
TY  - JOUR
A1  - Turner, HN 
A1  - Dolling, CHS 
A1  - Sheaffe, PHG 
T1  - Vital statistics for an experimental flock of Merino sheep. I. Death rates in adult sheep, in relation to method of selection, age and sex
JF  - Australian Journal of Agricultural Research
JO  - Aust. J.  Agric. Res.
Y1  - 1959
VL  - 10
IS  - 4
SP  - 581
EP  - 590
KW  - 
UR  - https://doi.org/10.1071/AR9590581 
N2  - Estimates of death rates are given for four mating groups in a flock of approximately 1000 Merino ewes, for each year of age from 1&#189; to 10&#189;. Three of the groups are under selection for clean wool weight and other characters, and the fourth is an unselected control. The flock is run under extensive grazing conditions, and death rates are based on ewes dead or missing between one pen-mating and the next. Between 1951 and 1957, the average death rate for ewes 1&#189; to 7&#189; years old was 2.2 per cent. per annum, while at the older ages the average was no higher than 7.3 per cent. During the drought year 1957-58 losses averaged 3.8 per cent. for ewes up to 6&#189; years old, then rose steeply with age to 45.6 per cent. for ewes 9&#189; years old. In neither period did the selected groups differ from the unselected control. Starting with the 1953 drop, all rams in the unselected control group have been retained for the study of age effects on them. Average losses to date in each age group have been less than 5 per cent. 
ER  -

