EVALUATION OF DIFFERENT PROTOCOLS FOR PROSTAGLANDIN SYNCHRONIZATION TO IMPROVE REPRODUCTIVE-PERFORMANCE IN DAIRY HERDS WITH LOW ESTRUS DETECTION EFFICIENCY

The objective of this study was to evaluate different PGF(2 alpha) pro tocols against control protocols for herds with estrus detection effic iencies of 35, 55, and 75% using modeling and simulation: 1) PGF(2 alp ha) treatments based on the presence of a corpus luteum diagnosed by r ectal palpation, 2) PGF(2 alpha) treatments based on the presence of a corpus luteum diagnosed by an on-farm milk progesterone enzyme immuno assay, and 3) PGF(2 alpha) treatments based on a 14-d fixed treatment schedule without prior screening for ovarian status. After the start o f each protocol, estrus detection efficiency was 75% for 7 d after tre atment and 35 or 0% for the following week. For the third protocol, an additional modification at estrus detection efficiencies of 85 and 55 %, respectively, in the Ist and 2nd wk after treatment was evaluated t o establish a protocol for best case assumptions. All protocols improv ed reproductive performance relative to that of controls with estrus d etection efficiencies of 35 and 55%. The mean number of days open was reduced from 124.3 d in the control herd to 95.9, 95.0, and 92.7 for t he protocols based on rectal palpation, milk. progesterone test, and t he fixed treatment schedule, respectively. The protocols based on a fi xed treatment schedule were superior to protocols based on rectal palp ation and on-farm milk progesterone tests and resulted in better repro ductive performance and a higher increase in net return per cow per ye ar. Relative to a control herd with an estrus detection efficiency of 55%, it was cost effective to spend up to $10 per dose of PGF(2 alpha) , $9 per milk progesterone test, and $6 per rectal palpation.