Broodmare Management Research Articles

Follicle Deviation in Miniature Mares

Endometritis constitutes a major problem in the management of broodmares; hence, diagnostic tests with a high sensitivity and specificity are highly appreciated. The aim of this study was to compare the results from endometrial, cytologic, and bacteriologic examinations obtained by a newly developed, double-guarded, flushing technique versus standard diagnostic tests, the double-guarded swab and biopsy. The described double-guarded flush technique requires the use of a disposable uterine flushing tube, a sanitary sleeve, a sterile steel speculum, and a 250 mL fluid bag. Endometrial biopsies, swabs, and low-volume lavage samples were obtained from 34 research mares at six different time points in four estrous cycles and were evaluated cytologically and bacteriologically. Endometrial biopsies from the first cycle (n = 34) were examined for the presence of polymorphonuclear neutrophils (PMNs) in the stratum compactum and stratum spongiosum and used as a gold standard for calculation of diagnostic sensitivity and specificity. In all samples, Escherichia coli was most frequently isolated (lavage, 30%; swab, 21%; and biopsy, 12%) followed by β-hemolytic streptococci (lavage, 11%; swab, 8%; and biopsy, 7%). Positive cytology was less likely to occur when E coli was isolated from the diagnostic tests compared with the growth of β-hemolytic streptococci. Isolation of pathogens from uterine samples was highly associated with the presence of PMNs in the stratum compactum and straum spongiosum on histology. Using the presence of PMNs in the tissue specimens as the gold standard for diagnosing endometritis, the sensitivity of low-volume lavage culture was 0.75 and the specificity was 0.72. In conclusion, the double-guarded, low-volume, lavage technique was a rapid and accurate method for diagnosing mares with endometritis, and the risk of false-positive samples is considered to be minimal compared with other flushing techniques described.

Progesterone and 5α-dihydroprogesterone (DHP) in Cyclic Mares, and in Ovariectomized Mares and Geldings After Progesterone Administration

Endometritis constitutes a major problem in the management of broodmares; hence, diagnostic tests with a high sensitivity and specificity are highly appreciated. The aim of this study was to compare the results from endometrial, cytologic, and bacteriologic examinations obtained by a newly developed, double-guarded, flushing technique versus standard diagnostic tests, the double-guarded swab and biopsy. The described double-guarded flush technique requires the use of a disposable uterine flushing tube, a sanitary sleeve, a sterile steel speculum, and a 250 mL fluid bag. Endometrial biopsies, swabs, and low-volume lavage samples were obtained from 34 research mares at six different time points in four estrous cycles and were evaluated cytologically and bacteriologically. Endometrial biopsies from the first cycle (n = 34) were examined for the presence of polymorphonuclear neutrophils (PMNs) in the stratum compactum and stratum spongiosum and used as a gold standard for calculation of diagnostic sensitivity and specificity. In all samples, Escherichia coli was most frequently isolated (lavage, 30%; swab, 21%; and biopsy, 12%) followed by β-hemolytic streptococci (lavage, 11%; swab, 8%; and biopsy, 7%). Positive cytology was less likely to occur when E coli was isolated from the diagnostic tests compared with the growth of β-hemolytic streptococci. Isolation of pathogens from uterine samples was highly associated with the presence of PMNs in the stratum compactum and straum spongiosum on histology. Using the presence of PMNs in the tissue specimens as the gold standard for diagnosing endometritis, the sensitivity of low-volume lavage culture was 0.75 and the specificity was 0.72. In conclusion, the double-guarded, low-volume, lavage technique was a rapid and accurate method for diagnosing mares with endometritis, and the risk of false-positive samples is considered to be minimal compared with other flushing techniques described.

Preovulatory Follicle Dynamics, and Ovulatory and Endometrial Responses to Different Doses of hCG and Prediction of Ovulation in Mares

A more precise characterization of the effects of human chorionic gonadotropin (hCG) treatment on the preovulatory follicle is needed to improve reproductive efficiency in broodmare management. The objectives of this study were (1) to study the effects of different hCG doses within and among three consecutive estrous cycles on ovulatory response, preovulatory follicle dynamics, and endometrial echotexture; (2) to study the temporal relationship among changes in preovulatory follicle diameter, endometrial echotexture, and estradiol levels; and (3) to analyze a system for prediction of ovulation. In experiment 1, mares were treated with 2,500 IU hCG, 1,500 IU hCG, 500 IU hCG, or saline (controls) and examined by ultrasonography every 6 hours across three consecutive preovulatory periods (n = 135). Similar treatment groups were utilized in experiment 2 (n = 177 preovulatory periods) with examinations performed every six, 12, or 24 hours to test the effectiveness of a prediction of ovulation system. Effective hCG doses (2,500 and 1,500 IU) led to cessation of growth rate and reduction of the preovulatory follicle diameter concurrently with a reduction in systemic estradiol concentration and endometrial echotexture score. A system of prediction of ovulation, based on preovulatory follicle ultrasonographic signs of impending ovulation, was highly accurate for the diagnosis of positive and negative outcomes in both hCG-treated and control groups. However, the effectiveness of this prediction system was reduced due to the false-negative diagnoses that were a reflection of a lack of sensitivity for the detection of nonovulation.

