Influence of shearing on oxidative stress and some physiological parameters in ewes.

The aim of the present study was to evaluate the effect of shearing on physiological and oxidative stress parameters in ewes. Twenty Comisana ewes were used and divided into two groups. Ten ewes were left unshorn as a control group (Group A) and 10 ewes were shorn (Group B). All measurements were taken before and after shearing, and repeated 8 h after shearing and 1, 2, 3, 4, 5, 10 and 15 days after shearing. Reactive oxygen species (dROMs), antioxidant barrier (oxy-adsorbent), thiol antioxidant barrier (SHp) and packed cell volume (PCV) were assessed in blood samples collected by means of jugular venipuncture. Rectal temperature (RT), respiratory rate (RR) and heart rate (HR) were also measured. Two-way repeated measures analysis of variance (ANOVA), followed by Bonferroni's test, was used for the assessment of significant effects due to shearing and time. The statistical analysis showed significant increases (P < 0.01) of dROMs, oxy-adsorbent, SHp, and a significant decrease (P < 0.01) of RT and RR associated with time and shearing. Our results indicate that shearing causes a change in the ewe's homeostatic balance that leads to oxidative stress.

Photic and non-photic entrainment on daily rhythm of locomotor activity in goats.

We studied the photic (L/D cycle) and non-photic (restricted feeding) entrainment on the patterns of daily rhythm of total locomotor activity in goats. Six female Maltese goats were subjected to three different artificial L/D cycles: 12/12 L/D, 12/12 D/L and constant light. During the 12/12 L/D and 12/12 D/L, food and water were available ad libitum. During constant light, animals were subjected to a restricted feeding treatment. Total activity was recorded by means of an actigraphy-based data logger (Actiwatch-Mini). Our results showed that goats exhibited clear daily rhythms of activity in 12/12 L/D cycle, 12/12 D/L cycle and constant light, although they showed FAA prior the feeding time during the restricted feeding treatment. Goats were diurnal, with activity consistently beginning promptly following the onset of light. Even when the L/D cycle was delayed by 12 h on some days, to the daily rhythm was re-established. During the constant light period, the onset of activity was linked to the time of food administration. Our study evidences two factors for the rhythm of total locomotor activity in goats: light stimuli (photic) and food access (non photic), strongly coupled to permit organisms the adaptive temporal coordination of behaviour with stable and unstable environmental periodicities.

Impact of an acoustic stimulus on the motility and blood parameters of European sea bass (Dicentrarchus labrax L.) and gilthead sea bream (Sparus aurata L.).

The physiological responses of fish to underwater noise are poorly understood and further information is needed to evaluate any possible negative effects of sound exposure. We exposed European sea bass and gilthead sea bream to a 0.1-1 kHz linear sweep (150 dB(rms) re 1 microPa). This band frequency is perceptible by many species of fish and is mainly produced by vessel traffic. We assessed the noise-induced motility reaction (analysing the movements) and the haematological responses (measuring blood glucose and lactate, and haematocrit levels). The noise exposure produced a significant increase in motility as well as an increase in lactate and haematocrit levels in sea bream and sea bass. A significant decrease of glucose was only observed in sea bream. A linear correlation between blood parameters and motility in fish exposed to the noise was observed. The acoustic stimulus produced intense muscle activity.

Influence of time of day on body temperature, heart rate, arterial pressure, and other biological variables in horses during incremental exercise.

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 temperature increased; these changes were the same during the a.m. and p.m. sessions. We conclude that there is no indication in horses of a difference in the responses of HR, BP, and BT to exercise between the a.m. and p.m. The circadian oscillations, however, alter the absolute values of these variables both at rest and during exercise, raising the possibility that the safety margins against hyperthermia and hypertension may decrease during p.m. exercise.

Circadian activity rhythm in sheep and goats housed in stable conditions.

The aim of this study was to establish the circadian rhythm of total activity in sheep and goats kept in housed conditions. For our study five Comisana breed sheep and five Maltese breed goats were kept in an individual box of 12 m2 under artificial 12/12 light/dark cycle for 14 days. We equipped the animals with Actiwatch-Mini, by means of collars. A two-way ANOVA was used to determine significant differences between experimental treatments. A paired Student t-test was used to evaluate the differences between photophase and scotophase. The results show that activity in sheep and goats is mainly diurnal, the activity rhythm reaches its peak in the middle of the day. In conclusion small ruminants can be classified as diurnal animals, even though they show a variable amounts of activity.

