Comparison of HCG, buserelin and luprostiol for induction of ovulation in cycling mares

Sixty nonlactating light-horse mares were used to compare the efficacy of hCG, buserelin (a GnRH analog) and luprostiol (a PGF₂α analog) for induction of ovulation in cycling mares. Mares were assigned to 1 of 4 treatments: 1) controls; 2) 40 μg buserelin IM at 12 hr intervals during estrus until ovulation; 3) 7.5 mg IM luprostiol; and 4) 3,300 IU hCG. Treatments were given once a mare obtained a ≥35mm follicle and had been in estrus ≥2 days. Both buserelin and hCG shortened (p<0.05) the interval from treatment to ovulation compared to controls; whereas, luprostiol failed to hasten ovulation. Number of follicles ovulated was similar among all 4 groups. Although buserelin and hCG were equal in their ability to induce ovulation, an average of 3.8 injections of buserelin was required for hastening of ovulation.     

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.     

Efficacy of the gnrh agonist deslorelin acetate for inducing ovulation in mares relative to age of mare and season

Deslorelin acetate (Ovuplant™, Fort Dodge), a GnRH agonist, is commonly used to induce ovulation in cycling mares. Although its efficacy in hastening ovulation has been previously reported, the effects of age of mare and month of administration on percent of mares responding and interval to ovulation have not been studied.Data was gathered from reproduction records of 376 mares receiving deslorelin acetate at the Equine Reproduction Laboratory, Colorado State University, from 1995 to 1999. Age of mare, date of administration, size of largest follicle at treatment, and interval to ovulation were recorded. Age of mare was categorized into five groups: 2–4, 5–9, 10–14, 15–19, and greater than or equal to 20 years. Date of administration was divided into four groups: March and April, May and June, July and August, and September and October.A higher (p < 0.05) percentage of mares aged 10–14 (98.5%) ovulated in response to deslorelin acetate than mares aged 2–4 or 5–9 (90.2% or 91.0%, respectively) or mares aged 15–19 or ≥ 20 (87.9% or 83.8%, respectively). Mares ≥ 20 had the lowest ovulation rate (83.8%). However, mares ≥ 20 that responded to deslorelin acetate had a shorter (p < 0.05) interval from treatment to ovulation (1.7 ± 0.1 days) than mares 2–4 and 5–9 years of age (1.9 ± 0.1 and 1.9 ± 0.0 days, respectively).Deslorelin acetate was more effective in inducing ovulation in the July and August (95.4%) (p < 0.01) and September and October (95.7%) (p = 0. 04) than in the March and April (81.1%). Mares treated in May through October also experienced shorter (p < 0.05) intervals to ovulation than mares treated in March and April.     

Assessing the fertility of two mares cloned from the same founder animal

Two cloned mares, produced from the same sample of skin fibroblasts, were bred during four breeding seasons from their second year of age, as embryo donors, in exactly the same conditions, using the same stallions for both cloned mares. The aim of this study was to test the embryo donor potential of cloned mares and to compare the results obtained from two cloned mares of the same mare with other embryo donor mares (n = 31–39 per breeding season) at the same stud. For both cloned mares, 19 embryos were recovered by 43 collection attempts (44%) (7/22 for one; 12/21 for the other), 16 (84%) pregnancies (5/7 for one, 11/12 for the other) were obtained at day 14 post-ovulation (D₁₄), and 12 (3/7 for one; 9/12 for the other) foals were born. One cloned mare was a less efficient donor mare than the other (p < .05), In control donor mares, 623 embryo collections were performed, with a recovery rate (80%—496/623) significantly higher than for cloned mares. The recovery rate in the subpopulation of 2–5-year-old control donor mares (same age of cloned mares) (89%—127/143) and The recovery rate in the subpopulation of 12 control mares bred with the seven same stallions as clones (55%—17/31), were both higher than for cloned mare (p < .05). The success rate of transfer was not different between embryos produced by cloned mares (84%—16/19) and those produced by control donor mares (79%—392/496). However, the foaling rate per embryo collection was significantly lower for cloned mares (28%—12/43) than for control donor mares (52% - 325/623) (p < .05).     

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.     

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.     

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.     

