Efficiency of vaginal electrical resistance measurements for oestrous detection and insemination in Rathi cows

Abstract

AbstractThe efficiency of vaginal electrical resistance (VER) measurements for oestrous detection was determined in four experiments. The mean VER during oestrus, metoestrus, dioestrus, pro-oestrus and anoestrus was 32·68±0·46, 41·26±1·17, 50·23±0·55, 43·52±0·54 and 55·86±0·57 ohms, respectively. There were significant (P < 0·01) differences between VERs at the different oestrous cycle stages, except those during pro-oestrus and metoestrus which were similar. Twelve cows were induced in oestrus using prostaglandin (PG) administration to study the changes in VER during the peri-oestrus period. VER values changed both on a within-day (P < 0·05) and day-today (P < 0·001) basis following PG administration. Of the eight cows that responded, all were classified as in oestrus by VER in comparison to five detected in oestrus by a teaser bull. There was a significant association between VER and probability of conception (P < 0·01). Conception rates were 84, 61 and 20% when animals were inseminated at VER ranges of 26 to 30, 31 to 35 and 36 to 40 ohms, respectively. In the final experiment VER was recorded each day at the time of milking in 22 cyclic cows for 60 days. Animals were inseminated when the VER declined below 35 ohms. Of these 22 cows five cows showed overt signs of oestrus and 11/22 (50%) became pregnant. Twenty-one days post AI, five cows returned to oestrus, based on low VER, whereas 17 continued to show a high VER but eight of these (8/17) were subsequently classified as non-cyclic. It is concluded that VER can effectively be used for oestrus detection and identification of the optimum time for insemination but has limited value for pregnancy diagnosis. Cows should be inseminated when a VER reading of less than 36 ohms is recorded.