Performing an ovariohysterectomy at the time of c-section does not pose an increase in risk of mortality, intra- or postoperative complications, or decreased mothering ability of the bitch.

OBJECTIVE: Ovariohysterectomy (OVH) is frequently recommended at the time of c-section in canines, yet prior literature suggests poor mothering ability and increased morbidity to the bitch with c-section with concurrent OVH (CSOVH). The study objective was to compare maternal survival, complications, and mothering ability between bitches that underwent c-section alone (CS) or CSOVH. ANIMALS: 125 bitches. PROCEDURES: Medical records from 2014 through 2021 were retrospectively reviewed; owners were surveyed for information up to weaning. RESULTS: 80 bitches undergoing CS and 45 bitches undergoing CSOVH were identified. There was no difference in anesthesia duration, intraoperative complications, postoperative complications, mothering ability, puppy survival to weaning, or other variables compared between groups. CSOVH bitches had longer surgery times (P = .045; 54.4 ± 20.7 min vs 46.9 ± 16.6 min) and longer time from delivery to nursing (P = .028; 75.4 ± 22.3 min vs 65.2 ± 19.5 min). Ninety (72%) owners responded to the survey. All 90 bitches survived until puppy weaning. CSOVH bitches were more frequently perceived as painful postoperatively (P = .015). CLINICAL RELEVANCE: Performing an OVH at the time of c-section does not pose a significant increase in risk of mortality, intraoperative complications, postoperative complications, or decreased mothering ability of the bitch. The increased duration of surgery and increased time from delivery to nursing in the CSOVH group were clinically insignificant. Appropriate postoperative pain management should be emphasized post-CSOVH. Based on these results, OVH should be performed concurrently with c-section if indicated.

Analytical validation of five diagnostic tests for the detection of polymorphonuclear cells in stallion semen.

The objectives of this study were to evaluate the ability of five diagnostic tests to detect polymorphonuclear cells (PMNs) in stallion semen, and to determine the concentration of PMNs that affects sperm motility. We hypothesized that all tests have diagnostic value, and even low concentrations of PMNs affect motility. One ejaculate was obtained from six stallions. Aliquots of 50 × 106 purified sperm were incubated, in triplicate, with six concentrations of purified PMNs: 1) no PMNs, 2) 0.25 × 106 PMN/ml, 3) 0.5 × 106 PMN/ml, 4) 2.5 × 106 PMN/ml, 5) 5 × 106 PMN/ml, 6) 10 × 106 PMN/ml. The PMNs were quantified using a hemacytometer, cytology, a leucocyte esterase dipstick test (LEDT), a peroxidase test, and CD13 immunolabeling. Sperm motility was evaluated after 4 h at 38 °C. The number of leucocytes detected with the LEDT differed among treatments (P<0.0001), from negative results in control samples to moderate or large numbers in the samples with the highest PMN concentration. The hemacytometer count and CD13 immunostaining detected differences with the control treatment at the lowest PMN concentration (2.5 × 106 PMN/ml; P<0.001). Sperm motion was lower in samples with ≥5 × 106 PMN/ml (P<0.0001). Thus, a sample was considered leucospermic if it contained ≥5 × 106 PMN/ml. The LEDT had the best sensitivity (100%), followed by cytology (78%), peroxidase test (60%), CD13 immunostaining (56%) and hemacytometer count (47%). The LEDT had the lowest specificity (65%), which was 95% for all other tests. In conclusion, the LEDT was a simple, economic and sensitive stall-side test to screen semen for presence of PMNs. Because of the lower specificity, positive LEDT results should be confirmed with the identification of peroxidase-positive cells or CD13-positive cells.

Risk factors for neonatal mortality prior to hospital discharge in brachycephalic and nonbrachycephalic dogs undergoing cesarean section.

