Relationships between conformation and calving interval in Holstein cows.
Type information collected by the Holstein Association of Canada from 1976 to 1983 was matched with calving interval records from the Record of Performance program of Agriculture Canada. Type traits considered were final class, major scorecard breakdown traits (general appearance, dairy character, capacity, rump, feet and legs, mammary system, fore udder, rear udder), and eight descriptive traits (stature, size, style, dairyness, chest floor, loin strength, thurl width, pin setting). The edited data consisted of 22,791 records on first calf heifers by 2548 sires in 9272 herd-round of classification groups. Sire evaluations for both type and calving interval were available for 3312 sires. Heritability of calving interval was estimated to be .04. Heritability estimates of type traits ranged from .06 for style to .33 for size. Phenotypic correlations between the type traits and calving interval were essentially zero. The highest favorable genetic correlations with calving interval were for chest floor (-.42), rear udder (-.37), capacity (-.34), and highest antagonistic correlations were for dairyness (.43) and dairy character (.38). Direct selection for improved calving interval was estimated to be more efficient than indirect selection on any of the type traits considered.
D000818:Animals; D001721:Birth Intervals; D001824:Body Constitution; D002417:Cattle / Q000033:anatomy & histology*; D005260:Female; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*