Effects of Body Condition Score on the Reproductive Physiology of the Broodmare: A Review

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.     

Induction of Parturition with Daily Low-dose Oxytocin Injections in Pregnant Mares at Term: Clinical Applications and Limitations

The aim of the present study was to evaluate the clinical applications and limitations of daily low-dose oxytocin injections for the induction of parturition in pregnant at term mares, the attention was focussed on the efficacy of the treatment and on its possible negative effects on mare and foal. Three-hundred and fifty pregnant full term Standardbred mares were used: 176 were allowed to foal spontaneously, 174 were treated daily with 3.5 IU of oxytocin i.m. when mammary secretion showed a calcium concentration ≥ 200 ppm. For each mare, gestational length, outcome and duration of foaling, placenta expulsion time were recorded. Physical and behavioural characteristics of each foal were also recorded. Administration of oxytocin resulted in the delivery of a normal foal within 120 min in 68.9% of treated mares: 51.3% responded to the first oxytocin administration, 14.2% to the second and 3.4% to the third. No significant difference between treated and control mares was observed in the gestational length (340 ± 8 days vs 337 ± 7 days), duration of foaling (10 ± 5.6 min vs 11 ± 4.9 min), incidence of dystocia (1.4% vs 1.7%) and failure of rupture of the allantochorion (0% vs 0.6%). No significant difference was observed in the incidence of placental retention between treated and control groups (8.1% vs 6.3%). Physical and behavioural characteristics were normal in foals of both groups. In conclusion, daily injections of low doses of oxytocin in at term mares showed only moderate efficacy for inducing parturition. However, the easy applicability and the complete safety for both mare and foal, of this method of foaling induction makes it a useful tool to simplify the management of mares in commercial stud farms.     

Transplacental infection of a foal with Anaplasma phagocytophilum

This is the first report to document transplacental transmission of Anaplasma phagocytophillum in the horse. A 4-year-old late-term pregnant mare presented for a recent onset of pyrexia due to equine granulocytic anaplasmosis (EGA). She was hospitalised for treatment with oxytetracycline and monitoring of high-risk foaling due to significant thrombocytopenia. Parturition occurred overnight, and the foal was PCR positive for A. phagocytophilum at birth. The foal was slow to stand and nurse, with signs of neonatal encephalopathy and anaplasmosis (thrombocytopenia). Therapy with oxytetracycline resulted in complete clinical recovery of the mare and foal within 5 days. Congenital anaplasmosis should be considered in any foal delivered to a mare suffering from EGA during late-term pregnancy and guide appropriate antimicrobial therapy.     

Retained fetal membranes in the mare: A retrospective study

A retrospective study of 3456 deliveries was conducted from the records of four Standardbred broodmare farms where mares were bred by artificial insemination and maintained under close veterinary supervision. Retained fetal membranes (RFM) were observed in 10.6% of the deliveries. Retained fetal membranes occurred more frequently (p < 0.05) after dystocia and in mares which had RFM the previous year. Retained fetal membranes after normal foaling had no significant effect on the reproductive performance (pregnancy rate, pregnancy loss rate, or foaling rate), nor on the general health of the mares, regardless of the duration of RFM (3 to 144 hours). Postfoaling laminitis was not observed. Oxytocin therapy of mares with RFM starting at two hours postpartum significantly reduced the incidence of RFM ≥ 8 hours. Mares with RFM which had received intrauterine antimicrobials between foaling and first breeding had a foaling rate similar to mares with RFM which had not received intrauterine therapy.     

Typing of rabbit haemorrhagic disease virus from New Zealand wild rabbits

Abstract

AIMS: To examine the gestation lengths and occurrence of daytime foaling of Standardbred mares foaling outdoors at stud farms in Southland, New Zealand (latitude 45?S).