Clinical and Luteolytic Effects of Fenprostalene (A Prostaglandin F(2)alpha Analogue) in Mares

A study was carried out to determine the luteolytic effect of fenprostalene, a prostaglandin F₂α analogue, in mares Ten mares, that included seven cyclic mares, lactating mares and a pregnant mare were used in two experiments. In the first experiment, seven mares were treated subcutaneously with 250 μg fenprostalene and in the second experiment ten mares, including the seven mares used in the first experiment, were treated with fenprostalene and artificially inseminated during the induced estrus. Fenprostalene caused luteolysis in the normal cycling mares and the pregnant mare. Mares showed estrus within one to five days after treatment. Six of the ten mares conceived during the induced estrus and a further two conceived during the next estrus. The compound produced a side effect consisting of a small, raised, sometimes painful skin swelling at the injection site, which lasted for one to two days.     

Some Factors Associated With Fertility of Thoroughbred Stallions

The results of 3 years (2005–2007) of observations and mating (5,646 estrous cycles of 3,788 mares bred to 1 of 15 stallions) at one Thoroughbred breeding farm in central Kentucky were analyzed by a multiple logistic regression model using Bayesian statistics to evaluate the relationship between data entries (factors) and pregnancy outcomes. Factors found to be significantly (P < .05) associated with pregnancy outcome included stallion (one stallion had lower OR for pregnancy higher odds ratio [OR] for pregnancy, and one had, than other stallions), date of mating (OR for pregnancy declined slightly in May – July), mare age (OR for pregnancy were higher for mares <13 years old, and lower for mares >18 years old), mare beginning status (foaling mares had a higher OR for pregnancy), mating on foal heat (lowered OR for pregnancy), mating of the day for the stallion (OR for pregnancy was 4.16 times lower for fifth compared with first mating of day), reinforcement breeding (increased OR for pregnancy), dismount semen neutrophil score (lowered OR for pregnancy when neutrophils were present in dismount semen samples), and tranquilization before breeding (lowered OR for pregnancy in foaling and barren mares). The influence of dismount sample sperm motility scores on OR for pregnancy was weak, so motility scores were not included in the final logistic regression model. The majority of variation in pregnancy outcome was because of mare factors, with only approximately one-third of the variation in fertility explained by stallion.     

Reproductive performance of Thoroughbred mares in the Waikato region of New Zealand: 2. Multivariable analyses and sources of variation at the mare,stallion and stud farm level

Abstract

AIM: The objective of this study was to utilise multivariable statistical methods appropriate for clustered data to identify mare-related explanatory variables that significantly affected the reproductive performance of Thoroughbred mares in the Waikato region of New Zealand. In addition, we aimed to determine the relative contribution of the mare, stallion and stud farm to reproductive performance.

METHODS: A prospective cohort study was performed involving five stud farms in the Waikato region of New Zealand during three consecutive breeding seasons (2006–2008). A total of 1,482 individual mares contributed 2007 mare years and 3,402 oestrous cycles over the three breeding seasons. Reproductive performance was measured using three parameters; (a) first-cycle pregnancy rate (FCPR), (b) end-of-season pregnancy rate (SPR), and (c) the start-of-mating to conception interval.

RESULTS: When controlled for the effects of serving stallion, stud farm and year of study the only significant mare-related variables included in the final models of FCPR, SPR and conception interval were the age of the mare and her reproductive status (classified as dry or foaling). Advancing mare age significantly reduced reproductive performance regardless of reproductive status and foaling mares had significantly poorer reproductive outcomes compared with dry mares when controlled for age. For each additional increase in year of age, the FCPR was reduced by a factor of 0.94 (95% CI=0.92–0.96) and the SPR was reduced by a factor of 0.91 (95% CI=0.88–0.93). Mares older than 14 years of age took longer to conceive after the start-of-mating compared with younger mares. The daily hazard of conception for mares 14 years and older was 0.64 (95% CI=0.47–0.83) times less than mares younger than 9 years of age. Determining the relative contribution of the mare, stallion and stud farm to the FCPR indicated that 95.9% of the variation was at the mare level, 4.1% was at the stallion level and 0% was at the stud farm level. For the SPR the variance components indicated that 92.5% of the variation was at the mare level, 6.7% was at the stallion level and 0.8% was at the stud farm level.

