K.L. Vernon

Exercise affects both ovarian follicular dynamics and hormone concentrations in mares

The objectives were to evaluate the effects of exercise on ovarian folliculogenesis and related hormones in mares. Mares (n = 11) were randomly assigned into a control (non-exercised) or treatment (exercised) group. Treatment mares (n = 5) were moderately exercised for 30 min, 6 d/wk. All mares underwent daily transrectal ultrasonographic examinations and ovarian follicles > 6 mm were measured. Blood samples were collected during the first (Cycle 1) and last (Cycle 4) cycle, and serum concentrations of cortisol, LH, and FSH were determined. Mean cortisol concentrations were elevated (P < 0.05) in exercised mares, 6.29 ± 0.22 compared with 5.62 ± 0.16 ng/dL (mean ± SEM), 30 min post exercise. There were no significant differences between groups in mean FSH concentrations; however, exercised mares had lower (17.3 ± 6.4 vs 41.1 ± 5.5 ng/mL; P < 0.05) peak LH concentrations. Furthermore, exercised mares experienced a longer (24.7 ± 0.8 vs 22.2 ± 0.8 d; P < 0.05) mean interovulatory interval for all cycles combined, fewer (P < 0.05) follicles 6 to 20 mm in diameter, and an increased (P < 0.05) number of follicles >20 mm following deviation. The dominant and largest subordinate follicle in exercised mares had a greater (P < 0.05) mean diameter on the day of deviation, suggesting delayed deviation. Exercised mares also tended (P = 0.06) to have an increased number of cycles with at least two dominant follicles compared to control (62 vs 36%, respectively), indicating a decreased ability of the largest follicle to assert dominance. Under the conditions of this study, moderately exercising mares induced higher cortisol concentrations, lowered peak LH concentrations, and altered ovarian follicular dynamics.

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

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.

Dietary supplementation of conjugated linoleic acid in horses increases plasma conjugated linoleic acid and decreases plasma arachidonic acid but does not alter body fat.

Studies using dietary supplementation of eicosapentaenoic and docosahexaenoic fatty acids (FA) in horses report inconsistent anti-inflammatory results but consistently report an increase in plasma arachidonic acid (C20:4), the major substrate of cyclooxygenase (COX) II inflammatory pathway. Conjugated linoleic acid has shown anti-inflammatory effects in laboratory and food animal species, but effects of CLA supplementation in horses have not been reported. Our objective was to determine the effects of CLA supplementation on plasma CLA and C20:4 and body fat in healthy horses at maintenance. In a crossover study, 12 mature mares were blocked by breed, age, and BCS and separated into 2 treatment groups (n = 6/group). Groups were fed CLA and corn oil (CO; isocaloric control) for two 6-wk feeding periods, separated by a 4-wk period during which treatment was withheld. Corn oil or CLA supplement (55% mixed CLA isomers) was incorporated into diets at 0.01% BW/d. Mares were fed individually and restricted to dry lots to control forage intake. Rump fat thickness (RFT), BW, and BCS were measured before (d 0) and after (d 42) each feeding period. Blood was collected on d 0, 14, 28, and 42 of each 6-wk period for GLC analysis of plasma CLA isomers (cis-9, trans-11; trans-10, cis-12; and trans-9, trans-11) and C20:4. An ANOVA was conducted to compare the response of RFT, BW, and BCS of CLA-treated and control mares. A mixed methods analysis with repeated measures was used to detect differences in plasma FA concentrations. There were no differences in BW, RFT, or BCS between treatment groups. All CLA isomers present in the CLA supplement were greater in plasma of horses fed CLA compared with controls (P < 0.01). Additionally, plasma concentrations of C20:4 were decreased in horses fed CLA (P < 0.05). This decline in C20:4 may impact the COX II pathway and warrants further investigation. These results suggest that in an equine model, dietary CLA increases circulating concentrations of supplemented CLA isomers and decreases circulating C20:4. Examining physiological effects of CLA supplementation in horses at varying levels of growth, exercise, and progression of joint disease may offer insight to potential benefits of CLA in the horse.

