New Zealand Journal of Agricultural Research abstracts
Herbage intake, ingestive behaviour and diet selection, and effects of
condensed tannins upon body and wool growth in lambs grazing Lolium
perenne and Holcus lanatus swards in summer
F. MONTOSSI*
J. HODGSON
Department of Plant Science
Massey University
Private Bag 11-222
Palmerston North, New Zealand
S. T. MORRIS
Department of Animal Science
Massey University
Private Bag 11-222
Palmerston North, New Zealand
*Present address: Estación Experimental del Norte, Instituto Nacional de
Investigación Agropecuaria (INIA), Ruta 5, km 386, Tacuarembó,
Uruguay
Abstract A comparative study was undertaken in New Zealand to
investigate the effects of low concentrations of condensed tannins (CT) on diet
selection, herbage intake, and performance in lambs grazing on four 0.2 ha
paddocks each of perennial ryegrass (Lolium perenne) or Yorkshire fog
(Holcus lanatus) with less than 10% white clover (Trifolium
repens), continuously grazed at a constant height of approximately 6 cm
from December 1992 to March 1993. The effects of CT on rumen metabolism and
animal production were assessed by twice daily oral administration of
polyethylene glycol (PEG; MW 4000) to half of the lambs on each sward.
Bite weight was greater for Yorkshire fog swards than for ryegrass swards
during January (111 vs 85 +/- 5 mg OM/bite, P < 0.01), but not in
December. In both December and January, grazing, ruminating, and idling times
were similar between swards, while in January, the rate of biting in ryegrass
swards was higher than in Yorkshire fog swards (64 vs 61 +/- 1 bites/min,
P < 0.05). The organic matter digestibility (OMD) of the herbage
selected was higher in ryegrass swards in December (81 vs 78 +/- 0.04 %,
P < 0.01), but not in January (80 vs 79 +/- 0.05 %). The herbage
intake achieved by lambs grazing ryegrass swards was 23% higher than that
achieved on Yorkshire fog swards in December (990 vs 800 +/- 36 g OM/lamb/day,
P < 0.05) whereas, in January, herbage intakes did not differ
significantly. Lambs grazing on ryegrass swards had higher clean wool growth
(1147 vs 1085 +/- 15 ug/cm2 per day, P < 0.10) and carcass
weight (17.5 vs 16.3 +/- 0.22 kg, P < 0.05) than lambs grazing on
Yorkshire fog swards. The stocking rate maintained on ryegrass plots was 25%
greater than on Yorkshire fog plots.
Low concentrations of CT were recorded in the diets of sheep on ryegrass and
Yorkshire fog swards (<= 0.2% on a DM basis). The low levels of CT had no
significant effects on diet selection, herbage intake, grazing behaviour
patterns, or lamb performance. However, the lambs grazing on Yorkshire fog
swards showed small and non-persistent responses to CT in terms of wool growth
and liveweight gain. The results of this study indicate that: (i) under high
fertility conditions and intensive management, perennial ryegrass/white clover
swards appear to have higher feeding value than Yorkshire fog/white clover
swards for lamb production and (ii) the low CT concentrations (<= 0.2% in
the DM) observed in both swards did not influence lamb performance
significantly.
Keywords Lolium perenne (perennial ryegrass);
Holcus lanatus (Yorkshire fog); Trifolium repens (white clover);
polyethylene glycol (PEG); condensed tannins (CT); herbage intake; diet
selection; grazing behaviour and lamb production
New Zealand Journal of Agricultural Research, 1997, Vol. 40: 449-461
0028-8233/97/4004-0449 $7.00/0 (c) The Royal Society of New Zealand
1997
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