Management of horses with focus on blanketing and clipping practices reported by members of the Swedish and Norwegian equestrian community.

Limited information is available on the extent to which blankets are used on horses and the owners' reasoning behind clipping the horse's coat. Research on the effects of those practices on horse welfare is scarce but results indicate that blanketing and clipping may not be necessary from the horse's perspective and can interfere with the horse's thermoregulatory capacities. Therefore, this survey collected robust, quantitative data on the housing routines and management of horses with focus on blanketing and clipping practices as reported by members of the Swedish and Norwegian equestrian community. Horse owners were approached via an online survey, which was distributed to equestrian organizations and social media. Data from 4,122 Swedish and 2,075 Norwegian respondents were collected, of which 91 and 84% of respondents, respectively, reported using blankets on horses during turnout. Almost all respondents owning warmblood riding horses used blankets outdoors (97% in Sweden and 96% in Norway) whereas owners with Icelandic horses and coldblood riding horses used blankets significantly less ( < 0.05). Blankets were mainly used during rainy, cold, or windy weather conditions and in ambient temperatures of 10°C and below. The horse's coat was clipped by 67% of respondents in Sweden and 35% of Norwegian respondents whereby owners with warmblood horses and horses primarily used for dressage and competition reported clipping the coat most frequently. In contrast to scientific results indicating that recovery time after exercise increases with blankets and that clipped horses have a greater heat loss capacity, only around 50% of respondents agreed to these statements. This indicates that evidence-based information on all aspects of blanketing and clipping has not yet been widely distributed in practice. More research is encouraged, specifically looking at the effect of blankets on sweaty horses being turned out after intense physical exercise and the effect of blankets on social interactions such as mutual grooming. Future efforts should be tailored to disseminate knowledge more efficiently, which can ultimately stimulate thoughtful decision-making by horse owners concerning the use of blankets and clipping the horse's coat.

Milk processing quality of suckled/milked goats: effects of milk accumulation interval and milking regime.

Milk with a high concentration of fat and casein is required for cheese production, and these components have a major impact for both quality and yield of the curd. Recent observations have shown that suckling can elevate milk fat concentration in goats and our aim was therefore to check the hypothesis that animal welfare and cheese-processing properties of goat milk could be optimised by appropriate management of suckled/milked goats. Twelve Swedish dairy goats were kept together with one kid each in 4 different mixed management-systems (milking combined with partial suckling) in a cross-over design. Two milk accumulation intervals were tested; Short = dams and kids were together for 16 h (T16) and Long = ; dams and kids were together for 8 h (T8 h). In addition, two milking regimes were used; Suckled Before Milking = S and Milked Before Suckling = M. Milk accumulation interval referred to how long dams and kids were separated. The milk yield available for processing (milk offtake), was weighed and analysed from each milking occasion and the suckled milk yield was estimated by a weigh-suckle-weigh method (WSW) in combination with observing the suckling behaviour during the free suckling periods. Milking managements, such as 'suckling before milking (S)', increased milk fat concentration compared to milking before suckling (M) and 'Short accumulation treatments (T16)' gave higher milk fat, casein concentration and individual curd yield (%) compared to the 'Long accumulation treatment (T8)'. The total individual curd yield (g) was the same despite treatment, but the animal welfare was most likely higher in T16 where dams and kids spent more time together.

Daytime shelter use of individually kept horses during Swedish summer.