Chronobiologic blood pressure assessment: maturation of the daily rhythm in newborn foals.

Circadian rhythmicity of physiological processes in animals has been described for some variables. In order to investigate the daily rhythmicity of blood pressure, seven foals (Equus caballus) were used for 40 days after birth. Measurements of blood pressure were done by means of an oscillometric apparatus (Argus TM-7, Schiller, Barr Switzerland) with the foals in a standing position and the cuff placed around the tail. Blood pressure was recorded twice a day, 1 hour before dawn and 1 hour before dusk for the first 10 days of life, every 2 days from the 11th to the 32nd day, on the 36th and on the 40th day. Two-way repeated measures analysis of variance (ANOVA) were used to determine statistically significant differences between the mean values recorded at dawn and dusk during the study. Analysis of variance showed a significant effect of time (p<0.0001), during the first 40 days of life. This study confirms a strong correlation between age and blood pressure in horse and the absence of blood pressure maturation in foals 40 days old. The results on the maturation of the daily rhythm of blood pressure in foals is a contribution to the study of the development of circadian rhythms in mammals. These results are also useful for the chronophysiological assessment of blood pressure in the horse.

Daily rhythmicity of glycemia in four species of domestic animals under various feeding regimes.

Daily rhythmicity of physiological processes has been described for numerous variables in numerous species. A major source of this rhythmicity is a circadian pacemaker located in the mammalian hypothalamus, but very little is known about how the pacemaker generates the multiplicity of bodily rhythms. Research on rats has shown that the rhythm of blood glucose concentration is not a mere consequence of the rhythm of food ingestion, but is rather generated directly by the pacemaker. In this study, we investigated the rhythm of blood glucose concentration in four different species of domestic animals under four different feeding regimes. Our results suggest that, as in rats, the rhythm of blood glucose concentration is not a mere consequence of the rhythm of food ingestion in sheep and cattle. In dogs and horses, however, the rhythmicity of blood glucose concentration seems to be contingent on the presence of a feeding regime.

Chronobiologic blood pressure assessment: Maturation of the daily rhythm in newborn foals

Circadian rhythmicity of physiological processes in animals has been described for some variables. In order to investigate the daily rhythmicity of blood pressure, seven foals (Equus caballus) were used for 40 days after birth. Measurements of blood pressure were done by means of an oscillometric apparatus (Argus TM-7, Schiller, Barr Switzerland) with the foals in a standing position and the cuff placed around the tail. Blood pressure was recorded twice a day, 1 hour before dawn and 1 hour before dusk for the first 10 days of life, every 2 days from the 11th to the 32nd day, on the 36th and on the 40th day. Two-way repeated measures analysis of variance (ANOVA) were used to determine statistically significant differences between the mean values recorded at dawn and dusk during the study. Analysis of variance showed a significant effect of time (p<0.0001), during the first 40 days of life. This study confirms a strong correlation between age and blood pressure in horse and the absence of blood pressure maturation in foals 40 days old. The results on the maturation of the daily rhythm of blood pressure in foals is a contribution to the study of the development of circadian rhythms in mammals. These results are also useful for the chronophysiological assessment of blood pressure in the horse.

Daily rhythm of salivary and serum urea concentration in sheep.

BACKGROUND: In domestic animals many biochemical and physiological processes exhibit daily rhythmicity. The aim of the present study was to investigate the rhythmic pattern of salivary and serum urea concentrations in sheep. METHODS: Six 3-year-old female sheep kept in the same environmental conditions were used. Sheep were sampled at 4 hour intervals for 48 consecutive hours starting at 08:00 of the first day and finishing at 04:00 of the second day. Blood samples were collected via intravenous cannulae inserted into the jugular vein; saliva samples were collected through a specific tube, the "Salivette". Salivary and serum urea concentrations were assayed by means of UV spectrophotometer. ANOVA was used to determine significant differences. The single Cosinor procedure was applied to the results showing significant differences over time. RESULTS: ANOVA showed a significant effect of time on salivary and serum urea concentrations. Serum and salivary urea peaked during the light phase. In the dark phase serum and salivary urea concentrations decreased, and the diurnal trough occurred at midnight. Cosinor analysis showed diurnal acrophases for salivary and serum urea concentrations. Daily mean levels were significantly higher in the serum than in the saliva. CONCLUSION: In sheep both salivary and serum urea concentrations showed daily fluctuations. Urea is synthesized in the liver and its production is strongly influenced by food intake. Future investigation should clarify whether daily urea rhythms in sheep are endogenous or are simply the result of the temporal administration of food.