CONCLUSIONS: The reproductive performance of Thoroughbred mares in the Waikato region of New Zealand is influenced by two main mare-related factors; the age of the mare and her reproductive status (dry or foaling). The majority of variation in reproductive performance was associated with mare-level factors and the contribution of the stallion and stud farm was relatively minor.     

A review of mare endometritis in Iran

One hundred eleven mares were examined and selected on the basis of some criteria (history of recent genital discharge and/or abortion, dystocia, retained placenta, rectovaginal rupture and/or failing to conceive after repeated services), rectal palpation, and ultrasound examination of genital tract. The mares were classified in 3 groups (young, middle age and old). During estrus, a specimen was taken by uterine swab and endometrial biopsy. Endometritis was diagnosed and graded on the basis of pathology results and treatment was done on the basis of culture and antibiogram tests. At the first step of treatment, uterine lavage with warm saline followed by intrauterine administration of a specific antibiotic, or povidone iodine solution, was done daily during estrus. If the mare had not responded to the first treatment, in the next steps systemic antibiotic therapy was also added to the mentioned treatment. The results showed that Escherichia coli was the most frequently isolated pathogen and response to the treatments was significantly better in the young mares with category IIA fibrosis of uterine pathology than that of two other groups. It was also found that there is no relationship among age and kind of pathogen to mare endometritis.

Introduction

Bacterial endometritis is the most common cause of subfertility.[1, 2, 3 and 4] In 1992, Kenney argued against the general use of the term “endometritis” to describe the two often quite separate conditions of endometrium: the degenerative changes often associated with age and parity. He suggested the use of the term “endometriosis” instead of the term “chronic degenerative endometritis” (CDE): the inflammatory infection that is divided to “acute endometritis” and “chronic infiltrative endometritis” (CIE). [5]In some mares, the bacteria becomes established and uterine infection develops in which the sources of uterine contamination include coitus, parturition, and reproductive examination.[2, 4 and 6] These mares remain persistently infected and are termed “susceptible” mares, which may have conformation defects such as pneumovagina, uterine pooling, and foaling injuries, which predispose them to endometritis. [7] There are some data indicating that age, parity, and barren years may have important bearing on the breeding prognosis of the mare. [8 and 9] In general, loss of resistance to infection is associated with advancing age and multiparity, factors that are frequently associated with increasing value of mares. [10] By far, Streptococcus zooepidemicus followed by E coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae are the most frequently isolated pathogens,[7 and 10] but there are a few reports that E coli, K pneumoniae, and Corynebacterium spp. are the most frequent isolates.[4 and 11] Endometrial cytology and culture samples often reveal evidence of inflammation and infection. To improve reproductive management of mares in Iran, this study was conducted to assess main causes of mare endometritis and also the relation of age and kind of pathogen to mare endometritis, plus the efficacy of treatment methods in problem mares.

