The Fate of Tannins from Birdsfoot Trefoil and Their Effect on the Nitrogen Balance in Growing Lambs Fed Diets Varying in Protein Level.

Two experimental periods were employed to investigate the fate of ingested CT from BT and their effects on the intake, digestibility, and N balance in lambs fed diets differing in CP levels. In period 1, 24 lambs were fed a basal diet either treated with polyethylene glycol (PEG+) to deactivate CT or without polyethylene glycol (PEG-). In period 2, the same lambs were used in a 2 × 2 factorial design and fed either the basal diet (BP) or a high protein diet (HP), again treated with or without PEG. In both experimental periods, feeding lambs diets without PEG caused a reduction in the dry matter (DM) intake and an increase in the DM digestibility. Urinary and total N excretion decreased in lambs fed diets without PEG, but only in absolute terms and not in relation to the N intake. The total N intake, total N excretion, and body N retention were higher with a higher dietary CP level. Related to the CT intake, less soluble and protein-bound CT were excreted by lambs fed diets without PEG, and more protein-bound and fiber-bound CT were excreted by lambs fed BP diets. Regardless of the PEG treatment and CP level, not all CT that are ingested are also excreted. The effect of PEG treatment on the N excretion pathway was independent of the CP level.

Desorption Resistance of Polycyclic Aromatic Hydrocarbons in Biochars Incubated in Cow Ruminal Liquid in Vitro and in Vivo.

Biochar is a new, promising, and sustainable feed additive alternative in agricultural production, which may, however, contain a considerable amount of polycyclic aromatic hydrocarbons (PAHs). As a measure of their bioaccessibility to ruminants, we quantified PAH concentrations in biochars before and after three different incubation experiments. Specifically, the biochars were subjected to (1) an aqueous cyclodextrin suspension with a contaminant trap as (infinite) sink, (2) an in vitro experiment with cow ruminal liquid and a contaminant trap, and (3) an in vivo experiment within cow rumen. Three different biochars were used that contained 13-407 mg/kgdw of the sum of 16 U.S. EPA PAHs before the exposure. While experiment (1) resulted in no or minimal bioaccessibility (desorption resistance) of the PAHs expressed by their largely unaltered concentrations, experiments (2) and (3) caused concentration reductions on average by 35 and 56%, respectively, presumably mainly due to the presence of the ruminal fluid in (2) and (3), and the extended sorption capacity in (3). Thus, simple and "abiotic" passive sampling methods may not capture all processes contributing to bioaccessibility in complex biological systems. A comparison with average daily PAH intake of ruminants suggests that quality-controlled biochar containing <10 mg/kgdw PAHs will not pose an increased risk when applied as a feed additive.

Palatability in sheep and in vitro nutritional value of dried and ensiled sainfoin (Onobrychis viciifolia) birdsfoot trefoil (Lotus corniculatus), and chicory (Cichorium intybus).

Three temperate forages, sainfoin, birdsfoot trefoil, and chicory, characterized by elevated contents of plant secondary compounds, were compared to a ryegrass-clover mixture (control) in dried (Experiment 1) and ensiled form (Experiment 2) in their palatability and nutritional value. Palatability was measured in adult wethers (n = 6) allowed to choose between the familiar control forage and one of the three test plants. Palatability index was calculated from differences in intake of control and test plants measured after given times. Generally at first contact, palatability of the unfamiliar plants was low. Lag time until palatability index approached or exceeded a value of 100 was 2-5 d, but could not be related to the content of condensed tannins. Sainfoin had a high palatability, the highest content of condensed tannins (77.4 +/- 10.23 g/kg DM), a high content of duodenally utilisable crude protein (94.7 +/- 16.87 g/100 g CP), and a high content of metabolizable energy (9.5 +/- 0.38 MJ ME/kg DM), making this plant most promising for various purposes including anthelmintic action.

Effect of feeding dehydrated and ensiled tanniferous sainfoin (Onobrychis viciifolia) on nitrogen and mineral digestion and metabolism of lambs.

The effects of tanniferous sainfoin on digestion and metabolism have been investigated in 12 lambs in an incomplete cross-over design (n = 6). Effects of condensed tannins (CT) were evaluated by comparing dehydrated and ensiled sainfoin treated with and without polyethylene glycol (PEG). Dehydrated and ensiled grass-clover mixtures served as controls. The lambs were fed the treatment diets, including a mineral supplement, for 21 d. During the last 7 d excreta, rumen fluid and blood were sampled. The CT of sainfoin decreased rumen fluid ammonia concentration (p < 0.001) and increased the plasma concentration mainly of essential amino acids (p < 0.001). Body retention of phosphorus, calcium and magnesium was lower with sainfoin compared to PEG-treated sainfoin (p < 0.05). Sainfoin without PEG resulted in lower digestibilities of organic matter and neutral detergent fibre than sainfoin with PEG and the grass-clover mixture (p < 0.001). Ensiling of sainfoin led to the lowest N-retention. In conclusion, the reduction in ruminal ammonia and urine-N losses by sainfoin CT did not improve N-retention.