METHODS: Data were collected prospectively at two commercial Standardbred stud farms (Farms A and B), during the 2008/9 and 2009/10 breeding seasons (October to February). For each foaling, the identity of the mare, date and time of foaling, gender of foal, time the mare passed the fetal membranes, time the foal stood, and foaling problems including dystocias, were recorded. The effect of farm, season, gender of foal, month of artificial insemination (AI) or foaling, age and parity of mare on gestation length, percentage of mares foaling during daylight hours, and percentage of foalings recorded as dystocia, were examined.

RESULTS: A total of 614 foaling records were obtained from 507 mares. For 594 foalings with complete records, mean gestation length was 349 (SE 0.5) days. Mean gestation length was shorter for fillies (347.8 (SE 0.6) days) than colts (350.3 (SE 0.6) days) p = 0.021) and decreased with month of AI, from October to February (p = 0.001). The time of foaling was bimodally distributed with the primary peak around 0200 hours and a secondary smaller peak around 1300 hours. The percentage of mares foaling in daylight was lower on Farm A (69/285 (24%)) than Farm B (128/313 (41%)) (p = 0.001). Colt foals were less likely to be born during the day than fillies (OR = 0.63; (95% CI = 0.44–0.88); p = 0.008), but there was no effect of age or parity of mare or month of foaling (p>0.05).

CONCLUSIONS AND CLINICAL RELEVANCE: Mean gestation length of mares in this study was longer than that previously reported from other countries. Longer gestation length decreases the time available for these mares to get back into foal in the same season. It is important that managers take this into account and ensure optimum conditions for conception; breeding at the first postpartum oestrus may be essential. There were more mares foaling in daylight hours on one stud than has previously been reported. Under these conditions mares should be monitored for foaling during daytime as well as at night.     

Observations and procedures at foaling on a thoroughbred stud

The behaviour and management of Thoroughbred mares prior to, and at foaling time, is detailed. There is a discussion of the losses that occur at birth, traumatic injuries to the mares, and the subsequent treatment of these. The postnatal behavioural patterns of the mare emphasise that she must be isolated at foaling. The normal feeding of the foal and the consequences of this not occurring, the lack of normal bowel function, and the retention of the foetal membranes by the mare are postnatal conditions likely to cause most losses.     

Granulosa cell tumour: An interesting case in a pregnant mare

This report describes the successful management of a pregnant 14‐year‐old seven‐eighths Thoroughbred mare with an ovarian granulosa cell tumour. The mare initially presented with unilateral ovarian enlargement whilst being managed for artificial insemination, demonstrating normal ovarian function with ovulation from the contralateral ovary leading to conception. The mare subsequently re‐presented with stallion‐like behaviour at 3.5 months gestation and ovarian suppression was evident. The mare maintained her pregnancy and delivered a live colt foal at term. Ovariectomy was performed 3 months post foaling and the mare regained cyclic activity 9 months post surgery. The mare then conceived and became pregnant once more. The diagnostic and therapeutic challenges during pregnancy are discussed.     

Preliminary studies of mammary secretions in the mare to assess foetal readiness for birth

The status of the mare and foetus in relation to readiness for birth was assessed by measurement of the electrolytes sodium, potassium and calcium in mammary secretions pre-partum. Sixteen Thoroughbred mares were allowed to foal spontaneously and the ionic status of their mammary secretions was measured over three to five weeks pre-partum. From these measurements, a scoring system was developed where an ionic score of 35 points or more suggested that the mare was within 24 h of foaling. On the basis of this ionic score, 10 pony mares were induced with either oxytocin or fluprostenol and assessment of foal maturity was made by physical, behavioural and physiological criteria. Eight pony mares, induced when the ionic score was 35 points or more, delivered full term foals; two mares were induced when their scores were 30 and 20 points and delivered a full term and slightly immature foal respectively. These results suggest that foetal maturity may be related to electrolyte concentrations in mammary secretions and that an ionic score of 35 points or more may indicate that induction would be successful in terms of maturity of the newborn foal.     

