Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: March 5, 2007
Publication Date: July 8, 2007
Citation: Norman, H.D., Wright, J.R., Kuhn, M.T., Hubbard, S.M., Cole, J.B. 2007. Genetic and environmental factors that affect gestation length. Journal of Dairy Science. 90(Suppl. 1):264(abstr. T73). Technical Abstract: Genetic and environmental factors that might affect gestation length (GL) were investigated so that more accurate predictions of calving dates could be provided to dairy producers. Data from >8 million calvings from 1999 through 2005 for 5 dairy breeds were assembled from lactation, reproduction, and dystocia records from across the United States. Effects examined were calf’s birth year, interaction of herd and calf’s birth year, calving month, interaction of dam’s age and parity, interaction of multiple-birth status and calf gender, dam’s lactation length, dam’s milk yield, service sire, dam’s sire, and dam. All effects were fixed except for service sire, dam’s sire, and dam. Mean GL was 279.5 d for Holsteins, 280 d for Jerseys, 282 d for Ayrshires, 286 d for Guernseys, and 288 d for Brown Swiss. Estimated standard deviation of GL was greatly affected by data restrictions but appeared to be near 6 d in all breeds. For Holstein cows, year differences in GL were small, but effect of calving month was large; mean GL was 278.2 d for July compared with 280.4 d for November. Mean GL for Holsteins with twins was 274.9 d compared with 279.4 and 280.5 d for those with single-birth females and males, respectively. Mean GL was 279 d for first-parity Holsteins compared with 279.5 d for the next 4 parities. Holsteins with lactations of <=250 d had a mean GL of 280.1 d compared with 278.5 d for cows that were milked for >500 d. Holsteins with standardized yield of <=6,000 kg had a mean GL of 279.0 d compared with 279.8 d for cows with yield of >16,000 kg. Heritability estimates for Holstein GL from cows (parity 2 to 5) were 24% for service sire and 8% for dam’s sires. Better prediction of time of parturition can help herd managers to fulfill the nutritional needs of pregnant cows and to administer better preventive health care so that metabolic diseases are minimized during high risk phases of cows’ lives.