Homozygous grey Karakul lambs are born with a lethal genetic factor responsible for death at
weaning age. When put in a high roughage diet under field conditions they develop distended, thin-walled
rumens and sand impacted abomasa. Homozygous white Karakul lambs have a similar factor
but survive for a longer period. Black Karakul lambs are not affected. The present study was undertaken
to compare by image analysis the number and size of the myenteric ganglia, and the number of
myenteric neurones in the walls of the fore-stomach and abomasum of 24-h-old grey, white and black
Karakul lambs. One square centimetre samples were taken from analogous areas of the rumen, reticulum,
omasum and abomasum of 38 embalmed Karakul lambs. Haematoxylin and eosin stained histological
sections of each sample were studied with a Vids 2 Image Analyzer. One way analysis of
variance indicated a significant difference between the groups regarding the number and size of the
myenteric ganglia and in the number of myenteric neurones in the reticulum, rumen and abomasum.
The number and size of the ganglia and the number of neurones was greatest in the black lambs and
decreased progressively in the white and grey lambs. The omasum was not affected. It is suggested
that the paucity of myenteric ganglia and neurones in the regions examined is instrumental in causing
the lethal condition described above.