In Sweden, no provision for summer shelter to protect horses from heat and insects is required, although access to shelter for horses kept outdoors 24 h during winter is a requirement. This study investigated horses' daytime shelter-seeking behavior in relation to weather conditions and insect activity during a 2-wk period in summer. Eight Warmblood riding horses had access to 2 shelters of different design to test which shelter design is preferred by horses. Furthermore, rectal and skin temperatures and insect-defensive behavior were measured to test whether horses would benefit from the provision of shade. The horses were kept alone in paddocks for 4 d. During 2 d, horses had access to 2 shelters: 1) open shelter with roof and uncovered sides and 2) closed shelter with roof, wind nets on 2 sides, and opaque plastic opposite the entrance. Weather conditions (ambient temperature, relative humidity, solar radiation, wind speed) were recorded every 10 min. The number of insects (flies, mosquitos) was counted from insect traps placed in each shelter and outside. Behavior (shelter use, insect-defensive behavior, locomotion, grazing) was recorded at 5-min intervals between 0900 to 1200 h and 1300 to 1600 h and rectal and skin temperatures were measured at 0800 h, 1200 h, and 1600 h. Data were analyzed with PROC MIXED and GLIMMIX procedure for Generalized Linear Mixed Models. Ambient temperature ranged from 16 to 25°C (average temperature humidity index 65.7 ± 1.4). Five horses preferred the closed shelter and were observed inside up to 2.5 h continuously. Greater wind speed decreased the likelihood of observing horses inside the shelter ( < 0.001), as did lower numbers of flies ( < 0.001). The insect-defensive behaviors, skin shiver and ear flick, were performed less frequently when horses were using the closed shelter ( < 0.001), indicating that they were less disturbed by insects. Thirty-minute shelter use had no effect on rectal and skin temperatures ( > 0.05). Results showed that horses made use of shelters during the summer even when weather conditions were moderate. A shelter with roof and covers on 3 sides was preferred over a shelter with roof only and can reduce insect-defensive behavior.

Report of the Federation of European Laboratory Animal Science Associations Working Group on animal identification.

The primary aim of this report is to assist scientists in selecting more reliable/suitable identification (ID) methods for their studies. This is especially true for genetically altered (GA) animals where individual identification is strictly necessary to link samples, research design and genotype. The aim of this Federation of European Laboratory Animal Science Associations working group was to provide an update of the methods used to identify rodents in different situations and to assess their implications for animal welfare. ID procedures are an indispensable prerequisite for conducting good science but the degree of invasiveness differs between the different methods; therefore, one needs to make a good ethical evaluation of the method chosen. Based on the scientific literature the advantages and disadvantages of various methods have been presented comprehensively and this report is intended as a practical guide for researchers. New upcoming methods have been included next to the traditional techniques. Ideally, an ID method should provide reliable identification, be technically easy to apply and not inflict adverse effects on animals while taking into account the type of research. There is no gold standard method because each situation is unique; however, more studies are needed to better evaluate ID systems and the desirable introduction of new and modern approaches will need to be assessed by detailed scientific evaluation.

Milk production and feeding behavior in the camel (Camelus dromedarius) during 4 watering regimens.

Camels survive and produce milk during recurrent prolonged hot and dry periods. The objective was to evaluate how different watering intervals affected milk production and feeding. Eight lactating camels (Camelus dromedarius) were recruited and subjected to 4 watering regimens in a Latin square design experiment performed at Haramaya University in Ethiopia. Each regimen lasted 16 d with 5 d of daily watering between periods: water was offered at 1,315 h once daily (W1); on d 4, 8, 12, and 16 (W4); on d 8 and 16 (W8); and on d 16 (W16). One camel became sick in the second period and its results were excluded. Camels were kept in a pen with minimal shade and a noon temperature of 30.9±0.1°C. They had free access to hay and were offered 2 kg of concentrates 3 times daily. At noon on d 1, 4, 8, 12, and 16, a blood sample was taken from the jugular vein before watering. All calves were kept together in a separate pen. Morning and afternoon calves stimulated milk let-down before the camels were hand-milked, after which the calves suckled, emptying the udder. Camels maintained the milk volume during water deprivation for about 1 wk, but they produced less milk during the second week during W16. Morning milk osmolality increased from 315±3 on d 1 to 333±3 mosm/kg on d 4 during W4 and from 321±3 on d 1 to 342±3 mosm/kg on d 8 during W8. After watering at 1315 h, milk osmolality decreased to 316±3 and 323±3 mosm/kg, respectively, the same afternoon and then increased during recurrent water deprivation to 338±3 (W4) and 347±3 mosm/kg (W8) on d 16, respectively. During W16, osmolality increased from 318±3 to 336±3 mosm/kg during the first 4 d of water deprivation, but during the remaining 12 d the further rise in osmolality was not higher compared with that on d 4. The change in milk osmolality was linearly correlated to plasma osmolality (r=0.8), but milk lactose content did not increase. Contrary to widespread belief, camels did not dilute their milk when dehydrated. Instead milk osmolality increased in parallel to blood osmolality. This study provides further support to earlier observations on camels' adaptation to their environment.