Evaluation of conjugated linoleic acid supplementation on markers of joint inflammation and cartilage metabolism in young horses challenged with lipopolysaccharide

Seventeen yearling Quarter Horses were used in a randomized complete block design for a 56-d trial to determine ability of dietary CLA to mitigate joint inflammation and alter cartilage turnover following an inflammatory insult. Horses were blocked by age, sex, and BW, and randomly assigned to dietary treatments consisting of commercial concentrate offered at 1% BW (as-fed) supplemented with either 1% soybean oil (CON; n = 6), 0.5% soybean oil and 0.5% CLA (LOW; n = 5; 55% purity; Lutalin, BASF Corp., Florham Park, NJ), or 1% CLA (HIGH; n = 6) top-dressed daily. Horses were fed individually every 12 h and offered 1% BW (as-fed) coastal bermudagrass (Cynodon dactylon) hay daily. This study was performed in 2 phases: phase I (d 0 to d 41) determined incorporation of CLA into plasma and synovial fluid; phase II (d 42 to d 56) evaluated potential of CLA to mitigate intra-articular inflammation and alter cartilage metabolism. Blood and synovial fluid were collected at 7- and 14-d intervals, respectively, to determine fatty acid concentrations. On d 42, carpal joints within each horse were randomly assigned to receive intra-articular injections of 0.5 ng lipopolysaccharide (LPS) derived from Escherichia coli 055:B5 or sterile lactated Ringers solution. Synovial fluid samples were obtained at preinjection h 0 and 6, 12, 24, 168, and 336 h postinjection, and analyzed for prostaglandin E2 (PGE2), carboxypeptide of type II collagen (CPII), and collagenase cleavage neopeptide (C2C). Data were analyzed using PROC MIXED procedure of SAS. Horses receiving the CON diet had undetectable levels of CLA for the duration of the study. A quadratic dose response was observed in concentrations of CLA in plasma and synovial fluid (P < 0.01). A negative quadratic dose response was observed for plasma arachidonic acid (20:4) with a reduction in concentration to d 14 in HIGH horses (P = 0.04). Synovial fluid 20:4 tended to decrease in horses receiving the HIGH diet (P = 0.06). Post LPS injection, synovial PGE2 was not affected by dietary treatment (P = 0.15). Synovial C2C was lower in HIGH horses (P = 0.05), and synovial CPII tended to be greater in LOW horses than HIGH and CON horses (P = 0.10). In conclusion, dietary CLA incorporated into plasma and synovial fluid prior to LPS challenge. Dietary CLA did not influence inflammation; however, there was a reduction in cartilage degradation and an increase in cartilage regeneration.

Dietary supplementation of conjugated linoleic acid in horses: establishment of baseline values on bone turnover, synovial prostaglandin E2, and gait kinematics

Conjugated linoleic acid (CLA) has shown anti-inflammatory effects in laboratory and food animal species by modulating production of proinflammatory cytokines and inhibiting cyclooxygenase 2 (COX2), reducing prostaglandin E2 (PGE2) production. Bone remodelling may also be affected by CLA. Thus, CLA may reduce inflammation consistent with joint disease. Effects of CLA supplementation in horses have not been previously reported. This study aimed to determine baseline values of CLA supplementation on bone turnover, synovial PGE2 and gait kinematics in mature, idle horses. It was not expected that CLA would affect bone metabolism or gait kinematics in this animal model, as COX2 pathway should not be upregulated. In a crossover study, 12 mature mares were blocked by breed, age, and body condition score and separated into two treatment groups (n=6 per group) fed CLA or corn oil (CO; isocaloric control) for two 6-week feeding periods, separated by a 4-week period when oil treatment was withheld. Corn oil or CLA ...