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

doi:10.1016/S0737-0806(01)70109-8

Journal of Equine Veterinary Science

Volume 21, Issue 3, March 2001, Pages 131-136

https://doi.org/10.1016/S0737-0806(01)70109-8 Get rights and content

Abstract

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.

Introduction

Pregnancy rates achieved by breeding at the foaling heat have generally been reported to be 10 to 20% lower than those obtained by first breeding at subsequent estrous periods1, 2 and most of the reported pregnancy rates have been less than 50%.3, 4, 5 Nevertheless, the factors that influence the conception rate in mares bred at the foal heat have not been clarified sufficiently. Most horse breeders would like foaling mares to become pregnant as soon as possible after foaling because foals born early in the season are physically more advanced at time of sale and also have a greater likelihood of realizing their performance potential earlier as draft horses. Improvement in reproductive performance at the foaling heat is, therefore, an important consideration in draft horse breeding districts.

The authors have reported that the pregnancy rate following breeding at the foal heat decreased with an increase in the placental retention time after foaling in heavy draft horses.7, 8 The mean placental retention time was found to vary significantly from year to year. Significant differences were also observed in the pregnancy rate following breeding at the foaling heat.4, 7 Uterine bacterial contamination was implicated as a likely cause of the decreased pregnancy rate following breeding at the foaling heat, and this was thought to be associated with prolonged placental retention time.7, 9 The present study was undertaken, therefore, to clarify what factors reduced the pregnancy rate following breeding at the foal heat with specific reference to the role of the placental retention time.

Section snippets

Materials and methods

This study was conducted in Eastern Hokkaido, Japan during the period 1991 to 1994. It involved a total of 422 mares varying from four to 20 years in age and located on 54 farms. The mares were purebred or of mixed breed and belonged to Breton, Percheron or Belgian Draft horse breeds. Natural breeding was used throughout the entire study period. All of the mares gave birth naturally and placental retention times were noted. A total of 264 mares which exhibited signs of estrus when teased at the

Comparison of annual reproductive performance

During the four years of the study the overall pregnancy rate following breeding at the foal heat was 60.2%. The pregnancy rate following breeding at the foal heat was highest in 1991(67.7%) and lowest in 1992 (44.1%). The difference in rates between these two years was significant (p=0.01). When comparing the placental retention time, on the other hand, it was found that the mean retention time of 183 minutes in 1992 was significantly higher (p=0.01) than that in 1991(119 min.). A significant

Discussion

The foal heat has been reported to occur usually from 4 to 14 days after parturition and finish 11 to 20 days after parturition.³ In another report, 93% of foaling mares came into foal heat 5 to 18 days after parturition, and 77% of foaling mares 7 to 10 days after parturition.⁵ Within the 8 to 21 day foal heat period after parturition the last day on which mares were bred nearly followed a normal distribution with a mean of 14 days. For the purposes of this study, mares bred up to 21 days

Conclusions

Detailed analysis of the results of this study revealed some factors that decrease the pregnancy rate in heavy draft horses bred at the foal heat. It appears that a decreased pregnancy rate following breeding of mares at the foal heat is related to prolonged placental retention time. The stress of low winter temperatures was considered to be one of the factors prolonging placental retention time. The prolonged placental retention time affected not only the pregnancy rate in mares bred at the

Acknowledgements

The authors wish to thank Professor Peter Timoney, Gluck Equine Research Center, University of Kentucky for reviewing the initial draft of this paper, Professor Kunitada Sato, Obihiro University of Agriculture and Veterinary Medicine for valuable advice and Mr. Jay Andrus for technical assistance.