OBJECTIVES: To compare neonatal survival to discharge rates between brachycephalic and nonbrachycephalic dogs undergoing cesarean section (c-section) and identify risk factors for neonatal mortality. STUDY DESIGN: Retrospective study. ANIMALS OR SAMPLE POPULATION: A total of 480 puppies from 90 bitches undergoing 106 c-sections. METHODS: Medical records of c-sections performed between January 2012 and September 2021 were reviewed. Data collected included brachycephalic versus nonbrachycephalic breed, elective versus emergency c-section, litter size (c-section and total [including those born prior to and via c-section]), and neonatal survival to discharge. A generalized linear mixed model (univariable and multivariable) was performed to evaluate variables versus neonatal survival. RESULTS: Overall neonatal survival to discharge was 93.1% (447/480); survival was similar between brachycephalic and nonbrachycephalic breeds (p = .221, 202/213 [94.8%] brachycephalic survival, 245/267 [91.8%] nonbrachycephalic survival). Puppies delivered via elective c-section were more likely to survive compared to emergency c-section (p < .001, 238/240 [99.2%] elective survival, 209/240 [87.1%] emergency survival). Puppies delivered in larger c-section litters were more likely to survive (p < .004) compared to smaller litters. Total litter size had no effect on survival. CONCLUSION: Brachycephalism had no effect on neonatal survival. Puppies delivered via elective c-section were more likely to survive compared to puppies delivered via emergency c-section. CLINICAL SIGNIFICANCE: Outcomes following c-section are similar between brachycephalic and nonbrachycephalic breeds. While it is preferable to encourage selective breeding for bitches that are able to whelp naturally, elective c-section should be considered in bitches at high risk for dystocia to maximize neonatal survival.

Steroidogenic Enzyme and Steroid Receptor Expression in the Equine Accessory Sex Glands.

The expression pattern and distribution of sex steroid receptors and steroidogenic enzymes during development of the equine accessory sex glands has not previously been described. We hypothesized that equine steroidogenic enzyme and sex steroid receptor expression is dependent on reproductive status. Accessory sex glands were harvested from mature stallions, pre-pubertal colts, geldings, and fetuses. Expression of mRNA for estrogen receptor 1 (ESR1), estrogen receptor 2 (ESR2), androgen receptor (AR), 3ß-Hydroxysteroid dehydrogenase/Δ5-4 isomerase (3ßHSD), P450,17α hydroxylase, 17-20 lyase (CYP17), and aromatase (CYP19) were quantified by RT-PCR, and protein localization of AR, ER-α, ER-ß, and 3ßHSD were investigated by immunohistochemistry. Expression of AR, ESR2, CYP17, or CYP19 in the ampulla was not different across reproductive statuses (p > 0.1), while expression of ESR1 was higher in the ampulla of geldings and fetuses than those of stallions or colts (p < 0.05). AR, ESR1 and ESR2 expression were decreased in stallion vesicular glands compared to the fetus or gelding, while AR, ESR1, and CYP17 expression were decreased in the bulbourethral glands compared to other glands. ESR1 expression was increased in the prostate compared to the bulbourethral glands, and no differences were seen with CYP19 or 3ß-HSD. In conclusion, sex steroid receptors are expressed in all equine male accessory sex glands in all stages of life, while the steroidogenic enzymes were weakly and variably expressed.

Sexual Differentiation and Primordial Germ Cell Distribution in the Early Horse Fetus.

It was the aim of this study to characterize the development of the gonads and genital ducts in the equine fetus around the time of sexual differentiation. This included the identification and localization of the primordial germ cell population. Equine fetuses between 45 and 60 days of gestation were evaluated using a combination of micro-computed tomography scanning, immunohistochemistry, and multiplex immunofluorescence. Fetal gonads increased in size 23-fold from 45 to 60 days of gestation, and an even greater increase was observed in the metanephros volume. Signs of mesonephros atrophy were detected during this time. Tubular structures of the fetal testes were present from day 50 onwards, whereas cell clusters dominated in the fetal ovary. The genital ducts were well-differentiated and presented a lumen in all samples. No sign of mesonephric or paramesonephric duct degeneration was detected. Expression of AMH was strong in the fetal testes but absent in ovaries. Irrespective of sex, primordial germ cells selectively expressed LIN28. Migration of primordial germ cells from the mesonephros to the gonad was detected at 45 days, but not at 60 days of development. Their number and distribution within the gonad were influenced (p < 0.05) by fetal sex. Most primordial germ cells (86.8 ± 3.2% in females and 84.6 ± 4.7% in males) were characterized as pluripotent according to co-localization with CD117. However, only a very small percentage of primordial germ cells were proliferating (7.5 ± 1.7% in females and 3.2 ± 1.2% in males) based on co-localization with Ki67. It can be concluded that gonadal sexual differentiation in the horse occurs asynchronously with regard to sex but already before 45 days of gestation.