Materials and methods

One hundred eleven mares of different breeds (Thoroughbred, Arab, cross-bred, and two native breeds including Kord and Turkaman) from 4 to 26 years of age were examined and selected during April 1996 to June 2001. They had a history of recent genital discharge and/or abortion, dystocia, retained placenta, rectovaginal rupture, and/or failing to conceive after repeated services. The sanitary condition of the foaling boxes was also noted. The mares were classified in three groups according to the age: (1) young (4-9 years old), (2) middle age (10-14 years old), and (3) old age (≥15 years old).Each mare was restrained in a stock. The vulvar discharge and pneuomovagina were recorded if present. Rectal palpation and ultrasound examination of genital tract were done to determine uterine tone and presence of uterine fluid. During the estrus, a double-guarded swab was passed per vagina into the uterus. The swab was kept in contact with the endometrium for a minimum of 20 seconds and was placed in transport media. In the laboratory the swab was cultured as described by Rickets.[12] An endometrial biopsy specimen was also taken, fixed, and processed as described by Rickets. [13] Endometritis was graded as described by Kenny and Doig. [14] Briefly, they are Grade I (Absent), Grade IIA (Mild), Grade IIB (Moderate), and Grade III (Severe). After specifying the causal organism of endometritis, treatment was done on the basis of culture and antibiogram tests as described by Asbury et al, [10] the antibiotics used for treatment were: gentamicin (intrauterine administration, 2-3 g), amikacin (2 g, intrauterine administration), potassium penicillin G (5 million units, intrauterine administration), and chloramphenicol (3 g, intrauterine administration). [10 and 15] A diluted solution of povidone iodine (0.2%) as uterine lavage was also used in cases whose uterine culture results were yeasts. The following protocol was carried out to treat bacterial endometritis at the first step:Uterine lavage with warm saline followed by intrauterine administration of specific antibiotic or povidone iodine (on the basis of uterine culture and antibiotic sensitivity test results) was done daily during estrus. Casslick operation was done in pneuomovaginal cases. In the next estrus, the uteri were examined by rectal palpation and ultrasonography procedure. If they were involuted, had enough tone and had no fluid, the mares were clinically defined to be treated and bred artificially with fresh semen collected from an approved fertile stallion (about 500 million progressive motile sperm) in Kenney's extender. If there was recurrent endometritis or the uterus was not involuted and/or had not enough tone or had some fluid in it, another specimen was taken by a double-guarded swab. On the basis of culture and antibiotic sensitivity test results, mares that had not responded to the first treatment were treated again with the first step protocol plus systemic antibiotic therapy (gentamicin, amikacin, or procaine penicillin G in bacterial-caused endometritis) or just flushed the uterus with saline and 0.2% povidone iodine solution (in yeast-caused endometritis and/or endometriosis). This treatment was also carried out daily during the estrus. Some of the mares that had not responded to the second treatment protocol were treated again (based on uterine culture and antibiotic sensitivity test results) for one to two times more in the next estrus phases as in the second step. The data were analyzed by χ² test.

Results

Table 1 shows the pathogens isolated in three successive cultures from the uteri of the mares. Among 197 swabs were taken from the uteri of 111 mares, the cultures were positive in 175 instances in which the mixed organisms were isolated in 20 cases. The interesting point in these 3 successive cultures was the persistence of one Klebsiella infection detected in a mare belonging to the second group, in the all-performed treatments. The isolated P aeruginosa in a mare belonging to the third group had the same result. The combination of Candia albicans with E coli and/or E coli with Enterobacteriaceae were the most common feature of mixed micro-organisms isolated in the culture plates.     

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.     

Protective factors in mammary gland secretions during the periparturient period in the mare

Changes in mare mammary secretion composition were characterized prior to and after foaling. Eighteen mares were used for collection of mammary secretions from 23 days prepartum through 44 days postpartum. Concentrations of lactose, total protein, IgG and lysozyme (activity assay) were determined. Considerable variabilty was observed among mares. Mean lactose concentrations by mare were lower (P<.05) in the prepartum period compared with the postpartum period. Mean total protein and immunoglobulin G concentrations by mare were higher (P<.05) in the prepartum period compared with the postpartum period. Mean lysozyme activities by mare tended to be lower (P<.08) during the prepartum period compared with the postpartum period. Mammary secretion protein profiles, characterized by SDS-PAGE, were consistent with changes in concentrations of specific proteins measured in the secretions. Dynamic changes occurring in mammary secretions during the transition from prepartum accumulation of colostrum to postpartum production of milk include factors like IgG and lysozyme which have protective roles in the neonatal foal.     

Effect of eFSH on Ovarian Cyclicity and Embryo Production of Mares in Spring Transitional Phase

