Relationship between the Placental Retention Time and the Reproductive Performance at the Foal Heat in Thoroughbred and a Comparison with Heavy Draft

The aim of this study was to clarify the relationship between the placental retention time (PRT) and the reproductive performance following mating at the foal heat in Thoroughbreds. For this purpose, we interviewed 292 farmers over a period of 3 years with questionnaires evaluating foaling, expulsion of placenta and reproductive performance at the foal heat in 1,432 mares. The obtained data were later compared with a previous study of heavy draft mares. The average of the PRT of the 1,432 Thoroughbred mares was 58 ± 88 min (mean ± SD). The mean PRT of Thoroughbreds was significantly shorter than that of the148 min of heavy draft mares. The incidences of retained placenta (RP) occurring in the Thoroughbred mares were 5.2 and 4.0%, for over 3 and 4 hr after foaling, respectively. The incidence of RP over 4 hr was significantly lower than that of 25% in heavy draft mares. The pregnancy rate at foal heat of the mares in which PRT was less than 3 hr was 37%, and it significantly decreased to 11% for those with PRT of more than 3 hr. In the comparison of the reproductive performance between Thoroughbred and heavy draft mares, the pregnancy rate of Thoroughbreds dropped drastically to 10% when PRT exceeded 40, and in consequence, the pregnancy rate of Thoroughbreds was significantly lower than the 30% of heavy draft mares, which had a PRT of over 4 hr. In conclusion, the Thoroughbred mares had a low incidence of RP, however, a PRT exceeding 3 hr severely affected the reproductive performance at the foal heat.     

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.     

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.     

Management Strategies Aiming to Improve Horse Welfare Reduce Embryonic Death Rates in Mares

The objective of this retrospective study was to evaluate the effect of management strategies aiming to improve animal well‐being on pregnancy and embryonic death (ED) rates. Breeding records of a cohort of 1206 Thoroughbred mares brought to a stallion station facility, to be bred with the stallions housed there, were evaluated during ten breeding seasons. Mares were blocked according to management strategies in two groups: Stress and Relax. Strategies used to improve animal well‐being (Relax group) were as follows: stopping the teasing routine, reducing or eliminating stall confinement, reducing the number of mares per group and maintaining herd stability during the breeding season. In barren mares, the pregnancy rate was higher in the Relax group (91.8%) when compared to the observed in Stress group (84.7%). However, no difference in pregnancy rates were observed (Stress = 85.2% vs. Relax = 86.2) in foaling mares. ED rate was higher in barren and foaling mares of the Stress group mares (25.5% and 26.8%, respectively) compared with the Relax group (16.1% and 14.7%, respectively). No significant differences were observed on foal heat pregnancy rate between groups; yet, the embryo loss on foal heat was significant reduced in Relax mares (Relax = 8.7% vs Stress = 24.5%). In conclusion, management strategies aimed to reduce social stress can reduce early pregnancy losses and the average cycles per pregnancy, improving reproductive performance in mares.     

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.     

Analysis of post-partum fertility in mares on a Thoroughbred stud in southern Victoria

This project surveys the reproductive performance of 154 foaling Thoroughbred mares on a commercial stud in southern Victoria. Of these, 96 were served on foal heat (FHS) and 58 were served at a subsequent prostaglandin-induced oestrus (PGS). The PGS group of mares performed more favourably in all aspects except the foaling-to-conception interval where there was a 9.4 day advantage to the FHS group. The first service conception rate in the FHS group was 47.9% compared with 55.2% in PGS mares. Second heat period conception rates were 46% vs 57.7% for FHS and PGS mares, respectively. Overall conception rates at the end of the breeding season were 83.3% in the FHS group and 89.7% in the PGS group. Pregnancy losses before day 45 and after day 45 were 10% and 9.3% in FHS mares and 3.9% and 3.6% in the PGS mares. Served oestrous periods per conception numbered 1.7 and 1.4 in the FHS and PGS groups, respectively.     

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.     

