ABSTRACTS
79
carrying this character in a heterozygous form, it is obvious that from crosses of a Dorset
Horn male and a Rambouillet female all porgeny will be horned. HH HmHm × HH
hmhm gives HH Hmhm. All progeny is horned as H is dominant in the male whereas
in the female hmhm is necessary for horn modification.
A number of clean-polled purebred Rambouillet rams has been found. Warwick
et al. furnish evidence of a dominant horn-inhibiting gene in this breed. They designate
it H, but since the authors of the present paper have used this symbol in another sense,
Ih is used instead. Ihih female Rambouillets have horn pits or- depressions, whereas
ihih females do not; otherwise no evidence exists to show Ih inhibits horn production in
them. The observations of both Warwick et al. and the present authors agree that in
ihih Rambouillet females scurs or knobs were always found. It is concluded that hm
when homozygous does not completely inhibit all indications of horn formation. The
composition, therefore, of the ordinary purebred Rambouillet is HH hmhm ihih, whereas
that of the true breeding strain of polled sheep of this breed is HH hmhm IhIh.
The Southdown, a hornless breed, also carries Ih, although most hornless breeds, as
already stated, are PP. Arkell crossed a Dorset Horn ram with several Southdown ewes.
Of seven lambs, four were horned females and three hornless males. A reciprocal cross
produced three horned males and one hornless female. The production of ' hot house '
lambs by crossing the Southdown ram to grade Rambouillet or Dorset Horn ewes almost
always gives progeny which is hornless like the sire. The Southdown appears, therefore,
to be homozygous for Ih, ' or at least for a gene having the same effect.'
The genetics of scurs is not well known. When Ih is present, scur seems to be absent.
Twenty-six Rambouillet ewes at Kansas State College were examined for scurs. Fourteen
were found without scurs, ten had small scurs and two had large scurs. Those without
scurs had bony protuberances of the skull, varying somewhat in size, under skin devoid
of wool. The authors feel that the evidence supports the theory that Sc is an incom-
pletely dominant gene, expressing itself only when horns are absent. They suggest a
homozygous dominant ScSc has long scurs, a heterozygous Scsc has short scurs and a
homozygous scsc has no scurs. Warwick et al. refer to results of a scurless Rambouillet
ram crossed to many typical Rambouillet ewes, some with scurs and some without, to
show that Ih prevents the expression of Sc in Scsc females but not in males of this com-
position.
Note.—W. E. Castle [1940], a well-known geneticist of the University of California,
criticizes this paper in a note in the J. of Heredity 31, 11, 486. He gives three reasons
why he prefers the triple allelic hypothesis for the inheritance of horns in sheep which was
suggested by Warwick and Dunkle [1939], J. of Heredity, 30, 8, 325, an abstract of which
has appeared in December (1941) issue of the Indian Journal of Veterinary Science
and Animal Husbandry. Castle states in his note of criticism, ' The triple allelic hypothe¬
sis is to be preferred (1) for its simplicity, (2) for its exact correspondence with the three
different conditions found among pure breeds of sheep and (3) as an adequate explanation
of the consequences of making crosses between these three types '.
[J. N. W.]
The comparative nutritive value of butter-fat and certain vegetable oils.
E. J.SCHANTZ, C. A. ELVEHJEM and E. B. HERT (1940) J. Dairy
Sci. 23, 181.
I N this paper the authors studied the effect of different fats from vegetable origin
on growth, general health and reproductive capacity by rat feeding experiments
and compared their results with that obtained with butter-fat. In the preliminary
experiment the animals were about 21 days old and weighed about 40 gms. Three groups
of animals were fed on the following diets : (1) skimmed milk plus butter-fat, (2) skimm.
ed milk plus corn oil fat, (3) skimmed milk plus cocoanut oil fat. The diets were specially
prepared and the fat concentration in each diet was made upto 4 per cent. The diets
were made complete by the addition of extra β -carotene and essential minerals. The
animals were irradiated every day for ten minutes. Weekly weights were recorded.
The animals were treated as nearly alike as possible and milk was fed ad libitum. The
results from the preliminary experiment indicated that the animals on butter-fat made
F2