Lamb production from Merino-type ewes lambing in May and August
in Victoria
K.F. Thompson and J.M. Obst
Animal and Veterinary Sciences Group, Lincoln College,
Canterbury and Pastoral Research Institute, Victorian Department of
Rural Affairs, Box 180, Hamilton, Victoria 3300, Australia
Proceedings of the New Zealand Society of Animal Production.
1989, 49: 261-264
Lamb production from May or August lambing by Merino and
Comeback ewes was compared from 1982 to 1985 in a factorial design
experiment at Hamilton, Western Victoria. Groups of 50 ewes were
stocked at 500 kg live weight/ha or 12.4 Merinos/ha and 10.8
Comebacks/ha. Natural fertility levels were similar for all treatments
with an average of 5% ewes not lambing. Comeback ewes had a higher
lambing rate (lambs born/ewes joined) at August compared with May
lambing (1.28 v 1.19 sed 0.052) whereas the Merinos had similar lambing
rates (1.03 v 1.07 sed 0.02), indicating that the Western Victorian
Merinos were relatively insensitive to seasonal effects (photoperiod) on
fecundity. Lamb mortality was higher at August compared with May
lambing (18.5 v 14.5% sed 1.8%) and was associated with higher chill
factors in August due to cooler, wetter weather. The effects of lamb
mortality lead to similar weaning rates (lambs weaned/ewes joined) for
Comebacks at May and August lambing and lower weaning rates for Merinos
at August compared with May lambing. Lamb weaning weights were similar
for both lambing times, except in 1985 when severe internal parasite
infections before weaning in groups lambing in May restricted lamb
growth. The lower stocking rate (ewes/ha) balanced the higher per head
production for Comeback ewes and lead to no significant differences
between breeds or lambing times in weight of lamb weaned per ha.
Keywords: NZSAPAB;
Sheep; autumn; lambing; spring lambing; lamb production
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Last Updated 18-03-1997