Retrospective study on vulvar conformation in relation to endometrial cytology and fertility in thoroughbred mares

Changes in the conformation of the vulva predispose the mare to uterine infection. Vulvoplasty for closure of the upper vulvar lips improves fertility. Not all mares are resutured after parturition, but are resutured after mating. No clinical data have hitherto been published on the reproductive outcome in mares that are resutured or not after parturition. The objectives of the present study were to investigate relationships between vulvar status (not Caslick-operated, group A; previously Caslick-operated and/or not resutured after the last parturition, groups B and C respectively) and endometrial cytology, conception rate and live foal rate for different age groups and categories of Thoroughbred mares. A careful examination of the vulvar area, and endometrial sampling for bacteriology and cytology was performed. The mares were naturally mated once during oestrus (never foal heat) by one of two stallions. Mares belonging to vulvar status group A had the highest conception rate and live foal rate, whereas the lowest conception rate and live foal rate occurred in mares with vulvar status group C. A multifactorial analysis revealed that the vulvar status at arrival had a significant effect on pregnancy rate and live foal rate, but not on fetal loss. Stallion, year and age group had no significant effect on any of the three variables analysed. In conclusion, optimizing managerial factors such as resuturing Caslick-operated mares immediately after parturition to minimize growth of micro-organisms with a subsequent endometritis will contribute to their conception and that they carry a pregnancy to term.     

A field study of patterns of unobserved foetal loss as determined by rectal palpation in foaling, barren and maiden thoroughbred mares.

Records of 1,009 pregnancies in 574 foaling, barren and maiden Thoroughbred mares on a single stud farm, over a period of 12 years were examined. The farm is situated in the eastern Cape Province of South Africa, at an elevation of 1,800 m, and in an area of climatic extremes. Records of 604 pregnancies in 249 foaling Thoroughbred mares were examined. For these purposes, those pregnancies in which a mare conceived in the same breeding season during which she had foaled were considered as pregnancies in foaling mares. Pregnancy was confirmed by rectal palpation by a single experienced practitioner. Of the 604 pregnancies examined, conceptus attachment occurred in the horn opposite the previously gravid horn in 345 cases (57%), and in the previously gravid horn in 259 cases (43%; P less than 0.005). Unobserved foetal loss after pregnancy diagnosis amounted to 30 (9%) in the former group, while in the latter group (pregnancy established in the postgravid horn) 46 pregnancies were lost (18%; P less than 0.005). This study confirmed that conceptus attachment tends to occur in the uterine horn opposite the previously gravid horn in foaling Thoroughbred mares conceiving during the same season. A significantly higher incidence of foetal loss accompanied conceptus attachment in the postgravid horn. Of 242 pregnancies in 162 previously barren mares, 95 (39%) occurred in the left uterine horn and 147 (61%) in the right horn (P less than 0.005). The incidence of pregnancy failure in this group was 7%. The side of attachment did not affect the rate of loss. Evaluation of the records of 163 maiden mares revealed that conceptus attachment occurred in the left uterine horn in 58 (36%) pregnancies and in the right horn in 105 (64%) pregnancies (P less than 0.005), which is consistent with previously reported observations. Pregnancy failure was recorded in 4% of maiden mares. Side of attachment did not influence rate of loss in this group.     

Reproductive performance and factors that decrease pregnancy rate in heavy draft horses bred at the foal heat