Mechanisms of water economy in lactating Ethiopian Somali goats during repeated cycles of intermittent watering.

We investigated the physiological and behavioural strategies by which lactating Ethiopian Somali goats endure repeated periods of water deprivation. The experiment lasted for 32 days and was divided into four periods of 8 days each. Measurements were taken during the first 4 days in each period. Seven does (W1) were watered once daily and seven does (W4) were watered once every 4th day. Rectal temperature was taken at 0800 and 1715 h. Blood samples were taken in the evening and milk samples in the morning. The goats were on pasture between 0900 to 1215 h and 1315 to 1630 h with behaviour recorded every 5 min. The does were supplemented with 300 g of concentrates per head per day. Plasma and milk osmolality were determined by freezing point depression. Plasma total protein was measured on a TS refractometer. Plasma vasopressin concentrations were analysed by radio-immunoassay. The mean daily water intake of W1 was 1897 ml compared with the calculated mean of 1075 ml in W4 (P < 0.001). The mean diurnal variation of the rectal temperature was 3.5°C in both groups. Afternoon rectal temperature in W4 during period 1 was higher than that in the W1 on the days of water deprivation (P < 0.05). With repeated periods, plasma osmolality in W4 increased less over the days of water deprivation. It was 336, 321, 311 and 306 mosm/l on the 4th day at periods 1, 2, 3 and 4, respectively. The corresponding vasopressin concentrations were 10.0, 9.2, 4.2 and 4.4 pmol/l. Total plasma protein concentration during period 1 on days 3 and 4 were higher in W4 than in W1 (P < 0.01). During the subsequent periods, it did not increase more in W4 compared with W1, but it was lower in W4 on the days after watering. W4 milk production decreased by 22% compared with W1 in all periods. With increasing days of water deprivation, the W4 goats spent less time in the sun, grazed shorter time and frequently ate cactus (Opuntia ficus-indica) as compared with W1. Results suggested that dehydrated lactating Ethiopian Somali goats economised on water by diurnal variations of rectal temperature, storing water in the extracellular fluid, by changing behaviour at grazing and by decreasing milk production.

Exercise response, metabolism at rest and digestibility in athletic horses fed high-fat oats.

REASON FOR PERFORMING STUDY: High starch intakes increase the risk for metabolic disorders and therefore alternative feedstuffs are of interest. High-fat oat varieties have a lower starch and higher energy content than regular oats and may therefore be useful in this context. HYPOTHESIS: Feeding high fat oats causes no adverse effects on the response to exercise and that the total amount of oats offered could be reduced compared to feeding with regular oats. METHODS: Twelve Standardbred trotters were fed regular oats (diet C), high-fat oats (F), and a mixture (50:50) of C and F (M), together with haylage (30:70), in a Latin square design trial. High-fat oats replaced regular oats in a 0.9 to 1.0 ratio in diets F and M. On Day 18 in each 21 day experimental period, horses were subjected to a standardised near-maximal treadmill exercise test with collection of blood samples and muscle biopsies before and after exercise. This was followed by a 3 day period of total collection of faeces and urine. RESULTS: There were no significant effects of dietary treatments on bodyweight, heart rate, plasma lactate and glucose, or on muscle glycogen and lactate concentrations following exercise. However, plasma insulin was reduced during exercise on diets F and M compared to diet C. The total tract digestibility of dry matter, fat, protein, NDF and organic matter were higher for diet F than for diet C. CONCLUSION: High-fat oats can replace regular oats in the diet of athletic horses without any adverse effects on metabolism and exercise response. POTENTIAL RELEVANCE: Due to the high energy content and a high digestibility of dietary components in high-fat oats the daily allowance of oats can be reduced and thus the intake of starch.

