Seasonal variation in the estrous cycle of mares in the subtropics

Dowsett, K. F.; Knott, L. M.; Woodward, R.A.; Bodero, D. A. V.

doi:10.1016/0093-691x(93)90250-9

Cited by 10 publications

(10 citation statements)

References 12 publications

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“…The anoestrus length in the non‐breeding season varied among females, as has also been described for mares (Dowsett et al. ). In jennies, the average length reported for seasonal anoestrus ranged from 39 to 72 days, for females located in Wisconsin (Ginther et al.…”

Section: Discussionsupporting

confidence: 53%

“…For this particular female, ovulation was achieved following an increase of BCS to four points, by mid-April. The anoestrus length in the non-breeding season varied among females, as has also been described for mares (Dowsett et al 1993). In jennies, the average length reported for seasonal anoestrus ranged from 39 to 72 days, for females located in Wisconsin (Ginther et al 1987), to 166 AE 63 days, in Brazilian standard jennies (Henry et al 1987).…”

Section: Discussionmentioning

confidence: 75%

“…While in mares a shortening of oestrus during the non‐breeding season and a protracted oestrous cycle has been reported (Dowsett et al. ), in jennies an protraction of ovulatory oestruses in the early and late breeding season has been described by Henry et al. (), with dioestrus remaining unaffected.…”

Section: Discussionmentioning

confidence: 92%

“…Average body condition score (BCS) AESD in January (Jan) and its variation from October (Oct) to January and from January to April (Apr), for jennies in anoestrus (GrA), silent oestrus (GrSE) or remaining cyclic (GrC) in the non-breeding season GrA (n = 5) GrSE (n = 3) GrC (n = 3) p-value* BCS (1-9) in Jan 3.95 AE 0.447 (a) 5.17 AE 0.878 (a,b) the animals' age or their nutritional plan (Ginther et al 2004). While in mares a shortening of oestrus during the non-breeding season and a protracted oestrous cycle has been reported (Dowsett et al 1993), in jennies an protraction of ovulatory oestruses in the early and late breeding season has been described by Henry et al (1987), with dioestrus remaining unaffected. The present study found no differences in the interovulatory interval in jennies that cycled year-round, with or without signs of oestrus, during the non-reproductive season.…”

Section: Discussionmentioning

confidence: 93%

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Reproductive Patterns in the Non‐Breeding Season in Asinina de Miranda Jennies

Quaresma

Silva

Payan-Carreira

2015

Reprod Domestic Animals

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This study aims to characterize the reproductive patterns in Asinina de Miranda jennies during the non-breeding season. Reproductive activity was surveyed in 12 females, aged between 3 and 18 years old, using ultrasound and teasing with a jack. The animals were monitored from September to April, six in each consecutive year. Of these 12 females, nine showed disruption to the normal pattern of ovarian activity during the non-breeding season. Loss of normal cyclicity included anoestrus (41.7%), silent ovulatory oestrus (25%), and persistence of corpus luteum (8.3%). Only three females maintained a regular cyclic pattern with oestrous behaviour during the non-breeding season. Anoestrus began in early November and lasted for an average of 147 ± 28 days (113-191 days), ending near to the spring equinox. Onset of silent oestrous cycles began more erratically, between October and February. In both groups the first behavioural ovulation of the year occurred around the time of the spring equinox. Disrupted reproductive activity was preceded by a shorter oestrous cycle only in females entering anoestrus. The mean follicle size in the first ovulation of the year was larger than in the reproductive season (44.7 ± 2.45 mm vs 39.2 ± 3.60 mm) in anoestrous jennies with protracted oestrus. Though age and body condition score (BCS) were associated, changes in BCS below a threshold of four points (for anoestrus) and five points (for silent oestrus) contributed greatly to disruption of reproductive cycles. BCS in females with regular oestrous cycles during the winter season remained unchanged or exceeded five points prior to the winter solstice.

