Periparturient characteristics of mares and their foals on a New Zealand Thoroughbred stud farm.

AIMS: To describe selected periparturient variables in a sample of Thoroughbred mares and their foals on a commercial stud farm in New Zealand. METHODS: Data were collected for 969 foaling records, from 592 mares, by foaling attendants from one Thoroughbred stud farm in the Waikato region of New Zealand for the breeding seasons 2008-2013, inclusive, and collated retrospectively. The associations between mare- and foal-level variables and gestation length, time of birth (expressed as the number of hours after midday), fetal membrane retention time, time for the foal to stand and suckle after birth, and foal mortality were quantified using linear and logistic regression models. RESULTS: Mean gestation length for mares in this study was 350 (min 296, max 429) days, and was shorter for filly foals (348 (min 296, max 429) days) compared with colt foals (350 (min 310, max 404) days) (p=0.001). Overall, 517/968 (53%) foalings occurred between 19:00 and 01:00 and 212/968 (22%) foalings occurred during daylight. Overall, 815/855 (95%) expelled their fetal membranes within 4 hours of parturition. The mean interval from birth to standing and to suckling was shorter (p<0.001) for filly foals than colts by 13 (95% CI=9-17) and 17 (95% CI=8-26) minutes, respectively. Dystocia was reported for 81/968 (8.4%) foalings with relative fetal oversize being the most common cause (36/81 (44%) cases). Perinatal foal death was recorded for 26/966 (2.7%) foalings. The odds of foal mortality decreased with increasing length of gestation (p=0.027), and were greater for colt than filly foals (p=0.042) and when dystocia was reported (p<0.001). CONCLUSIONS: Gestation length was influenced by the sex of the foal, as was the time taken for the foal to stand and suckle after birth. One fifth of mares foaled during daylight hours. The majority of mares in this study population expelled their fetal membranes within 4 hours of foaling. CLINICAL RELEVANCE: Accurate measures for periparturient behaviour can be important in the management of mares and newborn foals. Clinically relevant differences appear to exist between mares and foals in New Zealand and those in the Northern Hemisphere for some key parameters, likely as a result of differences in management and environment. The results of this study suggest that mares should be considered to have retained their membranes if not passed within 4 hours of parturition.

The role of Type 1, P and S fimbriae in binding of Escherichia coli to the canine endometrium.

Escherichia coli (E. coli) is the most commonly isolated infectious agent causing pyometra in bitches. Many E. coli strains isolated from the uteri of infected dogs carry several adhesin genes (fimH, papGIII and sfa). The objective of this study was to investigate the role of each adhesin gene product, acting alone or expressed in combination, in the bacterial binding to canine endometrium. E. coli strain P3, which was isolated from a uterus of a bitch naturally affected with pyometra, was shown by PCR to carry all three known fimbrial adhesin genes fimH, papGIII and sfa. Knockout (KO) mutants of this wildtype (P3-wt) strain were generated using insertional inactivation. Adhesion assays on anoestrous uteri of three post-pubertal bitches were undertaken. Overall, the number of bacteria adhering to canine endometrial biopsies was comparable between strains and no significant difference in the number of bound bacteria was found between the P3-wt strain and the single or double KO-strains. However, the triple knockout strain displayed less binding to the canine endometrium compared with the P3-wt strain. This study shows that a pathogenic E. coli strain (P3) isolated from the uterus of a bitch with pyometra was able to fully compensate for the loss of two of its three known adhesin genes. It was necessary to inactivate all three known adhesin genes in order to see a significant decrease in binding to canine endometrium.

Uropathogenic virulence factor FimH facilitates binding of uteropathogenic Escherichia coli to canine endometrium.

Pyometra is a potentially life-threatening condition in bitches and is often caused by Escherichia coli infection. Both pathogenic and non-pathogenic E. coli strains commonly carry the genes for type 1 fimbriae that mediate bacterial adhesion onto host epithelium. To investigate whether the type 1 fimbrial adhesin, FimH, facilitates the binding of uropathogenic E. coli to canine endometrium, the fimH gene was insertionally inactivated in a pathogenic E. coli strain. The ability of E. coli to bind to canine endometrial epithelial cells was determined in vitro using canine uterine biopsies. Binding of the fimH mutant was only 0.3% of that of the wild type. Complementation of the mutation restored the phenotype to that of the parent. This study has developed an in vitro model that allows quantitative and qualitative assessment of bacterial binding to canine endometrium and has demonstrated that the fimH gene plays a role in adherence of pathogenic E. coli to canine endometrium.

Effect of simulated stages of the canine oestrous cycle on Escherichia coli binding to canine endometrium.