On-the-farm incidence and nature of equine dystocias

The characteristics of parturition and dystocia were recorded on standardized forms by foaling attendants on 8 farms for 517 spontaneous parturitions. Dystocias were classified from examination of the forms into those with malposition (involving the fetal body), malposture (involving fetal extremities), and normal position and posture in which traction was considered essential. Dystocias occurred in 58 of 517 (11.2%) parturitions and involved normal fetal position and posture (31.0%), malposition of body (22.6%), and malposture of extremities (41.4%). Other recorded frequencies were for emergence of an intact chorioallantois at the labia (2.0%), hiplock (1.2%), posterior presentation (0%), uterine torsion (0%), deformed fetal limbs *8.4%), stillbirth (1.2%), death of foal within 24 hours (1.2%), life-threatening injury to the mare (1.5%), and retained placenta (13.5%). The frequencies of a prolonged or excessive Stage 1 culminates in rupture of chorioallantois, (11.5%), deformed foal limbs (24.0%), relatively large foal (26.8%), and retained placenta (22.0%) were greater (P<0.05) for mares with dystocia than for mares without dystocia (2.6, 6.7, 7.9 and 10.5%, respectively).Ten of 14 (72%) dystocias with normal position and posture were attributable to a relatively large foal or weak maternal contractions. All of 16 malpositions of the body involved a tendency toward the dorso-pubic position (upside-down) and 31% were accompanied by malpostures of the extremities. Observations suggested that alternate standing and lying by the mare played a role in preventing and aiding in the self-correction of malpositions. Most (55%) of 24 malpostures involved retention of a front foot. The primary indicators of a problem were the absence of any fetal parts or membranes at the labia for a prolonged time after rupture of the chorioallantois (28% of dystocias) or the emergence of only one foot (34%).The interval from foal delivery to placental discharge was shorter (P<0.01) for Miniature Horses (17±3 min; n=17) than for the larger breeds (54±2 min; n=395). In 3 of 19 (16%) miniatures, the placenta and foal were delivered simultaneously. It was judged necessary to rupture manually an intact amnion in 2 of 5 miniatures on one farm.     

Effect of ω-3 Fatty Acid Supplementation to Gestating and Lactating Mares: On Milk IgG,Mare and Foal Blood Concentrations of IgG,Insulin and Glucose,Placental Efficiency,and Fatty Acid Composition of Milk and Serum From Mares and Foals

Limited research has been conducted to evaluate effects of fatty acid (FA) supplementation on mare and foal FA profiles and foal immunity. Dietary polyunsaturated FAs, particularly ω-3 FAs, increase fluidity of intestinal cell membranes. Fluidity of mammary tissues may also be altered to allow more incorporation of immunoglobulin G (IgG) into milk. Therefore, the goal of this study was to determine effects of incorporating dietary ω-3 FAs on mares, her milk, and her subsequent foal. Pregnant mares were assigned to one of three diets beginning 28 days before expected foaling date until 84 days after foaling. Diet 1 was a commercial feed (CON); diet 2 was diet 1 plus a fish oil blend (FO); and diet 3 was diet 1 plus a blend of fish and soybean oil (FSO). Mare serum FA concentrations were not affected by treatment (P > .05) with the exception of 20:5, which had a treatment × time interaction (P < .05). Mare milk FA concentrations were not affected by treatment (P > .05) with the exception of 16:1 and 20:5. Foal serum FA concentration was not affected by treatment with the exception of 18:2, which had a treatment × time interaction, and 20:5 (P < .0001), which was greatest in FO foals and least in CON foals. Dietary supplementation of ω-3 FAs did increase 20:5 in mare serum, milk, as well as serum of their subsequent foals. No differences were found for mare plasma IgG (P = .1318), serum insulin (P = .3886), plasma glucose (P = .2407), or milk IgG (P = .1262) concentrations for treatment. Foal plasma IgG (P = .2767), serum insulin (P = .4843), or plasma glucose (P = .1204) were not affected by treatment. Omega-3 FA in mare serum, milk, and foal serum were able to be manipulated by diet; however, IgG concentration was unchanged.     

