Breed-specific adjustment factors for reproductive traits in Duroc, Hampshire,Landrace, and Yorkshire swineM. S. Culbertson, J. W. Mabry, J. K. Bertrand and A. H. NelsonJ ANIM SCI 1997, 75:2362-2367.The online version of this article, along with updated information and services, is located onthe World Wide Web at:http://jas.fass.org/content/75/9/2362www.asas.orgDownloaded from jas.fass.org by guest on July 13, 2011
Breed-Specific Adjustment Factors for Reproductive TraitsHampshire, Landrace, and Yorkshire Swinein Duroc,M. S. Culbertson 1 , J. W. Mabry 2 , J. K. Bertrand, and A. H. NelsonAnimal and Dairy Sciences Department, University of Georgia, Athens 30602-2771ABSTRACT: Number born alive (NBA) and litterweaning weight (LWT) can be influenced by manyfactors, including environment, parity, age at farrowing,lactation length, and genetic merit as well asnumber of pigs after transfer (NAT) and weaning age(WNAGE) for LWT. The objectives of this study wereto estimate adjustment factors for NBA and LWTusing all effects in the model and to refine parityeffects by including age of the sow in parity 1 (P1)and parity 2 (P2). The models used included fixedeffects of contemporary groups and parity/age class,random direct genetic and permanent environmenteffects, as well as the fixed effects of NAT andWNAGE for LWT. A large effect due to age of the sowat breeding within P1 and P2 was found and newadjustments were found to differ from previousstudies. In the Yorkshire population, for example, theaverage P1 adjustment was 1.0 pig in this study,compared to the current .69; however, this rangesfrom 1.46 for the youngest P1 females to .57 for theoldest. Similarly, in P2 the average adjustment wasfound to be .50, with an adjustment of .99 for theyoungest P2 and 0 for the oldest. Also, age of dam wasfound to contribute variation to P1 litter records forLWT. A residual analysis showed nonsignificantdifferences ( P > .60) across the age classes after usingthe new adjustments; however, significant differences( P < .01) remained after using the current adjustments.Key Words: Pigs, Litter Traits, AgeJ. Anim. Sci. 1997. 75:2362–2367IntroductionRate of genetic improvement depends on the use oftools that allow producers to accurately measureperformance and estimate genetic merit. Traditionally,adjustment factors have been used to standardizeperformance records and better allow for isolation ofthe genetic component of observed variation. Currentlitter adjustment factors are provided by the NationalSwine Improvement Federation (NSIF, 1987) andwere assumed common to all breeds. Litter adjustmentsfor the American Landrace and Yorkshirepopulations were updated by Brubaker et al. (1994)and found to differ between breeds and from the NSIFfactors.Reproductive performance of sows can be affectedby many factors (Clark and Leman, 1986; Almond,1992). Litter size can be affected by, but not limitedto, contemporary group (environment), parity, age atfarrowing, previous lactation length, weaning toconception interval, and genetic merit. Litter weight isinfluenced by those factors and age at weaning andnumber weaned. Current adjustment factors werederived by accounting for parity, weaning age ornumber after transfer, and the environment. Factorssuch as genetic merit and age at farrowing have beenignored. However, computing power and programshave advanced and now allow for the use of animalmodels that include a variety of fixed and randomeffects. The inclusion of these additional effects,including genetic merit, should increase the accuracyof estimating adjustment factors.Therefore, the objectives of this study were 1) toderive new litter adjustment factors using a morecomplete estimation model, 2) to analyze the need forbreed-specific adjustments for the major breeds ofswine, and 3) to analyze the efficacy of theseadjustment factors compared with those currently inuse.Materials and Methods1 Present address: Cotswold USA, 15491 State Hwy. 941, Alden,IA 50006-9103.2 To whom correspondence should be addressed.Received December 16, 1996.Accepted May 22, 1997.DataDuroc, Hampshire, Landrace, and Yorkshire litterrecords were obtained from the National Swine2362Downloaded from jas.fass.org by guest on July 13, 2011
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