Diagnostic double-guarded low-volume uterine lavage in mares

Endometritis constitutes a major problem in the management of broodmares; hence, diagnostic tests with a high sensitivity and specificity are highly appreciated. The aim of this study was to compare the results from endometrial, cytologic, and bacteriologic examinations obtained by a newly developed, double-guarded, flushing technique versus standard diagnostic tests, the double-guarded swab and biopsy. The described double-guarded flush technique requires the use of a disposable uterine flushing tube, a sanitary sleeve, a sterile steel speculum, and a 250 mL fluid bag. Endometrial biopsies, swabs, and low-volume lavage samples were obtained from 34 research mares at six different time points in four estrous cycles and were evaluated cytologically and bacteriologically. Endometrial biopsies from the first cycle (n = 34) were examined for the presence of polymorphonuclear neutrophils (PMNs) in the stratum compactum and stratum spongiosum and used as a gold standard for calculation of diagnostic sensitivity and specificity. In all samples, Escherichia coli was most frequently isolated (lavage, 30%; swab, 21%; and biopsy, 12%) followed by β-hemolytic streptococci (lavage, 11%; swab, 8%; and biopsy, 7%). Positive cytology was less likely to occur when E coli was isolated from the diagnostic tests compared with the growth of β-hemolytic streptococci. Isolation of pathogens from uterine samples was highly associated with the presence of PMNs in the stratum compactum and straum spongiosum on histology. Using the presence of PMNs in the tissue specimens as the gold standard for diagnosing endometritis, the sensitivity of low-volume lavage culture was 0.75 and the specificity was 0.72. In conclusion, the double-guarded, low-volume, lavage technique was a rapid and accurate method for diagnosing mares with endometritis, and the risk of false-positive samples is considered to be minimal compared with other flushing techniques described.

The effect of hCG, administered in diestrus, on luteal, ovarian and uterine blood flow, peripheral progesterone levels and pregnancy rates in mares

Although advances in the management of brood mares have led to an increase in conception rates, early embryonic loss is still a major concern in equine practice. However, administration of hCG in diestrousmares has been reported to increase pregnancy rates and progesterone production. The aim of this study was to analyze the effects of a postovulatory hCG-treatment on luteal, ovarian and uterine blood flow, peripheral serum progesterone concentrations and pregnancy rates in the mare. Thirty-four mares were inseminated, 17 with cooled and 17 mares with frozen semen, and randomly assigned to three experimental groups after ovulation (D0). Group 1 (n 1⁄4 12) served as untreated control, Group 2 (n1⁄411) received a single intravenous injection of 2500 IU hCG on D5, and Group 3 (n 1⁄4 11) got an analogous hCG-application on D 11 of the cycle. On D0 during the first 12 h post ovulation colour Doppler ultrasonography was performed every 4 h, and afterwards in 12-h-intervals until D3 in all groups. The control group was examined once daily until D13. Mares in the treatment groups were examined once daily until the hCG-administration. Thereafter ultrasonographic examinations were performed every four hours for the first 12 h and in 12-h-intervals for the following three days. The total as well as the perfused luteal area, and the blood flow

Osteochondrosis in foals

THE recent paper by Vander Heyden and colleagues (2013) concludes that ‘It appears that mares fed concentrate during their gestation are more likely to produce foals that subsequently develop osteochondrosis (OC) compared with other mares’. This comment could have consequences for veterinarians' advice to owners of brood mares, practical horse management on studs and for the manufacturers of horse feeds. The conclusion is dubious and we, therefore, are concerned that uninformed persons could be easily misled by this paper, resulting in a negative effect on brood mare management. The questionnaire that the authors distributed to collect the data incorporated in the analysis used the term ‘concentrate’ as a ‘catch-all’, including straight cereals and all manner of things, embracing complete feed. Furthermore, there was no quantification …

