Cervix-Deep Rectal Temperature Differential on the Day of Ovulation is Correlated With Embryo Recovery Results in Mares.

Variations in temperature throughout the reproductive tract have been noted in many species. A recent study found the cervix-rectum temperature differential (CR-TD) in cattle was related to fertility. The present study aimed to assess the CR-TD in mares around the time of ovulation and relate it to embryo recover. Over 52 cycles, mares were inseminated with a fertile stallion and embryo recovery was undertaken on Day 7 post ovulation. Further 10 control mares were not inseminated. Rectal and cervical temperatures were measured using a precision thermometer on four or five occasions: the day of deslorelin administration and insemination, the day before ovulation, the day of ovulation (Day 0), the day after ovulation and, for inseminated mares, before embryo recovery on Day 7. One-way ANOVA showed that the CR-TD was significantly lower on the day of ovulation in the 36 positive cycles, in which an embryo was recovered, versus the 16 in which the embryo flush was negative (0.21 ± 0.17 vs. 0.40 ± 0.09°C; p < 0.001). Control cycles showed equivalent CR-TD to positive (0.13 ± 0.22 vs. 0.21 ± 0.17°C; p = 0.196) but not negative cycles (0.13 ± 0.22 vs. 0.40 ± 0.09°C; p < 0.001). A positive embryo recovery was associated with lower CR-TDs from the time of insemination and deslorelin to the day after ovulation compared to the day of embryo flushing (RM ANOVA; p < 0.001; Pairwise comparisons; p ≤ 0.01, in all cases). Rectal or cervical temperatures per se showed no significant differences between positive, negative or control cycles at any time point. In conclusion, a thermoregulatory process occurs close to ovulation which results in a lower CR-TD in cycles that produced an embryo versus those which did not. Further characterisation of TDs within the reproductive tract of the mare would increase our understanding of the conditions required for optimum fertility.

Successful vitrification of equine embryos >300 microns without puncture or aspiration.

BACKGROUND: Equine embryos >300 µm require puncture before vitrification. Protocols that do not require pre-puncture would make vitrification easier and allow for its widespread use. OBJECTIVES: To design a successful vitrification protocol for embryos >300 µm without puncture as a pre-treatment. STUDY DESIGN: Experimental in vivo study. METHODS: Thirty-eight embryos were divided into 3 groups (G1: ≤300 µm, n = 11; G2: >300-500 µm, n = 20; G3: >500 µm, n = 7). Embryos were vitrified using a human vitrification kit. Following a 15 min exposure to equilibration solution (ES; 7.5% DMSO +7.5% ethylene glycol [EG] in a base medium [BM] of M199 HEPES-buffered medium [H199] + hydroxypropyl cellulose + gentamycin), embryos were exposed for ≤90 s to a vitrification solution (15% DMSO +15% EG + 0.5 M trelahose in BM), loaded onto a Cryolock and plunged into LN2. Warming was undertaken by plunging the Cryolock tip into 1 mL of H199 + 20% FBS + pen/strep +1 M sucrose at 42°C for 1 min. The embryos were then moved to a 0.5 M sucrose solution for 4 min, then placed in Vigro Hold for 4 min prior to transfer to a recipient. RESULTS: Pregnancy rates were 81.8% (9/11) for G1, 80% (16/20) for G2, and 0% (0/7) for G3. The largest embryo to survive was 480 µm. MAIN LIMITATIONS: Limited numbers and only one pregnancy was followed to term. CONCLUSIONS: Equine embryos ≤480 µm can be successfully vitrified using a protocol with a longer exposure time to the ES. This does not appear to have a negative effect on early embryonic development.

The effect of embryo reduction and transfer on luteostasis in the mare.

This study investigated the effects of embryo reduction and transfer of Day 11 embryos, with or without subsequent reduction, on luteostasis in the mare. In Experiment 1, reduction of embryos at Days 10 (n = 15), 11 (n = 47), 12 (n = 36), 13 (n = 27), 14 (n = 5) and 16 (n = 2) of pregnancy resulted in luteostasis in 13%, 47%, 78%, 89%, 80% and 100% mares. Mares undergoing > 1 embryo reduction showed consistency in when luteostasis occurred. In Experiment 2, transfer of Day 11 embryos to recipient mares 10 (n = 9), 11 (n = 8), 12 (n = 9) and 13 (n = 8) days post ovulation resulted in luteostasis in 78%, 87.5%, 78% and 37.5% of mares. Only 22%, 37%, 0% and 12%, respectively, of these mares remained pregnant. In the Day 10, 11 and 12 recipients luteostasis occurred on at least one occasion when an embryo was detected at 24 h but not at 48 h post transfer. In the Day 12 recipients luteostasis occurred on three occasions (3/9;33%) when the transferred embryo was not detected at 24 h. In Experiment 3 reduction of a Day 11 embryo 24 h after transfer to a Day 10 (n = 4), 11 (n = 6), 12 (n = 6) or 13 (n = 6) recipient resulted in luteostasis in 100%, 83%, 100%, and 83% of mares. All five Day 11 recipients that had an embryo reduced 12 h post transfer became luteostatic. These results suggest there is plasticity overall, but individual rigidity, in the timing of maternal recognition of pregnancy. Furthermore, an intact embryo need only be present in the uterus for 12 h to cause luteostasis.

A new strain of Taylorella asinigenitalis shows differing pathogenicity in mares and Jenny donkeys.

BACKGROUND: Three horse mares inadvertently inseminated with semen from a Tayorella asinigenitalis-positive Jack donkey developed severe, purulent endometritis whereas two Jenny donkeys mated naturally to the same Jack donkey did not develop clinical signs of infection. OBJECTIVES: To isolate and identify the causative agent. STUDY DESIGN: Case report. METHODS: Endometrial swabs from the infected mares were cultured on selective and non-selective media under aerobic and microaerophilic conditions. Isolates were subjected to Gram staining, oxidase and catalase tests, the Monotayl Latex Agglutination test and PCR to test for both T. equigenitalis and T. asinigenitalis. In vitro antimicrobial susceptibility testing was performed and the bacterial isolate was genotyped using MLST. RESULTS: A new sequence type of T. asinigenitalis was confirmed. MAIN LIMITATIONS: A limited numbers of mares and donkeys are described. CONCLUSIONS: This strain of T. asinigenitalis causes a severe venereal infection in mares but not in Jenny donkeys.