ALBERT

Description: SUMMARYAn experiment was conducted at Palmerston North, New Zealand, to determine the effect of condensed tannins (CT) on the true and apparent digestion of methionine and cysteine in the small intestine (SI) of sheep fed fresh Lotus comkulatus. The lotus contained c. 30 g total CT/kg dry matter (DM) and was fed hourly to sheep in metabolism crates. Four sheep were prepared with rumen and abomasal cannulae which enabled the indigestible liquid phase marker, chromium ethylene diamine tetra-acetic acid (Cr-EDTA), to be infused into the rumen to estimate digesta flow. True digestibility of plant methionine and cysteine in the SI and their site of absorption in the SI were determined from 35S-labelled L. corniculatus homogenate continuously infused into the abomasum. After 9 h infusion of the 35S-labelled lotus homogenate, the sheep were slaughtered and digesta samples were taken at intervals along the small and large intestines. The effect of CT was determined by comparing two control sheep (CT-acting) with two sheep given a continuous intraruminal infusion of polyethylene glycol (PEG, MW 3500) to bind and inactivate the CT.The CT reduced the true digestibility of plant methionine (0·72 v. 0·88) and cysteine (0·65 v. 0·81) in the SI relative to sheep receiving PEG. Condensed tannins also appeared to alter the site of digestion of both [35S]methionine and [35S]cysteine in the SI, and increased the flux of both amino acids in the mid and latter thirds of the SI. CT did not affect the apparent digestibility of total methionine (0·82 v. 0·84) in the SI but reduced the apparent digestibility of total cysteine from 0·77 to 0·66. In control sheep CT increased the abomasal flux (as a proportion of eaten) of total digesta methionine (0·88 v. 0·76) and total digesta cysteine (0·74 v. 0·62). The apparent absorption of total methionine (plant + microbial + endogenous) was increased by the action of CT (0·72 v. 0·63 g/g eaten) but was similar for total cysteine (0·49 v. 0·48 g/g eaten) in both groups. It was concluded that CT reduced the true digestibility of plant methionine and cysteine in the SI. However, it was calculated that the action of CT actually increased the total amounts (g/g eaten) of plant methionine and cysteine absorbed from the SI, due to its effect in increasing abomasal flux.

Description: SUMMARYA feeding trial was undertaken in Palmerston North, New Zealand in 1991, to determine the extent to which condensed tannins (CT) in Lotus pedunculatus were able to affect the nutritive value of ryegrass (which does not contain CT) for sheep. The trial involved three groups of 11 male cryptorchid sheep held in metabolism crates so that intakes, digestibilities and nitrogen balances could be measured over a 42-day feeding period. One group was fed freshly cut ryegrass (Lolium perenne L.) as a sole diet (Grass group) and the other two groups were given a mixture of about one third freshly cut lotus and two thirds ryegrass (dry matter (DM) basis). This mixture contained c. 1·8% CT in the DM. One group given the mixed diet was drenched twice daily with polyethylene glycol (PEG; PEG group) to bind and remove the effects of the CT from the diet, whilst those not drenched were designated the ‘Tannin’ group. Intakes of all groups were constrained to that of the Grass group of sheep.Condensed tannins in the lotus had a major effect on the digestion of ryegrass. When the forages were immature, apparent digestibility of nitrogen (N) was substantially reduced in the Tannin sheep (65·3%)compared to the PEG (77·5%) and Grass (77·9%) groups (P 〈 0·001). With mature forages, the respective values were 48·8, 62·5 and 53·7% (P 〈 0·01). Rumen ammonia concentrations and plasma urea concentrations were also reduced by CT. Condensed tannins reduced DM digestibility by 3·7 percentage units (P 〈 0·05) mainly through the effects on N digestion. Concentrations of acetate, propionate and butyrate in rumen liquor were not affected by treatment, but CT reduced the proportions of the minor volatile fatty acids (VFA; isobutyrate, valerate and isovalerate). Treatment did not affect liveweight gain (131—164 g/day), or wool growth from mid-side patches, and N retention was not reduced by CT, so that the nutritive value of the forage was maintained despite the reduction in N digestibility. The principal finding was that CT in Lotus pedunculatus were able to affect the digestibility of both grass and lotus when fed together, and that as little as 1·8% of CT in the dietary DM had a substantial effect on rumen function.

Description: The extent to which condensed tannins (CT) in Lotus corniculatus were able to affect protein degradation and the nutritive value of pasture were evaluated at Palmerston North, New Zealand in 1992 in an indoor feeding trial with sheep and using in vitro incubations. The feeding trial involved three groups of seven young wether sheep held indoors in metabolism crates for the 32-day experimental period with one group fed freshly cut ryegrass/clover pasture (Pasture group) whilst the other two groups received a mixture of c. 37% freshly cut Lotus corniculatus and 63% pasture (dry matter (DM) basis). One of the latter groups was given twice daily oral drenches of polyethylene glycol (PEG) to bind with and remove the effects of the CT (PEG group) whilst the remaining sheep (Tannin group) were not drenched. Intakes of sheep given the mixed diets were constrained to that of the pasture group. The CT concentration in the lotus was 26·1 g/kg DM so that the mixed diets contained c. 10g CT/kg DM. Effects of CT on digestion and sheep performance were minimal. Apparent digestibility of N was lower in the Tannin group (76·4%) than PEG (79·8%) or Pasture (79·4%) sheep (P