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Postpartum reproductive activities and gestation length in Martina Franca jennies, an endangered Italian donkey breed
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Citation Excerpt :
Although FH spontaneously occurs [9] because of a high PR expression in feral pony populations [10], however, a definitive evaluation of this crucial reproductive parameter in farming household mares is still debated [11,12]. In particular, the results describing the incidence of pregnancy losses in FH-bred mares and the factors affecting FH PR remain inconclusive for the reduced case studies [13,14], because of the heterogeneity of the mare breeds considered [15,16], the management systems employed [17,18], and the low accuracy of the transrectal palpation technique still used [19,20]. Starting from these premises, the present study was designed to increase the information regarding the reproductive PP parameters concerning an Italian donkey breed, Martina Franca, kept under semi-intensive housing conditions.
The donkey reproductive physiology is still partially known despite the increasing risk of extinction involving several breeds. The present study was designed to describe the postpartum (PP) reproductive performance of an Italian endangered breed: the Martina Franca donkey. To this aim, 52 jennies were monitored to define the foal-heat (FH) and the first and second PP estrus episodes (1st PPe and 2nd PPe). The data indicate that jennies spontaneously recovered reproduction in approximately 10 days after delivery. Then heats occur with a regular interval of approximately 23 days. Estrus length was 1 week in FH and the 2nd PPe and significantly shorter in the 1st PPe. Estrus–ovulation, and delivery–ovulation interval and follicle growth were similar in all animals tested. Pregnancy rate (PR) was lower when natural mating occurred during the FH and 2nd PPe (approximately 60%) than during the 1st PPe (approximately 70%; P < 0.01). In addition, the higher PR (>80%; P < 0.01) was recorded in jennies when the FH occurred after the first week PP and it dropped (<50%) in early FH animals. The PR was also affected by the season and by age: it significantly declined during the autumn–winter season and in subjects older than the sixth year of age. For the first time, the reproductive performance of PP donkeys were defined on a large number of Martina Franca jennies thus offering useful information to improve farm management with an immediate benefit to increase livestock production. This aspect of management improvement might be particularly important if applied to an endangered breed such as Martina Franca donkeys.
Factors Influencing the Frequency of Pregnancy Loss among Thoroughbred Mares in Hidaka, Japan
2012, Journal of Equine Veterinary Science
Citation Excerpt :
Our results suggest that a more careful selection of mares suitable for foal heat mating may explain the decrease in the differences in reproductive performances. Loy [17] and Ishii et al. [18] reported higher pregnancy rate in mares bred on the first postpartum estrus if ovulation occurred after day 10. The results of the present study were that the pregnancy loss rates (days 17-35 and day 35 until foaling) did not differ for those becoming pregnant ≤10 days after foaling and those becoming pregnant >10 days after foaling.
Pregnancy loss in mares is thought to be a main problem associated with reproductive efficiency. To clarify the situation of pregnancy loss in Thoroughbred mares in Japan, the occurrence of pregnancy loss before and after 35 days of gestation was investigated with 1,476 Thoroughbred mares in Hidaka, Japan, from 2007 to 2009. Pregnancy loss on days 17-35 was determined by ultrasound examination between 17 and 35 days after the last mating. Follow-up surveys were conducted between 35 days and foaling to determine pregnancy loss on day 35 until foaling in 843 of these mares. Using multiple logistic regression analysis, we assessed the influence of mare age, reproductive status, twin pregnancy reduction, body condition score (BCS), estrus type in foaling mares (foal heat or not), progesterone therapy, and endometrial cysts on pregnancy loss rates on days 17-35 and on day 35 until foaling in this population of mares. The pregnancy loss rates on days 17-35 and on day 35 until foaling were 5.8% and 8.7%, respectively. The overall pregnancy loss rate (day 17 until foaling, including parturient losses) was 14.7%. Risk factors for pregnancy loss included decrease in BCS between 17 and 35 days, <5 BCS at day 35, mating during foal heat, and endometrial cysts. In all, 14.7% of pregnancies were lost between day 17 and birth, contributing significantly to reduced reproductive efficiency in Thoroughbred mares in Japan. These observations indicate that mares should be maintained at high BCS and should be prevented from mating in foal heat to decrease the pregnancy loss rates.
Proliferation and Apoptosis in Fetal Membranes and Endometrium During Placental Retention in Heavy Draft Mares
2012, Journal of Equine Veterinary Science
Citation Excerpt :
The retardation in the endometrial involution and regeneration leads inevitably to problems with breeding at foal heat. A previous study revealed that placental retention can lead to difficulties with breeding at foal heat and suggested that uterine damage is the cause [22]. To evaluate exact effect of the RP on the postpartum endometrial regeneration, the biopsies obtained on days after the delivery should be investigated.
