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Asian-Australas J Anim Sci > Volume 11(5); 1998 > Article
Animal Breeding and Genetics
Asian-Australasian Journal of Animal Sciences 1998;11(5): 463-469.
DOI: https://doi.org/10.5713/ajas.1998.463    Published online October 1, 1998.
Factor Analysis of Genetic Evaluations for Type Traits of Canadian Holstein Sires and Cows
A. K. Ali, K. R. Koots, E. B. Burnside
Abstract
Factor analysis was applied as a multi-variate statistical technique to official genetic evaluations of type classification traits for 1,265,785 Holstein cows and 10,321 sires computed from data collected between August 1982 and June 1994 in Canada. Type traits included eighteen linear descriptive traits and eight major score card traits. Principal components of the factor analysis showed that only five factors explain the information of the genetic value of linear descriptive traits for both cows and sires. Factor 1 included traits related to mammary system, like texture, median suspensory, fore attachment, fore teat placement and rear attachment height and width. Factor 2 described stature, size, chest width and pin width. These two factors had a similar pattern for both cows and sires. In contrast, Factor 3 for cows involved only bone-quality, while in addition for sires, Factor 3 included foot angle, rear legs desirability and legs set. Factor 4 for cows related to foot angle, set of rear leg and leg desirability, while Factor 4 related to loin strenth and pin setting for sires. Finally, Factor 5 included loin strength and pin setting for cows and described only pin setting for sires. Two factors only were required to describe score card traits of cows and sires. Factor 1 related to final score, feet and legs, udder traits, mammary system and dairy character, while frame/capacity and rump were described by Factor 2. Communality estimates which determine the proportion of variance of a type trait that is shared with other type traits via the common factor variant were high, the highest > 80% for final score, stature, size and chest width. Pin width and pin desirability had the lowest communality, 56% and 37%.
Results indicated shifts in emphasis over the twelve-year period away from udder traits and dairy character, and towards size, scale and width traits. A new system that computes final score from type components has been initiated.
Keywords: Factor Analysis; Communalities; Principal Component; Genetic Evaluation; Type Traits


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