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

Souza, João Ricardo Malheiros de; Gonçalves, Paulo Bayard Dias; Bertolin, Kalyne; Ferreira, Rogério; Ribeiro, Ana Silvia Sardinha; Ribeiro, Djacy Barbosa; Rechsteiner, Sandra Mara da Encarnação Fiala; Araújo, R.R.; Pimentel, Cláudio Alves; Pimentel, Anelise Maria Hammes

doi:10.1016/j.jevs.2020.102982

Cited by 7 publications

(4 citation statements)

References 38 publications

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“…Based on a retrospective descriptive data analysis, the present work aimed to study the follicular dynamics in mares bred under permanent grazing in a humid tropical farm from three days before foaling until the first postpartum ovulation occurring during the foal heat. Information available on follicular dynamics of the estrous cycle in the mare, its endocrinology, and factors affecting it [ 2 , 11 , 41 ], and on follicular dynamics of foal heat in donkeys [ 8 , 37 ] and mares [ 4 , 15 , 17 , 31 , 35 , 36 ] have not been evidenced in Colombian Paso Fino mares bred under permanent grazing conditions, as found in the present study. This study reports the follicular dynamics from three days before foaling, the day of foaling, and from the postpartum days 5 to 13 in CPF mares.…”

Section: Discussioncontrasting

confidence: 53%

“…The age of the mares in our study, which ranged between 6.58 (pregnant group) and 7.1 years (non-pregnant group), did not significantly differ. On the contrary, authors reported lower gestation rates due to higher embryonic mortality in mares older than ten years bred at foal heat than mares younger than ten years [ 35 ].…”

Section: Discussionmentioning

confidence: 99%

“…Studies undertaken in mares from breeds other than CPF provided insights on the follicular dynamics and estrous cycle endocrinology in the mare; affecting factors including high altitude [ 11 ], endocrine factors and their interaction [ 2 , 34 ], and factors affecting follicular dynamics of the foal heat including postpartum uterine involution [ 4 ], the effect of placental retention [ 15 ], gestation rates according to the previous pregnant uterine horn [ 17 ], season and parity [ 31 ], age of the mare [ 35 ], postpartum first mating schedules [ 36 ]; and in donkeys [ 8 ], age [ 20 ], breed, and season [ 37 ]. Sharma et al [ 31 ], found that 93% of the mares presented foal heat in the first 21 days postpartum in India, with no statistically significant effect of variables such as stud farm, region, time of year, number of mating, or parity [ 20 , 31 ].…”

Section: Introductionmentioning

confidence: 99%

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Follicular Dynamics and Pregnancy Rates during Foal Heat in Colombian Paso Fino Mares Bred under Permanent Grazing

Cardona-García,

Jiménez-Escobar,

Ferrer

et al. 2024

Animals

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No studies have evaluated the peripartum follicular dynamics resulting in foal heat under tropical environments. We aimed to assess retrospectively the peripartum follicular dynamics in Colombian Paso Fino mares that were inseminated at the foal heat, becoming pregnant or not. Records including follicular dynamics of pregnant mares prepartum and from foaling until foal heat ovulation were assessed in Colombian Paso Fino mares (CPF, n = 24) bred under permanent grazing in a tropical herd in Colombia. The number of ovarian follicles >10 mm before foaling and the largest follicle (F1) growth rate (mm/day) from foaling until the F1 reached the largest diameter (pre-ovulatory size) at the foal heat were assessed. Mares were inseminated at foal heat with 20 mL of semen (at least 500 million live spermatozoa) with >75% motility and 80% viability from a stallion of proven fertility. Ovulation was confirmed the day after follicles had reached the largest diameter. Quantitative data from follicular growth, the day at ovulation, from mares that became pregnant (PM) or not (NPM) at 16 days post-insemination were compared by one-way ANOVA, repeated measures ANOVA (follicle growth rate data) or Chi-square test (edema and cytology scores data). Epidemiological data, gestation length, and the number of follicles on third prepartum days did not significantly differ between PM and NPM (p > 0.05). Seventy-one percent of mares (17/24) got pregnant. Ovulatory follicles grew faster in the NPM group (n = 7), which ovulated between the seventh and ninth postpartum days, compared to PM (n = 17), which ovulated between the 11th and 13th postpartum days. Pre-ovulatory follicle diameter in PM (48.57 ± 0.8 mm) was significantly larger than in NPM (42.99 ± 1.0 mm) (p < 0.05). In addition, the PM edema score (2.93 ± 0.32 mm) on ovulation day was significantly lower (p < 0.05) than NPM (4.47 ± 0.05 mm). First postpartum ovulation occurred at 12.6 ± 0.3 and 8.5 ± 0.4 days (p < 0.05) in PM and NPM, respectively. Colombian Paso Fino mares bred under permanent grazing under tropical rainforest conditions with no foaling or postpartum complications showed a 71% gestation rate when inseminated at foal heat when ovulation occurs between the second and third postpartum week.

