9050197

Abstract

Simple SummaryIn the last years, there has been increasing interest in the use of forages containing condensed tannins (CT) in ruminant nutrition. Condensed tannins can reduce the methane emissions and the ruminal degradation of protein, improving the animal performances to different extents depending on the source and dose of CT. In vitro fermentation of sainfoin has not been studied in fresh forage. The effect of CT can be studied in comparison with a similar CT-free forage or using polyethylene glycol (PEG), which is a tannin-blocking agent. The maturity stage influences the chemical composition to a different degree depending on the legume species, and can affect the content and fractions of CT. The aims of this trial were to compare the fermentation parameters of sainfoin with or without PEG, to detect the differences due to CT, at different maturity stages (vegetative, start-flowering, and end-flowering) and compare them with the fermentation parameters of alfalfa. The main results were that sainfoin had greater in vitro organic matter degradability (IVOMD) and lower ammonia and acetic:propionic ratio than alfalfa. Sainfoin CT had effect on ammonia and individual fatty acid proportions. In conclusion, fermentation end products were affected both by the chemical composition and CT contents. Alfalfa and sainfoin are high-quality forages with different condensed tannins (CT) content, which can be affected by the stage of maturity. To study the effects of CT on fermentation parameters, three substrates (alfalfa, sainfoin, and sainfoin+PEG) at three stages of maturity were in vitro incubated for 72 h. Sainfoin had greater total polyphenol and CT contents than alfalfa. As maturity advanced, CT contents in sainfoin decreased (p < 0.05), except for the protein-bound CT fraction (p > 0.05). The total gas and methane production was affected neither by the substrate nor by the stage of maturity (p > 0.05). Overall, sainfoin and sainfoin+PEG had greater in vitro organic matter degradability (IVOMD) than alfalfa (p < 0.05). Alfalfa and sainfoin+PEG presented higher ammonia content than sainfoin (p < 0.001). Total volatile fatty acid (VFA) production was only affected by the stage of maturity (p < 0.05), and the individual VFA proportions were affected by the substrate and the stage of maturity (p < 0.001). In conclusion, alfalfa and sainfoin only differed in the IVOMD and the fermentation end products. Moreover, CT reduced ammonia production and the ratio methane: VFA, but the IVOMD was reduced only in the vegetative stage.

Highlights

There is increasing interest in legume-based forage production systems because of their low reliance on fertilizer nitrogen, potential environmental benefits, and high protein content that contribute to low-input and sustainable livestock production systems [1]
The use of gas production technique is a good tool to evaluate the effect of condensed tannins (CT) on fermentation parameters, but the fermentation is influenced by the time of incubation, species of the animal donor and the diet [31,32]
The higher c in alfalfa when compared to sainfoin agrees with the results reported by Hatew et al [11], the effect on c depends on the types and concentrations of sainfoin CTs

Summary

Introduction

There is increasing interest in legume-based forage production systems because of their low reliance on fertilizer nitrogen, potential environmental benefits, and high protein content that contribute to low-input and sustainable livestock production systems [1]. The majority of studies that compared the ruminal fermentation of alfalfa and sainfoin have been performed using hays [3,4,8]. To the best of our knowledge, the ruminal fermentation of both species was compared in fresh forages only by McMahon et al [9] and Chung et al [10]. Depending on their content, characteristics, and properties [11], CTs from sainfoin alter both the breakdown of protein in the rumen to ammonia and methane, gas and the production of total volatile fatty acids (VFAs) [3,4,12]

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