A case of a twin surviving to term following the abortion of its co-twin at 9 months in an Arabian mare.

Twin pregnancy in mares is one of the leading causes of abortions. Abortion invariably impacts both fetuses. This report describes an unusual case of a twin surviving to term following the abortion of its co-twin at 9 months in a 7-year-old Egyptian Arabian mare. At the time of abortion at 9 months of gestation, the size of the aborted fetus was equivalent to one of approximately 5 months of age while the age of the live co-twin was 9 months. Both fetuses were males. A skin sample was collected from the aborted fetus and hair samples were collected from the dam, sire and live foal for parentage analysis. The parentage analysis confirmed that both fetuses were by the same dam and sire stallion. The authors suggest several scenarios to explain this condition. This report describes a unique case of a twin surviving to term following the abortion of its co-twin at 9 months in a mare.

Effect of dose and day of treatment on uterine response to oxytocin in mares.

To determine the effect of dose and day of oxytocin treatment on intrauterine pressure, 6 normal mares were treated with 10 or 25 IU oxytocin 2 days before ovulation, on the day of ovulation and 2 days after ovulation. Intrauterine pressure (IUP) was measured using micro-tip-catheters (one placed intrauterine, a second and third serving as reference sensors in the vagina and external to the mare) and transmitted by telemetry for 30 min to establish a baseline before saline was administered, iv, and for an additional 30 min after saline administration. Oxytocin was then given, iv, and IUP was recorded for 60 min. No change in IUP was observed after saline injection. The administration of both 10 (n=16) and 25 (n=10) IU oxytocin induced a response (P<0.01). The intensity of response depended on the day of administration (P<0.01) and the dose of oxytocin (P<0.001). The variation of response was significantly greater after 10 IU oxytocin (CV 15.78%) compared with 25 IU oxytocin (CV 6.42%). The uterine response was greatest on Day 2 prior to ovulation and lowest on Day 2 after ovulation. The response was negatively correlated to increasing plasma progesterone (10 IU oxytocin: r = -0.435, 25 IU oxytocin: r = -0.265). There was no correlation between the uterine response and plasma estradiol-17beta concentration (P<0.01). In conclusion the results of this study show that oxytocin administration to mares before ovulation provides a greater response than after ovulation. A decline in the intensity of response after ovulation can be compensated for with a higher dose of oxytocin. Furthermore, the use of the multiple catheter technique is an effective method for assessing changes in uterine pressure.

PGFM response to exogenous oxytocin and determination of the half-life of oxytocin in nonpregnant mares.

We investigated the half-life of oxytocin in reproductively normal mares and the prostaglandin response after oxytocin administrations. Mares were given oxytocin, 10 or 25 iu, i.v., on the day of, or 2 days after, ovulation, and frequent jugular blood samples were collected for analysis of oxytocin and Prostaglandin F metabolite (PGFM) by RIA. Neither dose of oxytocin nor day of treatment affected the half-life of the exogenous oxytocin, which was determined to be 6.8 min. A significant increase in PGFM was observed within 6 min of oxytocin administration and peak values were observed within 10 min. PGFM response after oxytocin administration on the day of ovulation appeared elevated compared to the response 2 days after ovulation.

The effect of the gonadotrophin-releasing hormone analog, buserelin, administered in diestrus on pregnancy rates and pregnancy failure in mares.

Two trials involving 578 mares were performed to investigate the effect of a single intramuscular treatment of 40 microg buserelin, an analog of gonadotrophin releasing hormone, on pregnancy rate in mares. All mares were bred by natural mating and were allocated into pairs One mare in each pair was injected with buserelin either on Day 10 or 11 (Trial 1) or on Days 8 to 10 (Trial 2) after ovulation. Pregnancy status of mares was determined by transrectal ultrasonographic examination on Day 14 or 15 after the day of ovulation and was repeated between Days 28 and 30 of pregnancy. In Trial 1, buserelin treatment increased the pregnancy rate at Days 14 and 15 (72.5 vs 66.6%, P < 0.01). At the second pregnancy examination, pregnancy losses were lower in the treated group of mares (4.1 vs 7.4%; P < 0.05). In Trial 2, buserelin also improved the pregnancy rate (57.2 vs 53 5%; P < 0.05) at Days 14 and 15 Pregnancy losses between the first and second examinations were lower in the treated group of mares (6.5 vs 12.0%; P < 0.05). Buserelin increased pregnancy rates after breeding at the first estrus in both trials. In addition, buserelin treatment increased the pregnancy maintenance rate at Days 28 to 30.

Assessment of the effect of three treatments to remove intrauterine fluid on pregnancy rate in the mare.

