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Heterosis in crossbred hill sheep

Published online by Cambridge University Press:  02 September 2010

H. P. Donald ,
J. L. Read  and
W. S. Russell
H. P. Donald
Affiliation:
A.R.C. Animal Breeding Research Organisation, Edinburgh 9
J. L. Read
Affiliation:
A.R.C. Animal Breeding Research Organisation, Edinburgh 9
W. S. Russell
Affiliation:
A.R.C. Animal Breeding Research Organisation, Edinburgh 9
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Summary

1. For ten years purebred Blackface and Swaledale ewes have been kept on a small hill grazing together with first crosses and backcrosses to the Swaledale. The total flock of about 120 ewes was mated and lambed on sown pastures where ewes with twins remained from lambing until weaning. Four new rams (two of each breed) were used each year.

2. It is concluded that the Swaledales produced fewer lambs than the other ewes, but these were of greater birth weight (5 %) and cannon bone length (2 %); moreoever, they were better mothers than Blackface (4 %) when rearing singles on hill grazing but not if rearing twins on sown grass.

3. Blackface sheep showed greater weights at weaning (5%), at mating (5%), and of fleece (15%) than did pure Swaledales.

4. First cross sheep were equal to or slightly superior to the parental mean in birth weight, weaning weight and cannon-bone length. They exceeded the better parent in ewe weight, first fleece weight, and weight of weaned lambs.

5. Backcross sheep although not always statistically distinguishable from Swaledale in cannon-bone length and fleece weight or from first cross sheep in reproductive characters tend to confirm the interpretations placed on the relations between the purebred and first cross sheep.

6. Heterosis estimated as a superiority of first cross sheep over the mean of the two parental breeds varied from 0% for cannon-bone length to 9·5% for prolificacy of 4-year-old ewes.

Type
Research Article
Information
Animal Production , Volume 5 , Issue 3 , October 1963 , pp. 289 - 299
Copyright
Copyright © British Society of Animal Science 1963

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References

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