A one-stage repair of third-degree perineal lacerations and rectovestibular fistulae in 17 mares.

Third-degree perineal lacerations or rectovestibular fistulae in 17 mares were repaired surgically by a one-stage method. Primary healing occurred in 14 mares; there were one complete dehiscence and two partial dehiscences with fistula formation. Twelve of 13 mares that were bred became pregnant; nine carried foals to term and two are still pregnant. Two mares have each produced one unthrifty foal. One mare repeatedly aborts in the first trimester. Four mares have produced several healthy foals with no further problems. One mare suffered further perineal trauma while foaling.     

Changes in Serum Concentrations of Prolactin,Progestagens, and Estradiol-17β and Biochemical Parameters During Peripartum in an Agalactic Mare

The purpose of this study was to investigate the changes in serum concentrations of prolactin (PRL), progestagens, and estradiol-17β and biochemical parameters during peripartum in an agalactic mare, as well as to study the periparturient indices of the foal. A 4-year-old Thoroughbred, primiparous, pregnant mare was diagnosed as agalactic from clinical conditions such as absence of observable udder development and weight loss of her foal after parturition. Serum PRL concentrations of the agalactic mare during prepartum tended to be lower than those of the control mares (19.5 ng/mL and 67.0 ± 15.0 ng/mL on the day of parturition, respectively). The progestagens and estradiol-17β concentrations were not markedly different between the agalactic mare and the control mares. Concentrations of γ-glutamyl transferase of the agalactic mare were higher than those of the control mares (P < .05). Although the serum immunoglobulin G concentrations of the foal of the agalactic mare after 24 hours of age were lower than those of the foals of the control mares (P < .05), all periparturient indices regarding the agalactic mare were considered to be within the normal range. In contrast, insufficient udder development and milk production was observed in the agalactic mare through the pre- and postpartum periods. We have ruled out the known causes for agalactia in mares based on other parameters, clinical symptoms, and nutritional causes. Clinical symptoms and PRL parameters in this case report are consistent with the category of agalactia in mares of unexplained causes, and we have determined additional blood parameters associated with agalactia in mares that are consistent with this category.     

Reproductive performance measures among Thoroughbred mares in central Kentucky,during the 2004 mating season

Reason for performing study: To improve efficiency at the farm level, a better understanding of how farm management factors impact reproductive performance is important. Objective: To assess reproductive efficiency and effectiveness among Thoroughbred mares in central Kentucky. Methods: A cohort of 1011 mares on 13 farms in central Kentucky was followed during the 2004 mating and 2005 foaling season. Information on farm level practices was collected via interviews with farm managers. Reproductive records were collected for each mare mated to obtain information on mare characteristics. The influence of mare age and status (maiden, foaling, barren) on Days 15 and 40 post mating pregnancy rates, foaling rates and total effective length of the mating season were assessed. The influence of stallion book size on reproductive performance measures was also examined. Results: Per season pregnancy rates on Days 15 and 40 post mating and live foal rate were 92.1, 89.3 and 78.3%, respectively. Per cycle rates for the same time periods were 64.0, 58.3 and 50.8%. There were no significant associations between stallion book size and reproductive performance outcomes. The mean s.d. interval from the beginning of the mating season to the last mating of the mare was 36.5 ± 26.1 days. Conclusions: Mare age had a significant impact on efficiency of becoming pregnant, maintaining pregnancy and producing a live foal. Overall, fertility did not decrease among stallions with the largest book sizes. Total interval length of the mating season can be reduced if managers ensure maiden and barren mares are mated at the beginning of the season and foaling mares are mated at the earliest oestrus after acceptable uterine involution has been achieved. Potential relevance: Measures identified in the study can be used by owners, farm managers and veterinarians to improve mare reproductive performance and identify parameters to assist with the implementation of effective culling practices.     