Reproductive performance and factors that decrease the pregnancy rate in heavy draft horses bred at the foal heat were investigated. The study was based on a total of 422 mares varying from 4 to 20 years in age, which had foaled during the period 1991 to 1994. Over the four years, the percentage of the mares bred at the foal heat was 62.6% and the pregnancy rate was 60.2%. The pregnancy rate following breeding at the foal heat in 1991 (67.7%) was significantly higher than that in 1992 (44.1%). Significant correlation was observed between the pregnancy rate and the mean placental retention time and also between the pregnancy rate and the mean temperature during the winter season. When compared on a monthly basis, the pregnancy rate following breeding at the foal heat in February was 53.3% and in May, 48.2%. The mean number of covers per mare at the foal heat was 2.3; this figure decreased to 1.8 for those bred in May. The mean number of days from parturition to the first breeding date was 11.3 days and the number of days from parturition to the last breeding day at the foal heat was 14.0 days. The number of days from parturition to the last breeding day at the foal heat decreased to 12.5 days in May. The latter may have been influenced by factors involving the stallion. When compared on a monthly basis, the mean placental retention time was longest in January (219 min.) following which it decreased gradually up to mid-summer. The mean placental retention time of mares which were not bred at the foal heat was significantly longer (197 min.) than in mares bred at the foaling heat (143 min.) and also in mares that conceived following breeding at the foal heat (135 min.). The pregnancy rate was less in mares bred shortly after parturition. The findings of this study would suggest that certain factors decrease the pregnancy rate in mares bred at the foal heat. The stress of low temperature in winter, prolonged placental retention time, breeding too early after parturition and factors pertaining to individual stallions may be involved. Expulsion of the placenta as soon as possible after foaling and appropriate breeding timing are significant factors that can influence the pregnancy rate following breeding at the foal heat.     

Age-Dependent Effect of Foal Heat Breeding on Pregnancy and Embryo Mortality Rates in Thoroughbred Mares

The aim of the present study was to evaluate the correlation of age and heat cycle to determine reproductive efficiency in young and aged Thoroughbred mares bred on foal heat (FH) or on second heat (SH) after foaling. Embryo mortality (EmbM) was determined every time a mare was found open after a positive pregnancy diagnosis. Parturition to breeding interval, pregnancy rate (PregR) and EmbM rate were the dependent variables and the treatments were breeding on the FH or on SH. The cutoff age to obtain above-average probability for the EmbM was 10 years old. PregR in mares bred on FH was lower compared with SH (P < .01); however, it was neither affected by the age of mares (P > .05) nor by the age group of mares (P > .05). Regarding FH and SH, there was a difference in PregR in young mares (P < .01), unlike in aged mares (P > .05). EmbM rate was not different between mares bred on FH or SH (P > .05) although it was affected by age of mares (P < .01). EmbM was higher in oldest than young mares (P < .01). Aged mares bred on FH had a significantly higher EmbM rate compared with the young group also bred on FH (P < .01). In conclusion, the reproductive efficiency of Thoroughbred mares bred on FH is dependent of the age. Aged mares (≥10 years old) should be bred at their SH to reduce EmbM and improve reproductive performance.     

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.     

Factors Affecting Recipients' Pregnancy,Pregnancy Loss,and Foaling Rates in a Commercial Equine Embryo Transfer Program

During 11 breeding seasons, 351 7- to 10-day-old horse embryos were nonsurgically transferred into recipients that ovulated between 3 and 10 days earlier. Pregnancy rates at 14 and 40 days and foaling rates were 77.8% (273/351), 69.2% (243/351), and 64.4% (226/351), respectively. Pregnancy loss between 14 and 40 days was 11% and between 40 days and delivery was 7%. The transfer of quality grade 3 to 4 embryos resulted in a significantly lower pregnancy rate at 14 days compared with the transfer of grade 1 to 2 embryos (46.2% vs. 79%; P < .05). Eight-day-old embryos resulted in significantly lower pregnancy losses than day 9 or 10 embryos, as occurred for embryos between 400 and 1200 μm compared with embryos <400 μm. Embryos recovered from mares >20 years resulted in a significantly higher pregnancy loss rate than those recovered from younger mares. The same happened for embryos coming from mares affected by reproductive pathologies compared with healthy mares performing sport activity. None of the evaluated parameters influenced recipients' foaling rate significantly.     

