Tenascin-XB (TNXB) amino acid substitution E2004G is associated with mature weight and milk score in American Rambouillet, Targhee, Polypay, and Suffolk sheep

Sheep are economically important worldwide, and growth-associated genetic variants, such as a TNXB charged amino acid substitution E2004G and a silent DGAT1 single nucleotide polymorphism (rs409119650), could improve sheep profitability. However, both were identified in single reports using small groups of sheep from outside the U.S. We evaluated 896 U.S. sheep from one location to investigate an association of TNXB E2004G and DGAT1 rs409119650 with growth and lifetime production. For TNXB E2004G, glutamic acid homozygotes had greater body weights in spring and fall at ages 3 and 4 (all P ≤ 0.05) and greater milk scores at ages 3 and 4 (P < 0.05). These data provide the first report of an association with milk score and confirm a prior report showing association of the ancestral glutamic acid allele with increased growth. While DGAT1 rs409119650 was associated with increased 4-year-old body weight and lifetime greasy fleece weight (P < 0.05), these results should be interpreted with caution given a low minor allele frequency (4.9%). Overall, confirmation that TNXB E2004G is associated with increased mature weight in divergent breeds and multiple countries may suggest a useful role in selective breeding programs.