Genet. Sel. Evol.
Volume 37, Number 6, November-December 2005
|Page(s)||615 - 634|
A simulation study for the analysis of uncertain binary responses: Application to first insemination success in beef cattleRobyn L. Sappa, Matthew L. Spanglera, Romdhane Rekayaa, b and J. Keith Bertranda
a Animal and Dairy Science Department, The University of Georgia, Athens, Georgia 30602, USA
b Department of Statistics, The University of Georgia, Athens, Georgia 30602, USA
(Received 5 July 2004; accepted 6 August 2005)
Abstract - A simulation was carried out to investigate the methods of analyzing uncertain binary responses for success or failure at first insemination. A linear mixed model that included, herd, year, and month of mating as fixed effects; and unrelated service sire, sire and residual as random effects was used to generate binary data. Binary responses were assigned using the difference between days to calving and average gestation length. Females deviating from average gestation length lead to uncertain binary responses. Thus, the methods investigated were the following: (1) a threshold model fitted to certain (no uncertainty) binary data (M1); (2) a threshold model fitted to uncertain binary data ignoring uncertainty (M2); and (3) analysis of uncertain binary data, accounting for uncertainty from day 16 to 26 (M3) or from day 14 to 28 (M4) after introduction of the bull, using a threshold model with fuzzy logic classification. There was virtually no difference between point estimates obtained from M1, M3, and M4 with true values. When uncertain binary data were analyzed ignoring uncertainty (M2), sire variance and heritability were underestimated by 22 and 24%, respectively. Thus, for noisy binary data, a threshold model contemplating uncertainty is needed to avoid bias when estimating genetic parameters.
Key words: binary data / fertility / fuzzy logic / simulation / threshold model
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© INRA, EDP Sciences 2005