68
ABSTRACTS
It is obvious that grass and hay will tend to rectify the deficiency. Whether we
can get the additional 45 per cent of the requirement from fodder grasses cannot be
accurately estimated. Much more than this is certainly potentially available and it
is for this reason that grass land improvement measures and better utilisation of forest
areas are of so much importance.
[H. B. S. ]
The theory of chromosomes. Discussion of unlike twin brothers. A. LEWIS
OSWALD (1940). Jersey Bul. 59, 773.
A BREEDING establishment does not exist on possession of a bull. One soon
notes that great bulls have brothers of mediocre or poor quality, even when bred
to the same cows. This is observed in the human family where full brothers vary to
a great extent in the success they attain in life. One may celebrate prematurely on
bringing together a bull with a good pedigree with cows having good pedigrees. Inquiry-
explains how this is possible.
Each cow or bull has 32 ' atoms of the flesh ' or chromosomes, of which 16 came from
its mother and 16 from its father. These numbers never vary. No one, however, has
been able to explain what determines which 16 of the 32 are passed on to the progeny by
the parent. Do they struggle among themselves for this privilege ? In passing 16 of
the 32 chromosomes to the progeny there is no loss to the parent, at least there is no
evidence to the contrary ; they are replaced immediately by 16 identical ones.
Each chromosome has one vote for a particular character, brown eyes or blue eyes
for example. If the chromosomes for this character from each of the parents vote for
one colour ; that colour wins ; if they vote for different colours, the stronger or dominant
one wins. Brothers may have eyes of different colours for this reason. Likewise, bulls
which are full brothers may sire progeny that are greatly different. If two full brothers
have received identical chromosomes from each parent they will be identical. The
mathematical possibility of this ever occurring is, however, quite remote. It is thereby
possible for twins to be as similar or as dissimilar as full brothers born at different times.
All brothers and sisters have many characters in common, very rarely are they identical.
Each bull has 32 chromosomes and passes. 16 to his progeny. It is probable that
he passes a different combination of 16 each time. Bulls which transmit, in some un-
known manner, almost the same combination of 16 chromosomes each time have progeny
that are ' as similar as the proverbial peas in the pod '. A sire, therefore, which has been
well bred for generations will be most apt to produce good calves. A bull whose one
parent was good and the other bad will give about 50 per cent good calves and 50 per cent
poor ones.
' The cow is important, but the bull is the old boy that counts. He is the " papa "
of the whole crop of calves, while each " mamma " has just her own child '. On the
other hand a dairyman breeds for cows ; he has no need for a barn full of bulls. The
breeding of cows which produce large quantities of good quality milk and reproduce
their kind is the goal of the dairyman.
(NOTE. —The writer considers cattle to have 16 pairs of chromosomes. In his book entitled Animal Breeding
Plans (Collegiate Press, Ames, Iowa, U. S. A. ) J. L. Lush gives a summary of recent reports of chromosomes in mam-
mals and poultry. Here one finds that three different ideas exist as to the chromosome number in cattle : (1) 30
pairs according to Krallinger, 1931; (2) 19 pairs according to Wodsedalek, 1920 ; and (3) 17 pairs according to Masui-
1919. This paper further considers both the male and female of the bovine species homogametic, whereas Lush re-
ports that in practically every species of mammal the male is heterogametic or has an uneven number of chromosomes ;
the female mammal is homogametic or has an even number of chromosomes.
The paper does, however, give the general idea of genetic constitution of an individual and does so in terms which
are easily understood. The information, if properly interpreted, should be very helpful to the animal breeder.)
[J. N. W. '
Color genes in Holstein-Friesian by Brown Swiss crosses. RALPH J. BUSHNELL
(1940). J. Hered. 31, 253.
BROWN SWISS males were crossed with Holstein-Friesian females. The data
obtained add to the probable gene constitution of the Brown Swiss breed and
illustrate the result of crossing white-faced Holstein-Friesians with a self-coloured breed.