Single Nucleotide Polymorphisms Associated with Feed Efficiency in Sheep

Identification of genetic markers for traits of economic importance may enable livestock producers to better utilize marker-assisted selection.  A previous genome-wide association study using both meat and wool breed sheep (n = 502) identified 50 SNP nominally (P < 0.001) associated with feed efficiency using a dominant multi-locus mixed model.  The objective of this study was to validate eight of these SNP in an external population of Targhee ewes of known feed efficiency status.   Briefly, individual feed intake data were collected on Targhee ewes (n = 80) for 70 d, and feed efficiency estimated for each ewe.  Blood samples were collected from the 25% most efficient (n = 20) and the 25% least efficient (n = 20) ewes, and DNA was extracted and amplified.  Genotypes for the eight SNP of interest were determined in selected ewes, using appropriate restriction enzymes, and visualized using standard gel electrophoresis.  The effect of each individual SNP genotype on feed efficiency was estimated using the GENMOD procedure of SAS, assuming a binomial distribution for feed efficiency status (high efficiency or low efficiency).  Only one SNP, on chromosome 15, tended (P = 0.098) to segregate with feed efficiency status in the Targhee ewes; no other SNP were associated with feed efficiency.  These results suggest that while one SNP associated with feed efficiency was confirmed, many SNP are likely to be population specific and caution should be exercised in using such SNP across different groups of sheep.