New Zealand Journal of Agricultural Research abstracts
Digestibility and effects of condensed tannins on digestion of sulla
(Hedysarum coronarium) when fed to sheep
MARCIA STIENEZEN1
G. C. WAGHORN
G. B. DOUGLAS
AgResearch Grasslands
Private Bag 11008,
Palmerston North, New Zealand
1Present address: Department of Agronomy, Haarweg 333, 6709 RZ
Wageningen, The Netherlands.
Abstract Sulla (Hedysarum coronarium) is a short-lived
perennial legume with an erect growth habit which is grown as a fodder crop in
Mediterranean regions but is not common in New Zealand agriculture. Recent
experimental work has shown potential benefits of sulla for reducing the impact
and numbers of intestinal nematodes in sheep and possible benefits for wool
production, so that a feeding trial was undertaken to determine its
digestibility. Twelve sheep aged about 6 months were held in metabolism crates
and fed sulla as a sole diet for the 20-day experimental period. Sulla contains
condensed tannins (CT) so that one group of 6 sheep were given twice-daily oral
drenches of polyethylene glycol (PEG) to bind with and deactivate the CT (PEG
group) enabling a comparison with the undrenched Tannin group. The dry matter
(DM) content of the sulla was 15.5%, comprising (DM basis) 33% leaf, 41% stem,
and 26% flower, and all portions of the plant were eaten. The DM contained
about 7.2% CT and 3.0% nitrogen (N). DM intakes averaged 1160 g/day and DM
digestibility was lower in Tannin animals (70.5%) than those given PEG (72.5%;
P = 0.015). Condensed tannin substantially reduced N
digestibility (63.1%) relative to those given PEG (77.1%; P < 0.001)
and this was associated with a reduction in rumen ammonia concentration
((mol/ml) in Tannin (155) versus PEG (259) animals. Plasma urea concentrations
(umol/ml) were also lower (P < 0.001) in Tannin sheep than in those
given PEG (7.4 vs 8.8) which suggests that the CT affected the digestion,
absorption, and metabolism of nutrients.
Keywords sulla; Hedysarum coronarium; digestibility;
condensed tannins; sheep
New Zealand Journal of Agricultural Research, 1996, Vol. 39: 215-221
0028-8233/96/3902-0215 $2.50/0 (c) The Royal Society of New Zealand
1996
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