Cristina Cravana

Effects of competition experience and transportation on the adrenocortical and thyroid responses of horses

To evaluate whether the amount of experience of sport horses and the stress of transport affected their adrenocortical and thyroid responses, the plasma concentrations of total cortisol and total and free iodothyronine of 63 horses were studied before and after show jumping competitions. There were 14 trained inexperienced jumpers (group 1), 20 trained experienced jumpers (group 2), 10 trained inexperienced jumpers that had been transported just before the competition (group 3) and 19 trained experienced jumpers that had been transported just before the competition (group 4). The concentrations were measured under basal conditions and five and 30 minutes after the competition. There were significant increases relative to the basal values in the total cortisol concentrations of all four groups of horses at five and 30 minutes (P<0·001), but there were no significant differences between the groups. In contrast, there were no significant changes in the concentrations of triiodothyronine, thyroxine and free thyroxine after the competition and there were no significant differences between the groups. However, the horses in group 2 had significantly lower basal concentrations of free triiodothyronine than the horses in groups 1, 3 and 4 and the difference was maintained at five and 30 minutes after the competition.

Comparative endocrinological responses to short transportation of Equidae (Equus asinus and Equus caballus)

In order to evaluate the effects of short transportation on β-endorphin, adrenocorticotropic hormone (ACTH) and cortisol changes, 12 healthy stallions of Equidae (Equus asinus and Equus caballus) were studied before and after transportation of 50 km. Blood samples were collected 1 week before transportation in basal conditions, immediately before loading and after transportation and unloading, on their arrival at the breeding station. Compared to basal and before values, donkeys showed an increase in circulating ACTH (P < 0.001) and cortisol (P < 0.0005) levels after transportation and higher ACTH (P < 0.01) levels than horses after transportation. A positive and significant correlation (r = 0.885; P < 0.01) between ACTH and cortisol levels after transportation was found. No significant differences were observed for β-endorphin levels. Compared to basal and before values, horses showed higher cortisol (P < 0.005) levels after transportation and no significant differences were observed for ACTH and β-endorphin levels in donkeys. Horses facing forward (direction of travel) showed higher (P < 0.01) β-endorphin levels after transportation than donkeys; horses facing backward (the opposite direction of travel) showed lower (P < 0.05) ACTH levels after transportation. The results indicate that short transportation induces a preferential activation of the hypothalamus-pituitary-axis (HPA), with significant release of ACTH and cortisol in donkeys and only of cortisol in horses, suggesting that transportation for donkeys may be more stressful than horses.

Effects of competitive and noncompetitive showjumping on total and free iodothyronines, β-endorphin, ACTH and cortisol levels of horses

REASONS FOR PERFORMING STUDY Limited knowledge exists about the differentiated effects of competitive and noncompetitive showjumping on thyroid function and relationships with hypothalamic-hypophysis-corticoadrenal hormones. OBJECTIVES To obtain preliminary data about differentiated effects of competitive and noncompetitive showjumping on total and free iodothyronines, β-endorphin, ACTH and cortisol of horses. MATERIAL AND METHODS Five trained healthy jumper horses were studied during competitive and noncompetitive showjumping, performed in the same circuit design over 10 fences of 1.10 m. Hormone levels before, 5 and 30 min post exercise were recorded. Serum iodothyronines and cortisol concentrations were measured in duplicate utilising EIA kits. Serum ACTH and plasma β-endorphin concentrations were analysed in duplicate utilising RIA kits. Two-way RM ANOVA was applied to test for effects of interaction between different type of session and time. Significant differences between post exercise and basal values were established using Bonferronis multiple comparison test. A linear correlation analysis (Pearsons method) was performed to analyse the relationships between total and free iodothyronines and between iodothyronines and β-endorphin, ACTH and cortisol. RESULTS In sampling times adopted no statistical different effects of type of session were recorded on hormone variables. Sampling time affected ACTH (F = 4.25; P < 0.02) and T(4) (F = 4.43; P < 0.02) post exercise changes. During the noncompetitive session, significant correlations existed between T(4) and β-endorphin (r = -0.56), ACTH (r = -0.65), between β-endorphin and ACTH (r = 0.52) and between T(3) and fT(3) (r = 0.72); during competition between β-endorphin and T(3) (r = -0.67), fT(3) (r = -0.59). CONCLUSIONS These preliminary results could demonstrate correlations between thyroid hormones and β-endorphin response to showjumping, although no definitive conclusion can be produced concerning the relationships between HPA and thyroid function during exercise.

