The Effect of Inbreeding and Environmental Factors on the Weaning Weight and Post-weaning Growth of Range Hereford Cattle PDF Download

Author: Geoffrey Oswald Harwin
Publisher:
ISBN:
Category : Cattle
Languages : en
Pages : 158

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Book Description
The present study was initiated to determine the effects of inbreeding and certain environmental and genetic factors on the weaning weight of range Hereford calves. The study was also extended to include an investigation of the effect of these variables on post-weaning traits of range Hereford females including yearling gain and weight at 18 months, 2 1/2 years and 3 1/2 years of age. The data used in the study were obtained from a long term cattle breeding project initiated by Colorado State University in 1946 at the San Juan Basin Experiment Station and included onservations from 16 inbred lines of Hereford cattle, crosses between yhese lines and a control herd. The preliminary phase of the study was concerned with the development of appropriate mathematical models enabling minimum variance unbiased estimates of the various genetic and ebvironmental factors under investigation. The interactions between the various main effects as they affect weaning weight were investigated simultaneously by means of a least squares analysis. The interactions of sex x mating system, sex x age of dam and year x age of dam were significant. Investigation of the within year regression of weaning weight on age of calf also indicated a significant interaction between age of calf and year. Preleminary investigation indicated a marked curvilinear decline in weaning weight with inbreeding and differential response to inbreeding of both lines and sexes. The results of the preliminary studies were used in developing the final models...