|Thallman, Richard - Mark|
|Cushman, Robert - Bob|
|Smith, Timothy - Tim|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2006
Publication Date: 2/1/2007
Citation: Allan, M.F., Thallman, R.M., Cushman, R.A., Echternkamp, S.E., White, S.N., Kuehn, L.A., Casas, E., Smith, T.P. 2007. Association of a single nucleotide polymorphism in spp1 with growth traits and twinning in a cattle population selected for twinning rate. Journal of Animal Science. 85(2):341-347. Interpretive Summary: Use of DNA markers to account for genetic variation for quantitative traits provides producers a tool to assist in genetic selection of superior animals. While some marker-assisted selection is currently practiced in the beef cattle industry, a limited number of markers have been developed for use by cattle producers and explain a relatively small proportion of the genetic variation for a limited number of traits. Therefore, there is a continued need for more genetic markers associated with economically important traits. The objective of this study was to evaluate the DNA marker in the osteopontin gene (SPP1) to confirm its role in yearling growth and to assess if it is having an effect on pre-yearling growth traits and reproduction. Results found SPP1 DNA marker to have a significant effect on birth, weaning and yearling weights. Selection for the favorable genotype of the SPP1 marker will increase weaning and yearling weight. Beef cattle producers need to take into account the increase in birth weight if using this marker to enhance weaning and yearling weight production.
Technical Abstract: Continued validation of genetic markers for economically important traits is crucial to establishing marker-assisted selection as a tool in the cattle industry. The objective of the present study was to evaluate the association of a single nucleotide polymorphism (T9/T10) in the Osteopontin gene (SPP1) with growth rate in a large cattle population spanning multiple generations and representing alleles from 12 founding breeds. This population has been maintained at the U.S. Meat Animal Research Center since 1981 and subjected to selection for twinning rate. Phenotypic records for this population included twinning rate and ovulation rate, providing an opportunity to examine potential effects of SPP1 genotype on reproductive traits. A set of 2,701 animals were genotyped for the T9/T10 polymorphism at SPP1; the genotypic data, including previously genotyped markers on chromosome 6 (BTA6), were used in conjunction with pedigree information to estimate genotypic probabilities for all 14,714 animals with phenotypic records. The genotypic probabilities for females were used to calculate independent variables for regressions of additive, dominance and imprinting effects. Genotypic regressions were fit as fixed effects in a mixed model analysis where each trait was analyzed in a two trait model where single births were treated as a separate trait from twin births. Association of the SPP1 marker with birth weight (P < 0.006), weaning weight (P < 0.007), and yearling weight (P < 0.003) is consistent with previously reported effects of SPP1 genotype on yearling weight. Our data supports the conclusion that the marker successfully tracks functional alleles affecting growth in cattle. The previously undetected effect of the marker on birth and weaning weight suggests that SPP1 marker genotype may explain a portion of the phenotypic variance explained by QTL for birth and hot carcass weights on BTA6.