J. PHILIPSSON

English

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GENETIC ASPECTS OF FERTILITY IN CATTLE
J. PHILIPSSON
Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences
S-750 07 Uppsala /Swcden
The problem area of female fertility has been discussed, especially as regards its genetic
variation and correlations with production, in the light of recently published results. Further-
more the implications in selection of parameters found have been illuminated.
It is concluded that the magnitude of the additive genetic variance in several fertility
traits is considerable, despite the generally low heritability values of individual insemination
results. The genetic effect of cow culling within herds for poor fertility is almost negligible,
while progeny testing bulls for daughter fertility offers valuable information to be used for
selection purposes.
Several recent investigations appear to indicate antagonistic relationships between pro-
duction and fertility. However, the findings are somewhat ambiguous. Though when unfavour-
able correlations do exist, even though not very strong, detrimental effects on fertility will occur
as a consequence of intense long-term selection for yield, if the fertility of daughters is not
considered simultaneously with production in selection programmes.
SELECTION FOR FERTILITY ON THE BASIS OF A.I. DATA
O. SYRSTAD
Department of Animal Genetics and Breeding Agricultural Univetsity of Norway,
1432 As-NLH /Norway
i. Conception rate and calving interval are determined by the fertility of the bull and the fertility
of the cow jointly. One unit of genetic improvement in male fertility is therefore of equal
importance to one unit of improvement in female fertility.
2. The heritability of bull fertility, as measured by the N.R.-rates from a few hundred insemi-
nations, is large enough to provide a basis for efficient selection. The genetic standard
deviation is, however, considerably less for male than for female fertility.
3. The genetic correlation between male and female fertility is slight, and the same holds true
for the genetic correlation between male fertility and milk production.
q. In the final selection of progeny tested bulls due attention should be given to the estimated
breeding value of the bull with respect to male fertility.
GENETIC INFERENCES FROM THE FREQUENCY DISTRIBUTION
OF RETURN INTERVALS IN DAIRY COWS
R. BAR-ANAN
The Institute of Animal Science, The Volcani Research Center Bet Dagan lisyaci
Several investigations have pointed out that cycles between inseminations are longer by
about two days than cycles between estri. These differences are in concord with slaughterhouse
findings of very early embryonic death, which may postpone the recurrent estrus very slightly
or not at all. The main difference between regular breeding cows and repeat breeder cows
was not in fertilization but in the survival of the zygote above one week.
Heritability values for implantation failure, estimated by the skewness of return intervals
within 3i days were zero for the effect of the mating sire and about o.i by the sire of the cow.
Low fertile bulls had high proportions of regularly returning mates and low fertile daughter-
groups had skewed return intervals.
Heritability estimates for abortions post pregnancy tests were very low. The hypothesis
was advanced of additive genetic variation among males in fertilization and among females in
implantation and of non-additive mutations in the embryo.


GENETIC ASPECTS OF FERTILITY IN CATTLE

http://www.gse-journal.org/10.1051/gse:19800420/pdf

GENETIC ASPECTS OF FERTILITY IN CATTLE

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