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Title: EVALUATION OF SIRE PREDICTED TRANSMITTING ABILITIES FOR EVIDENCE OF X- CHROMOSOMAL INTERITANCE IN NORTH AMERICAN SIRE FAMILIES

Author
item BOETTCHER, P - UNIVERSITY OF GUELPH
item JAIRATH, L - UNIVERSITY OF GUELPH
item Vanraden, Paul

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: This study tested for difference between genetic merits of sons and daughters of sires and for evidence of segregating quantitative trait loci on the X chromosomes of North American Holsteins. Son PTA adjusted for sire PTA was used as the dependent variable to test for biases and for genes that were passed from sire to daughter but not to son. The test of variability across sires of sons merely indicated an unaccounted source of variation, for which genes on X chromosomes might be responsible. Critical values for this test and power were determined by simulation for a variety of populations and traits differing in heritability, size of the X chromosome effect, and allelic frequency. Simulated genes on the X chromosome were detected with high power at intermediate frequencies of the favorable allele. The power of the test increased as the size of the effect increased and as genetic variance attributed to autosomes decreased. The test was then applied to recently evaluated data for the US and Canadian Holstein populations. Genetic evaluations for >17,000 bulls from the US and >9000 from Canada were included. Results suggested that a small amount of extra variation was present for some traits formally evaluated in North America, but that genes on the X chromosome were unlikely to be the cause.

Technical Abstract: This study tested for difference between genetic merits of sons and daughters of sires and for evidence of segregating quantitative trait loci on the X chromosomes of North American Holsteins. Son PTA adjusted for sire PTA was used as the dependent variable to test for biases and for genes that were passed from sire to daughter but not to son. The test of variability across sires of sons merely indicated an unaccounted source of variation, for which genes on X chromosomes might be responsible. Critical values for this test and power were determined by simulation for a variety of populations and traits differing in heritability, size of the X chromosome effect, and allelic frequency. Simulated genes on the X chromosome were detected with high power at intermediate frequencies of the favorable allele. The power of the test increased as the size of the effect increased and as genetic variance attributed to autosomes decreased. The test was then applied to recently evaluated data for the US and Canadian Holstein populations. Genetic evaluations for >17,000 bulls from the US and >9000 from Canada were included. Results suggested that a small amount of extra variation was present for some traits formally evaluated in North America, but that genes on the X chromosome were unlikely to be the cause.