Circadian rhythm in horses refers to the natural, internal process that regulates the sleep-wake cycle and other physiological patterns within approximately a 24-hour period. This biological rhythm is influenced by environmental cues such as light and temperature, impacting various aspects of equine behavior and physiology, including feeding, hormone release, and activity levels. In horses, the circadian rhythm helps coordinate daily activities and physiological functions to optimize performance and health. This topic encompasses research studies and scholarly articles that explore the mechanisms underlying circadian rhythms in horses, their effects on behavior and health, and the potential implications for equine management and welfare.
Ayodele BA, Pagel CN, Mackie EJ, Armour F, Yamada S, Zahra P, Courtman N, Whitton RC, Hitchens PL.Musculoskeletal injuries (MSI) are common in racehorses and have been of increasing concern in horses travelling internationally to compete. Understanding the differences in bone turnover between local horses and international horses following long-distance air transportation may inform MSI prevention strategies. Objective: To understand the differences in bone turnover markers and risk of MSI between local horses and international horses following long-distance air transportation. Methods: Prospective cohort. Methods: The concentrations of bone turnover markers (OCN and CTXI), markers of stre...
Carvalho Seabra J, Martinez do Vale M, Spercoski KM, Hess T, Patricio Viviani de Moura P, Dittrich JR.Keeping horses in single stalls can lead to the development of abnormal and stereotypic behaviors (ASB). Opportunities for social interactions and stall architecture can influence behavior. The current study aimed to identify how three different stall architectures influenced time-budget and physiological parameters in horses. Stall types included: (1) 3.2 × 3.7 m with tactile contact between horses (B1); (2) 2.6 × 3.5 m with visual contact between horses and outside view (B2); (3) 2.3 × 3.4 m with visual contact and outside view (B3). Ten horses from B1 and B3, and nine from B2 were ...
Collery A, Browne JA, O'Brien C, Sheridan JT, Murphy BA.Hair follicles (HF) represent a useful tissue for monitoring the circadian clock in mammals. Irregular light exposure causes circadian disruption and represents a welfare concern for stabled horses. We aimed to evaluate the impact of two stable lighting regimes on circadian clock gene rhythmicity in HF from racehorses. Two groups of five Thoroughbred racehorses in training at a commercial racehorse yard were exposed to standard incandescent light or a customized LED lighting system. The control group received light from incandescent bulbs used according to standard yard practice. The treatment...
During husbandry, domestic animals are exposed to many factors that can influence their circadian physiology organization leading to an increase in animals' discomfort. Thermal homeostasis is at the basis of animal wellness, the aim of the present study was to investigate the daily fluctuation of serum concentrations of 3,5,3'-triiodothyronine (T3) and thyroxine (T4) in association with the daily fluctuation of uncoupling protein 1 (UCP1) and clock gene Per2 in healthy horses housed in individual box, to improve the knowledge on this matter. Seven clinically healthy female Italian Saddle horse...
Giannetto C, Aragona F, Arfuso F, Piccione G, De Caro S, Fazio F.Thermoregulation is an important mechanism to ensure thermal homeostasis. In horses, different housing conditions could influence this mechanism by exposing animals to different microclimates. The circadian rhythm of body temperature is well known. For this reason, we wanted to investigate the daily rhythm of cutaneous (jugular, shoulder, inner thigh and croup) temperature in comparison to rectal temperature in athletic horses kept under two different housing conditions. Ten clinically healthy Italian Saddle horses were divided into two equal groups: the first group was housed in individual bo...
Giannetto C, Arfuso F, Giudice E, Di Pietro S, Piccione G.Recent studies evidenced that the circadian rhythm of Per2 is involved in adaptive thermogenesis by the modulating transcription of uncoupling protein 1 (UCP1). For this purpose, we investigated the linkage between the daily rhythm of Per2 and UCP1 in ruminant and non-ruminant mammalian species. Five clinically healthy, not pregnant, and not lactating Maltese female goats and five clinically healthy, not pregnant, and not lactating Italian Saddle horses were enrolled in the study. All animals were housed under natural photoperiod (sunrise 05:05, sunset 20:55) and environmental temperature and ...
