176
ABSTRACTS
Purebred and crossbred pigs. Comparison of rate of growth and economy
of gains. F. B. HEADLEY (1940). Bull. Nevada Agric. Expt. Sta.
153.
H YBRID vigour in both plants and animals is a well-known phenomenon. In
the case of pigs, faster and more economical growth are practical manifestations of
this vigour. Crossbred Duroc-Poland China pigs were studied under Nevada conditions.
Feeding was the same for each pig ; it included four pounds of skim milk and a quarter
pound of a mixture of four parts fish meal plus three parts linseed meal daily. Alfalfa
pasture was provided in the summer; in the winter three pounds of alfalfa meal were
added to the fish and linseed meal mixture. In addition they were given barley according
to body weight, varying from 1.2 lb. daily at 30 lb. to 6.2 lb. daily at 200 lb.
In the summer trials using paired crossbred and purebred Duroc pigs of the same
weight and sex, the days required for one cwt. gain were 68±1.1 for crossbred and
73±0.8 for purebred pigs. The pounds of concentrates required for one cwt. gain in
body weight were 277±5.2 and 2.89 ±3.4 respectively. In group trials using eight pigs
each in crossbred and purebred groups on pasture, the days required for one cwt. gain in
body weight were 67±1.0 and 71 ±2.3 respectively ; the daily gains were 1.49±0.014
and 1.41± 0.025 and the pounds of concentrates required for one cwt. gain in body
weight were 263 and 268 respectively.
Finally individual and group trials similar to those above were run in the winter.
The feeding was the same except that in place of alfalfa pasture, three pounds of alfalfa
meal were fed daily. In the trials using paired crossbred and purebred Duroc pigs, the
days required for one cwt. gain in body weight were 70±1.2 and 78±1.8 respectively.
The pounds of concentrates required for one cwt. gain in body weight were 287±5.2 and
321±6.2 respectively. In the winter group study the days required for one cwt. gain in
body weight were 66±1.0 and 70±1.4 and the pounds of concentrates required were
285 and 303 respectively for the crossbred and purebred groups.
It is obvious from these trials that greater gains can be obtained more economically
from crossbred Duroc-Poland China pigs than from purebred Duroc pigs.
[J. N. W.]
Breeding for egg production. L. W. TAYLOR AND I. M. LERNER (1938).
Bull. Calif. Agric. Expt. Sta. 625.
T HE annual production of a hen is a measure of the contributions of all her egg-
producing characters. These characters are best studied separately to facilitate
selective breeding of a more intense nature.
The age of sexual maturity determines the onset of production. This is easily de-
termined by the age at which the first egg is laid. Climate, nutrition, health, etc. affect
this age independent of the heredity of a bird and must be considered in selecting for
early maturity. At least two pairs of genes are involved, one of which is sex-linked.
Three kinds of pauses, although admitted by the authors as a term difficult to define,
are also important. (1) It is not established as yet that winter pausing is entirely here-
ditary. The breeder can, however, and should select for breeding only members of those
families in which winter pausing is at a minimum or is absent. (2) Broodiness is a charac-
ter which varies with the breed but is always present. Selection should be made, accord-
ing to the authors, by the California breeders against broodiness. Two pairs of domi-
nant complimentary genes are involved. Either one alone has no effect, but when both
occur in the genotype then the character appears in the phenotype. This fact
makes it difficult to eliminate broodiness completely. The importance of broodiness in
the annual record of a bird depends both on the number of times the bird becomes broody
and on the length of time in each case before the bird resumes laying. (3) Finally,
spring and summer pauses occur. It is not known at present whether this character is
hereditary, although, such pauses do not occur in the best producers. Selection against
it is, therefore, possible for the breeder.
Persistency, or the length of the laying period before the onset of the annual moult,
is another important character. The date the hen was hatched seems to have more
effect on the age at last egg than on the date at last egg before moulting. Selection for