Housing-related activity in rats: effects on body weight, urinary corticosterone levels, muscle properties and performance.

The cage systems commonly used for housing laboratory rats often result in sedentary and overweight animals, as a consequence of restricted opportunities for physical activity combined with ad libitum feeding. This can have implications both for animal well-being and for the experimental outcome. Physical activity has several known positive effects on health and lifespan, and physical fitness might therefore be incorporated into the animal welfare concept. The aim of this study was to investigate if and how pen housing affects the physical activity and fitness of rats. Thirty-two juvenile male Sprague-Dawley rats were randomly assigned to two different housing systems for a 4-week period. Sixteen rats were kept individually in standard Makrolon type III cages (42x26x18 cm) furnished with black plastic tubes (singly-housed, SI). The remaining rats were kept in groups of eight, housed in large floor pens (150x210 cm), which were furnished with various objects to increase environmental complexity (pen-housed, PH). The body weight gain, and food and water intake of the rats were measured. During weeks 3 or 4, home cage behaviour, urinary cortiosterone/creatinine ratios (CO/CR), and muscle strength on an inclined plane, were measured. Enzyme activities and glycogen content were measured in tissue samples from m. triceps brachii taken after euthanization at the end of the study. There were no significant differences between groups for food and water intake, but PH rats weighed 14% less than SI rats after 4 weeks, and PH rats also had a more diverse behavioural pattern than SI rats. PH rats had significantly higher oxidative capacity (28% more citrate synthase (CS)) and greater glycogen content (28%) in their muscle samples than SI rats. The PH rats performed significantly better on the inclined plane, both in the muscle strength test (mean angle 75+/-0.5 degrees for PH rats and 69+/-0.4 degrees for SI rats) and the endurance strength test (mean time 233+/-22 s for PH rats and 73+/-14 s for SI rats). There was a negative correlation between body weight and results on the inclined plane for the PH rats. There were no significant differences between housing types with respect to CO/CR ratios. In conclusion, the large pen represents an environment that stimulates physical activity and more varied behaviour, which should be beneficial for the welfare of the animal.

Carbonic anhydrase activity and sweat gland morphology in trained and untrained Standardbred trotters.

Sweat gland morphology and carbonic anhydrase (CA) distribution was studied after exercise in trained and untrained horses using a histochemical technique and light microscopic image analysis. Three trained and 3 untrained Standardbred trotters performed an exercise test (20 min trot at 6 m/s with 5 min walk at 1.8 m/s in the beginning and end) on a high-speed treadmill at 35 degrees C. Skin biopsies were taken before exercise and after trot. The fluid loss after exercise was 10, 12 and 12 g/kg bwt in the untrained horses and 4, 6 and 11 g/kg in the trained. Trained horses had a larger cell area than untrained after exercise, which might be related to an increase in secretory capacity. The area of the cell occupied by CA was independent of training status, but increased with exercise in both groups. The CA activity was higher in untrained animals and increased after exercise in both groups. The change in CA during exercise might be a response to an increasing demand for HCO3- secretion during sweat formation. Therefore, the sweat gland undergoes morphological changes due to stimuli such as heat, exercise and training, but species differences are evident. To our knowledge, no one has previously studied the influence of training on the morphology of the equine sweat gland.

Human-animal interactions and animal welfare in conventionally and pen-housed rats.

