Effect of Ingestion of Endophyte-Infested Fescue on Post-exercise Recovery of Horses

The objective of this study was to determine whether consumption of endophyte-infested tall fescue (Festuca arundinacea) hay would affect recovery of respiration and heart rate when horses were exercised during the summer months. Twelve horses averaging 533 kg were fed either a control orchard grass (Dactylis glomerata) or fescue hay, which averaged 1,995 ppm ergot alkaloids. During the last 4 days of each 14-day period, horses were individually housed in 13.3 m² stalls so that individual intake and refusals could be recorded. On day 14 of each test period horses were subjected to an exercise tolerance test consisting of 4 minutes at a walk, 14 minutes at a trot, and 6 minutes at a lope/gallop with target heart rate ranges of 50 to 70, 71 to 110, and 111 to 150 beats per minute, respectively. Ergot alkaloids in urine samples from horses consuming fescue averaged 282.2 ng/mg creatine compared with 14.4 ng/mg creatine for those consuming orchard grass. Horses consumed more (P < .01) orchard grass than fescue (2.06% vs 1.69% body weight [BW]/day) and lost less (P < .01) weight (4.3 vs 29.3 kg) during the 14-day experimental periods. No increase was observed (P < .01) for pre-exercise or post-exercise rectal temperatures or pulse or respiration rates after 1, 5, and 10 minutes of recovery between treatment groups. Ingestion of fescue with high levels of ergot alkaloids did not affect post-exercise recovery when horses were subjected to a light workload.     

Evaluating the Technique of Using Nitrogen Retention as a Response Criterion for Amino Acid Studies in the Horse

Six Quarter Horse yearling fillies were used in a duplicated 3 × 3 Latin square experiment to evaluate the technique of using nitrogen retention as a response criterion for amino acid studies in the horse. Yearlings were paired by age and randomly assigned to one of three concentrates fed with medium-quality Coastal Bermudagrass hay. Diet A, a soybean meal–based concentrate, was amino acid sufficient. Diet B, a cottonseed hull–based concentrate containing 2% urea, was amino acid deficient. Horses fed diet C, identical to diet B, were orally dosed with synthetic essential amino acids and cysteine, immediately before eating, to match amino acid levels in diet A. Nitrogen retention was not different between diets A and B. There was a trend for horses fed diet C to have higher nitrogen retention, as a result of higher nitrogen intake. Nitrogen retained as a percent absorbed was lower (P < .05) for diet B than for diet A, whereas values for diet C were not different from diets A or B. Nitrogen retention was not an effective response criterion in this study. Differences in nitrogen retained as a percentage absorbed were observed between amino acid–sufficient and deficient diets. However, horses fed amino acid–deficient diets and dosed with synthetic amino acids likely require some modified dosage level to achieve the same or higher values as those for amino acid–sufficient diets.     

Endocrine Profile Comparisons of Fat Versus Moderately Conditioned Mares Following Parturition

The influence of progesterone, luteinizing hormone (LH), and estrogen on the mare's estrous cycle has been well researched and documented, but other endocrine profiles have not received as much attention. To evaluate endocrine concentrations in fat-conditioned (body condition score [BCS] of 7–8) versus moderately conditioned mares (BCS of 5–6), 24 mares were allotted to and maintained in respective groups from late gestation until pregnancy was confirmed after breeding on the second postpartum estrus. Serum concentrations of thyroxine (T₄), insulin-like growth factor-1 (IGF-1), and leptin were assayed to characterize circulating blood concentrations. Additionally, LH and progesterone serum concentrations were assayed to evaluate the estrous cycle status of the mares. Leptin and progesterone concentrations were not different (P > .05) between the groups. Nevertheless, serum concentrations of T₄ were higher (P < .01) and IGF-1 concentrations lower (P < .01) in moderately conditioned as compared with fat-conditioned mares during times of ovulation and the interovulatory period. Furthermore, serum concentrations of LH were found to be different between the groups only when the estrous cycle approached the second ovulation (P < .0001). Results of this study suggest that mares maintained in a BCS of 5 or greater are similar in terms of reproductive efficiency. Although the circulating serum concentrations of T₄ and IGF-1 are different after parturition, their influence does not affect reproductive capabilities of mares with a BCS of 5 or greater.     

