The following items were investigated to measure blood lactate in horses under field conditions using portable lactate analyzers recently developed for human athletes. 1) The precision of two types of portable lactate analyzer and the standard analyzer using the immobilized enzyme method, and correlation among the lactate concentrations measured by the three lactate analyzers. 2) The correlation between the lactate concentrations in peripheral blood collected by lancet puncture and jugular venous blood using Lactate-pro (L-pro). The study was performed in Thoroughbreds under training for races, using Accusport (AC) and L-pro as portable lactate analyzers and YSI1500 (YSI) for the standard analyzer using the immobilized enzyme method. The intra- and inter-assay coefficients of variation (CV) of L-pro was lower than AC at low and middle lactate concentrations. The precision of L-pro is better than AC when the blood lactate level is lower than 10 mmol/l, and hematocrit (Ht) is 57% or lower. The lactate concentration using L-pro in peripheral blood collected by lancet puncture through the neck skin was similar to the level in jugular venous blood. No infection or inflammatory symptom occurred after blood sampling and the examination is relatively safe. These findings suggest that blood lactate measurement using L-pro by lancet puncture through the neck skin under field conditions is simple and safe, requiring no blood sampling from the jugular vein, and it can be used for evaluation of aerobic capacity and intensity of exercise in daily submaximal training.

Different geographic regions in which thoroughbred yearling horses are bred have different climates and different types of forage in pasture and hay. These factors are likely to influence the energy metabolism and growth rate of yearling horses. However, the effects of the characteristics of geographic regions on the digestible energy (DE) intake and growth rate of thoroughbred yearlings has yet to be clarified in detail. Here, we have examined the effect of the breeding region on growth performance of young horses, by comparing the DE intakes and growth rates of thoroughbred yearlings in Hidaka (Hokkaido) and Miyazaki (Southern Kyushu) in Japan. Eighteen male thoroughbred yearlings were divided equally into two groups, and bred either at the Hidaka training and research center (HYF) or the Miyazaki yearling farm (MYF). Measurements were conducted in September (summer) and in February (winter), and the mean ages of the yearlings during these two periods were 18 months and 23-24 months old, respectively. The apparent digestible energy intake was measured by a double-indicator method using Cr2O3 and lignin. There was no significant difference in the DE intakes between the yearling horses at the HYF and MYF in either season. The warm land of Southwest Japan has been considered to be unsuitable for growing forage containing sufficient nutrients to feed thoroughbreds, but no nutritional disadvantage of this forage was detected in the yearlings bred at the MYF. On the other hand, the heart girth (HG) and cannon circumference (CC) were found to be significantly smaller in yearlings at the HYF, compared to those at the MYF, in the winter evaluation (p<0.05). Significant positive correlations between the ADG and DE intake/100 kg body weight were seen in animals at the HYF in the summer and in those at the MYF in both seasons; however, such a correlation was not found in horses at the HYF in winter. The reason for the smaller HG and CC and the absence of a significant correlation between the ADG and DE intake/100 kg body weight in the yearlings at the HYF in winter is unclear. It could be attributable to growth delay due to exposure to cold temperatures, or lack of supplementation to compensate for the increased energy requirement due to excess energy metabolism in cold weather. Closer attention must, therefore, be paid to the energy supply and nutritional composition of feedstuffs fed to thoroughbred yearlings at farms in regions with cold ambient temperatures.

There is no documentation on the diseases of horses in Zaria, Nigeria. A study was therefore conducted at the Ahmadu Bello University Veterinary Teaching Hospital (ABUVTH), Zaria, Nigeria to properly document the diseasesof horses in the Northern Guinea Savannah of Zaria, Nigeria. The most common disease encountered was helminthosis, accounting for 809 (82.3%) of all the diseases diagnosed. Tetanus and rabies, which were also diagnosed in horses in this study have long been recognised as major zoonoses. The public health significance of these diseases in Zaria, Nigeria is discussed. It is concluded that research should be conducted to develop parasite vaccines from parasite strains native to Zaria, Nigeria to ameliorate parasitic diseases of horses in this area.

The digestibility of nutrients and nutritive values of cereals (barley, corn, naked oat, oat and quinor), oil meals (cotton seed meal, linseed meal and soybean meal), brans (defatted rice bran, wheat bran and wheat bran with flour) and hays (Italian ryegrass and orchardgrass) were determined by the chromic oxide index method in adult male Thoroughbreds. Because the nutritive values of feedstuffs are affected by the processing and producing countries, the effect of processing of feedstuffs, flaking corn, expanding quinor, extruding soybean meal, and chopping hays and countries producing oats were examined. The digestibility of CP in oats was higher, but that of gross energy was lower than that of other cereals. Among oil meals and brans, the digestibility of all nutrients in soybean meal and wheat bran with flour was higher. When long hays were supplied, the digestibility of all nutrients in Italian ryegrass was lower, but when chopped hays were supplied, that in Italian ryegrass hay was similar to that in orchardgrass hay. By flaking corn and expanding quinor, the digestibility of all nutrients except ether extract in corn and CP in quinor was improved. By extruding soybean meal, the digestibility of nitrogen free extract was improved, but the digestibility of CP was not improved. By chopping hays, the digestibility of all nutrients in Italian ryegrass hay was improved, but the digestibility in orchardgrass hay was not affected. Australian oat contained the highest ether extracts and gross energy. Compared to Australian oat, Canadian oat contained the same amount of CP and lower crude fiber, and Hokkaido oat contained lower CP.

