ARS | Publication request: IDENTIFICATION OF QUANTITATIVE TRAIT LOCI AFFECTING PARASITE INDICATOR TRAITS IN A DOUBLE BACKCROSS POPULATION OF SHEEP.

Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract
Publication Acceptance Date: July 1, 2005
Publication Date: September 25, 2005
Citation: Sonstegard, T.S., Iraqi, F., Mugambi, J., Van Tassell, C.P., Garcia, F., Hanotte, O., Nagda, S., Gibson, J., Baker, L. 2005. Identification of quantitative trait loci affecting parasite indicator traits in a double backcross population of sheep. [abstract]. ADSA/ASAS Joint Meeting, Minneapolis, MN, number 252.

Technical Abstract: The natural genetic variability of the ruminant immune system provides a feasible means to control gastro-intestinal (GI) parasite infection. To initiate explanation of important allelic differences, a genome-wide analysis for quantitative trait loci (QTL) was initiated in a double backcross population generated by mating six F1 Red Maasai x Dorper Rams to both Red Maasai (resistant) and Dorper (susceptible) ewes. A total of 1,063 backcross lambs were monitored through two cycles of natural challenge on pasture. Only the phenotypic extremes (most resistant 10% and most susceptible 10%) for fecal egg count (FEC), packed cell volume (PCV) and the decline in PCV (PCVD) measured on 6 month old lambs were genotyped (N=371 lambs). A preliminary half-sib regression analysis was done on chromosomes (Chr) 6, 8, 9, 10, 11, 13, 14, 16, 20, 23, and 26. Significant QTL (f > 3.0) were detected for FEC and PCV indicator traits on Chr 6, PCV on Chr 20, and live weight on Chr 26. The QTL detected on Chr 6 is located in the approximate genome position containing QTL found in cattle and other sheep populations for parasite indicator traits. These results are an initial step in developing breeding schemes based on marker-assisted selection that will introgress genomic regions controlling resistance from one breed to another.