The use of equine FSH (eFSH) for inducing follicular development and ovulation in transitional mares was evaluated. Twenty-seven mares, from 3 to 15 years of age, were examined during the months of August and September 2004, in Brazil. Ultrasound evaluations were performed during 2 weeks before the start of the experiment to confirm transitional characteristics (no follicles larger than 25 mm and no corpus luteum [CL] present). After this period, as the mares obtained a follicle of at least 25 mm, they were assigned to one of two groups: (1) control group, untreated; (2) treated with 12.5 mg eFSH, 2 times per day, until at least half of all follicles larger than 30 mm had reached 35 mm. Follicular activity of all mares was monitored. When most of the follicles from treated mares and a single follicle from control mares acquired a preovulatory size (≥35 mm), 2,500 IU human chorionic gonadotropin (hCG) was administered IV to induce ovulation. After hCG administration, the mares were inseminated with fresh semen every other day until ovulation. Ultrasound examinations continued until detection of the last ovulation, and embryo recovery was performed 7 to 8 days after ovulation. The mares of the treated group reached the first preovulatory follicle (4.1 ± 1.0 vs 14.9 ± 10.8 days) and ovulated before untreated mares (6.6 ± 1.2 vs 18.0 ± 11.1 days; P < .05). All mares were treated with prostaglandin F_2α (PGF_2α), on the day of embryo flushing. Three superovulated mares did not cycle immediately after PGF_2α treatment, and consequently had a longer interovulatory interval (22.4 vs 10.9 days, P < 0.05). The mean period of treatment was 4.79 ± 1.07 days and 85.71% of mares had multiple ovulations. The number of ovulations (5.6 vs 1.0) and embryos (2.0 vs 0.7) per mare were higher (P < 0.05) for treated mares than control mares. In conclusion, treatment with eFSH was effective in hastening the onset of the breeding season, inducing multiple ovulations, and increasing embryo production in transitional mares. This is the first report showing the use of FSH treatment to recover embryos from the first cycle of the year.     

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.     

Reproductive performance of Thoroughbred mares on six commercial stud farms

The records of 1630 mare years from 6 Thoroughbred stud farms in south eastern Australia were analysed for the years 1981 to 1986. Overall pregnancy and foaling rates were 83.9% and 69.3%, respectively. When calculated per served oestrous cycle, pregnancy and foaling rates were 54.7% and 43.1%, respectively. Pregnancy and foaling rates were higher (P < 0.001) for mares 3 to 10 years of age than for older mares. There was no difference in the pregnancy rates of maiden, barren and foaling mares. The foaling rate was significantly higher (P < 0.001) in mares that became pregnant during the first served oestrous cycle (77.8%) than in mares that needed two served oestrous cycles to become pregnant (65.4%). Of all diagnosed pregnancies, 19.5% were not completed. Pregnancy loss was lower (P < 0.05) in maiden (12.4%) than in barren (19.7%) or foaling (20.9%) mares. Twins were diagnosed in 7.8% of all pregnancies. If one conceptus was lost without external interference, 84.1% of pregnancies went to term. If one conceptus was manually crushed, 55.9% of pregnancies were maintained. If prostaglandin was used to terminate twin pregnancies, 60% of mares so treated produced foals the following year.     

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.     

Retrospective study on the incidence of postinsemination uterine fluid in mares inseminated with frozen/thawed semen

Uterine fluid accumulation has been reported after insemination or natural breeding of mares. This retrospective study examined the factors affecting the incidence of uterine fluid after insemination of frozen semen. Specifically, this study determined the association between mare age, reproductive status, fluid accumulation, and pregnancy rates in mares. Records were available from 283 warmblood mares throughout 496 cycles. Mares were divided into maiden, foaling, and barren and age groups of 3 to 9, 10 to 16, and more than 16 years. Mares were inseminated only once with frozen semen within 4 to 8 hours before or after ovulation. Ultrasound examinations were performed 12 to 18 hours after insemination. A depth of at least 20 mm of fluid was considered significant. Mares with less than 20 mm were treated with oxytocin, and those with more than 20mm of fluid were given oxytocin and uterine lavage. Pregnancy determination was performed at 14 to 16 and 30 to 50 days after ovulation. Fluid level of more than 20 mm was recorded in 25% of the cycles. Barren mares and aged mares (10-16 and > 16 years) had a higher incidence of uterine fluid accumulations. Per-cycle pregnancy rate was lower (45%) in mares with uterine fluid than in mares without uterine fluid (51%). This difference was primarily due to the reduction in fertility of mares who were older than 16 years and retained fluid after insemination. Apparently, oxytocin and lavage treatments provided acceptable fertility in the other groups of mares that had uterine fluid.