Contreras-Aguilar MD, Lamy E, Escribano D, Cerón JJ, Tecles F, Quiles AJ, Hevia ML.This study aims to evaluate the circadian and circannual variations in a panel of analytes in horse saliva that have been previously described as biomarkers related to stress and disease, in order to interpret them correctly when they are measured in this species. This panel of analytes integrated cortisol, salivary alpha-amylase (sAA), lipase (Lip), total esterase (TEA), butyrylcholinesterase (BChE), adenosine deaminase (ADA), γ-glutamyl transferase (gGT), creatine kinase (CK), urea, total bilirubin, total protein (TP), and phosphorus. These analytes were measured in saliva obtained from a p...
Giannetto C, Carcangiu V, Luridiana S, Parmeggiani A, Piccione G.Photoperiodic treatments have been of practical interest in controlling seasonal reproduction in sheep, goats and horses. Melatonin is the principal mediator of the environmental photoperiodic message. To investigate the intra- and inter-subject variability of melatonin 24 h rhythm, ten female Italian Saddle horses (8-10 yrs old, mean body weight 525 ± 30 kg), ten female Sarda breed sheep (2-3 yrs old, mean body weight 40.5 ± 2.8 kg) and ten female Sarda breed goats (3-4 yrs old, mean body weight 38.9 ± 4.1 kg), housed individually in a 4 × 4 m soundproof box equipped with 50 Ã...
Giannetto C, Fazio F, Alberghina D, Giudice E, Piccione G.In mammals, behavioral and physiological processes display 24-hour rhythms that are regulated by the circadian system. In the present study, we investigated clock gene expression in peripheral leukocytes in horses. For this purpose, 10 Italian Saddle gelding horses (9-11 years old; 475 ± 28 Kg) were housed in individual boxes under natural photoperiod and natural environmental temperature. Blood samples were collected at 4-hour intervals over a 48-hour period. The day before the start of sampling, left jugular furrow of each horse was cannulated for the blood sample collection performed in ...
Murphy BA, O'Brien C, Elliott JA.Exposure to white light at night suppresses melatonin production, impacts circadian rhythms and contributes to ill-health in humans. Human interaction with horses frequently occurs at night. We tested the hypothesis that dim red light would not suppress the nightly rise in serum melatonin levels in horses. In a crossover design, six horses were maintained for consecutive 48h periods under a Light: Red (LR) and a Light: Dark (LD) photo-schedule. Transitions from light (>200lux, polychromatic white light) to red (5lux, peak wavelength 625nm) or dark (0.05). A robust main effect of time (P<...
Waddington B, Penitente-Filho JM, Neves J, Pinho RO, Chaya AY, Maitan PP, Silveira CO, Neves MG, Guimarães S, de Carvalho GR, Guimarães JD.This study was conducted to characterize the daily profile of testosterone secretion and its mean concentrations in the four seasons as well as to evaluate the semen characteristics and testicular biometry of Mangalarga Marchador stallions throughout the year in a tropical region. Three stallions were submitted to semen collections and evaluation of testicular biometry every 14 days along a year. Blood samples were collected once at the middle of each season, in a 20-min interval during 24 hr in order to evaluate the testosterone secretion profiles among seasons. Testosterone concentrations ...
van der Kraan PM.Osteoarthritis (OA) is the most common joint disease but an effective pharmacological therapy has not been developed yet. To identify targets for treatment and ways to interfere with OA development and progression both spontaneous and induced OA models are still needed. In this narrative review it is discussed what variables can be identified that lead to variation in OAÂ animal model studies. Literature was screened (Pubmed) with the following terms; OA animal models in combination with species, age, strain, gender/sex, housing, diet, fighting, circadian rhythm, transgenic. Relevant articles ...
Azarpeykan S, Dittmer KE, Gee EK, Marshall JC, Elder P, Acke E, Thompson KG.A study was conducted to determine the circadian rhythms and trends of vitamin D metabolites including 25-hydroxyvitamin D3 , 25-hydroxyvitamin D2 , 1,25-dihydroxyvitamin D and parathyroid hormone, in addition to serum calcium, phosphorus and magnesium concentrations in horses over 48Â h on the shortest and longest days of the year in 2013. Five healthy adult horses (Equus caballus) were on a constant pasture feeding regimen, and blood samples were collected from each horse every 3Â h over a 48-h period, starting at 07:00Â PM on day one and finishing at 07:00Â PM on day three, for the measurem...