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Section: Discussioncontrasting

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Follicular Dynamics and Pregnancy Rates during Foal Heat in Colombian Paso Fino Mares Bred under Permanent Grazing

Cardona-García,

Jiménez-Escobar,

Ferrer

et al. 2024

Animals

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“…In the literature, the effect of lactation on fertility is controversial as some studies observed that nursing mares are more fertile than non-nursing ones [2,8,30,50,51] while others do not observe any difference [4,7,10,14]. Insemination at foal heat was previously shown to reduce pregnancy rates [23,52] and to be associated with increased embryonic death [21,22,52]. Here, most foaling mares were bred on foal heat without adverse effect on pregnancy rates.…”

Section: Discussionmentioning

confidence: 99%

Reproductive outcomes in sport horse commercial French breeding farms: clinical relevance of mares’ age, parity and lactating status

Derisoud

Grimard

Gourtay³

et al. 2022

Preprint

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Fertility in mares depends on management and reproduction mode, but overall analyses have shown that there is an important and progressive decline in fertility in older mares. Age is often related to maternal parity, but the role of parity in the fertility decline in old mares is not known. Moreover, the positive or negative impacts of breeding mares yearly are a subject of controversy. The aim of this study was to identify whether these factors, as well as reproductive management, played a role on post-insemination endometritis and fertility in sports mares in commercial studs. Altogether, the breeding records of 277 mares (506 cycles) over one breeding season in two French commercial stud farms were analyzed. Age, parity, whether the mare was barren or suckling, follicular size before ovulation, the use of estrus and/or ovulation induction, artificial insemination (AI) protocol, post-breeding inflammation and treatment, Day 14 pregnancies and number of embryos, as well as subsequent foaling the next year were recorded. Data were analyzed using multivariate logistic regression models. The pregnancy rate by cycle was 41.9% and 76.5% of mares were pregnant at the end of the season. Mares older than 10 years, barren mares or mares inseminated in July or August were more likely to have inflammatory reaction after insemination (p<0.0001, OR=3.29, 5.389 and 3.329, respectively). Mares >10 years and mares inseminated with frozen semen were less likely to be pregnant on Day 14 vs younger mares and mares inseminated with fresh and refrigerated semen (p<0.05, OR=0.622 and 0.582, respectively). As expected, mares with multiple ovulations were more likely to be pregnant on Day 14 compared to mares that had only one ovulation (p<0.05, OR=1.791). Altogether, parity only tended to improve the likelihood of being pregnant on Day 14 (p=0.07, OR=1.434 in parous vs nulliparous) but in older mares (age >10), parity increased pregnancy rates (44.09% vs 30.89% in parous vs nulliparous, p<0.05). Post-breeding inflammation was not related to pregnancy rate on Day 14 (37.8% vs 44.2%, p=0.16) but all mares with post-breeding inflammation received a treatment. No effect of suckling at insemination was observed. None of the studied factor could be related to embryo/fetal mortality. In conclusion, maternal age seems to be more important than parity and lactating status for reproductive success in mare. Cumulative effects on parity and aging were observed on pregnancy rates.

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Female age and parity in horses: how and why does it matter?

Derisoud

Auclair-Ronzaud

Palmer

et al. 2021

Reprod. Fertil. Dev.

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Although puberty can occur as early as 14–15months of age, depending on breed and use, the reproductive career of mares may continue to advanced ages. Once mares are used as broodmares, they will usually produce foals once a year until they become unfertile, and their productivity can be enhanced and/or prolonged through embryo technologies. There is a general consensus that old mares are less fertile, but maternal age and parity are confounding factors because nulliparous mares are usually younger and older mares are multiparous in most studies. This review shows that age critically affects cyclicity, folliculogenesis, oocyte and embryo quality as well as presence of oviductal masses and uterine tract function. Maternal parity has a non-linear effect. Primiparity has a major influence on placental and foal development, with smaller foals at the first gestation that remain smaller postnatally. After the first gestation, endometrial quality and uterine clearance capacities decline progressively with increasing parity and age, whilst placental and foal birthweight and milk production increase. These combined effects should be carefully balanced when breeding mares, in particular when choosing and caring for recipients and their foals.

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

Cited by 7 publications

References 38 publications

Follicular Dynamics and Pregnancy Rates during Foal Heat in Colombian Paso Fino Mares Bred under Permanent Grazing

Follicular Dynamics and Pregnancy Rates during Foal Heat in Colombian Paso Fino Mares Bred under Permanent Grazing

Reproductive outcomes in sport horse commercial French breeding farms: clinical relevance of mares’ age, parity and lactating status

Female age and parity in horses: how and why does it matter?

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