Impact of reproductive efficiency over time and mare financial value on economic returns among Thoroughbred mares in central Kentucky

Reason for performing study: There have been no studies reporting the impact of reproductive efficiency and mare financial value on economic returns. Objective: To explore the economic consequences of differences in reproductive efficiency over time in the Thoroughbred mare. Methods: Complete production records for 1176 mares were obtained. Production history and drift in foaling date were calculated. Multiple logistic regression was used to identify factors influencing the probability of producing a registered foal in 2005. The ‘net present value’ and ‘internal rate of return’ were calculated for economic scenarios involving different initial mare financial values, levels of reproductive efficiency, and durations of investment. Results: Among mares that did not produce a foal every year (63%), the mean time before failing to produce a registered foal was 3.4 years. The majority of mares drifted later in their foaling dates in subsequent foaling seasons. Increasing mare age, foaling after 1st April, needing to be mated multiple times during the season, and producing a lower number of foals in continuous sequence during previous years decreased the probability of producing a registered foal. Over a 7 year investment period, live foals must be produced in all but one year to yield a positive financial return. Profitability was highest among mares of greatest financial value. Conclusions: Mares are long‐term investments due to the extended period before there is a return on the investment. Improving our understanding of mare, stallion and management factors that affect the likelihood of producing a live foal are critical to ensuring a positive financial return. Additional work is needed to test the robustness of the study's conclusions when the cost and revenue assumptions are varied. Potential relevance: This information can assist in assessing mare profitability and developing management strategies to maximise profitability.     

Monitoring of the mare during the perinatal period at the clinic and in the stable

Complications in late gestation are challenging problems for the equine clinician and are causes of considerable distress to owners. Health problems in a pregnant mare in each stage of gestation can adversely affect the pregnancy. It is important to obtain a thorough history and perform a detailed and systematic examination of the pregnant mare so that the mare may be classified as normal or high-risk. However, even after a thorough examination, practitioners may face problems with the interpretation and assessment of risk. Normal mares should foal in the stable or pasture. Mares classified as having a high-risk pregnancy need to be monitored precisely for signs of oncoming foaling with attendance of trained personnel when labour begins. A valuable method for monitoring of the high-risk mare is assessing fetoplacental well-being. Fetoplacental well-being is most accurately assessed with ultrasonography as well as several available hormone profiles. We are proposing our scoring system of the mare's health, which may be useful in the assessment of risk during pregnancy and help clinicians to decide whether sending the mare to the clinic is reasonable or unnecessary.     

Atrial fibrillation in a pregnant mare: treatment with quinidine sulfate

Atrial fibrillation in a pregnant, lactating, 15-year-old mare nursing a 70-day-old foal was converted to normal sinus rhythm, using quinidine sulfate. The maximum concentration of quinidine was 4.3 mg/L in the mare's milk and was 2.6 mg/L in the mare's serum. Treatment with quinidine did not interrupt the pregnancy. Six months after treatment, the mare developed acute volvulus of the large colon and died. At necropsy, the mare did not have macroscopic or microscopic cardiac lesions. The fetus was macroscopically and histologically normal.     

A Field Study of Serum,Colostrum, Milk Iodine,and Thyroid Hormone Concentrations in Postpartum Draft Mares and Foals