Murphy BA, Wagner AL, McGlynn OF, Kharazyan F, Browne JA, Elliott JA.Circadian rhythms are endogenously generated 24-h oscillations that coordinate numerous aspects of mammalian physiology, metabolism and behaviour. The existence of a molecular circadian clock in equine skeletal muscle has previously been demonstrated. This study investigates how the circadian 24-h expression of exercise-relevant genes in skeletal muscle is influenced by a regular exercise regime. Mid-gluteal, percutaneous muscle biopsies were obtained over a 24-h period from six Thoroughbred mares before and after an 8-week exercise programme. Real-time qPCR assays were used to assess the expr...
Rendle DI, Litchfield E, Heller J, Hughes KJ.There is little published information on whether measurement of plasma ACTH concentration at a single timepoint is a repeatable indicator of pituitary pars intermedia dysfunction (PPID). Objective: To determine whether ultradian or circadian fluctuations in ACTH production influence plasma ACTH concentration in normal horses and horses with PPID. Methods: Prospective observational study. Methods: Plasma ACTH concentration in 8 non-PPID horses and 8 horses with PPID was measured at 08.00, 11.00, 14.00 and 17.00 h on 5 nonconsecutive days within a 3 week period. In addition, at 08.30 h on one da...
Bohák Z, Szabó F, Beckers JF, Melo de Sousa N, Kutasi O, Nagy K, Szenci O.Daily fluctuations of cortisol concentration in the blood or saliva have been repeatedly reported. However, several contradictions in the existing literature appear on this subject. The present study was performed to definitively establish options for testing adrenocortical function. To the best of our knowledge, this is the first study to evaluate parallel circadian rhythms in salivary and serum cortisol concentrations during a 24-h period. Twenty horses were examined under the same conditions. Blood and saliva samples were taken every 2 h for 24 h to determine the daily changes in cortisol c...
Watts LM, Browne JA, Murphy BA.A comprehensive understanding of the equine circadian clock involves the evaluation of circadian clock gene expression. A non-invasive and effective method for detecting equine clock gene expression has yet to be established. Currently, research surrounding this area has relied on collecting tissue biopsies or blood samples that can often be costly, time consuming and uncomfortable for the animal. Methods: Five mares were individually stabled under a light-dark (LD) cycle that mimicked the external environmental photoperiod during a time of year corresponding with the vernal equinox. Hair foll...
Cordero M, Brorsen BW, McFarlane D.Cosinor analysis was used to evaluate whether pituitary and adrenal hormones exhibit circadian rhythmicity in horses. The effect of season and animal age on their respective rhythms was also determined. In addition, the usefulness of evaluating cortisol rhythmicity for the diagnosis of pituitary pars intermedia dysfunction (PPID) was assessed. Serum cortisol concentrations (P < 0.01), but not plasma ACTH or α-melanocyte-stimulating hormone (α-MSH), showed a significant circadian periodicity in horses. An effect of season on hormone concentration was observed with plasma ACTH and α-MSH co...
Ohmura H, Boscan PL, Solano AM, Stanley SD, Jones JH.To determine whether withholding of food affects autonomic nervous system balance by analysis of heart rate (HR), HR variability (HRV), and frequency of second-degree atrioventricular block in horses. Methods: 5 healthy Thoroughbreds. Methods: For two 24-hour periods in a crossover study, food was withheld from horses or horses were maintained on their regular feeding schedule (control conditions) in their stalls and Holter monitor ECG recordings were obtained. The ECGs were analyzed by use of fast-Fourier transformation, and power spectrum densities were calculated for low-frequency (0.01 to ...
Hemmann K, Raekallio M, Kanerva K, Hänninen L, Pastell M, Palviainen M, Vainio O.Crib-biting is classified as an oral stereotypy, which may be initiated by stress susceptibility, management factors, genetic factors and gastrointestinal irritation. Ghrelin has been identified in the gastric mucosa and is involved in the control of food intake and reward, but its relationship to crib-biting is not yet known. The aim of this study was to examine the concentration and circadian variation of plasma ghrelin, cortisol, adrenocorticotropic hormone (ACTH) and β-endorphin in crib-biting horses and non-crib-biting controls. Plasma samples were collected every second hour for 24h in ...
Tortonese DJ, Preedy DF, Hesketh SA, Webb HN, Wilkinson ES, Allen WR, Fuller CJ, Townsend J, Short RV.Abrupt alterations in the 24-h light : dark cycle, such as those resulting from transmeridian air travel, disrupt circadian biological rhythms in humans with detrimental consequences on cognitive and physical performance. In the present study, a jetlag-simulated phase shift in photoperiod temporally impaired circadian peaks of peripheral clock gene expression in racehorses but acutely enhanced athletic performance without causing stress. Indices of aerobic and anaerobic capacities were significantly increased by a phase-advance, enabling prolonged physical activity before fatigue occurred. Thi...