The effect of dietary protein on reproduction in the mare. VII. Embryonic development, early embryonic death, foetal losses and their relationship with serum progestagen

Sixty-four Thoroughbred and Anglo-Arab mares aged 6-12 years were randomly allocated to 4 dietary groups and fed diets that differed in the total protein content and quality (essential amino-acids). Forty mares were non-lactating and 24 lactating. Eight mares were withdrawn from the investigation owing to injuries or gynaecological pathology. An overall conception rate of 94.6% and a foaling rate of 80% was achieved. Five of 14 (35.7%) mares (Group 1) fed a low-quality protein diet suffered from early embryonic loss before 90 days of pregnancy compared to 3 of 41 (7.3%) mares in the remaining groups that received the higher-quality protein in their diets. Serum progestagen concentrations of mares in Group 1 that suffered foetal loss were indicative of luteal function insufficiency during the 1st 40 days post-ovulation. Non-lactating mares in all 4 groups gained on average approximately 30 kg in mass during the 90 days before the breeding period. Lactating mares in Group 1 (low-quality protein) lost on average 25 kg in mass during lactation, with no weight loss observed among the lactating mares in the other 3 groups. No difference in the diameter of the embryonic vesicle was found between dietary groups until Day 35 of pregnancy.     

The Pattern of Embryonic Fixation and its Relationship to Pregnancy Loss in Thoroughbred Mares

Ultrasonographic pregnancy records of 195 mares from six Thoroughbred stud farms, over a period of 7 years were retrospectively analysed to assess the effect of various factors on embryonic vesicle (EV) fixation pattern and pregnancy outcome. Of the total of 746 pregnancies analysed, significantly (p < 0.01) more EV fixations were evident in the right uterine horn than in the left (53.35% vs 46.65% respectively). There was no significant effect of either, the side of ovulation, or age of the mare, on the side of EV fixation. However, EV fixation, was significantly (p < 0.001) more likely to occur in the right uterine horn in maiden and barren mares (65.75% vs 57.45% respectively). The age and reproductive status of the mare as well as foal heat breeding failed to demonstrate a consistent effect on pregnancy loss relative to the side of EV fixation. In lactating and foal heat bred mares, EVs were significantly (p < 0.0001) more frequently established in the contralateral horn to the one from which the mare delivered her most recent foal. In lactating mares, significantly (p < 0.05) higher embryonic and pregnancy losses were observed in the ipsilateral horn. In conclusion, (a) side of EV fixation was (i) independent of the side of ovulation and mare age (ii) significantly (p < 0.001) affected by reproductive status, (b) neither age of mare nor reproductive status had any effect on pregnancy loss rates relative to the side of EV fixation and (c) in lactating mares the EV had a greater chance of fixation and survival in the horn contralateral to the one from which the mare delivered her most recent foal.     

Fertility effects of crossing thoroughbreds with don mares

Pregnancy rates, foal-heat conception rates, early and late embryo loss, polyovulations and delivery loss were compared on a Russian breeding farm between Don mares with a low percentage of Thoroughbred (TB) blood and those with more than 25% TB blood, called Budenny mares. The overall pregnancy rate in the two groups was not significantly different; 85.5% and 85.6%, respectively. There was a significant difference in the foal heat conception rate, with the Don mares at 54.9% and the Budenny mares at 50.3%. Embryo loss before Day 100 was only 4.9% for the Don mares, but was 9.1% for the Budenny mares. Embryo loss after Day 100 was similar in the two groups; 10.2% for the Don mares and 9.0% for the Budenny mares. The loss of foals in the process of delivery was 3.3% for the Don mares and 5.0% for the Budenny mares. Estrous cycles with polyovulations was 8.7% for the Don mares and 13.1% for the Budenny mares.     

Evaluation of early fetal losses on four equine farms in central Kentucky: 73 cases (2001)