Introduction

Use of equine frozen semen is accepted by the majority of horse registries. According to several field studies,[1, 2, 3, 4 and 5] insemination of frozen semen has resulted in acceptable pregnancy rates. Postbreeding fluid accumulation is a physiologic inflammation that clears the uterus of foreign material such as excess spermatozoa, seminal plasma, bacteria, and extenders. [6, 7, 8, 9 and 10] Uterine fluid can be easily diagnosed with ultrasonography. [10, 11 and 12] Persistent postbreeding uterine fluid has been associated with a decrease in fertility after natural mating or artificial insemination (AI) of fresh semen. [11, 12 and 13] Predisposing factors to persistent fluid accumulations are reduced myometrial contractions, poor lymphatic drainage, large overstretched uterus, and cervical incompetence. [7, 14 and 15] Normal mares are able to expel uterine fluid quickly after inseminations, whereas susceptible mares accumulate fluid in their uterine lumen for more than 12 hours after breeding or insemination. [10]It is commonly stated that insemination with frozen semen leads to greater post-AI fluid accumulation than insemination with fresh or cooled semen or after natural mating. Apparently, there is only 1 controlled study on this comparison.[7] The authors reported that infusion of frozen semen resulted in a greater inflammatory response than natural breeding. In a field study, [16] 16% of mares naturally mated had persistent postbreeding fluid accumulations compared with a 30% rate reported for mares inseminated with frozen semen. [1 and 2] More recently, Watson et al. [17] reported a postbreeding fluid accumulation rate of 16%, which is identical to that reported for natural mating. [16] It is difficult to compare studies because details of mare selection and insemination or breeding frequencies are not always reported. Obviously, a higher proportion of barren and aged mares in a study would increase the incidence of postbreeding fluid accumulation. [1 and 2]The study presented herein was a retrospective study designed to determine the incidence of postbreeding fluid accumulation in a large number of mares inseminated with frozen semen. Associations were determined between mare age, reproductive status and fluid accumulation, and pregnancy rate in mares with and without uterine fluid accumulation.

Materials and methods

Mares

Records were available from 283 warmblood mares inseminated with frozen semen at the Cristella Veterinary Clinic in Italy during 1998 to 2001. Mares ranging in age from 3 to 20 years were inseminated with semen that was frozen in 10 centers and was from 34 stallions. The broodmare population was subdivided into 3 reproductive groups: 89 maiden mares (mean age, 7.2 years), 106 foaling mares (mean age, 9.4 years), and 87 barren mares (mean age, 11.9 years). Maiden mares older than 7 years were selected with biopsy scores of 1 or 2 only. Barren mares were open for no more than 2 consecutive seasons and had negative cytology and bacteriology scores. Age groups were divided as follows: 3 to 9 years (n = 132), 10 to 16 years (n = 137) and older than 16 years (n = 14). Data from 496 cycles were used. Distribution of the estrous cycles was 172, 157, and 167 in the maiden, foaling, and barren groups, respectively; and 224, 244, and 28 in the youngest, intermediate, and oldest groups, respectively.

Mare reproductive management and artificial insemination protocol

During estrus, all mares underwent a daily ultrasound examination with a 5-mHz transrectal probe (SA 600 Vet; Medison Inc., Seoul, South Korea) until 1 or more 35-mm ovarian follicles were detected. Ovulation was then induced by the intravenous administration of 2000 IU of human chorionic gonadotropin (hCG). Ultrasound examination was performed 12 hours after hCG treatment and then every 4 to 8 hours until ovulation occurred. Mares were inseminated only once within a period of 4 to 8 hours before or after ovulation. The semen used was thawed according to the distribution center's instructions and had the following minimum post-thaw quality requirements: not less than 200 × 10⁶ progressively motile spermatozoa per dose and a minimum of 30% progressive spermatozoal motility. Foaling mares were not inseminated at their first postpartum (“foal heat”) estrous period, because pregnancy rates are recognized to be lower than during the subsequent estrous periods.[18] During the first postpartum estrus, ovarian ultrasound scan examinations were performed every 2 to 3 days until an ovulation was detected. A prostaglandin F₂α injection was given 5 days later to short-cycle the mare.