Piccione G, Giannetto C, Marafioti S, Faggio C, Alberghina D, Fazio F.The aim of this study was to evaluate the daily rhythms of peroxidative parameters in untrained and trained horses. Blood samples were collected every 4 h for a 48-h period for the determination of reactive oxygen metabolites test (d-ROMs), antioxidant barrier (Oxy-ads), thiol antioxidant barrier (SHp) and lipid peroxidation (LPO). Two-way anova showed a significant effect of time of day on all parameters studied, except on LPO. Higher values of Oxy-ads and SHp were observed in trained horses during both days of monitoring (p < 0.01). All studied parameters, except for LPO, showed rob...
Murphy BA, Martin AM, Furney P, Elliott JA.In contrast to studies showing gradual adaptation of melatonin (MT) rhythms to an advanced photoperiod in humans and rodents, we previously demonstrated that equine MT rhythms complete a 6-h light/dark (LD) phase advance on the first post-shift day. This suggested the possibility that melatonin secretion in the horse may be more strongly light-driven as opposed to endogenously rhythmic and light entrained. The present study investigates whether equine melatonin is endogenously rhythmic in extended darkness (DD). Methods: Six healthy, young mares were maintained in a lightproof barn under an LD...
Martin AM, Elliott JA, Duffy P, Blake CM, Ben Attia S, Katz LM, Browne JA, Gath V, McGivney BA, Hill EW, Murphy BA.Circadian rhythms are innate 24-h cycles in behavioral and biochemical processes that permit physiological anticipation of daily environmental changes. Elucidating the relationship between activity rhythms and circadian patterns of gene expression may contribute to improved human and equine athletic performance. Six healthy, untrained mares were studied to determine whether locomotor activity behavior and skeletal muscle gene expression reflect endogenous circadian regulation. Activity was recorded for three consecutive 48-h periods: as a group at pasture (P), and individually stabled under a ...
Murphy BA.The circadian system provides animals with a means to adapt their internal physiology to the constantly changing environmental stimuli that exist on a rotating planet. Light information is translated into molecular timing mechanisms within pacemaker cells of the mammalian hypothalamic suprachiasmatic nucleus (SCN) via transcriptional-translational feedback loops. Humoral and neural outputs from this 'master' clock result in circadian rhythms of physiology and behaviour. The larger circadian system involves SCN synchronisation of cellular clocks throughout the organism such that individual orga...
Piccione G, Assenza A, Borruso M, Fazio F, Caola G.In the sport field, non-esterified fatty acids (NEFA) are important for the physical performance during the aerobic exercise of short intensity and long duration. In man, rat, goat and in the sedentary horse studies on the chronometabolism showed the presence of a circadian rhythm of the plasmatic concentration of NEFA while data for the athletic horse are lacking. To define a chronogram helpful for a specific planning and the differentiation of the training programmme in the athletic horse, the circadian pattern of some fatty acids (NEFA, palmitic, stearic, oleic, linoleic and linolenic acids...
Bertolucci C, Giudice E, Fazio F, Piccione G.The present study was undertaken to investigate the existence of intraocular pressure (IOP) rhythms in athletic thoroughbred horses maintained under a 24 h cycle of light and darkness (LD) or under constant light (LL) or constant dark (DD) conditions. We identified an IOP circadian rhythm that is entrained to the 24 h LD cycle. IOP was low during the dark phase and high during the light phase, with a peak at the end of the light phase (ZT10). The circadian rhythm of IOP persisted in DD (with a peak at CT9.5), demonstrating an endogenous component in IOP rhythm. As previously shown in other mam...
Piccione G, Giannetto C, Assenza A, Casella S, Caola G.We examined the response to exercise of selected physiological variables in horses performing the identical routine for eight days, in the morning (a.m.) or in the afternoon (p.m.). Heart rate (HR), systolic and diastolic blood pressure (BP), and body temperature (BT) were all consistently greater in the p.m. For BP and BT, the absolute increase above the a.m. values was the same at rest and during exercise. For HR, the absolute increase was greater during exercise, but the percent increase was the same as during rest. During exercise, blood glucose decreased, while blood lactate and skin temp...
