|Miller, R - RETIRED, ARS|
Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: April 12, 2002
Publication Date: N/A
Technical Abstract: Genetic correlations among fertility, longevity, and other traits were estimated by multitrait REML. Five reproductive traits were compared using individual breeding data from 2,195,643 lactations of Holstein cows from 3447 sires and 3440 mating bulls. Heritabilities for cow fertility traits were 6.6% for days to first breeding, 4.0% for days to conception, 1.8% for number of inseminations, 1.0% for nonreturn rate, and 10% for gestation length. Days to conception were more correlated with days to first breeding (0.85) than with number of inseminations (0.61) or nonreturn rate (-.21). Mating bull fertility contributed 1.2% of phenotypic variance for 70-d nonreturn rate. Two longevity traits were compared using data from 1,062,791 Holstein cows born during 1992 through 1994 from 3080 sires. Productive life, which is limited to 10 mo of credit per lactation, was compared with lifespan, which included credit for all months between lactations. Heritabilities were 7.6% for productive life and 6.7% for lifespan; genetic correlation of the two traits was 0.986. Calving interval from first to second lactation was the measure of cow fertility. Cows culled after first lactation were assigned a mean calving interval of 415 d except those culled for reproductive failure, which were assigned the trait limit of 530 d. High protein and fat yields were correlated genetically (0.32) with long calving intervals. Fertility was more correlated with productive life (-0.59) than with lifespan (-0.46); somatic cell score also was more correlated with productive life (-0.31) than with lifespan (-0.28). Selection for productive life has reduced the decline in cow fertility, but direct selection on fertility evaluations could be more profitable.