Effects of condensed tannins in wrapped silage bales of sainfoin (Onobrychis viciifolia) on in vivo and in situ digestion in sheep

Abstract

The objective of this study was to characterize the condensed tannins (CTs) in wrapped silage bales of sainfoin (Onobrychis viciifolia) and examine their potential action on in vivo and in situ digestive characteristics in sheep. Silage was made from sainfoin, cut at two phenological stages. The first phenological stage, at which silage was made, was from the first vegetation cycle at the end of flowering and the second stage silage was made from regrowth, 5 weeks after the first cut, but before flowering. The silages made from the two phenological stages were fed to 12 rumen-fistulated sheep in a crossover design. Of the 12 sheep, six received polyethylene glycol (PEG) to bind with and remove the effects of CT, whereas the other six were dosed with water. Organic matter digestibility, total-tract N digestibility and N (N) balance were measured over 6 days. Kinetic studies were performed on total N, ammonia N (NH 3 -N) and volatile fatty acids (VFAs) in rumen fluid before and 1.5, 3 and 6 h after feeding. The kinetics of degradation of dry matter and N from Dacron bags suspended in the rumen were also determined. Biological activity of CT (protein-binding capacity) and CT concentration were greater for the silage made from sainfoin at the early flowering stage. Total-tract N digestibility was increased by the addition of PEG (P , 0.001) to the sainfoin silage before flowering (P , 0.001). CTs decreased N excretion in urine (P , 0.05) and increased faecal N excretion (P , 0.001), but had no effect on body N retention, which is beneficial for the animal. Ruminal N degradability was smaller in the presence of active CT ( P , 0.001) at both phenological stages; however, soluble N (P 5 0.2060) and NH 3 -N (P 5 0.5225) concentrations in rumen fluid remained unchanged. The results of this experiment indicate that CT in the sainfoin retain their ability to affect the nutritive value of preserved forage legumes.Keywords: feed value, in vivo measurements, tannins, polyethylene glycol, sainfoin silage ImplicationsSilage allows the use of good-quality forage throughout the year. Although numerous papers have focused on the effect of condensed tannins (CTs) on the nutritive value of fresh forages, only few reports give data on preserved tanniniferous forages. The potential of tannins in legumes has not been fully exploited in temperate regions where livestock production occurs, largely because the CT-containing fodder legumes have poorer agronomic characteristics than tannin-free legumes. This study assessed the nutritive value of sainfoinwrapped silage bales. The effect of CT on in vivo and on in situ rumen degradability of sainfoin, which had been ensiled at two stages of maturity, was investigated in sheep. In order to investigate the effects of CT, measurements were recorded with and without polyethylene glycol, which inactivates CT throughout the digestive tract.

Condensed Tannins in Sainfoin: Composition, Concentration, and Effects on Nutritive and Feeding Value of Sainfoin Forage

“…It seems that ruminal protozoa and methanogens are not sensitive to sainfoin phenolic compounds (Bouchard, 2011; Chung et al, 2013; Guglielmelli et al, 2010). The lack of antimethanogensis activity with sainfoin polyphenolic compounds was also observed in in vitro studies (Guglielmelli et al, 2011; Theodoridou et al, 2011b). Overall, phenolic compounds including CT in sainfoin have little effects on enteric methane production and therefore growth responses in ruminants fed sainfoin are unlikely to result from reduced enteric methane production.…”

“…This loss is associated with a reduction in the proportion of total forage mass during growth (Li et al, 2014). Koupai‐Abyazani et al (1993a) suggested that CT synthesis in the leaves is very dynamic and is most intensive in younger leaves and leaves that contain the greatest concentration of CT (Li et al, 2014; Theodoridou et al, 2010, 2011b). Within the context of the optimal defense theory, young plants are often much more susceptible to herbivory than adult plants, and therefore young plants should have greater concentrations of defense chemicals such as tannins (McKey, 1979).…”

“…The situation is further complicated by the fact that concentrations of CT in sainfoin vary considerably Table 1. Mean concentration of condensed tannins in four sainfoin populations preserved by different drying methods, harvested at different growth cycles and phonological stages, and growing under rain-fed or irrigated conditions (modified from Wang et al, 2008 observation is not fully understood, there is evidence that leaves account for a greater percentage of plant dry matter in regrowth than in primary growth (Theodoridou et al, 2010(Theodoridou et al, , 2011a(Theodoridou et al, , 2012. Furthermore, the biological activity of CT isolated from sainfoin regrowth is also greater than in primary growth (Theodoridou et al, 2010(Theodoridou et al, , 2011a.…”

“…However, reduced DM and OM digestibility was observed for levels of extractable CT that exceed this concentration (e. g., Azuhnwi et al, 2013b;Kaplan, 2011;Scharenberg et al, 2007b). Reduced total tract digestibility of protein was observed with sainfoin that contained CT (5-97 g kg -1 DM) in four studies that assessed the impact of CT on N digestion (Azuhnwi et al, 2013b;Scharenberg et al, 2007b;Theodoridou et al, 2010Theodoridou et al, , 2012. These studies showed that CT reduced both ruminal degradability and intestinal digestibility of crude protein (CP).…”

Production and transcriptional regulation of proanthocyanidin biosynthesis in forage legumes

“…The moderate quantities of PA (20-49 g/kg or 2-4.9 % dry matter) in forage significantly reduce the level of protein digestion during ensiling and rumen fermentation due to its great affinity for leaf protein after mastication which inhibited protein degradation, thereby protecting ruminants against pasture bloat (Tanner et al 1995;McMahon et al 2000). This leads to an increase of protein bypass to the ruminant's gut making the conversion of plant protein into animal protein more efficient, resulting in increased milk and meat production (McMahon et al 2000;Theodoridou et al 2012). It has been reported that the use of sainfoin PAs could enhance feed value when given with tannin-free legumes (lucerne) (Aufrère et al 2013).…”