Piccione G, Giannetto C, Fazio F, Giudice E.This study was designed to assess the daily rhythm of tear production in clinically healthy horses, to compare left eye and right eye, and to evaluate the influence of time and gender. Methods: For our study 18 horses (nine female and nine male) were subjected to three different light/dark (L/D) schedules: 12/12 L/D cycles, constant light (24/0 L/D) and constant darkness (0/24 L/D). Methods: In all subjects Schirmer tear tests were performed at 4-h intervals over a 24-h period. Results: A circadian rhythm of tear production was found during the 12/12 L/D period and during constant darkness. Al...
Bohák Z, Szabó F, Beckers JF, Melo de Sousa N, Kutasi O, Nagy K, Szenci O.Daily fluctuations of cortisol concentration in the blood or saliva have been repeatedly reported. However, several contradictions in the existing literature appear on this subject. The present study was performed to definitively establish options for testing adrenocortical function. To the best of our knowledge, this is the first study to evaluate parallel circadian rhythms in salivary and serum cortisol concentrations during a 24-h period. Twenty horses were examined under the same conditions. Blood and saliva samples were taken every 2 h for 24 h to determine the daily changes in cortisol c...
van der Kraan PM.Osteoarthritis (OA) is the most common joint disease but an effective pharmacological therapy has not been developed yet. To identify targets for treatment and ways to interfere with OA development and progression both spontaneous and induced OA models are still needed. In this narrative review it is discussed what variables can be identified that lead to variation in OAÂ animal model studies. Literature was screened (Pubmed) with the following terms; OA animal models in combination with species, age, strain, gender/sex, housing, diet, fighting, circadian rhythm, transgenic. Relevant articles ...
Irvine CH, Alexander SL.In horses, a circadian rhythm in plasma cortisol concentrations has been reported in some but not all studies. When a rhythm occurred, horses were accustomed to a management routine, comprising stabling, feeding and sometimes exercise, which may entrain a circadian pattern. In this work, we monitored plasma cortisol by collecting jugular blood through indwelling cannulae from four groups: 1): 10 untrained, unperturbed mares grazing excess pasture, bled hourly for 26 hr; 2) 4 mares housed in a barn for 48 hr before sampling every 15 min for 20-24 hr; 3) 5 mares placed in an outdoor yard for sam...
Cordero M, Brorsen BW, McFarlane D.Cosinor analysis was used to evaluate whether pituitary and adrenal hormones exhibit circadian rhythmicity in horses. The effect of season and animal age on their respective rhythms was also determined. In addition, the usefulness of evaluating cortisol rhythmicity for the diagnosis of pituitary pars intermedia dysfunction (PPID) was assessed. Serum cortisol concentrations (P < 0.01), but not plasma ACTH or α-melanocyte-stimulating hormone (α-MSH), showed a significant circadian periodicity in horses. An effect of season on hormone concentration was observed with plasma ACTH and α-MSH co...
Piccione G, Caola G, Refinetti R.Daily or circadian oscillation has been documented in a variety of physiological and behavioral processes. Although individual variables have been studied in great detail, very few studies have been conducted on the temporal relationships between the rhythms of different variables. It is not known whether the circadian pacemaker generates each and every rhythm individually or whether most rhythms are simply derived from a few clock-controlled rhythms. As a first step in elucidating this issue, 21 physiological variables were recorded simultaneously in horse and sheep. The results indicated tha...
Martin AM, Elliott JA, Duffy P, Blake CM, Ben Attia S, Katz LM, Browne JA, Gath V, McGivney BA, Hill EW, Murphy BA.Circadian rhythms are innate 24-h cycles in behavioral and biochemical processes that permit physiological anticipation of daily environmental changes. Elucidating the relationship between activity rhythms and circadian patterns of gene expression may contribute to improved human and equine athletic performance. Six healthy, untrained mares were studied to determine whether locomotor activity behavior and skeletal muscle gene expression reflect endogenous circadian regulation. Activity was recorded for three consecutive 48-h periods: as a group at pasture (P), and individually stabled under a ...
Murphy BA, Wagner AL, McGlynn OF, Kharazyan F, Browne JA, Elliott JA.Circadian rhythms are endogenously generated 24-h oscillations that coordinate numerous aspects of mammalian physiology, metabolism and behaviour. The existence of a molecular circadian clock in equine skeletal muscle has previously been demonstrated. This study investigates how the circadian 24-h expression of exercise-relevant genes in skeletal muscle is influenced by a regular exercise regime. Mid-gluteal, percutaneous muscle biopsies were obtained over a 24-h period from six Thoroughbred mares before and after an 8-week exercise programme. Real-time qPCR assays were used to assess the expr...