Seven horses were exercised five days a week for 12 months at different gaits on a treadmill, and eight horses were pastured freely in a paddock without any training programs. They were 60 days of age at the beginning of the experiment. We compared the number of C cells in the thyroid, ultrastructure of chief cells in the parathyroid and radiography of the third metatarsal bone of the training group with the control group. In the training group, the number of C cells was not increased and chief cells were not in a phase of secretion. In addition, the bone mineral content and the cortical area did not show high values. We considered that an additional exercise used in this study had suppressive effects on the thyroid and parathyroid. Our results also suggest an additional and/or intense exercise in early stage of life (foal to weanling) may have an adverse effect on bone growth and metabolism.

Isotype-specific antibody responses in 13 foals to Rhodococcus equi were studied during the first 20 weeks of life on a horse-breeding farm with a persistent incidence of R. equi infection. The levels of immunoglobulin (Ig) classes and IgG subclasses specific for R. equi antigens in the 13 foal sera were determined by ELISA and Western immunoblotting. Kinetics of the total amount of IgG and the number of WBC in the blood of 13 foals were also monitored. Soluble extract from R. equi strain ATCC 6939 was used as a routine EISA antigen. During the observation period, 8 of the 13 foals showed >0.3 OD value against ATCC 6939 antigen by a routine ELISA, which was tentatively fixed to be positive on the basis of readings made of healthy horse sera in previous studies. R. equi-specific IgGa was predominantly detected in these foals at 6 to 10 weeks after birth by ELISA with Tween 20-extracted ATCC 6939 antigens. Specific serum IgGb, and IgA were also detected, but they showed lower titers than IgGa antibodies in the foals. Specific IgG(T), IgGc and IgM was present consistently at low levels in most foals. On the other hand, IgGa and IgGb antibodies specific for 15-to 17-kDa antigens (VapA) were detected by immunoblotting at 5 to 7 weeks of age in most foals. Out of the 13 foals, 3 foals had a serum IgG concentrations less than 1,000 mg/dl (650 to 900 mg/dl) at the first week of birth. WBC counts tended to increase by 8 weeks with age in all foals. Virulent R. equi was isolated from the feces of foals during this study. This study suggests that R. equi-specific IgGa was predominantly measured by ELISA, and VapA-specific IgGa and IgGb were predominantly detected by immunoblotting in foals naturally exposed to R. equi on a farm with a persistent incidence of R. equi infection.

The D4 dopamine receptor gene (DRD4) polymorphic region, which is possibly related to the personality trait known as Novelty Seeking in humans, was examined in equids. Partial nucleotide sequences in exon 3 of DRD4 gene were compared among several species in genus Equus. Inter-and intra-species differences were observed, as well as between two domestic horse breeds, Thoroughbred and Kiso pony (Japanese native pony). In equids, these variations were consisted of as many as 9 fold repeats of 18 bp variable number of tandem repeat (VNTR) type polymorphisms and single nucleotide polymorphisms (SNPs).

A sero-epidemiological survey was conducted using a serum neutralization test in order to better understand the level of circulation of three equine rotavirus strains, HO-5 strain (G3, P[12]), FI23 strain (G14, P[12]), and L338 strain (G13, P[18]), among horses in the Hidaka region of Hokkaido, Japan. Sera used for the survey were collected from 50 1-year-old horses at 10 thoroughbred stud farms in the Hidaka region in February and March of 1999. Two horses were excluded from the study because they did not possess antibodies against any of the 3 strains. Of the remaining 48 horses, 35 (73%) showed highest antibody titers against HO-5 strain while 8 horses (17%) demonstrated highest titers against FI23 strain. The remaining 5 horses (11%) possessed similar antibody titers against HO-5 strain and FI23 strain. Predominant antibody titers against L338 strain were not observed in any of the horses. These results suggest that G3, P[12] type was the predominant rotavirus among horses in the Hidaka region of Hokkaido although G14, P[12] type also circulated. There was no evidence that horses in the Hidaka region were infected with the L338 strain.

The influence of long distance transport on various viral infections was investigated serologically by examining 29 young racehorses for infection by respiratory agents including equine herpesvirus, equine adenovirus and equine rhinovirus, as well as coronavirus which has been suggested to be an etiological agent of diarrhea and febrile disease in horses. Serological evidence of infections by these viruses was not shown in any of the 18 febrile horses. However 4 of 11 nonfebrile horses which were loaded on the same vehicle as two horses which were seropositive for coronavirus, seroconverted after transportation.

Hokkaido native horses (HH) were compared with light half-bred horses (LH) for digestibility and the number of bites and chews when fed non-chopped timothy hay at 90% of the maintenance level in the pen. Apparent digestibility of nutrient and energy in HH were similar to those in LH. The time budget of eating by HH per day was shorter than that by LH (P<0.05, 403.3 vs 557.5 min), while there was no difference between HH and LH in the eating rate. The rate of biting, bite size, chewing rate per a minute and the number of chews per 1 g DM intake in HH were similar to those in LH. Ingestion by HH was indicated to be more efficient than that by LH.