Two experiments were conducted to test the efficiency of using vaginal mucus conductivity measurements in sows to fix the breeding time for artificial insemination (Al). The apparatus used was the Heat Detector No 113 from Mitogiken Ltd. (Group Sumimoto, Toronto). In exp. 1, 57 crossbred sows were measured three times daily from 1 to 5 d after weaning (day 0) in order to characterize the pattern of vaginal mucus conductivity before estrus. In all females onset of estrus was checked twice daily in the presence of a sexually mature boar. Sow vaginal mucus conductivity readings (12 unit scale) averaged 4.1 units at weaning and 7.4 units at estrus. Only 60% of the sows reached the manufacturer's recommendation of 7–9 units at estrus. Conductivity increased by an average of three units between weaning and estrus in 62% of the sows. In exp. 2,201 crossbred sows were assigned randomly according to parity number to three groups. The first group was bred by Al when the sows showed a three-unit increase in vaginal mucus conductivity after weaning, without estrus detection by the boar. The two other groups of sows were checked once daily for onset of estrus using a mature boar, with a group bred by natural service and the other by Al. There was a large amount of variation between and within sows in absolute vaginal mucus conductivity readings. Only 29.3% of sows were inseminated at a reading of 7–9 units while 53.7% of the sows showed a differential of + 3 units after weaning, among which 50% reached a reading of 7–9 units at breeding. Sixteen (41.5%) sows showed behavioral estrus signs at an avg. conductivity reading of 4.0 units, without reaching the + 3 unit differential in conductivity. Conception rate and litter size of sows bred at a + 3 unit differential in conductivity were lower than the two groups of sows which were heat checked with a boar. No difference was observed among the latter two groups. The results indicated that vaginal mucus conductivity alone, without the use of a boar is not a reliable tool to fix the proper time to inseminate sows. Key words: Vaginal conductivity, artificial insemination, estrus, postweaning, sow
127 Comparison of long-term progestin-based protocols to synchronize estrus prior to fixed-time artificial insemination or natural service in Bos indicus-influenced beef heifers.
