SUMMARYBirthcoat samples from Lincoln and Welsh Mountain lambs born in an ova transfer experiment (Weiner & Slee, 1965) were examined to determine the fibre type arrays and any effect of ova transfer on manifestation of the prenatal check or the base (Dry, 1965).In the Lincoln breed arrays were Truncated Ravine or Truncated Valley thus showing central checking. Pre-curly tip fibres were mainly confined to central primary follicles. Post-natal medullation was plentiful, especially in peak curly-tips, but kemp was absent. In the Welsh lambs all identifiable arrays were either Plateau or Saddle, with the lateral primary fibres more checked than the centrals. Pre-curly tip fibres occupied almost all the primary follicles, with only a few curly-tips in primary laterals. Post-natal medullation was strongest in pre-curly tips and their successors.The effect of ova transfer was to decrease the manifestation of check in Lincoln-in-Welsh and increase it in Welsh-in-Lincoln, without affecting the base. Although this, in each case, changed the check of the lamb in the direction of that of the foster breed, it is suggested that this may not be due to any influence of maternal check on foetal check. The effect on pre-natal check may be due to foetal size, and in particular skin expansion, during a short period immediately following completion of primary follicle initiation. As compared to their respective controls, the Welsh transfer lambs had a higher S/P ratio at birth, whilst that of the transferred Lincolns was reduced.If increased prenatal fibre check is associated with increased foetal growth rate at the relevant period, it may also be correlated with increased lamb size at birth and therefore have been favoured in selection for meat production, at least in some breeds.
Evaluation of foetal growth, litter size and reproductive performance in rabbit after 18 generations of selection for growth rate using cryopreserved embryos