The main aim of the present study was to explore the significance of large group/greater pen housing (PH) versus standard Makrolon caging (ST) in three behaviour tests related to human-animal interactions in the adult male laboratory rat. The rats' perception of human interaction was tested in three behavioural tests, of which two reflected common practical procedures, capture and restraint, whereas the third was a human approach test in a Y-maze. The rats' anticipatory reactions to handling and the reactions to restraint did not differ between groups, but the ST rats approached a human hand more quickly than did the PH rats (P < 0.01). Although food intake did not differ, ST rats gained more weight (P < 0.01) and had higher total cholesterol values (P < 0.01) than PH rats. In conclusion, this study shows that housing rats in large groups in an enriched environment did not influence their anticipatory reaction to handling in normal handling situations. However, as the PH rats tended to have a longer approach latency than ST rats in the Y-maze there might be underlying differences in appraisal that are not detected in practical situations. In addition, the PH rats weighed less and had lower total cholesterol values than ST rats and their urine corticosterone values were higher. These effects are suggested to be due to higher physical activity in the PH rats, and the implications of this on the animal as a model is discussed.

Water intake and fluid shifts in horses: effects of hydration status during two exercise tests.

In the present study, the main objective was to study factors affecting postexercise voluntary water intake in horses. Four Standardbred horses (mean +/- s.e. bwt 500 +/- 8 kg) were used to study water intake and effects of altering hydration status before an incremental exercise test (INCR) and a 40 min constant velocity exercise test (CONST) on a treadmill. Exercise was performed during normohydration (N), after dehydration for 24 h (DEH) and after hyperhydration with 12 l water 30 min before exercise (HH). DEH resulted in a bodyweight loss of 3% and there were signs of some fluid uptake prior to exercise in both HH trials. By the end of the INCR, the calculated change in plasma volume (PVcalc) was -13 +/- 1, -21 +/- 1 and -11 +/- 3% in the N, DEH and HH trials, respectively. During the highest exercise velocities a hypotonic shift of fluid was seen in all INCR trials. There was a greater accumulation of plasma lactate (pLA) in HH-than in N-INCR, probably caused by the extra weight to be carried. CONST induced a similar fluid loss (3%) in all trials, but the decrease in PVcalc at the end of exercise was significantly smaller in HH (-7 +/- 2%) than in N (-14 +/- 1%) and DEH (-19 +/- 2%). In DEH-INCR and DEH-CONST, plasma sodium concentration (pNa) was higher than in N until drinking water was offered 1 h postexercise. In the presence of both an increased pNa and a decrease in PVcalc when dehydrated, the horses drank immediately when offered water postexercise. In N-CONST, there was a significant decrease in calculated PVcalc (-10 +/- 2%) but no increase in pNa when water was given and in this trial the horses rehydrated less rapidly. Plasma aldosterone concentration (PAC) had increased to the same magnitude in all trials after about 10 min, irrespective of type of exercise or hydration status. It was concluded that when both an osmotic and hypovolemic thirst stimulus was present, the horses rehydrated more rapidly postexercise.

Effect of water supply method and flow rate on drinking behavior and fluid balance in horses.

This study investigated three methods of water supply on drinking preference and behavior in six Standardbred geldings (2-9 years, 505+/-9 kg). The water sources were buckets (B), pressure valve (PV), and float valve (FV) bowls. In an initial drinking preference test, PV was tested at three flow rates: 3, 8, and 16 l/min (PV3, PV8, and PV16), and FV at 3 l/min (FV3). Water intake was measured in l and presented as the percentage of the total daily water intake from each of two simultaneously presented alternatives. The intake from PV8 was greater than from both PV3 (72+/-11% vs. 28+/-11%) and PV16 (90+/-4% vs. 10+/-4%). All horses showed a strong preference for B, 98+/-1% of the intake compared to 2+/-1% from PV8. Individual variation in the data gave no significant difference in preference between the two automatic bowls. In the second part of the study, drinking behavior and fluid balance were investigated when the horses drank from FV3, PV8, and B for 7 consecutive days in a changeover design. Despite a tendency for an increase in total daily drinking time from FV3, the daily water intake was significantly lower (43+/-3 ml/kg) than from PV8 (54+/-2 ml/kg) and B (58+/-3 ml/kg). Daily net water gain [intake-(fecal+urinary output)] was only 0.5+/-3 ml/kg with FV3, resulting in a negative fluid balance if insensible losses are included. These results show that the water supply method can affect both drinking behavior and fluid balance in the horse.