The effects on pregnancy rate of three different treatments to remove intrauterine fluid were assessed in 1267 mares. The mares were mated and allocated, in strict rotation, to four treatment groups: 1) untreated controls, 2) intrauterine infusion of broad spectrum antibiotics, 3) intravenous injection of oxytocin, 4) intravenous injection of oxytocin followed by intrauterine antibiotics. The pregnancy status of the mares was determined 13 to 15 days and 27 to 30 days after ovulation by transrectal ultrasonography. The pregnancy rate of group 4 (72 per cent) was higher than that of group 2 (64 per cent, P < 0.01) or group 3 (63 per cent, P < 0.01). The pregnancy rates of groups 2 and 3 were higher than that of group 1 (56 per cent, P < 0.01). The treatment with antibiotics and oxytocin appeared to have an additive beneficial effect which suggested two different modes of action of the combination treatment, namely antibacterial activity and fluid drainage. In the untreated mares more fluid accumulated in the uterine lumen after mating, and this was the most likely reason for their lower pregnancy rate.

Inflammatory components in uterine fluid from mares with experimentally induced bacterial endometritis.

Exudate and uterine flushings were collected at either 30, 60, 120 or 240 mins after intrauterine infusions of Streptococcus zooepidemicus in genitally normal mares during oestrus. Uteri were also flushed without prior induction of endometritis. Protein concentrations in exudate and flushings increased with time and exudate pH decreased with time; the pH of flushings did not alter. Lysozyme and lactate dehydrogenase were present in flushings from non-infected uteri, but concentrations increased with time after infection. Immunoreactive prostaglandin E2 was undetectable before infection, but concentrations rose after infection. No neutrophils were present in non-infected flushings but, by 30 mins, there were significant (P less than 0.01) neutrophil numbers in exudate and flushings; thereafter numbers increased, particularly in exudate. Acute endometritis resembled acute inflammation at other sites in the horse and a significant response had occurred by 30 mins after experimental infection.

Current views on the pathogenesis of bacterial endometritis in mares.

Mares with persistent and recurrent endometritis are said to be susceptible to infection; in particular they are unable to resolve the acute endometritis that always follows mating. It is thought, therefore, that these mares have a local immunological defect in the uterus that impedes the elimination of bacteria. Studies on immunoglobulins, opsonins and the functional ability of neutrophils in the uterus of susceptible mares have not confirmed the presence of an impaired immune response. It is concluded that factors involved in the production and drainage of uterine fluid may be important in the aetiology of the condition.

[The early chemotactic reaction of the equine uterus to acute inflammatory stimulation]. / Die frühzeitige chemotaktische Reaktion des equinen Uterus auf akute Entzündungsreize.

The uteri of normal pony mares in oestrus were infected experimentally with Streptococcus zooepidemicus. Uterine contents were collected 30, 60, 120 or 240 minutes later and were tested for their chemotactic effect on equine-neutrophils both with a morphological assay based on neutrophil shape changes and with a modified Boyden chamber technique. By 30 minutes after infection the uterine contents were markedly chemotactic for isolated peripheral neutrophils and remained so at the 240-minute collection. Uterine contents from uninfected mares had minimal chemotactic properties. These results could explain the early neutrophil response to acute endometritis in the mare which probably involves activation of an endogenous chemotactic system.

Equine neutrophil locomotion in response to Streptococcus zooepidemicus.

The neutrophil is involved in the defence of the mare's uterus against micro-organisms. The ability of Streptococcus zooepidemicus and its growth products to induce shape changes or directional locomotion (chemotaxis) of equine neutrophils was investigated; no effect was found.

Pre-chemotactic and chemotactic properties of uterine fluid from mares with experimentally induced endometritis.

Streptococcal endometritis was induced experimentally in pony mares during oestrus. Uterine fluid was collected 30, 60, 120 or 240 minutes later and tested for its effect on the in vitro morphology and chemotaxis of equine neutrophils by two independent methods. The maximal response occurred between 30 and 60 minutes after infection and persisted until 240 minutes. The chemo-attractant contained both heat labile and heat stable components and the latter appeared to be active at low concentrations.

The effect of various antibacterial preparations on the in vitro morphology and chemotactic response of equine neutrophils.

Two independent assay systems were used to study the effect of three antibacterial preparations on in vitro morphology and chemotaxis of equine neutrophils. Incubation of neutrophils with high (200 micrograms/ml) and medium (20 micrograms/ml) concentrations of neomycin impaired their response to standard chemoattractants. Trimethoprim/sulfadoxine (0.4/2.0 micrograms/ml-40/200 micrograms/ml) and benzylpenicillin (0.25-25 micrograms/ml) had no effect. Neutrophils collected from geldings 2 and 24 h after neomycin (5 mg/kg) administration had impaired responses to standard chemoattractants. Benzylpenicillin (13.2 mg/kg) had no effect.

Rapid, single-step isolation of equine neutrophils on a discontinuous Percoll density gradient.

A rapid single-step procedure for isolation of equine neutrophils (PMNS) from peripheral blood is described. A discontinuous gradient of two Percoll solutions (densities of 1.087 kg litre-1 and 1.108 kg litre-1 was used. The PMNS were isolated to more than 95 per cent purity with a viability of more than 99 per cent and a cell recovery of more than 83 per cent. The method used was rapid and reproducible and the equipment required is relatively simple. The function of the recovered cells was assessed in a chemotactic assay using a modified Boyden chamber technique.