Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 29, 2012
Publication Date: July 1, 2012
Citation: Norman, H.D., Miller, R.H., Wright, J.R., Hutchison, J.L., Olson, K.M. 2012. Factors associated with frequency of abortions recorded through Dairy Herd Improvement test plans. Journal of Dairy Science. 95(7):4074-4084. Interpretive Summary: Frequency of abortions recorded from 2001 through 2009 among lactating cows was 1.3% for 8.5 million lactations. Reported abortions were most frequent early in pregnancy: 4.4% for 152 to 175 d and 0.6% for 226 to 250 d. Frequency was highest for parity 1 (1.4%) and lowest for parity >=8 (1.0%). Recorded abortions were most frequent from May through August and least frequent from November through January. Cows with high milk yield had more recorded abortions than their lower yielding contemporaries. Early pregnancy losses because of recessives went unreported.
Technical Abstract: Frequency of abortions recorded through Dairy Herd Improvement (DHI) testing was summarized for cows with lactations completed from 2001 through 2009. Reported abortions were 1.3% for 8.5 million DHI lactations of cows with recorded breeding dates and that were >151 d pregnant at lactation termination. Effects of year, herd-year, month, and days pregnant at lactation termination (i.e., the last day the cow was milked); parity; breed; milk yield; herd size; geographic region; and state within region associated with recorded abortions were examined. Abortions reported through DHI, which has a minimum of 152 d to code an abortion) were more frequent early during gestation; least squares means (LSM) were 4.4, 3.3, 1.2, and 0.6% for 152 to 175, 176 to 200, 201 to 225, and 226 to 250 d, respectively. Frequency of recorded abortions was 1.4% for parity 1 and 1.0% for parity >=8. The most abortions were reported from May through August (1.4 to 1.5%) and the least from November through January (1.1 to 1.2%). Frequency of DHI-recorded abortions was lower for Jerseys (1.1%) than for Holsteins and other breeds (combined, 1.3%). No relationship was found between reported abortions and herd size. The percentages derived should provide an indication of effects that have an important association with the rate of abortions but still be considered an underestimate of actual frequencies and effect of abortions as most go undetected. Additional pregnancy terminations due to genetic recessives were unreported. Various nonreturn rates (NRR) were calculated (60, 80, …, 200 d) to document pregnancy loss based on absence of homozygotes in the population. Breeding records for April 2011 USDA sire conception rate evaluations were analyzed with the model used for official evaluations with the addition of an interaction between haplotype carrier status of the service sire (embryo’s sire) and cow sire (embryo’s maternal grandsire). Over 13 million matings were examined at 60 d NRR for Holstein lethal recessive traits (brachyspina and complex vertebral malformation) and undesirable lethal haplotypes (HH1, HH2, and HH3) as well as 61,888 for a Brown Swiss undesirable recessive haplotype (BH1) and 673,079 for a Jersey undesirable recessive haplotye (JH1). Embryo loss was found for brachyspina, HH3, and JH1 by 60 d after breeding and for HH2 by 100 d. Uniform losses across the entire gestation period were shown for complex vertebral malformation and HH1.