Relationships among udder shape, udder capacity, cow longevity and calf weights

Udder capacity and udder shape were scored on 3- to 10-yr-old cows from a large Hereford herd. Udder capacity was scored from 1 (small) and 5 (large) and udder shape was scored from 1 (balanced, udder level with ground) to 5 (unbalanced, funnel-shaped udder). Data were analyzed within age of cow for udder capacity scores from 1 to 4 and for udder shape scores from 1 to 3 because of the limited number of observations in other categories. Year of birth of cow was a significant source of variation in both udder capacity and udder shape. Days in lactation (ranging from 81 +/- 23 d in 3-yr-old cows to 71 +/- 25 d in 4-yr-old cows) was an important source of variation for udder capacity; as lactation progressed udder capacity score declined. Body condition of the cow was an important source of variation for udder capacity in 3- and 4-yr-old cows; cows with more external body condition had larger udder capacity scores. The heritability estimates of udder capacity and udder shape for 3-yr-old cows were .12 +/- .14 and .15 +/- .16, respectively; the repeatability estimates of scores over years were .14 +/- .02 and .16 +/- .03, respectively. Residual correlations between udder capacity and udder shape were low, ranging from -.10 in 3-yr-old cows to .10 in 6-yr-old cows. Neither udder characteristic affected the number of years a cow remained in the herd, but cows with unbalanced udders had more udder defects.(ABSTRACT TRUNCATED AT 250 WORDS)