Haritou SJ, Zylstra R, Ralli C, Turner S, Tortonese DJ.Equine pituitary pars intermedia dysfunction (PPID) is a common and serious condition that gives rise to Cushing's disease. In the older horse, it results in hyperadrenocorticism and disrupted energy metabolism, the severity of which varies with the time of year. To gain insight into the mechanism of its pathogenesis, 24-h profiles for peripheral plasma melatonin, serotonin, dopamine and cortisol concentrations were determined at the winter and summer solstices, and the autumn and spring equinoxes in six horses diagnosed with Cushing's disease and six matched controls. The nocturnal rises in p...
Dallaire A, Rucklebusch Y.For several weeks, three ponies kept in an environment with controlled light and temperature, were studied for behaviour (time spent in recumbency and time required to consume hay or oats) and for electrical activity of the brain (cortical and sub-cortical) during the night phase of the circadian rhythm. Recumbency was adopted by all the ponies for six or seven periods during the night. With a regimen of hay ad libitum, about four hours were cumulated in sternal recumbency and only one hour in complete lateral recumbency. Various degree of sleep, as identified by cortical and hippocampal elect...
Murphy BA, Martin AM, Furney P, Elliott JA.In contrast to studies showing gradual adaptation of melatonin (MT) rhythms to an advanced photoperiod in humans and rodents, we previously demonstrated that equine MT rhythms complete a 6-h light/dark (LD) phase advance on the first post-shift day. This suggested the possibility that melatonin secretion in the horse may be more strongly light-driven as opposed to endogenously rhythmic and light entrained. The present study investigates whether equine melatonin is endogenously rhythmic in extended darkness (DD). Methods: Six healthy, young mares were maintained in a lightproof barn under an LD...
Hemmann K, Raekallio M, Kanerva K, Hänninen L, Pastell M, Palviainen M, Vainio O.Crib-biting is classified as an oral stereotypy, which may be initiated by stress susceptibility, management factors, genetic factors and gastrointestinal irritation. Ghrelin has been identified in the gastric mucosa and is involved in the control of food intake and reward, but its relationship to crib-biting is not yet known. The aim of this study was to examine the concentration and circadian variation of plasma ghrelin, cortisol, adrenocorticotropic hormone (ACTH) and β-endorphin in crib-biting horses and non-crib-biting controls. Plasma samples were collected every second hour for 24h in ...
Bertolucci C, Giudice E, Fazio F, Piccione G.The present study was undertaken to investigate the existence of intraocular pressure (IOP) rhythms in athletic thoroughbred horses maintained under a 24 h cycle of light and darkness (LD) or under constant light (LL) or constant dark (DD) conditions. We identified an IOP circadian rhythm that is entrained to the 24 h LD cycle. IOP was low during the dark phase and high during the light phase, with a peak at the end of the light phase (ZT10). The circadian rhythm of IOP persisted in DD (with a peak at CT9.5), demonstrating an endogenous component in IOP rhythm. As previously shown in other mam...
Murphy BA, Elliott JA, Sessions DR, Vick MM, Kennedy EL, Fitzgerald BP.Rapid displacement across multiple time zones results in a conflict between the new cycle of light and dark and the previously entrained program of the internal circadian clock, a phenomenon known as jet lag. In humans, jet lag is often characterized by malaise, appetite loss, fatigue, disturbed sleep and performance deficit, the consequences of which are of particular concern to athletes hoping to perform optimally at an international destination. As a species renowned for its capacity for athletic performance, the consequences of jet lag are also relevant for the horse. However, the duration...
Bertolucci C, Giannetto C, Fazio F, Piccione G.Circadian rhythms reflect extensive programming of biological activity that meets and exploits the challenges and opportunities offered by the periodic nature of the environment. In the present investigation, we recorded the total activity of athletic horses kept at four different times of the year (vernal equinox, summer solstice, autumn equinox and winter solstice), to evaluate the presence of seasonal variations of daily activity rhythms. Athletic Thoroughbred horses were kept in individual boxes with paddock. Digitally integrated measure of total activity of each mare was continuously reco...
