Genetic and Environmental Effects Influencing Guernsey Type Classification Scores

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Abstract
American Guernsey Cattle Club type classification scores from 1956-1977 were examined. Herd explained 7-15%, year 1 to 9%, and herd-year 9-23% of variation in type traits. Age was important for most traits, increasing variation explained beyond a herd-year model by 1-7%. Month of classification and classifier increased multiple correlation squared beyond the herd plus year model by 0.5% or less for all traits. Two-way interactions between age, month of classification and classifer were small. Repeatabilities were 26-49%. Age-correction factors were developed. Heritabilities of 0.30 for final score, 0.23 for general appearnace, 0.19 for dairy character, 0.30 for body capacity and 0.19 for mammary system were estimated from 23,072 daughter-dam pairs. Other heritabilities ranged from 0.13 for suspensory ligament to 0.43 for stature. Genetic correlations with final score were 1.00 for general appearance, 0.78 for dairy character, 0.75 for body capacity, and 0.74 for mammary system and ranged from 0.65 to 0.80 for other subtraits. Phenotypic correlations with final score were 0.89 for general appearance, 0.63 for dairy character, 0.56 for body capacity and 0.67 for mammary system and ranged from 0.40-0.64 for other subtraits.