Sex steroids in serum of prepubertal male and female horses and correlation with bone characteristics

Effects of an extended photoperiod on body composition of young Thoroughbreds in training

The effects of an extended photoperiod (EP) on body composition of Thoroughbreds colts and fillies from December at one year old to April at two years old were investigated. Seventy-three Thoroughbreds reared and trained in Hidaka Training and Research Center, Japan Racing Association, Hokkaido were used. Forty-one horses were under the EP conditions from December 20 to April 15, and the 32 horses were under natural light alone as the control group. Body weight (BW), rump fat thickness (RFT), fat free mass (FFM) and percentage of fat (%F) were used as parameters of body composition. The present study revealed that BW and FFM increased with age in the EP group in colts. In fillies, BW increased with age in both the EP and the control group, however FFM increased with age only in the EP group. From December to April, only colts had a higher rate of increase in both BW and FFM in the EP group than in the control group. However, according to the mean rates of increase in FFM from January to March, the EP group was significantly higher than the control group in both sexes. Furthermore, monthly increase rate of FFM in March was significantly higher in the EP group than in the control group in both sexes. These results suggests that EP treatment to young Thoroughbreds in training at Hokkaido, which is shorter daylength in winter, accelerate the increase of FFM, representing muscle mass.

Relación de los niveles de Testosterona con el comportamiento del Toro Bravo durante la Lidia

Diversos estudios relacionan la concentración plasmática de testosterona con un comportamiento agresivo del animal. En ellos se han estudiado diferentes especies animales, pero se desconoce cómo es esta relación en el toro de lidia, perteneciente a una raza bovina singular por su selección etológica hacia la agresividad. En este trabajo se analizó de forma objetiva el comportamiento en el ruedo de 302 machos adultos de la raza bovina de lidia. Se registraron 33 parámetros etológicos, el número y gravedad de las caídas experimentadas por el animal y el tiempo de las cuatro fases del espectáculo, para correlacionar dicha información con la concentración plasmática de testosterona. Los resultados mostraron diferencias en la media de concentración plasmática de testosterona entre ganaderías y entre las líneas genéticas de procedencia estudiadas en la muestra. Igualmente se constata una correlación positiva entre la concentración de testosterona y un grupo de ocho parámetros etológicos, que señalan ejercicio físico del animal; por otro lado se observó una correlación negativa con los parámetros etológicos: “sale suelto”, “querencia” y “tardea”, sinónimos de falta de casta, lo que podría indicar una correlación positiva entre la testosterona y la agresividad, como indica la bibliografía.

Serum bone metabolism biomarkers in healthy filies and colts from weaning until one year of age

This study aimed to investigate the serum concentration of osteocalcin (OC), parathyroid hormone (PTH), calcitonin (CT), calcium (Ca), phosphorus (P), alkaline phosphatase (ALP) and acid phosphatase (AP) in healthy-weaned-foals from 8 months of age until the first year of life. Moreover, the correlation of investigated parameters and foals' age, as well as the relationship between the serum values of PTH and the other markers of bone remodeling were assessed. From 20 foals (10 fillies, 10 colts), blood samples were monthly collected (from 8 to 12 months of age, T1-T5) and the concentration of OC, CT, Ca, P, ALP, AP and PTH was assessed. Two-way repeated measures analysis of variance (ANOVA) showed age-related differences on OC concentration in both fillies (P = 0.008) and colts (P = 0.03) with higher OC values at T5 than T1 and T2. Sex-related effect on OC concentration was found with higher OC levels in colts compared to fillies (P = 0.01). A significant positive correlation between the OC, PTH, CT and APL values and foal's age was found in fillies and colts. PTH levels were positively correlated with the values of OC in fillies and colts. Obtained findings confirmed the dynamic bone turnover during growth in foals. The modification of PTH and OC confirmed the potential role of these parameters as indicator of bone growth and metabolism. The sex-related difference observed in OC concentration opens up new insights into the possible involvement of sex hormones in the regulation of bone metabolism in prepubertal foals.

Blood Biochemical Variables Found in Lidia Cattle after Intense Exercise

Simple Summary

There are limited published data in cattle on blood biological variables in response to intense work or after significant physical exertion. Stress should be considered in addition to exercise in the Lidia breed due to their agonistic behavioral characteristics. Therefore, changes in blood biological variables in response to intense exercise and stress were evaluated. Specifically, 438 bulls of the Lidia breed were sampled after a bullfight in order to determine the concentrations of different blood variables. We found that most of the measured blood variables clearly increased. Thus, severe hyperglycemia and an increase in various enzymes (LDH, AST, GGT, ALT, and particularly CK) were observed. The increase in all these variables is justified by the mobilization of energy sources, tissue and muscle damage, and dehydration, due to intense exercise and stress.

