Threshold Models Applied to Holstein Conformation Traits

¹ Department of Genetics and Animal Breeding, Agricultural Academy, Al. Mickiewicza 24/28, 30-059 Krakow, Poland
² Centre for Genetic Improvement of Livestock, Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada N1G 2W1

Threshold animal models were applied to five conformation traits of Canadian Holsteins. The estimated breeding values for sires from the threshold model allowed the calculation of predicted percentages of daughters in the desirable categories. Results were compared with those from a linear animal model in terms of their ability to predict future percentages of daughters in the desirable categories using an independent set of data. There was no advantage in a threshold model compared with a conventional linear animal model in its ability to predict future daughter performance. This was likely due to the 18 categories used in the classification of major type traits in Canada and the nearly normal distribution of observations across categories.

Key Words: threshold model • type traits • Holsteins

Submitted on December 13, 1990
Accepted on May 2, 1991