Daily rhythms of serum leptin in ewes: effects of feeding, pregnancy and lactation.

The aim of the present study was to test whether serum concentrations of leptin in ewes vary with a daily rhythm. For this purpose, we examined 24 h serum leptin profiles of ewes exposed to natural photoperiodic conditions and subjected to two different feeding schedules (regular feeding and fasting). The results show for the first time the existence of daily rhythm of plasma leptin in regularly fed ewes, with a minimum during the light phase and a peak during the dark phase. Daily rhythms of serum leptin persisted after 50 h of fasting, although fasting shifted the peak of the rhythm to the beginning of the light phase and significantly reduced daily leptin production. To gain a better understanding of the role of leptin in the temporal organization of physiological events related to pregnancy and lactation, we measured serum leptin profiles throughout 24 h in ewes either during pregnancy or lactation. Daily leptin rhythms were found to persist during pregnancy and lactation, but both physiological conditions altered leptin concentrations. Maternal serum leptin concentration rose between early and mid pregnancy, then decreased in the late pregnancy and during lactation. Daily serum leptin concentration was significantly lower in nonpregnant, nonlactating ewes, compared either to lactating or to early pregnant ewes.

Scaling the daily oscillations of breathing frequency and skin temperature in mammals.

Among mammals, the peak-trough difference (PTD) of the circadian pattern of body temperature (T(b)) drops very little with the increase in body mass (W), despite the large increase in heat capacitance and thermal inertia. We asked whether this might be contributed by systematic differences in the circadian pattern of breathing frequency (f) and skin temperature (Tskin), which are parts of the control mechanisms of heat loss. Measurements had been conducted on animals of eight species, chosen to cover a four-fold range in W, while resting and awake. The oscillation of f preceded that of T(b) in 7 of the 8 species, and its acrophase did not correlate with W. The daily mean and PTD of f scaled with W in a similar manner (respectively, W(-)(23) and W(-)(0.29)), the PTD averaging about 20% of the daily mean. The circadian oscillations of Tskin, measured in specimens of five species at three locations (abdomen, ear and thigh), were in phase with T(b). Neither the PTD nor the acrophase of Tskin changed systematically with W. The differences between T(b) and Tskin (means, peaks and troughs) decreased significantly with W; on average, the T(b)-Tskin difference scaled to W(-)(0.19). In conclusion, the relative amplitudes and the acrophase of Tskin and f did not show systematic inter-species differences. The progressive increase of Tskin with W could be a factor in maintaining the PTD of T(b) within a narrow range among mammals of very different size.

Central fatigue and nycthemeral change of serum tryptophan and serotonin in the athletic horse.

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 cannula inserted into the jugular vein. Tryptophan and serotonin concentrations were assessed by HPLC. Data analysis was conducted by one-way repeated measures analysis of variance (ANOVA) and by the single cosinor method. RESULTS: ANOVA showed a highly significant influence of time both on tryptophan and on serotonin, in all horses, on either day, with p values < 0.0001. Cosinor analysis identified the periodic parameters and their acrophases (expressed in hours) during the 2 days of monitoring. Both parameters studied showed evening acrophases. CONCLUSION: The results showed that serotonin and tryptophan blood levels undergo nycthemeral variation with typical evening acrophases. These results enhance the understanding of the athlete horse's chronoperformance and facilitate the establishment of training programs that take into account the nycthemeral pattern of aminoacids deeply involved in the onset of central fatigue.

Feeble weekly rhythmicity in hematological, cardiovascular, and thermal parameters in the horse.