Fluoroquinolone exposure in utero did not affect articular cartilage of resulting foals.

BACKGROUND: Recent studies have shown that fluoroquinolones, specifically, enrofloxacin and its active metabolite (ciprofloxacin), cross the equine placenta without causing gross or histological lesions in the first and third trimester fetuses or resulting foal. However, it is possible that in utero exposure to fluoroquinolones may cause subtle lesions not detectable by standard means; thus, a more in-depth assessment of potential toxicity is warranted. OBJECTIVES: To use quantitative magnetic resonance imaging (qMRI), biomechanical testing, and chondrocyte gene expression to evaluate the limbs of foals exposed to enrofloxacin during the third trimester of pregnancy. STUDY DESIGN: In vivo and control terminal experiment. METHODS: Healthy mares at 280 days gestation were assigned into three groups: untreated (n = 5), recommended therapeutic (7.5 mg/kg enrofloxacin, PO, SID, n = 6) or supratherapeutic (15 mg/kg, PO, SID, n = 6) doses for 14 days. Mares carried and delivered to term and nursed their foals for ~30 days. Two additional healthy foals born from untreated mares were treated post-natally with enrofloxacin (10 mg/kg PO, SID, for 5 days). By 30 days, foal stifles, hocks, elbows, and shoulders were radiographed, foals were subjected to euthanasia, and foal limbs were analysed by quantitative MRI, structural MRI, biomechanical testing and chondrocyte gene expression. RESULTS: Osteochondral lesions were detected with both radiography and structural MRI in foals from both enrofloxacin-treated and untreated mares. Severe cartilage erosions, synovitis and joint capsular thickening were identified in foals treated with enrofloxacin post-natally. Median cartilage T2 relaxation times differed between joints but did not differ between treatment groups. MAIN LIMITATIONS: A small sample size was assessed and there was no long-term follow-up. CONCLUSION: While further research is needed to address long-term foal outcomes, no differences were seen in advanced imaging, biomechanical testing or gene expression by 30 days of age, suggesting that enrofloxacin may be a safe and useful antibiotic for select bacterial infections in pregnant mares.

Congenital phimosis causing preputial swelling in a newborn foal.

An 18-hour-old colt was presented for abdominal discomfort, preputial swelling, and frequent posturing to urinate. Examination of the scrotum confirmed 2 testes and no scrotal or inguinal hernia. Transabdominal ultrasound identified a distended bladder and no free fluid in the peritoneal cavity. Inspection of the preputial cavity revealed that the internal lamina of the prepuce was mostly attached to the glans penis. The preputial cavity was lubricated and manual traction was applied to detach the internal lamina of the prepuce from the glans penis. The colt urinated spontaneously 1 hour after the procedure, and the preputial swelling slowly resolved over 7 days. Key clinical message: Congenital phimosis in a newborn foal was resolved by manual separation of the penile epithelium and preputial lamina.

Phimosis, une cause d'oedème du prépuce chez un poulain nouveau-né. Un poulain de 18 heures de vie a été examiné en raison d'un inconfort abdominal, d'un oedème du prépuce et d'une mise en position fréquente pour uriner. L'examen du scrotum a confirmé la présence de deux testicules et l'absence d'hernie scrotale ou inguinale. Une échographie abdominale a permis de confirmer une vessie dilatée et l'absence de liquide dans la cavité péritonéale. L'examen de la cavité préputiale a révélé que la couche interne du prépuce était complètement attachée au gland du pénis. La cavité préputiale a été lubrifiée et une traction manuelle a été appliquée à la couche interne du prépuce pour la détacher du gland du pénis. Le poulain a recommencé à uriner spontanément une heure après la procédure et l'oedème du prépuce s'est résorbé sur une période de sept jours.Message clinique clé :Le phimosis congénital chez un nouveau-né a été résolu par séparation manuelle de l'épithélium pénien et de la lame préputiale.(Traduit par les auteurs).