Rendle DI, Litchfield E, Heller J, Hughes KJ.There is little published information on whether measurement of plasma ACTH concentration at a single timepoint is a repeatable indicator of pituitary pars intermedia dysfunction (PPID). Objective: To determine whether ultradian or circadian fluctuations in ACTH production influence plasma ACTH concentration in normal horses and horses with PPID. Methods: Prospective observational study. Methods: Plasma ACTH concentration in 8 non-PPID horses and 8 horses with PPID was measured at 08.00, 11.00, 14.00 and 17.00 h on 5 nonconsecutive days within a 3 week period. In addition, at 08.30 h on one da...
Piccione G, Giannetto C, Fazio F, Giudice E.This study was designed to assess the daily rhythm of tear production in clinically healthy horses, to compare left eye and right eye, and to evaluate the influence of time and gender. Methods: For our study 18 horses (nine female and nine male) were subjected to three different light/dark (L/D) schedules: 12/12 L/D cycles, constant light (24/0 L/D) and constant darkness (0/24 L/D). Methods: In all subjects Schirmer tear tests were performed at 4-h intervals over a 24-h period. Results: A circadian rhythm of tear production was found during the 12/12 L/D period and during constant darkness. Al...
Collery A, Browne JA, O'Brien C, Sheridan JT, Murphy BA.Hair follicles (HF) represent a useful tissue for monitoring the circadian clock in mammals. Irregular light exposure causes circadian disruption and represents a welfare concern for stabled horses. We aimed to evaluate the impact of two stable lighting regimes on circadian clock gene rhythmicity in HF from racehorses. Two groups of five Thoroughbred racehorses in training at a commercial racehorse yard were exposed to standard incandescent light or a customized LED lighting system. The control group received light from incandescent bulbs used according to standard yard practice. The treatment...
Giannetto C, Fazio F, Alberghina D, Giudice E, Piccione G.In mammals, behavioral and physiological processes display 24-hour rhythms that are regulated by the circadian system. In the present study, we investigated clock gene expression in peripheral leukocytes in horses. For this purpose, 10 Italian Saddle gelding horses (9-11 years old; 475 ± 28 Kg) were housed in individual boxes under natural photoperiod and natural environmental temperature. Blood samples were collected at 4-hour intervals over a 48-hour period. The day before the start of sampling, left jugular furrow of each horse was cannulated for the blood sample collection performed in ...
Azarpeykan S, Dittmer KE, Gee EK, Marshall JC, Elder P, Acke E, Thompson KG.A study was conducted to determine the circadian rhythms and trends of vitamin D metabolites including 25-hydroxyvitamin D3 , 25-hydroxyvitamin D2 , 1,25-dihydroxyvitamin D and parathyroid hormone, in addition to serum calcium, phosphorus and magnesium concentrations in horses over 48Â h on the shortest and longest days of the year in 2013. Five healthy adult horses (Equus caballus) were on a constant pasture feeding regimen, and blood samples were collected from each horse every 3Â h over a 48-h period, starting at 07:00Â PM on day one and finishing at 07:00Â PM on day three, for the measurem...
Murphy BA, O'Brien C, Elliott JA.Exposure to white light at night suppresses melatonin production, impacts circadian rhythms and contributes to ill-health in humans. Human interaction with horses frequently occurs at night. We tested the hypothesis that dim red light would not suppress the nightly rise in serum melatonin levels in horses. In a crossover design, six horses were maintained for consecutive 48h periods under a Light: Red (LR) and a Light: Dark (LD) photo-schedule. Transitions from light (>200lux, polychromatic white light) to red (5lux, peak wavelength 625nm) or dark (0.05). A robust main effect of time (P<...
Piccione G, Assenza A, Fazio F, Percipalle M, Caola G.BACKGROUND: The serotonergic system is associated with numerous brain functions, including the resetting of the mammalian circadian clock. The synthesis and metabolism of 5-HT in the brain increases in response to exercise and is correlated with high levels of blood-borne tryptophan (TRP). The present investigation was aimed at testing the existence of a daily rhythm of TRP and 5-HT in the blood of athletic horses. METHODS: Blood samples from 5 Thoroughbred mares were collected at 4-hour intervals for 48 hours (starting at 08:00 hours on day 1 and finishing at 4:00 on day 2) via an intravenous...
