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Division of Genetics and Department of Dairy Science, University of Wisconsin, Madison
ABSTRACT
The outcomes of 1,404 inseminations from matings of known inbreeding coefficients and blood types were used to estimate the mutational and incompatibility components of the genetic load in dairy cattle.
Inbreeding of the zygote and dam, and homozygosity for blood group factors had a significant deleterious effect on embryonic mortality. The effect of maternal-fetal incompatibility due to isoimmune antibodies had a significant effect on fetal mortality, also. However, the method of measuring incompatibility provided only a crude estimate.
A new index of inbreeding, "ll", devised by Slatis (1961) to measure lethals was used, but the correlation between "ll" and F was very high. For this reason it was impossible to divide the genetic load into lethal and detrimental components.
The mutational load affecting embryonic and fetal death was estimated to be 0.862 ± 0.233 and 0.407 ± 0.243, respectively, and the B/A ratios were 1.75 and 1.88, respectively, suggesting that most embryonic and fetal deaths are not due to genes maintained by recurrent mutation.
1 Division of Genetics (Paper No. 884) published with the approval of the director of the Agricultural Experiment Station. This project was supported in part by the Research Committee of the Graduate School with funds supplied by the Wisconsin Alumni Research Foundation, and in part by a research grant (E 1643) from the Dept. H.E.W., National Institutes of Health, P.H.S., and a research contract (AT 11-1827) from the U.S.A.E.C.
2 Present address: Department of Biology, Western Reserve University, Cleveland, Ohio.
3 Present address: Department of Genetics, University of Hawaii, Honolulu, Hawaii.
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