Abstract
The associations between occurrence of diseases, milk yield, and body condition score on conception risk after first artificial insemination (AI) were analyzed in an observational study on a convenience sample of 43 farms participating in a herd health program. Data were taken from 9369 lactations, from 4382 cows inseminated between 20 and 180 d in milk from 1990 to 1996. Two logistic regression models, one containing data from all lactations and a subset containing data from 1762 lactations with body condition scoring, were used to determine pregnancy risk at first AI. The effects of herd deviation in test-day milk yield, body condition score loss, and milk fat to protein ratio changes in early lactation were significant predictors of pregnancy risk, independent of disease; days in milk; farm; and seasonal factors. Three different methods of disease parameterization (incidence rates, binomial classes dependent on the interval in days since last occurrence with respect to AI, and a linear variable weighted for this interval) produced similar results. Metritis, cystic ovarian disease, lameness, and mastitis gave odds ratios for pregnancy risk ranging from 0.35 to 1.15, largely dependent on the interval in days from final disease occurrence to first AI. Displaced abomasum, milk fever, and retained fetal membranes resulted in odds ratios for pregnancy risk of 0.25, 0.85, and 0.55, respectively. These diseases showed little relationship between fertility and the number of days since last occurrence. Results of this study confirm the negative effects of milk yield, body score condition loss, and disease on dairy cow fertility. The effects of some diseases on first service conception were strongly dependent on the interval since last disease occurrence. This was especially valid for clinical mastitis, which has an extremely weak effect on conception if occurring prior to AI and is associated with >50% reduction in pregnancy risk if occurring in the 3 wk directly after AI.
| Original language | English |
|---|---|
| Pages (from-to) | 2589-2604 |
| Number of pages | 16 |
| Journal | Journal of Dairy Science |
| Volume | 82 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - 1 Jan 1999 |
Funding
The authors thank Hans Wilmink of the National Cattle Syndicate for providing the data on milk yield and AI. My sincere thanks to the farmers, veterinarians, and veterinary students involved in data collection. Special thanks to Alie Dekker for data entry and Mart Prins for data conversions. Research funds were provided, in part, by the Research fund W&M Nederland, R.O. Mid-West and Animal Health Service. Aalt Dijk-huizen and Arie Brand are also thanked for their suggestions to the manuscript.
Keywords
- Body condition score
- Conception
- Mastitis
- Test-day milk yield