Effects of herbage mass and ewe condition score at lambing on
lamb survival and liveweight gain
A.J. Litherland, M.G. Lambert, P.N. McLaren
AgResearch, Grasslands Research Centre, Private Bag 11008,
Palmerston North
Proceedings of the New Zealand Society of Animal Production. 1999, 59: 104-107
Scanned, twin-bearing mixed aged ewes (n=1276) were set-stocked
(7.5 ± 0.1 ewes ha-1 ) over the lactation period at
either high or low condition score (CS) (2.51 vs 1.52) and high or low
herbage mass (HM) (1160 vs 880 kg DM ha-1 ) in an experiment
replicated on 5 farms in Wairarapa. Three farms lambed early (27 August
to 4 September 1997) and were summer-dry and two lambed later (22 to 27
September 1997) and were summer-wet. High ewe CS may have improved lamb
survival (167 vs 150%, P=0.13) through reduction in estimated lamb
mortality (17 vs 25%, P<0.01) on late lambing farms where weather
conditions were adverse at lambing, but had no effect on early lambing
farms where lambing conditions were more favourable. Ewe CS had no
effect on either lamb or ewe LWG. High HM may have reduced lamb
mortality on early lambing farms (10 vs 14%, P<0.05) where ewes were
under greater nutritional stress than on late farms. Additional HM at
set-stocking increased lamb LWG up to docking by 11 g d-1
per 100 kg DM ha-1 increase (P<0.03) on early farms but had no
effect on late farms. Lamb LWG from docking to weaning was unaffected by
set-stocking HM. The overall effect of an increase in set-stocking HM by
100 kg DM ha-1 was to increase lamb weaning weight by 2 kg
on early farms. Additional HM at set stocking increased ewe LWG from
birth to docking by 33 g d-1 per 100 kg DM ha-1 increase
(P<0.001) but decreased LWG from docking to weaning by 18 g d
-1 per 100 kg DM ha-1 increase. This response was
similar on early and late lambing farms. On early farms there was a net
increase in ewe liveweight at weaning of 1.6 kg for each 100 kg DM ha
-1 increase in lambing HM.
Keywords: NZSAPAB;
ewe; lamb, condition score; herbage mass; growth rate.
Last Updated 06-08-1999
