|Goodling, Jr, Robert - PENN STATE EXTENSION|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 18, 2005
Publication Date: May 1, 2005
Citation: Wiggans, G.R., Goodling, Jr, R.C. 2005. Accounting for pregnancy diagnosis in predicting days open. Journal of Dairy Science. 88(5):1873-1877. Interpretive Summary: The system for predicting days open for cows with between 130 and 249 DIM without a subsequent calving was revised to have different equations for cows confirmed to be pregnant, confirmed to be open, or with unknown pregnancy status. The largest difference was for lactations of cows confirmed to be open where the original system underpredicted days open by >96 d for the 130-to-149 DIM interval. This method to improve predictions of days open was applied for daughter pregnancy rate evaluations in November 2004.
Technical Abstract: The system for estimating days open for cows with no subsequent lactation was examined to determine if estimates should vary depending on pregnancy diagnosis. Pregnancy diagnosis information was unavailable when the original prediction system was developed. Reporting of diagnoses began in 2002. New prediction equations were estimated from nearly 1.1 million Holstein lactations for 20-d intervals from 110 to 250 DIM. Use of pregnancy diagnosis improved accuracy compared to the original system. The improvement was particularly evident for lactations of cows confirmed not to be pregnant in the 130-to-149 DIM interval, where predicted days open increased by >96 d. For lactations of cows with a confirmed pregnancy, predicted days open decreased by 18 d for the same interval. Prediction errors decreased with increasing DIM. Jersey lactations averaged fewer days open, but in most cases Holstein solutions provided adequate predictions. Specific adjustments were generated for lactations with no breedings reported. Those adjustments reduced the predicted days open averaged across parity by an amount that increased from 9 to 28 d with DIM interval. The new prediction equations were implemented for November 2004 evaluations for daughter pregnancy rate.