Submitted to: Brazilian Animal Science Society
Publication Type: Proceedings
Publication Acceptance Date: September 26, 2006
Publication Date: October 10, 2006
Citation: Silva, M.V., Van Tassell, C.P., Sonstegard, T.S., Cobuci, J.A., Gasbarre, L.C. 2006. Estimates of genetic parameters using random regression models for gastrointestinal helminthoid data in cattle. Brazilian Animal Science Society. CD-Rom - MEL036. pp. 105.
Accurate genetic evaluation of livestock is based on appropriate modeling of phenotypic measurements. Sometimes these phenotypes are measured several times over the life of the animal, so called longitudinal data. In ruminants, fecal egg count (FEC) is commonly used to measure resistance to nematodes. A series of repeated FEC measurements may provide information about the population dynamics of a group or individual. A total of 6,378 FEC measures were determined for 409 animals between 1992 and 2003 from Beltsville Agricultural Research Center Wye Angus herd. Original data were transformed using an extension of the Box-Cox transformation to approach normality and to estimate (co)variance components. The database was analyzed using Random Regression Models (RRM), by the Restricted Maximum Likelihood method. Within the different orders of Legendre polynomials used, those with more parameters (order 4) adjusted FEC data best. Results indicated measurements of FEC obtained in the period between 12th and 26th weeks are genetic correlated. RRM may be used as a new tool for genetic and non-genetic studies of FEC.