Physiological variables of horses after road transport.

In order to investigate the effects of short road transport stress on total and free iodothyronines, body weight (BW), rectal temperature and heart rate (HR) changes, 126 healthy stallions were studied in basal conditions, before and after transport. A total of 60 Thoroughbred and 66 crossbred stallions aged 4 to 15 years with previous travelling experience were transported by road in a commercial trailer for a period of about 3 to 4 h (distance under 300 km). Blood samples and functional variables were collected in each horse box, one week before loading and transport in basal conditions (control samples), one week later immediately before loading (pre-samples) and again after transport and unloading (about 3 to 4 h) in each new horse box, within 30 min of their arrival at the breeding stations (post-samples). Compared to the before-transport values, increases in circulating T3, T4 and fT4 levels (P < 0.01) were observed after transport, irrespective of breed, but not for fT3 levels. Lower T4 and fT4 levels were observed in basal II (at 1100 h) (P < 0.01) than in basal I (at 0800 h) conditions and before transport. Thoroughbreds showed higher fT3 (P < 0.05) and fT4 (P < 0.01) levels after transport than crossbred stallions. No significant differences were observed for T3 and T4. Compared to the before-transport values, significant increases in rectal temperature (P < 0.01) and HR (P < 0.05) were observed after transport. No differences were observed between basal I, II and before values for functional variables. Significant correlations between T3 and rectal temperature, BW and HR were found. The results indicate that short road transport induces a preferential release of T3, T4 and fT4 hormones from the thyroid gland in relation to different breed, and an increase in rectal temperature and HR. No significant changes in BW were observed. No differences were observed in relation to different ages. The data obtained suggest that the stallions thyroid hormones and functional variables may play an important role in assessing the effects of transport stress and a horses coping strategy.

Influence of endemic goitre areas on thyroid hormones in horses

The aim of this study was to investigate thyroid hormone levels in horses stabled in two different locations on the island of Sicily. The study was carried out on a total of 72 clinically healthy Sanfratellano horses ranging in age from 5 to 9 years and weighing 585 ± 40 kg. The results showed higher thyroxine values (P < 0.02) in horses stabled in an endemic goitre area (group II) than those observed in horses in a non-endemic area (group I). Unexpectedly, the T(4)/T(3) and the fT(4)/fT(3) rations were both lower in group I than in group II. The percentages of fT(4) to T(4) and of fT(3) to T(3) were both higher in group I than the percentages for group II. On the basis of gender, comparison between the two groups showed higher T(4) (P < 0.01) and fT(4) levels (P < 0.001) in males, and lower fT(3) (P < 0.001) and fT(4) levels (P < 0.005) in females stabled in the goitre endemic area. On the basis of age, younger horses (<7 years old) showed the highest thyroid hormone levels in both groups. Results suggest a physiological adaptive response of the equine species to an endemic goitre environment. The possibility that hypothyroidism is present in these horses is thus excluded and is supported not only by the lack of clinical signs, but also by the rarity of cases previously reported.

Effects of weaning on total and free iodothyronines in lambs

Background: Weaning is a crucial period in the management of lambs, resulting in physiological and mental challenges, that may have prolonged effects on lambs health and welfare. Hypothesis/Objectives: To evaluate the effect of weaning on total and free triiodothyronine (T3, fT3) and thyroxine (T4, fT4) concentrations in serum of lambs by enzyme immunoassay. Animal and methods: The study was performed on two groups of 17 clinically healthy Comisana cross-bred lambs (7 males and 10 females) with or without weaning at 10 weeks of age. Serum samples were collected at the age of 8 weeks, 24 h and 2 weeks after weaning in the experimental group and at similar times in the non-weaned control group. Enzyme immunoassay was performed. Statistical analysis was done by one-way analysis of variance. Results: Compared to control animals, weaned animals showed significantly decreased T3 and elevated T4 concentrations two weeks after weaning with higher concentrations in both males and females in contrast to 24 h after weaning. Body weight (BW) was significantly restored in both females (11% increase) and males (6%) two weeks after weaning as compared to 24 h after weaning. No gender effects were shown for total and free iodothyronine changes. Significant positive correlations were observed between BW and T4 concentrations in both females (r = 0.692) and males (r = 0.856), fT3 concentrations in males (r = 0.968) and fT4 concentrations in females (r = 0.862). Conclusion and clinical importance: Total iodothyronines could represent an indicator of their different metabolic activity with their magnitude altered two weeks following weaning.