Single-Layer Colloid Centrifugation as a Method to Process Urine-Contaminated Stallion Semen After Freezing-Thawing.

Urospermia is a major ejaculatory dysfunction affecting stallions. It has been thought that urine-contaminated semen should not be cryopreserved; however, on select cases, urine contamination of semen cannot be avoided. A recent study suggested that urospermic semen can be cryopreserved after cushion centrifugation and extension. Thus, this study aimed to assess the use of single-layer colloid centrifugation (SLC) to process frozen-thawed urine-contaminated stallion semen. Raw ejaculates (n = 55) from eight stallions were split into three groups: no urine, low (20%), or high (50%) urine contamination. Semen was extended 1:1, cushion-centrifuged, and resuspended at 200 million sperm/mL in BotuCrio. Resuspended semen was loaded in 0.5 mL straws and cryopreserved in liquid nitrogen. Samples were thawed (37°C for 30 seconds) and processed by SLC (400 g/30 minutes). Percentages of total motility (TM) and progressive motility (PM) were assessed with computer-assisted semen analyzer. Sperm viability (%VIAB) and yield were assessed with a NucleoCounter before and after gradient centrifugation. Data were analyzed with two-way ANOVA and Tukey's test. The motility parameters TM before SLC (control: 35 ± 2; low: 33 ± 0.7; high: 22 ± 1.8) after SLC (control: 51 ± 3.6; low: 42 ± 2.2; high: 25 ± 2.8) and PM before SLC (control: 24 ± 1.8; low: 21 ± 1.14; high: 12 ± 1.5) and after SLC (control: 40.3 ± 3.2; low: 31 ± 3.9; high: 14 ± 2) significantly decreased with increasing urine contamination. Urine contamination marginally reduced (P < .05) sperm viability after cryopreservation before SLC (control: 45 ± 0.7; low: 27 ± 0.2; high: 27 ± 0.3) and after SLC (control: 54 ± 0.5; low: 49 ± 0.7; high: 38 ± 0.6). Recovery rates of sperm after centrifugation were not significantly different between groups. In conclusion, urine contamination affects sperm motility parameters in a dose-dependent manner. Post-thaw SLC selected sperm with higher motility and viability in control and low groups but only selected sperm with higher viability in the high group.

Assessment of peripheral markers and ultrasonographic parameters in pregnant mares receiving intramuscular or intrauterine cloprostenol.

The present study aimed to compare two methods of prostaglandin-induced abortion in mares by determining blood markers (progesterone, estradiol-17ß, alpha-fetoprotein, 13,14-dihydro-15-keto-prostaglandin-F2α (PGFM)), B-mode ultrasonographic parameters, and time until loss of fetal heartbeat. It was hypothesized that intrauterine infusion of cloprostenol results in earlier fetal compromise than intramuscular administration. Ovarian structures (number and sizes of follicles and corpora lutea area), fetal heartbeat, and fetal mobility of thirteen singleton pregnancies were assessed daily by transrectal ultrasonography until induction of pregnancy termination (60 ±â€¯2 days of gestation). Mares received 500 µg of cloprostenol intramuscularly every 12 h (IM, n = 7) or once transcervically (TC, n = 6). After initial cloprostenol administration, ultrasonographic examinations were repeated at 6-h intervals until loss of fetal heartbeat was detected. Plasma progesterone, estradiol-17ß, and alpha-fetoprotein were assessed for five days before and after pregnancy loss. In addition, plasma PGFM concentrations were assessed immediately before cloprostenol administration (0 min), and then 15, 30, and 45 min, and 1, 2, 3, 4, 6, 12 h after administration. Data were analyzed using the MIXED procedure with repeated measures in SAS. Significance was set at P < 0.05. All mares lost their pregnancies within 48 h after initial cloprostenol administration, with no difference in time to pregnancy loss. There were significant effects of time starting by 12 h post-induction of pregnancy termination but there was no time by group interaction for progesterone concentrations. Estradiol-17ß and alpha-fetoprotein concentrations were not altered upon impending abortion. Concentrations of PGFM increased significantly by 2 h after cloprostenol administration, but there were no differences between groups. No time effects or time by group interaction for fetal mobility and heartbeat was detected. Expectedly, the number and area of corpora lutea decreased significantly after cloprostenol administration with no significant differences between groups. In conclusion, intrauterine administration of cloprostenol was not different from repeated systemic administration to terminate the pregnancy. Both models for early fetal loss were equivalent for the endpoints assessed herein. The present study provides evidence that transcervical cloprostenol administration technique is repeatable in different settings and results in negligible side effects. While systemic administration results in colic-like signs and may result in severe reaction.