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 had robust acute effects on the measured parameters, measurements conducted early in the morning or in the evening showed significant weekly rhythmicity only in one of the parameters (plasma concentration of lactic acid) in a few animals. This rhythmicity was feeble, was present only in athletic horses, and vanished if rigorous statistical criteria were applied. In contrast, 24 h rhythmicity was significant in all parameters in all horses. We conclude that the overall 7-day pattern in physiological parameters of the horse is feeble and is caused by the weekly schedule of activity. The available evidence does not support the notion of endogenous, circaseptan rhythms.

Influence of fasting and exercise on the daily rhythm of serum leptin in the horse.

The hormone leptin is secreted by white adipocytes and regulates food intake and energy expenditure in rodents and humans. The goal of the present study was to investigate the existence of a daily rhythm of serum leptin in horses and its dependence on fasting and physical exercise. A robust daily rhythm of leptin was found in both athletic and sedentary horses, with a daytime trough and a peak in the dark phase. While physical exercise never induced changes in circulating leptin, fasting reliably affected serum leptin levels. Food deprivation did not abolish the daily rhythm of serum leptin, but daily mean leptin levels in fasted horses were significantly lower than in regularly fed horses. This result indicates that leptin production is not a mere consequence of feeding behavior. The fact that in a large animal such as the horse a short fast decreases leptin without significantly changing the body weight demonstrates that changes in levels of circulating leptin associated with food restriction do not solely reflect changes in amount of body fat.

Daily rhythm of circulating fat soluble vitamin concentration (A, D, E and K) in the horse.

BACKGROUND: Many physiological processes of mammalian species exhibit daily rhythmicity. An intrinsic relationship exists between fat soluble vitamins (A, D, E and K) and several body functions. Few investigations on the rhythmic pattern of vitamins in domestic animals have been carried out. The present study evaluated the circadian rhythmicity of fat soluble vitamins in the horse. METHODS: Blood samples from 5 Thoroughbred mares were collected at four-hour intervals over a 48-hour period (starting at 8:00 hours on day 1 and finishing at 4:00 on day 2) via an intravenous cannula inserted into the jugular vein. Fat soluble vitamin concentration in the serum (A, D, E and K) was measured by HPLC. One-way repeated measures analysis of variance (ANOVA) was used to determine significant differences. p values < 0.05 were considered statistically significant. RESULTS: ANOVA showed a highly significant effect of time in all the horses for the vitamins studied (p < 0.0001). The application of the periodic model and the statistical analysis of the "Cosinor" enabled us to define the periodic parameters and their acrophases (expressed in hours) during the 2 days of monitoring: all the studied vitamins showed diurnal acrophases with values between 15:16 and 18:08 hours. CONCLUSION: Fat soluble vitamins exhibit daily rhythmicity with diurnal peak. Further investigations could help optimize the use of these substances according to their circadian (or other) rhythms.

Day/night pattern of arterial blood gases in the cow.

Both metabolic rate and pulmonary ventilation change throughout 24h with a circadian pattern. Because their changes occur almost in synchrony and by a similar amount, blood gases may remain steady within a narrow range. We tested this possibility in five cows (Bos taurus, Bruna Italiana breed), maintained in a stable at 29 degrees C, under natural light-dark (LD) regime, by measuring arterial blood gases every 3h for 2 days. All cows presented a clear day/night pattern of body temperature (T(b)), with an average peak-trough difference (PTD) of 0.5 degrees C. Breathing rate oscillated significantly in three out of five animals, with a group-mean PTD of 2 breaths per minute, and it was time-advanced with respect to the oscillation of T(b). Significant oscillations in arterial pH, bicarbonate, partial pressure of oxygen and partial pressure of carbon dioxide (Pa(CO2) ) were observed in, respectively, 1 cow out of 5, 1/5, 3/5 and 5/5. Of all these variables, group-mean analysis revealed a significant day/night pattern only for Pa(CO2), and even in this case the average PTD was less than 1 mmHg. We conclude that, in the cow, blood gases remain remarkably stable throughout the 24 h. Hence, the daily oscillations of body temperature, breathing rate, and probably of many other factors affecting metabolic rate and pulmonary ventilation do not preclude an excellent homeostasis of blood gases.

Blood lipids, fecal fat and chymotrypsin excretion in the dog: influence of age, body weight and sex.