OBJECTIVE: To determine features of an early fetal loss (EFL) syndrome and evaluate potential risk factors for EFL in Thoroughbred broodmares on 4 farms in central Kentucky. DESIGN: Retrospective study. ANIMALS: 288 pregnant broodmares. PROCEDURE: Year-2001 breeding records for 288 Thoroughbred broodmares were examined. Early fetal loss was defined as loss of a fetus that was viable at > or = 40 days of gestation but was subsequently lost by 5 months of gestation. RESULTS: Overall 2001 EFL rate was 25% (73/288), median gestational age at time of fetal loss was 77 days, and median date of loss was May 7. Mares on 1 farm had significantly fewer fetal losses (5%) than mares on the other 3 farms (26 to 35%). Fetal losses were higher for maiden (42%) and barren (42%) mares than for foaling mares (18%). Fetal losses were greater in young than in older mares. Effects of broodmare farm, mare age, and reproductive status were all significant. Fetal losses were not associated with sire used for mating or stud farm. CONCLUSIONS AND CLINICAL RELEVANCE: Greatest risk for EFL occurred during the period from late April to May (ie, in mares bred during February through March). Higher incidence of EFL in maiden and barren mares and lower incidence of EFL on 1 farm suggest management or environmental influences may have affected outcome. Risk factors that should be investigated include environmental differences among farms and differences in management procedures used for lactating versus nonlactating mares.     

Fertility at the first post partum estrous compared with fertility at the following estrous cycles in foaling mares and with fertility in nonfoaling mares

A retrospective study on the reproductive performance of 401 artificially inseminated trotter mares during six breeding seasons is presented. Mares, 279 post partum (PP) and 122 maiden and barren, or nonlactating (NL), were inseminated with fresh semen obtained from four fertile stallions of the same breed. Pregnancy rate (PR) of mares inseminated at the foal heat (182/253, 71.9%) was lower, but not significantly different, than the PR (22/26, 84.6%) of mares inseminated for the first time at the second post partum cycle and similar to the PR at the first and second cycle of NL mares (95/112, 77.8% and 25/33, 75.7%, respectively). PR of mares inseminated at the foal heat was higher, but nonsignificantly different, from PR of the post partum mares not pregnant after artificial insemination (AI) at foal heat and inseminated again at the following estrous cycle. The PR after AI at the foal heat was significantly higher than the PR when the AI was performed at the third or later cycle in NL mares (71.9% vs 22.2%, P<0.01). The estrus cycle/pregnancy ratio for the PP mares inseminated, for the first time at the foal heat or at the second heat and for NL mares was, respectively, 1.4, 1.2, 1.3 at first cycle and 1.4, 1.3 and 1.4 at the end of the season or when mares left the stud. The proportion of open mares at the end of the season or when leaving the stud was 7.1% (18/253), 3.8% (1/26) and 4.1% (5/122) for PP mares first inseminated at the first or second post partum cycle and for NL mares, respectively; the total rate of open mares was 6% (24/401). The foaling rate (FR) following conception at the foal heat (72.1%) was not statistically different from the FR following conception at any other cycle (50–100%). Based on the absence of significant differences in fertility at the first post partum estrus cycle versus any other estrus cycle, we conclude that breeding at the foal heat should be advisable.     

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.     

The Effect of Manual Removal of Placenta Immediately after Foaling on Subsequent Fertility Parameters in the Mare

Retained placenta is considered to be a common problem in postpartum mares. The incidence varies from 6% to 54% depending on the breed, with higher incidence in heavy draught mares than in light-weight mares. Retained placenta has been linked to lower postpartum oxytocin concentration, impaired uterine involution, and dystocia. The objective of this study was to assess the effect of early manual removal of placenta immediately postpartum on subsequent fertility parameters (development of free intrauterine fluid, inflammatory status of endometrium, and on pregnancy rates) and to compare them with mares with spontaneous expulsion of placenta. A total of 29 mares, mainly Irish draught, were closely monitored during foaling by closed circuit television and allocated to two groups: (1) mares that expelled the placenta spontaneously within 3 hours of foaling; and (2) mares that were cleansed manually immediately after foal delivery. All mares were examined and scanned 5 and 9 days postpartum, and free intrauterine fluid was recorded; endometrial swabs were taken 9 days postpartum for endometrial cytology and culture. None of the fertility parameters analyzed showed statistical difference between groups 1 and 2. Therefore, it can be concluded that early manual removal of placenta has no detrimental effects on subsequent fertility of mares and, therefore, can be recommended when a veterinarian attends a foaling.