A. Bagnato et Pa. Oltenacu, GENETIC-STUDY OF FERTILITY TRAITS AND PRODUCTION IN DIFFERENT PARITIES IN ITALIAN FRIESIAN CATTLE, Journal of animal breeding and genetics, 110(2), 1993, pp. 126-134
A data set of production records with breeding information was used to
analyse the relationship between open period, days to first breeding,
conception rate at first service, number of services per conception a
nd 305 day milk yield adjusted for age/month of calving and open perio
d in the Italian Friesian Cattle Breed. Separate analyses were perform
ed for the first three parities. Heritability estimates for reproducti
ve traits varied from .01 to .03 and for productive traits from .16 to
.22 depending on parities. Repeatabilities for fertility traits were
.02 to .08 while for milk yield they were between .49 and .59. Open pe
riod and days to first service were found to be highly correlated (gen
etic correlation: +.70/+.92) as were conception rate at first service
and number of services per conception (-.98). An antagonistic genetic
relationship was found between all reproductive traits considered and
production. The magnitude of the antagonistic genetic association betw
een production and fertility indicate that genetic deterioration of fe
rtility is to be expected if selection pressure continues to be applie
d to milk production only. For multiple trait selection, the reproduct
ive measures which complement each other are days to first service and
first service conception rate (or number of services per conception).