Growing more durable equine athletes

Discussions on growing more durable equine athletes often revolve around developmental orthopaedic disease (DOD). What degree of DOD, if any, is acceptable or inconsequential to long-term athletic performance remains a question. Much effort has been directed toward diminishing or eliminating the incidence and severity of DOD, but with limited success. We must continue to define what degree the management decisions affect the horse during different stages of its growth. It would seem logical that the most profound influence would occur during the most rapid periods of growth. Therefore, concerns have been directed toward the last third of gestation and the possible indirect effect that broodmare management has on foetal development. The early postnatal period is another period of rapid growth; thus, the effect of broodmare management on lactation may affect the growth of the foal. Management will also have a direct effect on growth and development from weaning through to maturity. Recent research in other species as well as in horse suggests that genetic predisposition is the primary determinant of DOD. Non-nutritional management also may have significant effects on articular and skeletal health and athletic durability. Much effort has been directed toward nutrition and potential impact on DOD, but with limited success. Except for overt deficiencies, or perhaps excessive imbalances, nutrition does not appear to be a primary determinant of DOD, particularly of focal lesions associated with osteochondrosis. However, nutrition may serve a secondary role in diminishing the severity and incidence of DOD in horses genetically predisposed to such conditions. Producing horses that will have long-term and productive athletic careers requires sound management that starts at conception and continues throughout the life of the horse.

Equine insulin resistance: The quest for sensitivity

The feeding management of broodmares is essential for breeding and successfully raising a healthy foal. A feeding regime will depend on the breed of mare, her age, body condition score (BCS), and general health and management. To maintain the broodmare in adequate body condition, her BCS should be ascertained and a feed regime implemented to maintain her optimum BCS and body weight, thus increasing fertility, milk yield, and the health of the mare and foal. Excesses and deficits in nutrition of the broodmare are regularly observed because nutritional recommendations are not well known or often not well instigated by horse breeders. Some short-term unbalanced rations are of little detriment to the health of the broodmare, but prolonged unbalanced rations can predispose the broodmare and foal to nutritional- and pathologic-related problems. By providing the broodmare with sufficient dietary energy, key nutrients, protein, and minerals in a balanced form, the risk of the foal developing orthopedic diseases will be greatly diminished. Obesity in the broodmare causes increased fetal adiposity, which can affect growth and performance of the adult horse. Conversely, undernutrition of the broodmare can cause intrauterine growth retardation of the fetus, resulting in altered development of the system(s) involved, which may have long-term effects on the horse that manifest during fetal, neonatal, or even adult life.

Pharmacokinetics of carbetocin, a long‐acting oxytocin analogue, following intravenous administration in horses

Current therapy protocols to treat persistent post mating endometritis and retained fetal membranes in mares typically include the administration of ecbolic drugs. Evaluation of the pharmacokinetics and tolerability of carbetocin, a long-acting oxytocin analogue, after i.v. administration is required. To determine the pharmacokinetic parameters (principally half-life) of carbetocin in horses. Five mature mares and one gelding received 0.175 mg carbetocin i.v. All animals were monitored periodically throughout the study for elevation in rectal temperature, heart rate, respiratory rate and signs of pain or discomfort. Plasma samples were collected for determination of carbetocin concentrations by radioimmunoassay. Administration of carbetocin was well tolerated by all horses and its half-life was 17.2 min. The half-life of carbetocin is greater than that previously reported for oxytocin (6.8 min). Carbetocin is an attractive alternative to oxytocin therapy in broodmare management.

Pregnancy and twinning rates in Thoroughbred mares following the administration of human chorionic gonadotropin (hCG)

AIM: To determine the effect of hCG administration to cycling Thoroughbred mares, on pregnancy and twinning rates and the number of serves in the treated cycle. METHODS: A retrospective case control approach was conducted involving 2119 mare ovulatory cycles, on 1110 mares over a 7-year period. Data were collected by 1 of the authors during routine stud work at 3 commercial Thoroughbred farms in the Waikato region of New Zealand. The hCG (1500 IU) was administered by intravenous injection to selected mares 24 h before the expected time of breeding. Mares were scanned for pregnancy (singleton or twins) 14 days after the onset of dioestrus or detection of ovulation. Multilevel logistic regression analyses were used to identify the risk factors associated with the outcomes of interest while simultaneously controlling for possible confounding factors. RESULTS: Treatment with hCG tended to improve the odds of pregnancy (p=0.06), produced a 3-fold increase in the odds of twins (p<0.001), and increased the odds of a mare having a single serve in the treated ovulatory cycle (p=0.036). The first ovulatory cycle of a season in which a mare was bred was associated with a lower odds of pregnancy (p=0.02), and a lower odds of twins (p=0.003), when compared with subsequent cycles. Lactating mares were less likely to be diagnosed with twins (p=0.005), and were more likely to have a single serve (p<0.001), in any one ovulatory cycle than non-lactating mares. CONCLUSIONS: This report supports the role of hCG as an important therapeutic tool in veterinary management of broodmares for optimal reproductive performance. Mares treated with hCG must be managed in the knowledge that they have an increased likelihood of twins.