Placental retention (retained placenta [RP]) is a serious and common peripartum disease in mares, but the etiology and pathogenesis of RP still remain unclear. The alteration of cell proliferation and apoptosis is considered to be an important factor in RP. Fetal membranes and endometrial biopsies were collected from mares with RP (n = 8) and from control mares (n = 10). The proliferation and apoptosis levels in the chorionic and the endometrial epithelia were assessed by proliferating cell nuclear antigen immunostaining and the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, respectively. The study revealed that there was an insignificant decrease in proliferation and a significant increase in apoptosis in the chorionic epithelium from mares with RP. This result excludes a proliferation imbalance from the possible causes of RP. In the area of the nonpregnant horn of the placenta, proliferation was negatively correlated and apoptosis was positively correlated with the degree of fetomaternal anchorage. It was observed that, in all mares with placental retention, the endometrial epithelium (both luminal and glandular) showed decreased proliferation and increased apoptosis, which may indicate a delay in postpartum uterine regeneration.
Factors affecting the incidence of postpartum oestrus, ovarian activity and reproductive performance in Thoroughbred mares bred at foal heat under Indian subtropical conditions
2010, Theriogenology
Decreased reproductive performance due to summer stress is a well known phenomenon in farm livestock. Whether this occurs in the mare and specifically how this might affect postpartum reproductive activity and performance, especially at Foal Heat (FH), is unknown. This study, therefore, aims to investigate this and the factors that might affect postpartum reproductive activity. Reproductive records of 228 Thoroughbred mares (694 mare years) bred in subtropical north-western India were retrospectively analysed. Overt oestrous activity occurred within 21 d postpartum in 92.94% (645/694) of mares. Significantly (p < 0.001) more April foaling mares (97.37%, 185/190) expressed postpartum oestrous activity than those foaling in January (83.61%; 51/61) and February (88.49; 123/139). Similarly significantly (p < 0.01) fewer multiparous mares failed to demonstrate oestrous activity than primiparous mares (6.12% vs.15.07%; 38/621 vs. 11/73, respectively). 190 of these 694 mares were additionally monitored to confirm ovulation; in these mares onset of FH (oestrus plus confirmed ovulation) occurred 8.42 ± 0.17 d and first ovulation 13.64 ± 0.20 d postpartum. Month, stud farm, year, and parity did not affect interval from parturition to FH onset or to first ovulation; or FH onset to ovulation. In FH bred mares Day 16 pregnancy rate and overall foaling rate were 53.76% (100/186) and 46.24% (86/186) respectively and were similar to those of mares bred later postpartum. FH pregnancy rates were not affected by stud, season, month, year, number of matings, or day of ovulation but were significantly (p < 0.008) lowered by increasing mare age. Significantly (p < 0.01) lower Day 16 pregnancy rates were observed in uterine treated mares compared to untreated mares (31.09% vs. 57.96%; 9/29 vs. 91/157, respectively), this difference was not evident during the rest of pregnancy. In conclusion, postpartum reproductive and ovarian activity appears to be affected by environment, i.e., delayed in subtropical kept Thoroughbred mares compared to those kept in temperate climates. However, resulting reproductive performance at FH and the factors affecting postpartum reproductive activity are similar.
Effects of vitamin E and selenium administration on pregnant, heavy draft mares on placental retention time and reproductive performance and on white muscle disease in their foals
2002, Journal of Equine Veterinary Science
This study investigated the effects of administering vitamin E and selenium to pregnant heavy draft horsemares on the incidence of retained placenta and postpartum reproductive performance and on the prevention of the white muscle disease in their foals. In study A, 1,000 mg of vitamin E and 50 mg of selenium (E-SE 20 mL) were given to 22 mares 3 weeks before expected parturition (335 days counted from last mating), whereas 28 mares were used as controls. In study B, E-SE were administered 2 weeks before expected parturition at 2 dose levels, with 25 mares receiving 20 mL E-SE, 19 mares receiving 10 mL, and 29 mares kept as controls. Vitamin E and selenium were assayed in serum collected from some of the mares before administration of E-SE and again postpartum and from the foals immediately after birth. Serum selenium concentrations before E-SE administration were deficient (<65 ng/mL) in all mares (n = 48) but were increased in the postpartum sample from treated mares regardless of the dose or timing of administration (n = 31) (P = .05). Only study B mares were deficient in vitamin E prepartum, and both dose levels of E-SE had corrected this in the postpartum sample (P = .01). All foals were selenium deficient regardless of whether their dams had received E-SE or not, although concentrations were higher in foals from treated study A mares than from controls (P = .05). Mares with the highest selenium concentrations prepartum (40 ng/mL and over) had shorter placental retention times than mares with lower selenium concentrations (P = .05) and did not respond to E-SE with a further reduction in retention time. By contrast, mares with prepartum selenium concentrations between 20 and 40 ng/mL tended to respond to E-SE with a shortened placental retention time (P = .07). E-SE administration reduced the mean number of days from parturition to last mating (nonpregnant term) in study B mares (P = .05) and in mares with adequate prepartum vitamin E concentrations (>300 g/mL, P = .05). We conclude that maintaining high level serum vitamin E and selenium concentrations of prepartum mares is expected to increase fertility of selenium-deficient mares. Therefore, the regimen of vitamin E and selenium administrations to selenium deficient mares should be developed.
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^☆: Authors' addresses: ¹Akan-Kushiro Veterinary Clinical Center, Kushiro District Agricultural Mutual Aid Association, 3-13-1 Chuo, Akan-Cho, Akan-Gun, Hokkaido, 085-0215 JAPAN Tel: (+81)-154-66-2711 Fax: (+81)-154-66-2813 E-mail: [email protected] ²Arekinai Veterinary Clinical Center, Kushiro District Agricultural Mutual Aid Association, Arekinai, Shibecha-Cho, Kawakami-Gun, Hokkaido, 088-2271 JAPAN Tel: (+81)-1548-7-8126 ³Hokkai Gakuen University, Faculty of Engineering, Minami 26-Jo, Nishi 11-Chome, Chuo-Ku, Sapporo, 064-0926 JAPAN Tel: (+81)-11-841-1161 E-mail: [email protected]