Effects of physiological variables (age, body weight and sex) on lipemia (total lipids, phospholipids, triglycerides and NEFA), fecal fat and chymotrypsin excretion were examined in dogs. On comparing various ages and body weights, they found statistically significant differences, while only total lipids showed a statistically significant difference between the two sexes. Moreover, there was a significant correlation between body weight and fecal fat and chymotrypsin excretion. The results obtained contribute to the evaluation of small intestine functionality, especially in relation to some diseases, as malabsorption, maldigestion and steatorrhea in the dog.

Daily and estrous rhythmicity of body temperature in domestic cattle.

BACKGROUND: Rhythmicity in core body temperature has been extensively studied in humans and laboratory animals but much less in farm animals. Extending the study of rhythmicity of body temperature to farm animals is important not only from a comparative perspective but also from an economic perspective, as greater knowledge of this process can lead to improvements in livestock production practices. In this study in cattle, we investigated the maturation of the daily rhythm of body temperature in newborn calves, characterized the parameters of the daily rhythm in young cows, and studied the oscillation in body temperature associated with the estrous cycle in adult cows. RESULTS: We found that the daily rhythm of body temperature is absent at birth but matures fully during the first two months of life. The mature rhythm had a mean level of 38.3 degrees C, a range of excursion of 1.4 degrees C, and was more robust than that of any mammalian species previously studied (90% of maximal robustness). Sexually mature cows also exhibited a robust estrous rhythm of body temperature. An elevation of about 1.3 degrees C was observed every 21 days on the day of estrus. Small seasonal variations in this pattern were observed. CONCLUSION: In conclusion, calves exhibit a very robust daily rhythm of body temperature, although this rhythm is absent at birth and develops during the first two months of life. Adult cows exhibit also 21-day rhythmicity in body temperature reflecting the duration of the estrous cycle.

Circadian rhythms of body temperature and liver function in fed and food-deprived goats.

Daily rhythms of body core temperature and liver function were recorded in goats maintained under various schedules of lighting and feeding. Concentration of urea in the blood was used as an index of digestion-driven hepatic activity, whereas concentration of cholesterol served as an index of autonomous hepatic activity. Body temperature exhibited robust circadian rhythmicity in the presence and absence of a light-dark cycle and/or a feeding regime. The rhythm was more responsive to shifts in feeding time than to shifts in the light-dark cycle. Urea concentration in the blood exhibited daily rhythmicity only in the presence of a daily feeding regime and, therefore, was driven by ingestive and digestive processes. The rhythm of cholesterol concentration persisted in the presence or absence of a light-dark cycle and/or a feeding regime, except when the feeding time was shifted under constant light. However, the cholesterol rhythm did not respond either to shifts in the light-dark cycle or, more importantly, to shifts in feeding time. Thus, based on this index of hepatic function, the liver cannot be identified as the site of the putative food-entrainable pacemaker.

Circadian modulation of starvation-induced hypothermia in sheep and goats.

Prolonged food deprivation is known to cause a fall in the core body temperature of homeotherms. In various species of small birds and mammals (body mass up to 2-3 kg), it has been shown that starvation-induced hypothermia is modulated by the circadian system, in the sense that hypothermia is observed primarily during the inactive phase of the daily activity cycle (i.e., during the night for diurnal animals and during the day for nocturnal animals), whereas relatively normal temperatures are recorded during the active phase. To investigate whether this modulation occurs also in larger animals, we investigated the effects of 4 d food deprivation on the body temperature rhythm of goats and sheep (body mass 30-40 kg). In goats, the body temperature rhythm was found to have a mean level of 39.0 degrees C with a mean daily range of excursion of 0.42 degrees C. The daily oscillation in body temperature persisted during the first day of fasting, but the rhythm was drastically damped, if not eliminated, over the next 3 d as body temperature descended from the baseline level of 39.0 to 38.2 degrees C. In sheep, the rhythm was found to have a mean level of 39.3 degrees C with a mean daily range of excursion of 0.34 degrees C. The daily oscillation in body temperature persisted through the 4 d of food deprivation, even though the mean level of body temperature gradually fell. Temperature fell more during the third and fourth nights than during the third and fourth days. Thus, circadian modulation of starvation-induced hypothermia was observed in sheep but not in goats.