Human chorionic gonadotropin (hCG): the effect of dose on ovulation and pregnancy rate in Thoroughbred mares experiencing their first ovulation of the breeding season

AIM: To determine the effect of hCG dose on ovulation and pregnancy rate in Thoroughbred mares experiencing their first ovulation of the breeding season. METHODS: Over 3 successive breeding seasons, a total of 101 mares were randomly assigned to 1 of 4 treatment groups (intravenous injection of either saline, 1500, 3000, or 6000 IU hCG), as they approached their first ovulation of the breeding season. Mares were bred 1 day post-injection to 1 of 11 stallions, and every other day until ovulation occurred. Data were analysed using multi variable logistic regression with correction for over-dispersion due to clustering. RESULTS: Mares treated with hCG were more likely to ovu- late within 72 h of treatment than mares treated with saline (p<0.001); there was no significant difference between doses of hCG on risk of ovulation (p>0.15). Farm also had a significant impact on the risk of ovulation (p=0.027). Mares treated with hCG were more likely to be diagnosed pregnant 14 days post ovulation than saline-treated mares (p=0.081, p=0.029 and p=0.026 for the 1500, 3000 and 6000 IU doses, respectively); there was no significant difference between doses of hCG on risk of pregnancy (p>0.45). CONCLUSIONS: A single injection of hCG (1500–6000 IU) is effective at inducing ovulation in late transitional mares and increases the likelihood of pregnancy at 14 days post ovulation. This paper supports the use of hCG as an integral part of optimal broodmare management.

Foaling-management practices associated with the occurrence of enterocolitis attributed to Clostridium perfringens infection in the equine neonate

Enterocolitis associated with Clostridium perfringens ( C. perfringens) infection in neonatal foals is often severe and has been associated with a high case-mortality risk. We designed a premises-based survey to evaluate the associations of regional foaling practices, premises environmental management, periparturient foal and brood-mare management, and periparturient brood-mare ration with the occurrence of neonatal enterocolitis attributed to C. perfringens infection. Potential risk factors individually associated with enterocolitis were breed type, housing type at foaling and in the first three days of life, ground/floor surface type at foaling and in the first three days of life, brood-mare ration before and after foaling, and the presence of livestock other than horses on the premises in the past. From the multivariable-logistic regression models, six variables were significantly associated with an increased risk of the outcome of interest ( p<0.05): foals of the stock horse type, housing in a stall or drylot in the first three days of life, other livestock present on the premises in the past, foal born on dirt, sand or gravel surface, and low amounts of grass hay and grain fed post-partum. Low grain amounts fed pre-partum represented a decreased risk of the outcome of interest.

Lack of correlation between exposure to lyme disease (Borrelia burgdorferi) and pregnancy loss in mares

Exposure to Borrelia burgdorferi, the agent of Lyme disease, has been incriminated as causing an increased incidence of reproductive failure in mares. To test this hypothesis, B. burgdorferi (Lyme) antibody concentrations and incidence of early embryonic death (loss of embryo <45 days gestation, EED) and abortion (loss of fetus >45 days gestation) were determined in mares on two farms, one with a high (66% in November, 1990) incidence of Lyme exposure (Farm A, n=78 mares) and one with a low (<3%) incidence of positive Lyme results (Farm B, n=47 mares). Broodmare management practices and nutrition were similar on the two farms. All mares were bred by artificial insemination and checked by ultrasound for pregnancy at 12-20 days and again at 34-45 days after breeding. Blood samples for ELISA determination of B. burgdorferi antibody concentrations were taken prior to thebreeding season (November, 1990) and at the 34-45 day pegnancy check (February - June, 1991). Farm A had a high incidence of Lyme exposure with 23 seroconversions recorded at the time of the second pregnancy check. Only one of the mares exhibited clinical signs of Lyme disease. There was no difference in the incidence of EED between the two farms (Farm A: 12.8%; Farm B: 7.3%; P=.25) though abortions after 45 days tended to be higher on Farm A (10%) than on Farm B (2%, P=.09). There was no correlation (P=.5) with the Lyme status of mares and occurrence of EED or abortion, however, on Farm A, Early embryonic loss (but not abortion) tended to be correlated with longer residence on Farm A(EED: 31±3 mo; no EED: 17±3 mo, P=.10) though length of residence did not affect Lyme status of the mares at the time of breeding (P=.85) nor was age of the mare correlated in the incidence of EED (P=.85). Exposure to B. burgdorferi does not significantly increase the risk of EED in mares. The effect of chronic exposure to B. burgdorferi on risk of abortion and resistance to clinical signs of the disease warrants further investigation.