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Section: Discussionsupporting

confidence: 53%

Section: Discussionmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 93%

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Reproductive Patterns in the Non‐Breeding Season in Asinina de Miranda Jennies

Quaresma

Silva

Payan-Carreira

2015

Reprod Domestic Animals

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“…Previously, studies with experimental formulations have demonstrated that vaccination against GnRH can have significant effects on reproductive function of colts and stallions 1–6 and prevention of the development of oestrus in the mare 1,7–11 . These studies demonstrated the feasibility of immuno‐contraception in male and female horses, confirming significant physical and endocrine effects.…”

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confidence: 83%

Suppression of behavioural and physiological oestrus in the mare by vaccination against GnRH

Elhay¹,

Newbold²,

Britton³

et al. 2007

Aust Veterinary J

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Objective To examine the immunogenicity of an equine immunocontraceptive vaccine and its efficacy in controlling hormone-related behaviour.Design A total of 24 mares at two sites in Australia were vaccinated with an immunocontraceptive vaccine comprising gonadotrophin releasing hormone (GnRH) conjugated to a carrier protein in immunostimulating complex as an adjuvant. Twelve animals at each site received a placebo of adjuvant alone and served as controls for seasonal oestrus, hormonal and behaviour patterns. Animals were observed for injection site reactions, ovarian and follicular activity, and serum levels of antibody, 17 β -oestradiol and progesterone in the weeks following vaccination. Mares were also examined for oestrous behaviour by teasing with a stallion.Results All mares responded to vaccination. Two weeks following the second vaccination there was a peak in antibody response to GnRH that declined gradually over the following weeks. Commensurate with the elevated anti-GnRH antibody there was a marked effect on ovarian activity with a reduction in 17 β -oestradiol and progesterone levels in the 24 vaccinated mares. There was also a reduction of oestrus-related behaviour as determined by a teaser stallion. This effect lasted a minimum of 3 months and correlated with the initial level of antibody response. ConclusionFollowing a conventional two-dose immunisation regime this commercially available equine immunocontraceptive vaccine was effective at inhibiting oestrous behaviour for at least 3 months. This vaccine has a high level of safety since there were no significant local reactions nor were there any adverse systemic responses to vaccination.

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Comparative analysis of breeding patterns and reproductive efficiency of mares in subtropical conditions of Pakistan

Mahmood,

Hassan,

Channa

et al. 2024

Veterinary Medicine & Sci

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Background and AimThe present study aimed to evaluate and compare the overall and breed‐specific seasonal breeding patterns, fertility rates, cyclicity, and follicular dynamics of Arab, Thoroughbred, and Percheron mares under the subtropical conditions of Pakistan.Materials and MethodsA retrospective analysis of climatic data and breeding records of eleven breeding studs spanning four years (2020–2023) was made to find out the overall seasonality in the breeding pattern of mares. Fifty mares of each breed (n = 150 in total) were scanned by ultrasonography for a calendar year to find the cyclicity pattern and follicular dynamics (follicular growth rate, size of ovulatory follicle, and days from estrus till ovulation).Results and DiscussionThe statistical analysis of breeding records demonstrated a clear pattern of seasonal breeding (p< 0.05). The highest monthly foalings were noted in March (247 ± 45.37), and overall breeding activities peaked in Spring season (p< 0.05). Breed‐specific results of Arab, Thoroughbred, and Percheron mares revealed that Arab mares maintained stable breeding activity throughout the year, with the highest activity in spring and peak conception rate in winter (56.25% ± 32.78; p > 0.05). Thoroughbred mares experienced significant seasonal declines from spring to winter with a peak conception rate in winter (63.89% ± 27.37, p > 0.05). Percherons showed the most pronounced seasonal effects, especially with a high fall conception rate (73.04% ± 19.61) and a sharp decrease in winter breeding metrics (p< 0.05). Furthermore, Thoroughbred and Percheron mares displayed the most pronounced seasonal effects on the percentage of cyclic mares 77.3% and 56% in winters (p< 0.05). Moreover, the follicular dynamics of the three breeds also exhibited significant differences (p< 0.05).ConclusionThe current study concludes that seasonal and breed‐specific variability exists among the reproductive parameters of Arab, Thoroughbred, and Percheron mares in subtropics, necessitating breed‐specific reproductive management measures to maximize mare breeding efficiency.

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Seasonal variation in the estrous cycle of mares in the subtropics

Cited by 10 publications

References 12 publications

Reproductive Patterns in the Non‐Breeding Season in Asinina de Miranda Jennies

Reproductive Patterns in the Non‐Breeding Season in Asinina de Miranda Jennies

Suppression of behavioural and physiological oestrus in the mare by vaccination against GnRH

Comparative analysis of breeding patterns and reproductive efficiency of mares in subtropical conditions of Pakistan

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