The effect of training sessions and feeding regimes on neuromodulator role of serotonin, tryptophan, and β-endorphin of horses

ABSTRACT We tested the hypothesis that diet affects equine feeding behavior and that diet composition affects a shift in energy metabolism characterized by a wide range of neuroendocrine changes. We investigated the effects of training sessions on circulating serotonin (5‐HT), tryptophan, and &bgr;‐endorphin (&bgr;‐EN) concentrations in horses to ascertain whether two different isoenergetic diets would affect this response. Thirty‐six Dutch Warmblood horses were randomly distinguished in 18 horses fed with a low‐fiber diet (LF) and 18 horses fed with a high‐fiber diet (HF). The training session was represented by a medium‐heavy exercise and consisted of 21 minutes/day of walk, 36 minutes/day of trot, 15 minutes/day of canter, for a total of 72 minutes/day. At the end of this session, a set exercise test was performed. There was a significant increase in plasma 5‐HT (P < 0.0001) and &bgr;‐EN (P < 0.0001) concentrations following exercise compared to baseline values, in both HF and LF groups. No significant changes were observed for plasma tryptophan concentrations after exercise. A two‐way analysis of variance showed significant effects of medium‐heavy workload exercise treatments and time points of sampling during exercise on 5‐HT and &bgr;‐EN changes. Plasma 5‐HT and &bgr;‐EN patterns are presumably linked to the workload exercise effect, as shown by their increasing trend in both HF and LF groups.

Breeding season and transport interactions on the pituitary-adrenocortical and biochemical responses of horses

ABSTRACT The aim of this study was to investigate the circulating adrenocorticotropin and cortisol changes in breeding stallions in response to road transport before and after the breeding season. Creatinine, creatine kinase (CK), aspartate aminotransferase, alanine aminotransferase, urea, and lactate dehydrogenase changes were also considered. Twenty‐seven healthy stallions were studied before and after transport over a distance of 200 km, before and after the breeding season. On the basis of the number of mares covered per stallion during the breeding season, each stallion was assigned to 2 groups: 17 stallions with a poor score, mean: 7.71 ± 4.67 mares per horse (group A); 10 stallions with a good score, mean: 35.50 ± 10.66 mares per horse (group B). Increases in circulating adrenocorticotropin concentrations were found after the first trip for group A stallions (P < 0.001), and after the first trip (P < 0.05) and return trip for group B stallions (P < 0.01). Increases in circulating cortisol concentrations were found after transport in both groups A and B (P < 0.001). Significant increases, as effect of the transport after the breeding season, were described for all biochemical parameters. Two‐way ANOVA showed significant differences between groups A and B only for increases in cortisol and CK as an effect of posttransport plus the postbreeding season. This study showed that the pituitary‐adrenocortical axis is efficiently stimulated by transport and that the breeding season augments the increase of cortisol and CK values of stallions as an effect of mental and physical arousal.

The contribution of total and free iodothyronines to welfare maintenance and management stress coping in Ruminants and Equines: Physiological ranges and reference values