Uterine responses and equine chorionic gonadotropin concentrations after two intrauterine infusions with kerosene post early fetal loss in mares.

Pregnancy loss during the normal lifespan of endometrial cups (∼37-120-150 days of gestation) may affect a mare's ability to conceive again in the same breeding season, as equine chorionic gonadotropin (eCG) secretion by retained endometrial cups can lead to abnormal ovulations and follicular growth. While intrauterine kerosene infusion has anecdotally been proposed as a treatment for endometrial cup retention, there are no controlled studies evaluating kerosene's ability to enhance endometrial cup regression following abortion. The objectives of this study were to assess uterine response, systemic side effects, and efficacy of intrauterine kerosene infusions after abortion. We hypothesized that kerosene infusions would hasten regression of endometrial cups without detrimental effects on the endometrium and the mare's general health. Twelve light-breed mares were enrolled in the study after an experimentally induced abortion with cloprostenol (n = 12) by 60 ± 2 days of gestation. Mares were randomly allocated to receive an intrauterine infusion with 500 mL of kerosene (n = 6) or 500 mL saline (n = 6) on days 21 and 35 after pregnancy termination. Uterine biopsies were collected at days 7, 21, 35, and 49 post-abortion to evaluate the degree of endometrial fibrosis with Picrosirius Red Stain and to be graded according to the Kenney & Doig 1986 classification. Furthermore, histomorphometry analysis of the endometrium lining, glandular epithelium and glandular density was performed. Endometrial lymphocyte B CD20+, lymphocyte T CD3+, and macrophage IBA-1+ cell populations were characterized by immunohistochemistry. Physical examinations, blood cell counts, and serum biochemistry were performed before, and for 2 days after each uterine infusion. Serum samples were collected for assessment of eCG concentrations. Continuous data were analyzed with MIXED procedure with repeated measures in SAS, categorical data with LOGISTIC procedure of SAS. Significance was set at p < 0.05. Kerosene infusion did not affect complete blood cell counts, serum chemistry parameters, or physical examinations. Concentrations of eCG decreased over time (p < 0.001), but there were no differences between groups or time by group interactions (p = 0.72). Histological evaluation of the uterus showed no signs of increased fibrosis or degeneration in the treatment group. In conclusion, while kerosene infusions did not appear to have detrimental effects on mare health, our findings suggest that the use of kerosene in the uterus does not enhance the regression of endometrial cups by 49 days post-abortion.

Key Aspects of Donkey and Mule Reproduction.

Donkeys are nonseasonal, polyestrous, territorial, and nonharem breeders. Although there are many similarities between horses and donkeys, there are also reproductive features that differ, from the longer cervix in the jenny to spermatogenic efficiency in the jack. Mules display reproductive cyclic activity but are rarely fertile. Frozen donkey semen has high pregnancy rates in mares, but lower rates in jennies. This article reviews key aspects of donkey and mule reproductive physiology, reproductive medicine, and assisted reproductive techniques that are useful for practitioners offering assisted reproductive techniques, and also for practitioners with the occasional client with a basic reproductive question.