Effects of Egg Yolk Source on the Cryopreservation of Stallion Spermatozoa

Three experiments were conducted to determine whether replacement of chicken egg yolk, as a component of freezing extenders, with egg yolk from other avian species would improve the post-thaw motility and percentage of intact acrosomes of stallion spermatozoa. In the first experiment, substitution of chicken egg yolk with chukar egg yolk, as a component of the lactose-ethylenediaminetetraacetic acid extender, improved (P ≤ .05) the post-thaw motility of stallion spermatozoa. These results were not replicated in (IMV Technologies, Maple Grove, MN, USA) a more expansive study comparing 2%, 4%, 6%, or 8% egg yolk combined with INRA 96 when a “slow freeze” method was used, or the same substitution at levels ranging from 13% to 22% when egg yolk was combined with lactose-ethylenediaminetetraacetic acid for diluents used for a “fast freeze” method of cryopreservation. In the third study, egg yolks from regular and high omega-3 chicken eggs as well as from turkey, chukar, and mallard duck eggs were analyzed for lipid content and fatty acid profile. The yolk from the turkey eggs was higher (1,300 mg/100 g) and that from mallard ducks was lower (560 mg/100 g) in cholesterol as compared with the two types of chicken eggs and chukar egg yolk (range, 1,046-1,094 mg/100 g). In addition, the high omega-3 eggs did test higher for fatty acids (4.51 g/100 g) than other types of eggs (range, 0.28-0.73 g/100 g). Substitution of chicken egg yolk with turkey, but not duck, egg yolk resulted in higher post-thaw total motility (P ≤ .05) for spermatozoa obtained from two of the three stallions used in the third experiment.     

Paraoxonase 1 (PON1) activity in serum,follicular fluid and seminal plasma of sheep

This work aimed to describe the activity of paraoxonase 1 (PON1) in serum, follicular fluid and seminal plasma of sheep. Average serum PON1 activity was 286.8 ± 96.2 U/ml in females and 237.6 ± 18.9 U/ml in males. There was a positive correlation between PON1 activity in serum and follicular fluid in females, being twice higher in serum than in follicular fluid (148.8 ± 15.7 U/ml). PON1 activity in males’ serum was 10‐fold higher than in seminal plasma (21.18 ± 14.2 U/ml), and there was no correlation between PON1 activity in both compartments. Finally, this work suggests that PON1 activity of in sheep is higher compared to other mammalian species, and there is an association between PON1 in serum and follicular fluid only.     

Effect of Ergovaline Ingestion on Recovery of Horses Subjected to an Anaerobic Standard Exercise Test

The objective of this study was to determine whether consumption of tall fescue seed which contained high levels of ergovaline would affect post-exercise recovery of horses subjected to an anaerobic exercise test. Ten Quarter horses were separated into two groups and fed alfalfa hay, commercial sweet feed, and either endophyte-infected (E+) or endophyte-free (E−) ground tall fescue seed. Diets contained 11.8% seed, which resulted in 459 ppb of ergovaline for the E+ diet. During the first 28 days, horses in group A received E+ and group B received E−. Diets were reversed during the next 28 days (crossover design). Horses were ridden for 5 days per week. On day 14, 28 (period 1), 42, and 56 (period 2), they were subjected to a standardized exercise test (SET) that consisted of 41 turns in 4 minutes and was designed to raise the horse’s heart rate (HR) beyond the anaerobic threshold (150 bpm). There was a horse effect (P < .05) on post-SET respiration rate, HR, and post-exercise whole blood lactate level, but not rectal temperature (RT). For these variables or period effects, there was no horse × treatment, period × treatment, or period × horse interactions (P < .05). Treatment had no effect on whole blood lactate level, RT, or HR at any time measured. Respiration rate did not vary by treatment at rest or 1 minute after SET but was higher for the E+ treatment at 5 and 10 minutes after SET (P < .005). Consumption of diets that averaged 450 ppb of ergovaline caused the horses expend more respiratory effort in an attempt to recover to resting RT.     

Effect of pyruvate and lactate on motility of cold stored stallion spermatozoa challenged by hydrogen peroxide

Numerous workers have shown that motility of cold stored spermatozoa from some stallions can be improved by removing most of the seminal plasma by centrifugation and resuspending the spermatozoa in an extender consisting of skim milk glucose extender (SKMG) supplemented with a salt media such as Tyrode's or phosphate-buffered saline. The salt media must contain pyruvate and lactate. In an effort to test the hypothesis that pyruvate may be acting as an antioxidant, a series of experiments were conducted using a H₂O₂ challenge to artificially produce damage due to lipid peroxidation. Results of these experiments indicated that addition of lactate or pyruvate and lactate to SKMG-Tyrode's media was not able to prevent the detrimental affects of H₂O₂. The addition of lactate to the SKMG-Tyrode's media resulted in an improvement of post-storage motility; however, increasing the concentration of pyruvate did not further improve motility. Therefore, because lactate dehydrogenase has been shown to be correlated with motility, and lactate has been shown to be preferred as an energy source by spermatozoa from other species, the beneficial effects of lactate and pyruvate as components of a modified SKMG extender are probable as energy sources.