In order to acquire a pattern of thyroid involvement in welfare maintenance in Ruminants and Equines, this review summarizes data concerning the reference values of total and free iodothyronines and their modifications in physiological conditions and in different management conditions (pregnancy, lactation, weaning, growth, isolation, restraint, shearing, confinement and transportation). Thyroidal and extrathyroidal tissues efficiently respond to management practices, giving a differentiated contribution to circulating iodothyronine changes. The hormonal response could be mainly attributed to the intracellular deiodination of T4 to T3. Triiodothyronine (T3) and free iodothyronines (fT3 and fT4) result more responsive to management stress, showing different pattern with species and to various conditions, as to environmental conditions in which activities are performed. Intrinsic seasonal changes of iodothyronines and a significant pregnancy effect for T3 were recorded in mares. Higher, although not significant, T3 and T4 concentrations in barren than pregnant mares were observed in donkeys. A positive significant correlation between T3 and T4 was described only in pregnant donkeys. Moreover, a significant effect of season on T3 and fT3 changes was observed both in pregnant and barren donkeys. A significant lactating effect compared with nonlactating stage for T3 and T4 was recorded in mares. In growing foals, body weight (BW) and age were positively correlated with T3 and negatively correlated with T4, fT4 and fT3. Weaning effects were shown for T3 and fT4 concentrations, indicating that weaning represents a severe stress and the presence of conspecific does not reduce psychological stress in this phase. Lambs showed significant decreased T3 and elevated T4 concentrations two weeks after weaning, with higher concentrations in both males and females compared to 24 h. Significant positive correlations were observed between BW and T4, fT3 and fT4 concentrations in lambs. A T3 decrease was detected after isolation, such as induced by confinement and weaning in lambs. Higher T3 concentration after restraint and shearing than after isolation and significant increases in T4, fT3 and fT4 values after restraint and shearing were recorded. The basal concentrations of fT3 in both the inexperienced and experienced transported horses were significantly higher than in untransported experienced horses. Moreover, increases of T3, T4 and fT4 after short road transportation, and significant correlations between T3 and rectal temperature (RT), body weight (BW) and heart rate (HR), confirmed their important role in coping strategy. Thyroid responsiveness to short transport is similar in domestic donkeys and horses, with a preferential release of T3 in horses. A greatest and constant release of T3 and T4, although differentiated, after simulated transportation and after conventional transport of horses confirmed that the degree of stress induced by confinement and additional stressful stimuli associated to road transportation could differently influence the iodothyronine release. Temperamental Limousin young beef bulls showed lower T4 and fT4 concentrations after prolonged transportation than calm subjects, and a concomitant decrease of circulating ACTH, cortisol, T3 and fT3 concentrations, probably induced by down regulation of HPA axis and cortisol negative feedback. These data reinforce the importance of taking into account the evaluation of iodothyronines, and notably of T3, as markers of welfare and stress and their role in ensuring energy homeostasis and productive and reproductive performances in Ruminants and Equines.

The Role of Circulating β-endorphin in Different Stress Models in Equines: A Review

ABSTRACT To evaluate whether &bgr;‐endorphin (&bgr;‐END) is a reliable marker of stress in equines, the reference values and changes in different models of stress (exercise, transportation) have been considered. Baseline circulating &bgr;‐END concentrations of horses showed seasonal and circadian fluctuations. Increased &bgr;‐END concentrations were associated with the severity and type of exercise stress and were positively correlated with both exercise speed and intensity. Positive correlations between &bgr;‐END or adrenocorticotropic hormone (ACTH) and cortisol were recorded after competitive and experimental jumping over different fence height, related to the emotional content of trials. In Standardbreds, an exercise effect on &bgr;‐END changes during both training and competition emerged. In trained horses, after exercise with psychomotor disables, no &bgr;‐END and ACTH changes were detected. After short road transport (100 km), concomitant variations in &bgr;‐END and ACTH concentrations suggested the effect of loading and confinement. In experienced stallions, after simulated transport, higher &bgr;‐END concentrations than basal, while lower concentrations than after conventional transport, were recorded. Positive correlations among &bgr;‐END, ACTH, and cortisol changes in both conventional and simulated transport were observed. After a very short road transportation (50 km), no significant differences in &bgr;‐END concentrations were recorded in experienced equines. Horses facing forward had significantly higher &bgr;‐END concentrations than horses facing backward. It can be supposed that, in equines, &bgr;‐END is released during the early stages of stress, so improving the hormonal cascade of hypothalamic–pituitary–adrenal axis and &bgr;‐END could facilitate the active coping strategies under stressful conditions and can be regarded as a precocious marker of stress. HIGHLIGHTS&bgr;‐endorphin in Equines is released during the early stages of stress.The contribution of &bgr;‐endorphin increase is to facilitate the hormonal cascade of HPA axis.Exercise stress produces increased concentrations of &bgr;‐endorphin, according to type and severity of exercise.Loading and confinement associated to transport stress produces increased concentrations of &bgr;‐endorphin.