Iodine, thyroxine (T4) and triiodothyronine (T3) are required for normal fetal growth, maturation, and neonatal survival. There is a lack of robust information on iodine levels found in colostrum, milk, and serum of mares and foals after a healthy pregnancy. Our objective was to characterize colostrum, milk, and serum iodine levels in healthy postpartum mares and foals (n = 10) and explore relationships with thyroid hormone concentrations. Colostrum, milk, and jugular blood samples from draft breed mares and foals with an estimated average iodine daily intake of 39 mg per mare during pregnancy were obtained at Day 0 (foaling date) and/or 10 days later. Parameters studied were (1) mare basal concentrations of serum: TT3, TT4, and iodine; (2) iodine in colostrum at Day 0 and milk iodine (Day 10); and (3) foal basal: TT3, TT4, and serum iodine (Days 0 and 10). Median ± median error colostrum iodine levels (165 ± 15.1 μg/L) were higher than milk (48 ± 5.6 μg/L; P = .007) levels. Median ± median error foal serum iodine (268.5 ± 7.6 μg/L), TT4 (1,225 ± 47.8 nmol/L), and TT3 (14.2 ± 1.1 nmol/L) at foaling date were higher than at 10 days (serum iodine: 70 ± 3.6 μg/L; TT4: 69.6. ± 20.4 nmol/L; and TT3: 5.4 ± 0.3 nmol/L). In conclusion, equine mammary tissue concentrates iodine beyond plasma levels, making colostrum and milk a significant source of iodine. Foal serum iodine levels are high in the neonatal period and are positively correlated with TT4, which is important for neonatal adaptation.     

Reproductive efficiency of intensively managed Thoroughbred mares in Newmarket

The findings of a retrospective survey of 1393 Thoroughbred mares visiting 22 studfarms in the Newmarket region of the UK during the 1998 mating season were compared with those of a similar study undertaken in 1983. The effects of mare age and status, stallion, month of mating, application of uterine treatments and other parameters on the rates of singleton and twin conception and subsequent pregnancy losses were analysed. Mare age and status significantly affected the per cycle pregnancy rate and the incidence of pregnancy loss. Overall, the mean number of matings per oestrus was 1.12 and the mean number of times a mare was mated until diagnosed pregnant at 15 days after ovulation was 1.88. An overall mean per cycle pregnancy rate of 59.9% at 15 days after ovulation resulted in 94.8% of the mated mares being pregnant at least once at 15 days after ovulation. This high initial pregnancy rate fell to 89.7% by Day 35 and 87.5% by the time of the October pregnancy test; 82.7% of the mares surveyed gave birth to a live foal at term, which compares favourably with the proportion of mares foaling in 1983 (77%). However, despite improvements in the foaling rates over the last 15 years, the overall rate of pregnancy failure remains high and represents a major loss to the Thoroughbred breeding industry.     

Effect of book size and age of mare and stallion on foaling rates in thoroughbred horses

The entire population data for Thoroughbred horses in the United States, Canada and Puerto Rico registered with the Jockey Club of America were utilized to study the effect of stallion book size, age of mare and age of stallion on live foal percentage for the 1987 and 1988 breeding seasons. There were 17,260 stallions bred to 179,009 mares, with a resulting overall live foaling rate of 58.1%. There was an increase in live foal percentage as book size increased (P<0.001) and a decrease in live foal percentage as mare age increased (P<0.0001). Stallion age had no effect on live foal percentage.     

Unusual ovarian activity in a mare preceding the development of an ovarian granulosa cell tumour

An 8-year-old mare, with a foal at foot, was inseminated on foal heat with frozen semen, with the resultant pregnancy lost between days 34 and 41. The right ovary developed a large anovulatory follicle that was non-responsive to multiple doses of ovulating agents. The follicle eventually appeared to luteinise, although plasma progesterone concentrations did not reflect this. Another follicle developed, responded to GnRH and resulted in a pregnancy from frozen semen that went to term with a healthy foal. When the mare was examined after foaling, the structure on the right ovary appeared to be a granulosa cell tumour; the left ovary was smaller than normal and non-functional. Surgical removal of the right ovary before increasing photoperiod resulted in a return to function of the left ovary and a pregnancy to frozen semen on the second cycle following removal. Figures showing concentrations of inhibin, progesterone, androstenedione, oestradiol and testosterone are presented for this entire period. Unusual ovarian activity in the mare might be a prelude to the development of a granulosa cell tumour.