Fetal Death Associated With Premature Mammary Gland Development and Lactation in a Mare Treated With Weekly Injections of Long-Acting Progesterone.

A 14-year-old, 530-kg, multiparous, pregnant Quarter Horse mare was referred for evaluation of premature mammary gland development and lactation. The mare was in the seventh month of gestation. The mare had a history of subfertility and was receiving weekly injections of long-acting progesterone, prescribed by the referring veterinarian. The last dose had been administered four days before presentation. Upon presentation, the mare had vital signs within normal limits, a moderately developed, nonpainful udder with galactorrhea, and no vulvar discharge. Transrectal palpation revealed a well-toned uterus and cervix and discreetly palpable fetal parts, however, ballottement of the fetus did not result in appreciable fetal movement. Transrectal ultrasound was unremarkable, but transabdominal ultrasound revealed one underdeveloped, immotile fetus in the left uterine horn with no heartbeat. Abortion was induced with repeated doses of cloprostenol. Fifty-four hours after the first cloprostenol injection, the mare displayed signs of labor, the cervix was manually dilated, and the fetus and fetal membranes were expelled with gentle manual manipulation. Standard postabortion care included uterine lavage and oxytocin for 48 hours before being discharged to the care of her owners. Fetal crown-rump length (53 cm) was consistent with a 6-month fetus rather than its gestational age of 7 months. The umbilical cord was edematous, and a distended, fluid-filled structure surrounded the cord at the intersection of the allantoic and amniotic segments of the umbilical cord. This structure was determined to be the severely dilated urachus. Microscopic findings included placental stromal mineralization, distended umbilicus adventitia, and dilated umbilical lymphatics with no other significant findings. Remaining abortion diagnostic tests were unremarkable. The mare recovered well and was discharged to the care of her owner two days after abortion. The following breeding season the mare carried a healthy foal to term.

Efficacy and outcome of foaling augmented with oxytocin using mammary calcium and pH criteria to guide the timing of augmentation.

Augmentation of parturition can be used to advance labor in mares to occur at a time when personnel is available to assist if necessary. We performed a retrospective study to determine the efficacy and safety of augmentation to manage foalings. Augmentation was performed with 3 IU oxytocin i.v. when mammary calcium concentrations were ≥250 ppm, mammary secretion pH ≤ 6.5, and the mare showed impending signs of parturition. Augmented parturitions (n = 19) were compared with three different control groups. The three control groups were: 1) Time Match control (n = 37) which were non-augmented foalings in the barn during the same time period; 2) Mare Match control (n = 32) which were the non-augmented parturitions of the augmented mares in previous years; and 3) Historic Match control (n = 165) consisted of foalings that occurred from 2006 to 2016 in the facility. All augmented mares foaled within two h with an average of 44 min (range 20-75) after oxytocin injection. The interval between foaling and the foal standing was shorter in augmented parturitions compared with historic match controls. The interval between foaling and the foal nursing was longer with augmented parturitions compared with time match and historic match controls. Duration of fetal membrane retention was not different between all groups. Augmentation of imminent parturition is potentially a safe and effective treatment for mares and foals. Implementation of augmentation as a routine procedure may increase the likelihood of enteral administration of colostrum to foals.

Nerve Growth Factor-ß production in the bull: Gene expression, immunolocalization, seminal plasma constitution, and association with sire conception rates.

