The time of ovulation in relation to estrus duration in gilts

The objective of this study was to determine time of ovulation, monitored b y transcutaneous ultrasonography, relative to the duration of estrus in gil ts. We exposed 92 cyclic gilts, Camborough x Canabrid terminal line, at Day 19 of their third estrous cycle to vasectomized boars every 6 h for the de tection estrus. Transcutaneous ultrasonography was performed every 6 h, sta rting 24 h after the onset estrus, to determine time of ovulation. Estrus d uration was, on average, 52.6 h (range: 30 to 72 h), and ovulation occurred between 30 and 60 h after the onset of estrus (mean: 44 h), about 85 % of the way through the estrus period. The time of ovulation during estrus was dependent on the duration of estrus (Time of ovulation = (duration of estru s) x 0.409 + 22.7; r = 0.57, P = 0.0001). Prediction of the time of ovulati on in relation to duration of estrus is important for determining the optim al time for inseminating gilts. This knowledge would contribute to an impro vement in the fertilization rate and in reproductive efficiency of the bree ding herd. (C) 2000 by Elsevier Science Inc.