Pyometra, a prevalent infectious uterine disease that affects intact middle-aged bitches, is typically associated with Escherichia coli. Our hypotheses were (i) that bacterial adhesion to canine endometrium differs between different stages of the oestrous cycle and (ii) that the adhesin FimH facilitates this adhesion. Twelve post-pubertal, ovariectomized greyhound bitches were treated with exogenous hormones to simulate different stages of the oestrous cycle. Tissue samples from each uterus were incubated with a pathogenic E. coli strain carrying the fimH gene, but no other adhesin genes (P4-wt)--or an E. coli strain in which fimH was insertionally inactivated (P4-∆fimH::kan)--or with phosphate-buffered saline as a negative control. After washing, tissue samples were homogenized for quantification of adherent bacteria. The differences in binding to canine endometrium at different stages of the oestrous cycle were not significant. However, the mean difference in binding of the P4-wt and the P4-∆fimH::kan across all stages of the simulated oestrous cycle was significant (p < 0.001 by paired t-test on geometric means). Individual differences in numbers of P4-wt bacteria bound between dogs might suggest genetic variations or epigenetic differences in FimH receptor expression by the endometrium, unrelated to the stage of the oestrous cycle.

Calcium, parathyroid hormone, oxytocin and pH profiles in the whelping bitch.

Despite the high prevalence of primary uterine inertia in whelping bitches, the underlying pathogenesis remains unclear. The objectives were to i) determine serum concentrations of total calcium, ionized calcium (iCa), parathyroid hormone (PTH), and blood pH in normally whelping bitches throughout the peri-parturient period; and ii) investigate relationships among iCa, PTH, and acid-base status, and the role that they and oxytocin may have in the underlying pathogenesis of canine uterine inertia. Bitches were randomly selected from a population of German Shepherd Dog bitches with a history of uncomplicated parturition (Group 1; n=10), and from a population of Labrador bitches with a clinical history of an increased incidence of uterine inertia and stillbirths (Group 2; n=20). Jugular blood samples were collected daily from -4 d to the onset of whelping (t=0 h), and then every 4h until the last pup was born. Overall, bitches from Group 2 had higher mean+/-SEM serum concentrations of PTH (4.72+/-2.45 pmol/L, P<0.001), lower iCa (1.31+/-0.08 pmol/L, P<0.05), and higher venous pH (7.41+/-0.03, P<0.005) than bitches from Group 1 (2.9+/-1.44 pmol/L, 1.38+/-0.06 mmol/L, and 7.33+/-0.02, respectively) during the periparturient period. However, there was no significant difference between Groups 1 and 2 for serum oxytocin concentrations during the periparturient period (45.5+/-40 and 65.5+/-82 pg/mL). We inferred that low iCa resulting from a rising pH and decreasing PTH during the periparturient period may have contributed to decreased uterine contractility and increased risk of stillbirths. Therefore, manipulating the cationic/anionic difference in diets of pregnant bitches, similar to the bovine model for hypocalcamia, may reduce the incidence of stillbirths in the bitch.

The use of deslorelin implants for the synchronization of estrous in diestrous bitches.

A novel approach to estrous induction in diestrous bitches is described. Twelve spontaneously cycling anestrous bitches served as controls. Thirteen anestrous and 15 diestrous bitches were induced to come into synchronous estrous using prostaglandin (diestrous bitches only) and deslorelin implants (Ovuplant). Implants contained either 2.1 or 1.05 mg deslorelin and were administered beneath the vestibular submucosa. All treated bitches came into estrous, regardless of implant size. Whereas all anestrous bitches ovulated, one of six diestrous bitches treated with the larger implant and three of nine treated with the smaller implant failed to ovulate. Induced bitches generally produced fewer corpora lutea than controls. Sixty-seven percent of control bitches became pregnant, with 0.63 fetuses per corpus luteum, whereas the pregnancy rate and fetuses per corpus luteum were 67 and 70% and 0.42 and 0.55 in the anestrous bitches induced with 1.05 and 2.1 mg deslorelin implants, respectively (not different from controls). Only 2 of 15 induced diestrous bitches conceived a detectable pregnancy, one of which was resorbed. In conclusion, although ovulatory estrous can be induced in bitches that had their most recent ovulation 40-100 days ago, these bitches are very unlikely to become pregnant during the induced estrous. The reason for the poor fertility in these diestrous bitches requires further study.

Failure of hCG to support luteal function in bitches after estrus induction using deslorelin implants.

Induction of estrus with deslorelin implants was followed by abortions in bitches that conceived during the induced estrus. Lowering the deslorelin dose and choosing a better implantation site prevented the abortions. This study investigated the hypothesis that induction of estrus with deslorelin is followed by reduced serum progesterone concentrations (SPC) during the ensuing diestrus. Assuming that reduced luteal function resulted from reduced LH secretion due to hypophyseal down-regulation of GnRH receptors, the effect of human chorionic gonadotropin (hCG) treatment on the SPC of diestrous bitches was also investigated. In Experiment 1, 10 spontaneously cycling bitches served as controls, whereas estrus was induced with deslorelin implants in 24 others. In Experiment 2, six diestrous bitches were treated with a single dose of hCG between Days 39 and 45 of diestrus. The SPC was lower in deslorelin-induced bitches from Days 35 to 56 of diestrus and hCG increased SPC during the first 24 h after treatment, followed by a dramatic decline thereafter. Although SPC recovered in pregnant bitches, it remained much lower (< or = 1 ng/mL) than in untreated, non-pregnant bitches. The suppression of progesterone secretion after hCG treatment suggested that decreased luteal activity in deslorelin-induced bitches may not be a simple consequence of down-regulation of hypophyseal GnRH receptors.