2009-Kuehn_et_al - Connectedness in Targhee and Suffolk...

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L. A. Kuehn, R. M. Lewis and D. R. Notter National Sheep Improvement Program Connectedness in Targhee and Suffolk flocks participating in the United States doi: 10.2527/jas.2008-1092 originally published online Oct 10, 2008; 2009.87:507-515. J Anim Sci http://jas.fass.org/cgi/content/full/87/2/507 the World Wide Web at: The online version of this article, along with updated information and services, is located on www.asas.org by on February 2, 2011. jas.fass.org Downloaded from
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ABSTRACT: Connectedness among animals in sepa- rate flocks reduces the risk of biased comparisons when selecting across flocks on EBV. The objective in this study was to assess levels of connectedness in the ge- netic evaluation of weaning weight among Targhee and Suffolk flocks participating in the US National Sheep Improvement Program (NSIP). Among flocks currently participating in the NSIP, a total of 25,404 weaning weight and 35,794 pedigree records were available for 16 Targhee flocks, and 14,017 weaning weight and 18,311 pedigree records were available for 24 Suffolk flocks. Connectedness was measured by using 2 different meth- ods. First, numbers of progeny with recorded weaning weights from linking sires (defined as sires with progeny in multiple flocks or sires born in one flock with progeny in another flock) were counted. Second, connectedness was measured by calculating the average prediction er- ror correlation of mean flock EBV (flock r ij ). Bench- marks for flock r ij were established, with 0.10 and 0.05 representing low and moderate risk of bias associated with comparing EBV among flocks, respectively. From 1995 through 2004, 44% of Targhee lambs with wean- ing weights were born to linking sires; in Suffolk lambs, that value was 23%. In 1990, 1995, and 2005, average flock r ij were 0.10, 0.19, and 0.28, respectively, among Targhee flocks, and 0.02, 0.02, and 0.04, respectively, among Suffolk flocks that participated in NSIP in all 3 yr. Among all active flocks in 2005, flock r ij aver- aged 0.13 in Targhees and 0.03 in Suffolks. Hierarchical clustering of flocks based on flock r ij revealed that all active Targhee flocks connected at a level near or above 0.10. In Suffolk flocks, 2 distinct clusters had formed, in which connectedness was relatively high within each cluster (flock r ij near 0.10) but was near zero between clusters. Risk of bias in comparing EBV among flocks in the Targhee was low; however, caution should be exercised when comparing EBV between Suffolk flocks from different clusters. Key words: connectedness, genetic evaluation, prediction error, sheep ©2009 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2009. 87:507–515 doi:10.2527/jas.2008-1092 INTRODUCTION Genetic evaluation in the US sheep industry is avail- able to individual producers through the National Sheep Improvement Program ( NSIP ; Notter, 1998). Through the NSIP, BLUP EPD are predicted for a variety of traits for animals in participating flocks. Producers can use these EPD to make selection decisions within and across flocks. However, comparisons of animals across flocks may be biased if base animals in different flocks have different genetic means (Lewis et al., 1999) and
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2009-Kuehn_et_al - Connectedness in Targhee and Suffolk...

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