Nerve Growth Factor-ß (NGF) is a seminal plasma protein that regulates sperm physiology in bulls, yet its production and association with fertility remain unclear. The objective of this study was to describe NGF distribution in bull accessory sex glands, quantify its seminal plasma concentrations, and determine its association with sire conception rates. Accessory sex glands were collected post-mortem from mature bulls (n = 3). Quantitative PCR and immunohistochemistry were performed in tissue samples. Pre-ejaculate and sperm-rich fraction of seminal plasma from Angus (n = 42) and sperm-rich fraction from Holstein (n = 10) bulls were collected by electroejaculation. Holstein (n = 76) and Jersey (n = 14) bulls were collected by artificial vagina, and those with available sire conception rate scores were allocated to: (1) negative/0 (n = 15); or (2) positive (n = 45). Seminal plasma NGF concentrations were measured using ELISA. Relative abundance of NGF mRNA was greatest in the vesicular, intermediate in ampulla, and lowest in prostate and bulbourethral glands (P ≤ 0.03). The most intense NGF staining was detected in the ampulla and vesicular glands (P < 0.05). Concentrations of NGF were greater in the sperm-rich fraction than in the pre-ejaculate and in samples collected by artificial vagina (P < 0.01). Seminal plasma NGF concentrations were greater in bulls with positive sire conception rate than those with negative/0 (P = 0.05). This study determined that NGF is produced in the ampulla and vesicular glands of bulls and is secreted into the sperm-rich fraction of the ejaculate. The positive association of NGF with bull fertility warrants further investigation.

Endocrine and metabolic profile of peripubertal Standardbred colts.

The objectives of this study were to determine the concentrations of reproductive and metabolic hormones during the peripubertal period and to assess their relationship with testicular development and body fat deposition. Blood samples were collected from 23 healthy Standardbred colts every four weeks for twelve months. Colts were weighed monthly, and percent of body fat and testicular volume estimated by ultrasound. Onset of puberty was determined as the month when testosterone was two standard deviations above the previous mean. Plasma FSH, LH, leptin, estradiol-17ß, androstenedione, IGF-1, insulin, inhibin-A, and inhibin-B were analyzed for a seven month peripubertal period. Spring born Standardbred colts underwent puberty at 13 months of age; onset of puberty coincided with exponential testicular growth but did not coincide with an increase in cutaneous body fat deposition or leptin (p > 0.05). Plasma inhibin-B concentrations were significantly increased in the postpubertal period (p < 0.05), but no increase was seen in inhibin-A, androstenedione, FSH, LH, or estradiol-17ß. In conclusion, the rise in testosterone and subsequent onset of puberty coincides with rapid testicular growth but is not correlated with an increase in gonadotropins, IGF-1, cutaneous body fat or leptin in the horse.

Variation in post-thaw sperm quality of white-tailed deer bucks (Odocoileus virginianus) during rut.

White-tailed deer farming is a growing industry in the United States, with breeding operations contributing significantly to the industry's economic impact. Artificial insemination with frozen semen allows for selection and dissemination of valuable genetics, yet surprisingly little is known regarding the best time throughout rut to perform semen cryopreservation. The objective of this study was to compare semen quality following cryopreservation of white-tailed deer bucks collected early in the breeding season (September, n = 6), at peak rut (December, n = 8), and late season (March, n = 7). We hypothesized that post-thaw semen quality would be enhanced at peak rut. Mature bucks were anesthetized with tiletamine-zolazepam and xylazine administered intramuscularly via projector. Semen was collected by electroejaculation and cryopreserved using Optixcell extender. Overall and progressive sperm motilities were assessed for each sample before and after cryopreservation using a computer-aided sperm analyzer. Flow cytometry was used for post-thaw assessment of sperm viability (SYBR-14/PI), acrosome integrity (FITC-PNA/PI), and DNA stability (acridine orange). Analysis of variance was applied to normalized data using a general linear mixed model with buck ID as a random variable, and a Tukey HSD test was performed as needed for post-hoc analysis. Pre-freeze overall and progressive sperm motilities were lowest in March, intermediate in September, and highest in December (p ≤ 0.04). Post-thaw overall and progressive motilities were lowest in September (p ≤ 0.02), but did not differ between December and March (p ≥ 0.12). The DNA Fragmentation Index was lowest in December, intermediate in September, and highest in March (p ≤ 0.05). The percentage of spermatozoa with intact plasma membrane was higher in December than September (p < 0.01), but the percentage of intact acrosomes per sperm with intact plasma membrane was highest in September (p = 0.03). This study confirms that post-thaw semen quality appears to be superior during peak rut (December) in bucks. Though semen collected early or late in rut may present acceptable motility, DNA stability is impaired, which could adversely affect fertility rates. This data suggests that semen cryopreservation during transitional periods should be avoided, though field studies evaluating the translation of these results into satisfactory pregnancy rates are warranted.