Abstract

There are limited published data in the bovine species on blood biological variables in response to intense work or after significant physical exertion. Lidia cattle, in addition to their exercise components, have some behavioral agonistic features that make them more susceptible to stress. The bullfight involves stress and exercise so intense that it causes significant changes in some metabolic variables. The study objective was to evaluate changes in blood biological variables in response to intense exercise and stress. After the fight in the arena, and once the bulls were dead (n = 438), blood samples were taken, and some biochemical and hormonal variables were determined in venous blood. A descriptive analysis was performed using the Statistica 8.0. computer program. The mean (±s.d.) results obtained were: total protein (85.8 ± 10.8 g/dL), albumin (3.74 ± 4.3 g/dL), triglycerides (39.65 ± 0.16 mg/dL), cholesterol (2.44 ± 0.03 mmol/L), glucose (22.2 ± 9.6 mmol/L), uric acid (340 ± 80 µmol/L), creatinine (236.9 ± 0.4 µmol/L), urea (5.93 ± 1.27 mmol/L), LDH (2828 ± 1975 IU/L), CK (6729 ± 10,931 IU/L), AST (495 ± 462 IU/L), ALP (90 ± 33 IU/L), GGT (50 ± 34 IU/L), ALT (59 ± 35 IU/L), cortisol (117.5 ± 46.6 nmol/L), and testosterone (20.2 ± 23.8 nmol/L). Most of the measured variables clearly increased; thus, we found severe hyperglycemia and increases in LDH, AST, GGT, and ALT enzymes, particularly in CK. The increases in all these variables are justified by the mobilization of energy sources, tissue/muscle damage, and dehydration due to continued stress and intense exercise.

Occipital condyle defects assessed by radiography or CT can be a normal finding in foals

Age of complete ossification of equine occipital condyles has not been published. Consequently, clinical significance of occipital condyle defects on radiographs or CT scans of young horses remains unknown. The goals of this single-center, retrospective, cross-sectional study were to characterize incidental occipital condyle defects and to define the age of complete ossification. The margin of occipital condyles was classified as regular or with defect(s). Analyses were made on 121 horses, including 106 radiographic and 19 CT studies showing the occipital condyles of horses less than 5 years of age obtained over 6 years in a referral hospital. Neurological signs and outcome were not associated with occipital defects. Horses with regular occipital condyles on radiographs had a median age of 974 days (median interquartile range = 707) compared with 47 days (interquartile range = 106) in the defect group. The odds of finding radiographically regular occipital condyles were 2.6% higher for each additional day of age (P = .011, 95% CI, 0.6-4.7%). In the CT group, univariate analyses demonstrated a significant effect of age on the aspect of occipital condyles (P = .016). Horses with regular occipital condyles were older (median age = 881 days; interquartile range = 1054) than horses with a defect (median age = 109 days, interquartile range = 318). All horses above 156 days (5.1 months) of age and 550 days (18.1 months) of age had regular occipital condyles on radiographic and CT images, respectively. This study describes occipital condyle defects as a potential normal finding in young horses and provides guidelines for interpretation of the occipital condyle ossification process.

Different effects of an extended photoperiod treatment on growth, gonadal function, and condition of hair coats in Thoroughbred yearlings reared under different climate conditions

One- to two-year-old Thoroughbred colts and fillies being reared in Miyazaki (warm climate) and Hidaka (cold climate), Japan, were administered extended photoperiod (EP) treatment between December 20 and the following April 10, and its effect on growth, endocrine changes, gonadal activation, and hair coat condition was investigated. In colts reared in Miyazaki, no effect of EP treatment was noted on the growth indices, including body weight (BW), height at withers (HW), girth, and cannon circumference (CC), whereas the BWs and CCs of fillies were significantly higher in the EP treatment group than the control. In Hidaka, the BWs and HWs of colts and HWs of fillies were significantly higher in the EP treatment group. Gonadal activation characterized by an increase in circulating hormone concentrations was earlier in the EP treatment group for fillies reared in Miyazaki [luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone (P4), and estradiol-17β (E2)] and in colts (LH, testosterone, and E2) and fillies (LH, FSH, P4, and E2) reared in Hidaka. Regardless of sex and climate, prolactin was significantly higher in the EP treatment group, whereas insulin-like growth factor (IGF-I) was not. Initial ovulation occurred before April in more of the EP treatment group than the control regardless of the climate. Molting of the hair coat, examined in March, was advanced in the EP treatment group regardless of sex and climate. These results suggest that EP treatment may promote growth and gonadal activation in fillies reared in Miyazaki and in colts and fillies reared in Hidaka and that the effect may be mediated by prolactin.

Immunolocalization of aromatase in stallion Leydig cells and seminiferous tubules

High levels of plasma estrogens constitute an endocrine peculiarity of the adult stallion. This is mostly due to testicular cytochrome p450 aromatase, the only irreversible enzyme responsible for the bioconversion of androgens into estrogens. To identify more precisely the testicular aromatase synthesis sites in the stallion, testes from nine horses (2-5 years) were obtained during winter or spring. Paraplast-embedded sections were processed using rabbit anti-equine aromatase, followed by biotinylated goat anti-rabbit antibodies, and amplified with a streptavidin-peroxidase complex. Immunoreactivity was detected with diaminobenzidine. Immunofluorescence detection, using fluoroisothiocyanate-conjugated goat anti-rabbit antibodies, was also applied. Specific aromatase immunoreactivity was observed intensely in Leydig cells but also for the first time, to a lesser extent, in the cytoplasm surrounding germ cells at the junction with Sertoli cells. Interestingly, the immunoreactivity in Sertoli cells appears to vary with the spermatogenic stages in the basal compartment (with spermatogonia) as well as in the adluminal one (with spermatids). Relative staining intensity in Leydig and Sertoli cells and testicular microsomal aromatase activity increased with age. The present study in stallions indicates that in addition to Leydig cells, Sertoli cells also appear to participate in estrogen synthesis, and this could play a paracrine role in the regulation of spermatogenesis.