^☆☆: Refereed.

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Journal of Equine Veterinary Science

Abstract

Introduction

Section snippets

Materials and methods

Comparison of annual reproductive performance

Discussion

Conclusions

Acknowledgements

References (19)

Effect of Placental Retention Time and Associated Treatments on Reproductive Performance in Heavy Draft Horses

Equine Vet Sci

Characteristics of postpartum reproduction in mares

Vet Clin N Amer Large Anim Pract

Comparative results of breeding on the first and second post-foaling heat periods

Proc Am Assoc Equine Pract

Veterinary Obstetrics and Genital Diseases

Some Common Problems in Horse Breeding

Cornell Vet

The Estrus Cycle of the Mare

Cornell Vet

Cervico-endometrial cytology and physiological aspects of the post-partum mare

J Reprod Fert Suppl

Relationship between Placenta Discharging, Time and Reproductive Efficiency in Heavy Horses

J Vet Cli (in Japanese)

Notes on Genital Infection in the Mare

Cornell Vet

Cited by (16)

Postpartum reproductive activities and gestation length in Martina Franca jennies, an endangered Italian donkey breed

Factors Influencing the Frequency of Pregnancy Loss among Thoroughbred Mares in Hidaka, Japan

Proliferation and Apoptosis in Fetal Membranes and Endometrium During Placental Retention in Heavy Draft Mares

Factors affecting the incidence of postpartum oestrus, ovarian activity and reproductive performance in Thoroughbred mares bred at foal heat under Indian subtropical conditions

Effects of vitamin E and selenium administration on pregnant, heavy draft mares on placental retention time and reproductive performance and on white muscle disease in their foals

Age related effect on pregnancy rate and pregnancy wastage in thoroughbred mares bred during different heat cycles postpartum under subtropical conditions

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

Abstract

Introduction

Section snippets

Materials and methods

Comparison of annual reproductive performance

Discussion

Conclusions

Acknowledgements

Equine Vet Sci

Characteristics of postpartum reproduction in mares

Vet Clin N Amer Large Anim Pract

Comparative results of breeding on the first and second post-foaling heat periods

Proc Am Assoc Equine Pract

Veterinary Obstetrics and Genital Diseases

Some Common Problems in Horse Breeding

Cornell Vet

The Estrus Cycle of the Mare

Cornell Vet

Cervico-endometrial cytology and physiological aspects of the post-partum mare

J Reprod Fert Suppl

Relationship between Placenta Discharging, Time and Reproductive Efficiency in Heavy Horses

J Vet Cli (in Japanese)

Notes on Genital Infection in the Mare

Cornell Vet

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