Physiological variations in reproductive and metabolic features of white-tailed deer (Odocoileus virginianus) bucks throughout the rutting season.

White-tailed deer farming is a growing industry in the United States, yet there is still a need to improve breeding practices in captive cervids. The objective of this study was to compare reproductive and somatic characteristics of white-tailed bucks early in the breeding season (September), at peak rut (December), and late breeding season (March). We hypothesized that reproductive parameters would improve at the peak of the breeding season. Young, mature bucks (n = 7-11, ages 2-3 yr) were anesthetized via projector with tiletamine-zolazepam and xylazine. Semen was collected by electroejaculation and evaluated for sperm output, motility, and morphology. The bulbourethral, vesicular, and prostate glands were measured by transrectal ultrasound. Body condition score, thoracic circumference, rump fat thickness, scrotal circumference, and testicular measurements were also recorded. Serum testosterone, estradiol, and IGF-I concentrations were measured. Body condition score and rump fat thickness were highest in September, intermediate in December, and lowest in March (p < 0.01), whereas thoracic circumference was lowest in September (p = 0.02). In September, serum IGF-I was highest (p < 0.01) and estradiol was lowest (p ≤ 0.02). Serum testosterone levels were lowest in March and highest in December (p < 0.01). Testicular volume and scrotal circumference were highest in September, intermediate in December, and lowest in March (p < 0.01). Bulbourethral gland length was greatest in March (p ≤ 0.05), whereas prostate length was greatest in September (p ≤ 0.02). Vesicular gland length and width were highest in December, intermediate in September, and lowest in March (p ≤ 0.02). Both overall and progressive sperm motilities were lowest in March (p < 0.01), but did not differ between September and December (p ≥ 0.12). In December, bucks had the highest percentage of normal sperm and lowest percentage of primary sperm defects (p ≤ 0.01). Collectively, our results demonstrated variation in reproductive and metabolic characteristics of white-tailed deer bucks throughout the breeding season at 40°N. The physiological variations described here will be useful for veterinarians and researchers performing reproductive evaluations in white-tailed deer bucks.

Cryopreservation of white-tailed deer (Odocoileus virginianus) semen using soybean-, liposome-, and egg yolk-based extenders.

The objectives of the present study were to compare the use of soybean-based (Andromed), liposome-based (Optixcell), and egg yolk-based (Ovine Red, Triladyl, and Biladyl) extenders for cryopreservation of white-tailed deer semen. In experiment 1, ejaculates obtained from six bucks were aliquoted into the following extenders: Andromed, Ovine Red, Triladyl, and Biladyl (containing 4%, 6%, or 8% of glycerol). In experiment 2, ejaculates obtained from eight bucks were divided amongst Andromed, Ovine Red, and Optixcell extenders. Total and progressive sperm motility were assessed for each sample before and after cryopreservation using a computer-automated semen analyzer. In experiment 2, flow cytometry was used for post-thaw assessment of sperm viability (SYBR-14/PI), acrosome integrity (FITC-PNA/PI), and chromatin stability (acridine orange). In experiment 1, both Andromed and Ovine Red extenders exhibited higher post-thaw total motility than Biladyl containing 4% or 6% of glycerol (p<0.05). Andromed also produced higher progressive motility than all other extenders (p<0.01) before and after cryopreservation with no differences amongst the other extenders (p≥0.11). In experiment 2, there were no differences in total and progressive motility between Andromed, Ovine Red, or Optixcell extenders (p≥0.39). Additionally, there were no differences in sperm viability (p=0.18), acrosome integrity in viable sperm (p≥0.10), or DNA fragmentation index (p=0.15). These results demonstrated that soybean (Andromed) and liposome-based (Optixcell) extenders are equally as effective at cryopreserving white-tailed semen as egg yolk-based Ovine Red extender, but are superior to egg yolk-based Biladyl or Triladyl extenders.