Field data analysis of lamb survival and mortality rates
occurring between pregnancy scanning and weaning
G.B. Nicoll, K.G. Dodds and M.J. Alderton
Landcorp Farming Limited, P.O. Box 44, Rotorua, New Zealand
Proceedings of the New Zealand Society of Animal Production. 1999, 59: 98-100
Ultrasonic scanning for pregnancy diagnosis in commercial sheep
flocks has highlighted the magnitude of lamb loss from scanning to
docking or weaning. From seven ram breeding flocks in Landcorp Farming
Limited, lamb survival rates were derived from the number of lambs per
ewe present at six stages: pregnancy scanning, birth, born alive, 48h
after birth, end of lambing and weaning. Differences in lamb survival
rates between adjacent stages provided the mortality rates for five
intervals: pregnancy scanning-birth; birth-born alive; born alive-48h
after birth; 48h after birth-end of lambing; end of lambing-weaning.
Flock-year affected lamb survival rate at all stages (P<0.001) but
varied with ewe age and lamb birth/rearing rank (P<0.001). Mean lamb
survival rates for 3- and 4-year-old dams were generally higher than
those of other dam age groups. Triplet-reared lambs had consistently
lower survival rates than single- or twin-reared lambs (P<0.001).
Lamb mortality rates for the five intervals were 0.03, 0.08, 0.03, 0.03
and 0.04 lambs per potential lamb at scanning, respectively. Lamb
mortality was highest at birth, with lower survival rate of triplet-born
lambs compared with single- and twin-born lambs (0.82±0.006 vs
0.93±0.004 and 0.93±0.002 lambs per potential lamb respectively;
P<0.001).
The results indicated when, and to what extent, lamb
losses occurred in the field between pregnancy scanning and weaning, and
the importance of applying appropriate ewe/lamb feeding and management
policies to minimise lamb mortality rates.
Keywords: NZSAPAB;
Sheep; ultrasonic scanning; pregnancy diagnosis; lamb survival
Last Updated 06-08-1999
