Viewing Abstract # 25180 for 2008 Joint ADSA-ASAS Annual Meeting

Viewing Abstract # 25180

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Breeding and Genetics

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Extension Education

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poster

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Abstract & Author Information

Factors that affect abortion frequency in dairy herds in the United States
R. H. Miller*, M. T. Kuhn, H. D. Norman, J. R. Wright; Animal Improvement Programs Laboratory, ARS, USDA, Beltsville, MD, USA

Frequency of abortions was studied for lactating cows with 2,980,527 records in the USDA national dairy database. Lactations had been terminated between 1995 and 2005, and cows had been >151 d pregnant at lactation termination. Records without breeding dates were excluded. Abortion frequency for 2005 was 1.6%. Analyses were conducted with PROC GLM to determine effects of herd, year, month, parity (1, 2, ..., 7, ≥8), and gestation stage (152 to 181 d, 182 to 211 d, 212 to 241 d, and ≥242 d pregnant) at lactation termination as well as effects of breed (Holstein, Jersey, and other breeds including crossbreds) and 305-d standardized milk yield. Supplemental analyses examined effects of herd size (50 to 99, 100 to 199, ..., 900 to 999, ≥1,000 cow-years) and location (state). Abortions were most frequent in July and least frequent in December (difference of 0.38%). Abortion frequency decreased from parity 1 to parities ≥8 (difference of 0.52%). Gestation stage had the greatest impact on abortion frequency. Abortions were most frequent at 152 to 181 d pregnant, and trend in abortion frequency was nonlinear across gestation stage. Compared with ≥242 d pregnant, abortion frequency was 3.14% higher at 152 to 181 d pregnant and 1.07% lower at 212 to 241 d pregnant. Abortions for Holsteins and Jerseys occurred more frequently (0.38 and 0.07%, respectively) than for other breeds. Regression of abortion frequency on lactation milk yield was 0.26%, 0.26%, and 0.19% per 1,000 kg of milk for Holsteins, Jerseys, and other breeds, respectively. Regression differences primarily reflect breed differences. Abortion frequency was 0.95% higher for herds with 700 to 799 cow-years than for herds with 50 to 99 cow-years. California herds had the highest abortion frequency (2.18% higher than North Dakota, the state with the lowest frequency). Increased knowledge of factors that affect abortion frequency can aid in the development of management practices for reducing the incidence of abortion, e.g., more intense monitoring of cows 2 to 6 wk after mid-gestation.

KEYWORDS
abortion frequency
gestation stage
lactation termination