The body size and weight of 584 Banei draft racehorses at Obihiro Racing Stable in Hokkaido, Japan, was investigated. Almost all the animals (94.7%) were cross-breed heavy draft horses; there were a few Percheron and Percheron grade (4.8%) and a Belgian breed (0.5%). The ages of the animals ranged from 2 to 10 years. Males accounted for 80.3%, females for 17.5%, and 2.2% were castrated. The mean body measurements of 2-year-old Banei draft racehorses were significantly smaller than those of the 3-to 4-year-old or 5-to 10-year-old horses. Hip width, croup width, and rump length of females were greater than those of males. In contrast, males had greater chest width and cannon bone circumference than females. Significant relationships among almost all body measurements were observed. A high correlation was found between body weight and chest girth, croup width and body length. A principle component analysis were applied to investigate the effect of body conformation on racing performance in terms of earnings and the time on the performance test. Performance was significantly related to the principle components of general body size and weight of the horses. The cannon bone, body length, and rump length were suggested to have an effect on earnings per race in 2-year-old male horses. In terms of body size and conformation, the Banei draft racehorses, which are large in general size and well balanced, seemed to show high performance.
Testicular fibrosis is considered to be a pathway leading to hypospermatogenesis. Two horses affected with aspermatogenesis of cryptorchidism and hydrocele, with reference to peritubular myoid cells, were examined histologically and immunohistochemically. In injured testes, the myoid cells became irregular in shape and resembled fibroblasts. Immunohistochemically, normal actin-positive myoid cells were decreased. But reactivity for α-smooth muscle actin, matrix metalloprotease-2 (MMP-2) and vimentin were clearly indicated in myoid cells. These morphological and immunohistochemical changes of myoid cells into myofibroblasts were recognized. The myoid cells seemed to develop into myofibroblasts for defense against testicular damage, and positively secreted extracellular matrix (ECM). Simultaneously, myofibroblasts seem to induce a morbid condition due to gelatinization of the basal lamina, which assists in the blood-testis barrier. The myofibroblasts, developed from myoid cell were thought to play an important role in the process of testicular fibrosis.
The fundamental aim of chronobiological analysis methods in the field of sport physiology in the horse is to establish the time interval in which the organism gives the best performance. Since it is well known that numerous physiological parameters (electrocardiographic, haemogasanalytic and haemodynamic) vary during physical exercise and influence athletic potential considerably, we studied the periodic variations in the following haematological parameters at a different frequency in 12 horses (6 athletes and 6 sedentary): erythrocytes (RBC), total leukocyte count (WBC), haemoglobin (Hb), packed cell volume (PCV), platelets (PLT), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC). Some of the parameters studied showed periodicity at different frequencies both in athletic and sedentary horses: in athletic horses -infradian (RBC, PCV), circadian (RBC, WBC, PCV), ultradian (RBC, WBC, Hb); in sedentary horses-infradian (RBC, Hb, PLT), circadian (RBC, PCV), ultradian (RBC, Hb). The results obtained, therefore, can suggest that physical exercise is an exogenous synchronizer which modulates the periodicity of the haematopoietic system and of the functions of the organs involved in athletic performance.
The expression of equine cytochrome P450 aromatase gene (CYP19) in various tissues include placenta and fetal gonads were examined by reverse-transcription polymerase chain reaction (RT-PCR), in addition to northern blot analysis of cytochrome P450 steroid 17α-hydroxylase/C17-20 lyase gene (CYP17) and 3β-hydroxysteroid dehydrogenase Δ5-Δ4 isomerase gene (HSD3B). Prior to this, testicular expression of CYP19 mRNA in adolescence was confirmed by RT-PCR and successive sequencing. The successful amplification of RT-PCR and nucleotide sequence of the PCR products meant the equine testis expresses CYP19 mRNA. In the RT-PCR of the pregnancy samples, CYP19 was expressed only in the placenta and not in the fetal gonads. The equine fetal gonads, which express CYP17, should convert progestins into androgens to supply substrates for aromatization in placenta expressing CYP19. It is suggested that the fetal gonads are the major androgen source in equine gestations, and this function will not be affected by the fetal gender.