The present study was conducted to investigate the effects of skim milk glucose (SMG), percoll and Brackett and Oliphant medium supplemented with BSA (BO-BSA) washing and glycosaminoglycans treatments (GAG) on lysophosphatidylcholin (LPC)-induced acrosome reaction (AR) in stallion spermatozoa. Freshly collected semen was washed with SMG (300 g for 10 min), percoll (700 g for 30 min) and BO-BSA (300 g for 10 min). Part of the semen after each washing step was treated with LPC to asses the rate of AR. After SMG, percoll and BO-BSA washing, the spermatozoa were cultured with in 5 different concentrations of GAG (chondroitin sulfate; CS and heparin; 0, 3, 10, 30, 100 μg/ml) for 0, 1.5, 3 and 6 h at 38.5°C in 5% CO₂ in air. The LPC-induced AR in fresh spermatozoa after washing with SMG, percoll and BO-BSA were 0.8%, 3.0%, 13.4% and 18.0%, respectively. A significant difference in the rate of AR was observed before and after percoll washing (P<0.05). The LPC-induced AR rates after CS and heparin treatments were 14.7-20.8% and 15.3-19.5%, respectively. No relationship was observed either with the concentration of GAG or culture time on the percentage of AR spermatozoa. Results of the present study indicate that the percoll and BO-BSA washing can potentiate the LPC induced AR in stallion spermatozoa. Moreover, CS or heparin may not be useful in inducing AR in stallion spermatozoa.

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Changes in the packed cell volume (PCV), blood lactate concentration [La^-] and osmotic fragility of circulating erythrocytes were determined in three horses subjected to treadmill exercises or treated with epinephrine. The osmotic fragility was taken as the haemolysis rate (HL) in 0.56% NaCl. Previous warm-up significantly decreased HL by 24%, and cantering at 8 m/s for 8 min (10% incline) increased HL by 92%; subsequent cool-down significantly decreased the rate by 23% to the initial resting level, but thereafter the rate gradually increased again, returning to the initial resting level. In contrast, continuous trotting at 5 m/s for 15 min (0% incline) decreased the HL by 50% to the initial resting level. Intravenous injection of epinephrine had little effect on the HL. Although the exercises in combination with the injection significantly increased PCV and [La^-], these changes in the experiments were not correlated with the HL, but the correlation coefficient for PCV and [La^-] and HL during cantering was positive: r=0.875 and 0.958, P<0.01, respectively. These results suggest that: 1) the release of red cells from the spleen into the circulation has no effect on changes in the osmotic fragility of erythrocytes during exercise; 2) heavy exercise increases the osmotic fragility, but 3) light exercise decreases it.

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To immunochemically determine molecular structural differences between three Tf subgroups (Tf-D · F₁ · F₂ · H₂, Tf-O · R and Tf-X) and the relationships between equine Tf variants and donkey Tf, equine Tf types were subjected to binding assay with a panel of monoclonal antibodies (mAbs) specific to equine Tf-D, F, H₂, O and R types and donkey Tf components. The results obtained were as follows: 1) Some mAbs produced against Tf-D and F type components showed group specific for only Tf-D · F₁ · F₂ · H₂, and did not react with Tf-O, R, X types or donkey Tf component. As a result, Tf-D, F₁, F₂ and H₂ could be immunochemically classified into the same group, but affinity for D variant differed within this subgroup. The F₂ variant showed the strongest affinity for the D variant, followed by the F₁ variant, then the H₂ variant. 2) Group specificity for only Tf-O and R types was recognized in some mAbs produced against Tf-R type substance, Tf-O · R could thus be distinctly distinguished from Tf-D, F₁, F₂, H₂ and X types. mAbs that react with Tf-O · R types, donkey Tf and Lf of horse and llama could also be developed. The Tf-R variant might be the most original Tf variant in equine Tf locus. 3) Antigen determinant of Tf-X variant differed from Tf-D · F₁ · F₂ · H₂ subgroup and Tf-O · R subgroup, and X type formed an independent subgroup.

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We carried out a cross-sectional study to determine the seroprevalence of seven different serovars of Leptospira interrogans in horses in New York State and examine the geographic distribution of the disease in the state. A random sample of 2, 967 horses was selected from the equine population in New York State using the 1988 New York State Equine Census as a sampling frame. The samples were tested for the presence of antibodies against seven serovars: L. pomona, L. hardjo, L. icterohaemorrhagiae, L. grippotyphosa, L. canicola, L. autumnalis, and L. bratislava. The microscopic agglutination test was used to determine seropositivity at a range of dilutions from 1:100 to 1:12800. A titer of ≥100 was considered positive. We also examined the association between seroconversion at higher (≥1600) titers among those serovars. Cluster analysis was used to examine the distribution of the disease for special pattern or clustering. The following prevalences were determined: L. pomona (7.6%), L. hardjo (1.0%), L. icterohaemorrhagiae (11.3%), L. grippotyphosa (6.5%), L. canicola (16.2%), L. autumnalis (35.1%), and L. bratislava (40.7%). The majority of the titers for all serovars were relatively low. Most of the samples tested positive for L. pomona had titers ranging from 100 to 400. For all the other serovars, most samples tested positive had titers ranging from 100 to 200. We found significant associations of seroconversion between all pairs of serovars except L. grippotyphosa and L. pomona, and L. grippotyphosa and L. autumnalis.

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The present study aimed to estimate the ovulation time in the mare on the basis of changes in urinary estrone sulphate (E₁S) concentrations by using an EIA kit, originally used for plasma. Urine samples were collected from mares during the preovulatory period until ovulation. The urinary E₁S concentrations showed a gradual increase from 153 ± 45 ng/ml urine and 210 ± 22 ng/mg creatinine (Cr) at D-5 and then reached a peak of 316 ± 43 ng/ml urine and 394 ± 35 ng/mgCr at D-2 in 81% of the mares in both groups. These findings indicate that daily determination of urinary E₁S concentrations allows us to estimate the ovulation day and subsequently decide the optimum mating service time in mares.

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