01658naa a2200217 a 450000100080000000500110000800800410001902400650006010000190012524500570014426000090020152010430021065000210125365000170127465000100129165000160130165000100131765000170132765000240134477300720136815215422025-07-22       1926    bl uuuu     u00u1 u    #d7 ahttp://dx.doi.org.sci-hub.org/10.1017/S00218596000077232DOI1 aNICHOLS, J. E.  aFertility in southdown sheep.h[electronic resource]  c1926  aAbstract: 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. The study of fertility in domestic animals is of considerable economic importance, but our knowledge of the variations of fertility in the different species is somewhat limited and is based chiefly on data abstracted from records kept by breeders.  aFemale fertility  aReproduction  aSheep  aFertilidade  aOvino  aReprodução  aReprodução animal  tThe Journal of Agricultural Sciencegv. 16, n. 3, p. 365-375, 1926.