Canine herpesvirus (CHV-1) causes neonatal deaths as well as infertility due to embryonal death, abortion and stillbirths in breeding kennels. The aim of this study was to determine the prevalence of antibodies against canine herpesvirus in the serum of dogs older than 1 year in breeding kennels in the Gauteng Province of South Africa. A serum neutralization test (SNT) and a newly developed enzyme linked immunosorbent assay (ELISA) were used to test the serum samples of 328 dogs in 38 breeding kennels. With SNT as well as ELISA, 22% of sera were positive (P > 0.9). Seventeen kennels (45% of total kennels) each had at least one positive dog on SNT compared with twenty kennels (53% of total kennels) that each had at least one positive dog on ELISA (P = 0.6). The prevalence of positive dogs in positive kennels was 42 ± 26% (n = 17 kennels) for SNT and 39 ± 26% (n = 20 kennels) for ELISA. Pairwise comparison of kennels showed that the prevalence of SNT positive dogs was similar to the prevalence of ELISA positive dogs (P = 0.3, n = 38 kennels). Seroprevalence was independent of age, gender or colony size. This study suggests that canine herpesvirus is sufficiently common in breeding dogs in the Gauteng Province of South Africa to pose a threat to neonatal survival and fertility.

Knowing when insemination of bitches with frozen-thawed spermatozoa yields the highest fertility is necessary to minimise the number of inseminations and insemination dose. A multi-sire insemination model with frozen-thawed spermatozoa was used to determine the best time for insemination with frozen-thawed spermatozoa relative to the day on which the concentration of progesterone in the blood plasma (PPC) first reached a value between 6 and 9 nmol/L (Day 0). Inseminations were performed on Days 5 and 6 (Group A, 6 bitches) or Days 6 and 7 (Group B, 6 bitches). A panel of 23 autosomal microsatellites and the presence of the amelogenin gene were used to determine the paternity and gender of the conceptuses obtained after ovariohysterectomy during the second quarter of gestation. Out of 103 ovulations (number of corpora lutea counted) 66 conceptuses were conceived (overall conception rate: 64%). The proportion of available 2 oocytes fertilized was 0.11 for Day 5 (6 bitches), 0.56 for Day 6 (12 bitches), and 0.27 (6 bitches) for Day 7. The odds of fertilization was 16.7 and 4.2 times higher from insemination on Day 6 compared to Day 5 (P < 0.001) and Day 7 (P = 0.013), respectively. The numbers of male-and female conceptuses were equal (33 each) and gender was independent of insemination day (P = 0.18). This study suggests that intrauterine insemination of bitches should best be done 6 days after PPC first reaches a value between 6 and 9 nmol/L with a second insemination one day later.

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The aim of this study was to determine whether flow cytometric evaluation of combined merocyanine 540 and Yo-Pro 1 staining (M540-YP) would identify viable dog sperm that had undergone membrane stabilization known to be associated with capacitation in other species, and whether such destabilization is detected earlier than when using the tyrosine phosphorylation and ethidium homodimer stain combination (TP-EH) with epifluorescence microscopy. Semen from nine dogs was collected and incubated in parallel in bicarbonate-free modified Tyrode"s medium (-BIC), in medium containing 15 mM bicarbonate (+BIC), in dog prostatic fluid (PF), and in phosphate buffered saline (PBS). Aliquots for staining were removed at various time points during incubation of up to 6 hours. Staining with M540-YP allowed the classification of dog sperm as viable without destabilized membranes, viable with 2 destabilized membranes, non-viable without destabilized membranes or non-viable with destabilized membranes. The percentage of viable sperm detected using EH (83.5 ± 1.37%; mean ± SEM) was higher than when using YP (66.7 ± 1.37%: P < 0.05; n=54 semen samples). On the other hand, M540-YP identified a higher percentage of viable sperm with destabilized membranes than TP-EH (75 ± 1.76% vs. capacitation was recorded during incubation in PBS. We conclude that YP identifies sperm committed to cell death earlier than EH, and that the M540-YP stain combination identifies membrane destabilization known to be associated with capacitation in other species earlier than the TP-EH stain combination.

In order to determine the inter-cyclic effect of oxytocin and carbetocin on equine myometrial tissue, the effect of the drugs was evaluated through pharmacokinetic and pharmaco-dynamic studies. The complete pharmacokinetic profile for oxytocin was unknown and had to be established. To do so, 25 IU of oxytocin were administered intravenously to six cycling mares and blood samples were collected before and 2, 4, 8, 2 and 15 min after administration. The half-life of oxytocin was determined to be 5.89 min, the clearance rate 11.67 l/min, MRT 7.78 min, T max 2 min, and C max 0.51 ng/ml. The effective plasma concentration was estimated to be 0.25 ng/ml. This was similar to the concentration achieved for the organ bath study where the EC 50 was calculated at 0.45 ng/ml. To determine the inter-cyclic effect of oxytocin and carbetocin uterine myometrial samples were collected from slaughtered mares in oestrus, dioestrus and anoestrus. The samples were mounted in organ baths and exposed to four ascending, cumulative doses of oxytocin and carbetocin. Area under the curve and amplitude, E max and EC 50 were studied for each agonist and statistically evaluated. The effect of oxytocin on equine myometrial tissue was higher during dioestrus, and surprisingly anoestrus, than during oestrus, whereas the effect of carbetocin was the same independent of the stage of oestrous cycle. A significant difference was found for oestrous and anoestrous samples when oxytocin was used but not when carbetocin was used.

Multiple conceptuses from one follicle due to multi-ovular follicles or monozygotic twins inflate the ratio between the numbers of conceptuses and corpora lutea and possibly the effect ascribed to experimental treatment. The aim of this study was to estimate the impact of multiple conceptuses per follicle on fecundity in the bitch. The numbers of conceptuses and corpora lutea of 105 bitches originated from 7 published experimental studies and of 132 from ovariohysterectomies done in a private practice and a welfare organisation. Ninety five bitches, producing 597 conceptuses, had at least as many conceptuses as corpora lutea; 83 had as many, 10 had one more and 2 had 2 more. Bootstrap resampling on these 95 bitches let us to conclude that 12.6% of bitches are expected to produce more oocytes that are each capable of yielding a conceptus than the number of follicles that ovulate and that 2.35% of conceptuses are expected to be in excess of the number of follicles that ovulate. Applying the results of the current study to 2 earlier studies showed that multiple conceptuses from one follicle may, at maximum, have increased the effect ascribed to prostatic fluid by 0.022 and 0.024 conceptuses per corpus luteum, which is minor in relation to the magnitude of the ascribed effects of 0.34 and 0.22 conceptuses per corpus luteum. The number of conceptuses relative to the number of corpora lutea provides a valid and precise measurement of fertility in the bitch.