Contreras-Aguilar MD, Lamy E, Escribano D, Cerón JJ, Tecles F, Quiles AJ, Hevia ML.This study aims to evaluate the circadian and circannual variations in a panel of analytes in horse saliva that have been previously described as biomarkers related to stress and disease, in order to interpret them correctly when they are measured in this species. This panel of analytes integrated cortisol, salivary alpha-amylase (sAA), lipase (Lip), total esterase (TEA), butyrylcholinesterase (BChE), adenosine deaminase (ADA), γ-glutamyl transferase (gGT), creatine kinase (CK), urea, total bilirubin, total protein (TP), and phosphorus. These analytes were measured in saliva obtained from a p...
Watts LM, Browne JA, Murphy BA.A comprehensive understanding of the equine circadian clock involves the evaluation of circadian clock gene expression. A non-invasive and effective method for detecting equine clock gene expression has yet to be established. Currently, research surrounding this area has relied on collecting tissue biopsies or blood samples that can often be costly, time consuming and uncomfortable for the animal. Methods: Five mares were individually stabled under a light-dark (LD) cycle that mimicked the external environmental photoperiod during a time of year corresponding with the vernal equinox. Hair foll...
Piccione G, Grasso F, Fazio F, Giudice E.The goal of this study was to investigate the influence of physical activity on the daily rhythm of platelet aggregation and body temperature in horses. Blood samples from 12 Thoroughbred horses, six sedentary animals and six athletes (studied both before and after a period of inactivity) were collected at 4h intervals for 48h via an intravenous cannula inserted into the jugular vein. Body temperature was recorded every 4h for 48h with a rectal probe. Platelet aggregation was measured with an aggregometer. Collagen was used to test the aggregation of the plasma samples. Statistical analysis of...
Murphy BA, Vick MM, Sessions DR, Cook RF, Fitzgerald BP.The master mammalian pacemaker in the brain controls numerous diverse physiological and behavioral processes throughout the organism. Timing information is continually transmitted from the master clock to peripheral organs to synchronize rhythmic daily oscillations of clock gene transcripts and control local physiology. To investigate the presence of peripheral clocks in the horse, quantitative real-time RT-PCR assays were designed to detect levels of equine clock genes. Expression profiles for Per2, Bmal1 and Cry1 were first determined in a synchronized equine cell line. Subsequently, express...
Giannetto C, Carcangiu V, Luridiana S, Parmeggiani A, Piccione G.Photoperiodic treatments have been of practical interest in controlling seasonal reproduction in sheep, goats and horses. Melatonin is the principal mediator of the environmental photoperiodic message. To investigate the intra- and inter-subject variability of melatonin 24 h rhythm, ten female Italian Saddle horses (8-10 yrs old, mean body weight 525 ± 30 kg), ten female Sarda breed sheep (2-3 yrs old, mean body weight 40.5 ± 2.8 kg) and ten female Sarda breed goats (3-4 yrs old, mean body weight 38.9 ± 4.1 kg), housed individually in a 4 × 4 m soundproof box equipped with 50 Ã...
Piccione G, Caola G, Refinetti R.The homeostatic control of physiological processes is affected by a variety of temporal programs, such as circadian rhythms, estrous cycles, and circannual rhythms. The existence of circaseptan rhythms (endogenous rhythms with the duration of a week) has been postulated but not properly verified. In this study, we compared plasma concentration of lactic acid, systolic and diastolic blood pressure, and rectal temperature in athletic horses (maintained under a weekly training schedule) with those in sedentary horses (maintained under a constant schedule throughout the week). Although exercise ha...
Murphy BA.The circadian system provides animals with a means to adapt their internal physiology to the constantly changing environmental stimuli that exist on a rotating planet. Light information is translated into molecular timing mechanisms within pacemaker cells of the mammalian hypothalamic suprachiasmatic nucleus (SCN) via transcriptional-translational feedback loops. Humoral and neural outputs from this 'master' clock result in circadian rhythms of physiology and behaviour. The larger circadian system involves SCN synchronisation of cellular clocks throughout the organism such that individual orga...
Ohmura H, Boscan PL, Solano AM, Stanley SD, Jones JH.To determine whether withholding of food affects autonomic nervous system balance by analysis of heart rate (HR), HR variability (HRV), and frequency of second-degree atrioventricular block in horses. Methods: 5 healthy Thoroughbreds. Methods: For two 24-hour periods in a crossover study, food was withheld from horses or horses were maintained on their regular feeding schedule (control conditions) in their stalls and Holter monitor ECG recordings were obtained. The ECGs were analyzed by use of fast-Fourier transformation, and power spectrum densities were calculated for low-frequency (0.01 to ...