Postinsemination monitoring

An ultrasound examination of the reproductive tract was performed 12 to 18 hours after insemination to detect any intrauterine fluid accumulation. The presence and depth of intrauterine fluid was recorded. Twenty millimeters or more of grade II or III intrauterine fluid[19] was recorded as a significant amount of fluid. Mares with less than 20 mm of fluid were treated with an intravenous injection of 20 IU oxytocin. For mares with more than 20 mm of fluid, oxytocin was administered, and the uterus was flushed daily with buffered saline solution: 1-L aliquots were infused and recovered until the recovered fluid was clear. In these mares, oxytocin treatment was repeated up to 3 times daily. Post insemination treatments were performed for no more than 4 days after ovulation had occurred.Pregnancy diagnosis was performed with ultrasound at 14 to 16 days after ovulation. Scans were then repeated at 30 and 50 days of gestation to confirm the presence in the uterus of an apparently healthy developing conceptus.

Statistical analysis

χ² Analysis was used to determine the effect of reproductive status and age on the incidence of fluid accumulation. In addition, the influence of persistent uterine fluid accumulation on pregnancy rates per cycle was determined for each reproductive class and age by using χ² analysis.

Results

The per-cycle pregnancy rate at 14-16 days after ovulation was 49.3% (245/496 cycles). By the end of the season, 245 of 283 mares (86.5%) were confirmed pregnant. Fluid level of at least 20 mm (grade II or III) was recorded in 126 of the 496 cycles (25.4%). Barren mares had a higher (P < .05) incidence of postbreeding fluid accumulation (64/167; 38.3%) than maiden (34/172; 19.7%) and foaling (28/157, 17.8%; Table 1) mares. The incidence of fluid accumulation was also higher in mares older than 16 years (19/28; 67.8%) than those aged 10 to 16 years (69/244; 28.2%) and 3 to 9 years (38/224; 17%). The incidence of uterine fluid was also higher (P < .05) for mares aged 10 to 16 years than those aged 3 to 9 years (Table 2). Overall, the per-cycle pregnancy rate was lower (P < .05) for mares with post-AI fluid accumulations than for those with no uterine fluid or only a small quantity of fluid (57/126, 41.9% vs 188/360, 56.2%). Pregnancy rates were similar (P > .05) for mares with or without uterine fluid when comparisons were made within maiden and barren mare groups. However, more foaling mares became pregnant when no fluid was detected after insemination. Pregnancy rate for this group (68.1%) was higher than that for maiden (44.2%) and barren (44.6%) mares (Table 3). Older mares with uterine fluid accumulations had a lower per-cycle pregnancy rate (36.8%) than mares in the same group but without fluid. Surprisingly, if no fluid was detected, the highest pregnancy rates were in mares older than 16 years ( Table 4).     

Relationship Between Fertility at Foal Heat and Blood Biochemistry Parameters Monitored During the Peripartum Period in Thoroughbred Mares

This study aimed to examine fertility at foal heat and its relevance to body condition score (BCS) and blood nutritional metabolites in Thoroughbred mares. Thoroughbred mares foaled from 2006 to 2009 were included and classified into two groups: group C (conception; n = 34), which included mares that conceived during foal heat (within 3 weeks after foaling), and group NC (nonconception; n = 39), which included mares that did not conceive despite mating during their foal heat. BCS and blood samples were obtained 1 month before the expected foaling date and 1, 2, 3, and 4 weeks after foaling. Total protein (TP), albumin (Alb), blood urea nitrogen (BUN), aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), total cholesterol (T-Cho), triglyceride (TG), nonesterified fatty acid (NEFA), calcium (Ca), inorganic phosphate (iP), and magnesium (Mg) levels were measured using an automatic clinical chemistry analyzer. Repeated measures analysis of variance (ANOVA) and Student t-test were used to examine the differences between the two groups. No significant differences were observed between the two groups in any of the above-mentioned parameters at 1 month before the expected foaling date (Student t-test). Furthermore, no significant differences were observed between the two groups in serum levels of TP, Alb, AST, GGT, T-Cho, NEFA, Ca, and Mg and BCS at postpartum periods (repeated measures ANOVA). Serum TG, BUN, and iP levels remained lower in group NC than in group C after foaling (P < .05, repeated measures ANOVA). Although the mechanism by which these nutritional factors affect a decline in reproductive performance remains unclear, our results suggest that blood biochemical tests can detect potential imbalances in nutrition and metabolism, even if there is no difference in BCS.