Overfeeding Extends the Period of Annual Cyclicity but Increases the Risk of Early Embryonic Death in Shetland Pony Mares.

Nicky M M D’Fonseca,Marta De Ruijter-Villani,Ellen Roelfsema,Charlotte M E Gibson,Tom A E Stout,Iris Hummel,Jan Van Den Broek,David A Van Doorn

doi:10.3390/ani11020361

Nicky M M D’Fonseca, Marta De Ruijter-Villani + Show 6 more

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https://doi.org/10.3390/ani11020361

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Abstract

Simple SummaryObesity has been associated with altered reproductive activity in mares and may negatively affect fertility. To examine the influence of long-term high-energy (HE) feeding on fertility, Shetland pony mares were fed a diet containing 200% of net energy (NE) requirements during a three-year study. The incidence of hemorrhagic anovulatory follicles (HAF) and annual duration of cyclicity were compared to those in control mares receiving a maintenance diet. Day-7 embryos were flushed and transferred between donor and recipient mares from both groups; the resulting conceptuses were collected 21 days after transfer to assess conceptus development. HE mares became obese, and embryos recovered from HE mares were more likely to succumb to early embryonic death. The period of annual cyclicity was extended in HE compared to control mares in all years. The incidence of HAFs did not consistently differ between HE and control mares. No differences in embryo morphometric parameters were apparent. In conclusion, consuming a HE diet extended the duration of cyclicity, and appeared to increase the likelihood of embryos undergoing early embryonic death following embryo transfer.Obesity has been associated with altered reproductive activity in mares, and may negatively affect fertility. To examine the influence of long-term high-energy (HE) feeding on fertility, Shetland pony mares were fed a diet containing 200% of net energy (NE) requirements during a three-year study. The incidence of hemorrhagic anovulatory follicles (HAF) and annual duration of cyclicity were compared to those in control mares receiving a maintenance diet. Day-7 embryos were flushed and transferred between donor and recipient mares from both groups; the resulting conceptuses were collected 21 days after transfer to assess conceptus development. HE mares became obese, and embryos recovered from HE mares were more likely to succumb to early embryonic death. The period of annual cyclicity was extended in HE compared to control mares in all years. The incidence of HAFs did not consistently differ between HE and control mares. No differences in embryo morphometric parameters were apparent. In conclusion, consuming a HE diet extended the duration of cyclicity, and appeared to increase the likelihood of embryos undergoing early embryonic death following embryo transfer.

Highlights

Obesity is an increasingly important health and welfare issue in horses, predisposing them to serious medical conditions such as insulin dysregulation [1], laminitis [2], and 4.0/).cardiovascular changes including myocardial hypertrophy [3], which collectively constitute the equine metabolic syndrome (EMS) [4]
Ponies retained into a second year, BCS and body weight (BW) did not return to starting values following a winter period at around maintenance diet
It is possible that the difference in outcomes is in part because we looked at the incidence of hemorrhagic anovulatory follicles (HAF) as a percentage of the total number of cycles while Vick et al [5] just reported the incidence of HAFs and periods of extended luteal activity

Summary

Introduction

Obesity is an increasingly important health and welfare issue in horses, predisposing them to serious medical conditions such as insulin dysregulation [1], laminitis [2], and 4.0/).cardiovascular changes including myocardial hypertrophy [3], which collectively constitute the equine metabolic syndrome (EMS) [4]. Obesity has been associated with altered reproductive cyclicity in mares, and is commonly believed to be detrimental to fertility [5]. Whether and how obesity affects fertility in mares has yet to be explored objectively. Ovulatory activity in mares is regulated primarily by changes in photoperiod. The physiological reproductive season begins in the spring, when the number of daylight hours increases, and ovulatory activity ceases again during late autumn and winter, when daylength shortens [6,7]. The duration of the period in which mares show ovulatory activity is an important potential contributor to fertility, because a larger number of normal estrous cycles equates to more opportunities for mating or insemination and fertilization

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