Impact of moderate exercise on ovarian blood flow and early embryonic outcomes in mares1

Abstract

The advent of embryo transfer has allowed horses to continue to train and compete during the breeding season. However, the associated stress of exercise may be detrimental to reproduction. The objectives of this study were to evaluate differing exercise protocols on reproductive blood flow and embryonic outcomes in mares. Light-horse mares were randomized into control (n = 4), partial-exercised (n = 6), and full-exercised (n = 6) groups. Partial-exercised mares were moderately exercised 30 min daily during the periovulatory period and rested after ovulation for 7 d. Full-exercised mares were exercised for 30 min daily throughout the reproductive cycle. Mares were artificially inseminated during estrus and subjected to uterine flush for embryo recovery on d 7 post ovulation. Blood flow through both ovarian arteries and vascular perfusion of the wall of the preovulatory follicle were examined by color Doppler ultrasonography. Results indicated exercise induced greater serum cortisol concentrations (P < 0.05). Embryo recovery rates were reduced in exercised (20/46, 43%) compared with control (14/21, 67%) mares (P < 0.10). When examined separately, embryo recovery rates for partial-exercised (11/25, 44%) and full-exercised (9/21, 43%) mares were not significantly different. Additionally, fewer quality Grade 1 embryos were recovered from partial-exercised mares compared with both control and full-exercised mares (P < 0.05). Blood flow through both ovarian arteries was greater in both exercised groups in the days leading up to ovulation (P < 0.05). However, vascular perfusion of the wall of the preovulatory follicle on the day before ovulation was less in both partial-exercised (45.9 ± 3.0%) and full-exercised (44.8 ± 3.4%) mares vs. control (54.9 ± 3.6%; P < 0.05). In exercised mares, vascular perfusion of the follicle wall was greater when an embryo was recovered (P < 0.01). No differences were found in follicle ovulatory diameter among exercised and non-exercised mares. When groups were combined, follicle diameter was greater when an embryo was recovered (44.9 ± 1.0 mm) compared with an unsuccessful embryo recovery attempt (42.8 ± 0.7 mm; P < 0.05). In conclusion, these data demonstrated that exercise increased ovarian arterial blood flow leading up to ovulation and decreased vascular perfusion of the wall of the preovulatory follicle. Mares given rest the day after ovulation up until an embryo collection attempt did not improve embryo recovery rates.

l-Arginine supplementation 0.5% of diet during the last 90 days of gestation and 14 days postpartum reduced uterine fluid accumulation in the broodmare

“…In our previous studies, mares fed a higher dose of 1% l-Arg once daily were reported to have greater vascular perfusion of the dominant follicle (Kelley et al, 2013) and hastened uterine involution rates (Kelley et al, 2013;Mortensen et al, 2011). Greater vascular perfusion of the dominant follicle in mares has been correlated with greater pregnancy rate (Silva et al, 2006) and embryo recovery (Smith et al, 2012). Additionally, delayed uterine involution has been shown to correlate with lower pregnancy rates in the first postpartum estrous (Ball, 1993;Macpherson and Blanchard, 2005).…”

Embryo transfer in competition horses: Managing mares and expectations

“…The effect of exercise as distinct from that of temperature on fertility ( Smith et al. 2012 ) was assessed by exercising mares moderately in conditions that gave rise to a smaller increase in rectal temperature than that reported in the study of Mortensen et al .…”

“…(2009) . The study of Smith et al . (2012) also tried to determine whether, if exercise does have a detrimental effect on fertility, that negative effect is on early embryonic development or on conception.…”

“…Blood flow through both ovarian arteries was greater in both exercised groups in the days leading up to ovulation (P<0.05) ( Smith et al. 2012 ).…”

<b>Estudo em larga escala dos efeitos da idade sobre os parâmetros reprodutivos e viabilidade de oócitos equinos após injeção intracitoplasmática de espermatozóide (ICSI) usando sêmen sexado</b>

“…On the other side, recovery of oocytes from live mares allows the use of the animal for competition or training while its oocytes can be used for further application in ART. It is however, worth to keep in mind that exercise might decrease oocyte quality and success of the ARTs potential (MORTENSEN et al, 2009(MORTENSEN et al, , 2010SMITH et al, 2012).…”