Abstract
Data from 26 flocks, involving a total of 5014 pure-bred Southdown ewes, were available for analysis and discussion. For ewes of all ages the proportion giving birth to twins is closely associated with the total yield of lambs, and while barrenness and abortion may to a certain extent be due to the same causes, it is those factors which cause abortion which also affect the yield by reducing the number of single births, rather than the number of multiple births.The low fertility of shearling ewes is due to barrenness through reduced or delayed ovulation.The writer wishes to express his thanks to the breeders who supplied the records of their flocks and particularly to the Honorary Secretary of the Southdown Sheep Society for his help in the collection of these records.
Publisher
Cambridge University Press (CUP)
Subject
Genetics,Agronomy and Crop Science,Animal Science and Zoology
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