Tenascin-XB (TNXB) amino acid substitution E2004G is associated with mature weight and milk score in rambouillet, targhee, polypay, and suffolk sheep

Authors: CINAR, MEHMET ULAS - Erciyes University; Mousel, Michelle; HERNDON, MARIA - Washington State University; Taylor, Joshua - Bret; White, Stephen

Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2018
Publication Date: 8/10/2018
Citation: Cinar, M., Mousel, M.R., Herndon, M.K., Taylor, J.B., White, S.N. 2018. Tenascin-XB (TNXB) amino acid substitution E2004G is associated with mature weight and milk score in rambouillet, targhee, polypay, and suffolk sheep. Small Ruminant Research. 166:129-133. https://doi.org/10.1016/j.smallrumres.2018.06.013.
DOI: https://doi.org/10.1016/j.smallrumres.2018.06.013

Interpretive Summary: Sheep are economically important worldwide, and DNA tests predictive of growth could improve sheep profitability. There are two genetic variants (in the TNXB and DGAT1 genes) that were identified in single reports of growth association using small groups of sheep from outside the U.S., but neither has been confirmed in additional animal sets. We evaluated 896 U.S. sheep to investigate an association of the TNXB E2004G and DGAT1 rs409119650 variants 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%), which suggests more research should be done in other sheep with higher allele frequencies to test for consistent association. Some producers may desire increased growth, and others may want to maintain a certain body size for efficient production in their environment. Either way, confirmation that TNXB E2004G is associated with increased growth in divergent breeds and multiple countries may suggest a useful role in selective breeding programs.

Technical Abstract: 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 and greater milk scores in spring and fall at ages 3 and 4 years (all 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 growth in divergent breeds and multiple countries may suggest a useful role in selective breeding programs.