Although programs combining prostaglandin (PGF2α) treatments and heat detection are very effective for dairy heifers, many producers have to rely on Timed A.I. protocols to get their heifers bred due to a number of different reasons. Unfortunately, when the original Ovsynch protocol is used in heifers, conception rates are — in general — much lower than conception results achieved with breedings performed following estrus detection. These lower results with Ovsynch in heifers seem to be related with faster follicular turn-over, lower ovulation rates, and higher percentage of heifers displaying premature estrus before scheduled A.I. (revised by Rivera et al., 2004). Most research groups tend to accept the fact that regular CIDRsynch-like protocols can efficiently reduce amount of heifers showing premature estrus during timed A.I. procedures; yet, conception rates don’t seem to be ideal, and most frequently inferior to conception results attained with breedings following estrus detection.

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