The 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.

Ascaris suum possesses a large number of FMRFamide-related peptides (FaRPs) of which KNEFIRFamide (AF1), KHEYLRFamide (AF2) and KSAYMRFamide (AF8/PF3) have been shown to modulate the intrinsic, rhythmic activity of the vagina vera of A. suum in vitro. In the present study, the effects of the nematode FaRPs, SDPNFLRFamide (PF1), SADPNFLREamide (PF2) and KPNFIRFamide (PF4) (from Panagrellus redivivus) and AVPGVLRFamide (AF3) and GDVPGVLRFamide (AF4) (from A. suum) on the in vitro activity of the vagina vera were examined. The effects of each of the peptides were qualitatively and quantitatively distinct. All 3 FaRPs from P. redivivus were inhibitory, causing a cessation of contractions. PF2 was 3 times more potent than PF1, with a threshold of 1 nM. Although PF4 was the least potent (threshold, 10 nM), its effects at [ges ]10 nM were quantitatively the greatest. Both AF3 and AF4 (1 μM) induced complex, multiphasic responses consisting of an initial contraction and spastic paralysis followed by a return of contractile activity of increased amplitude. AF3 was 3 times more potent than AF4. The effects of these peptides had some similarities to those observed on A. suum somatic body wall muscle in vitro, with PF1, PF2 and PF4 being inhibitory and AF3 and AF4 being excitatory.

Changes in vaginal epithelium are known to occur during the normal oestrous or menstrual cycle and in ovariectomised animals in response to various hormones. However, vaginal changes due to exogenous gonadotrophins superimposed on the normal hormonal milieu as occurs in in vitro fertilisation programmes have not previously been demonstrated. Female rats were hyperstimulated with follicle stimulating hormone and human chorionic gonadotrophin prior to mating. Control mated animals were not injected. Vaginal tissue was collected at 4.5, 5.5 and 6.5 d after mating. Tissue was processed for light microscopy. Hyperstimulation by the exogenous gonadotrophins caused mucification, a decrease in the number of epithelial layers and an increase in the thickness of the epithelium on d 4.5 of pregnancy. The mitotic index of the epithelial cells was depressed in the hyperstimulated rats with respect to control animals. Exposure to high levels of oestradiol and an altered progesterone[ratio ]oestradiol ratio appear to have caused the changes in the vaginal epithelium.

Ascaris suum contains a large number of FMRFamide-related peptides (FaRPs) of which KNEFIRFamide (AF1), KHEYLRFamide (AF2) and KSAYMRFamide (AF8, also called PF3) have been extensively studied and are known to exert actions on somatic muscle strips of the worm. In the present study, the effects of AF1, AF2 and AF8 on the activity of the vagina vera of female A. suum have been examined in vitro. The vagina vera is a muscular tube connecting the uterus and vagina uteri to the gonopore and is probably involved in regulating egg output. The tissue exhibited spontaneous, rhythmic contractions in vitro, which were modulated by each of the FaRPs tested. The effects of each of the peptides were qualitatively and quantitatively different, and in each case were reversible. AF1 (1 μM) caused a biphasic response in the form of a transient lengthening of the preparation, followed by a shortening; contractions were initially inhibited but resumed 5 min post-addition of the peptide. Lower concentrations ([les ]0·1 μM) induced a less marked effect, with rhythmic contractions returning 5 min post-addition. AF2 and AF8 reduced contraction frequency at concentrations [ges ]0·1 μM. Both peptides also caused the tissue to shorten, although the effects of AF8 on baseline tension were inconsistent. The apparent potencies of AF1 and AF8 on contraction frequency of the vagina vera were 10-fold greater than AF2 and, unlike their actions on A. suum somatic body wall muscles, the actions of AF1 and AF2 were qualitatively different. Indeed, the effects of each of these FaRPs on the vagina vera were markedly different from those observed on the somatic muscle.