Effects of feeding frequency and voluntary salt intake on fluid and electrolyte regulation in athletic horses.

The effect of feeding frequency and voluntary sodium intake (VSI) on fluid shifts and plasma aldosterone concentration (PAC) were studied at rest and after exercise in six athletic horses. The horses were fed twice a day (2TD) and six times a day (6TD) for 25 days for each protocol, according to a changeover design. VSI was measured by weighing each horse's salt block daily. Feeding 2TD or 6TD caused no major alterations in fluid shifts, but in the 2TD treatment there was a postprandial increase in plasma protein concentration and osmolality that lasted <1 h. PAC and VSI were not affected by feeding frequency. VSI ranged from 0 to 62 mg x kg body weight-1 x day-1 and caused significant alterations in PAC. At VSI <26 mg x kg body weight-1 x day-1, a diurnal rhythm for PAC was noted. Water intake, fecal concentrations of sodium and potassium, and packed cell volume during exercise were influenced by VSI. The response to exercise did not differ between treatments. In conclusion, VSI, but not feeding frequency, has significant effects on fluid and electrolyte regulation in athletic horses.

Sweat production and localisation of carbonic anhydrase in the equine sweat gland during exercise at two ambient temperatures.

The aim of this investigation was to study sweat production during exercise at 2 ambient temperatures (20 degrees C and 35 degrees C) and the concurrent localisation of carbonic anhydrase (CA) in the sweat gland. Horses develop alkalosis during prolonged exercise and the sweat contains HCO3-. Carbonic anhydrase is therefore of interest since it catalyses the reaction CO2 + H2O<-->HCO3- + H+. Four standardbred trotters performed an exercise test. Skin biopsies were taken from the neck, and sweat rate, blood and skin temperatures were measured. There was a close relationship between sweat rate, temperatures and work intensity at 20 degrees C. Temperatures and sweat rate were higher at 35 degrees C and did not fall when the work intensity dropped. A significant decrease in the sweat gland cell area was found after exercise at 35 degrees C with an accompanying decrease of vesicles. Strong CA activity was present at the luminal cell membrane and weaker basolaterally. The staining intensity increased after exercise. We suggest that CA might be of importance for counteracting the alkalosis developed after exercise by delivering HCO3- for generation of the alkaline pH in sweat.

Effects of potassium intake on potassium, sodium and fluid balance in exercising horses.

The aim of this study was to investigate the adaptation to an increased potassium (K+) intake in horses and to study whether the regulation of the post exercise K+, sodium (Na+) and fluid balances were altered by an increased K+ intake. Four Standardbred horses were fed 2 levels (4.1 and 5.4 mmol/kg bwt/day) of K+ for 17 days in a crossover design. The effects on K+, Na+ and fluid balance were studied both at rest and in response to 29 km exercise. K+, Na+ and fluid intakes and outputs were balanced within 24 h after a new diet had been introduced. Adaptation consisted primarily of an increased urinary K+ excretion, later followed by an increase in faecal excretion. The increased urinary K+ excretion was associated with an increased mass of urine (1.2-1.4 kg/day) compensated for by an increased water intake. The sweat Na+ concentration was increased on the highest K+ intake (from 123 +/- 5 mmol/l to 138 +/- 3 mmol/l) and the urinary Na+ excretion was lower post exercise on this diet. There were no differences in the magnitude of post exercise hypokalaemia between the diets, and plasma K+ concentration was still reduced 24 h post exercise even when the horses were fed the higher K+ diet. Adaptation to an increased K+ intake was rapid in these horses and consisted mainly of an increased urinary excretion. The response to exercise was unaltered by the increased K+ intake, except for an increased Na+ concentration in sweat.

Changes in plasma atrial natriuretic peptide concentration in exercising horses in relation to hydration status and exercise intensity.

OBJECTIVE: To investigate effects of hydration status and exercise intensity on plasma atrial natriuretic peptide (ANP) concentration in exercising horses. ANIMALS: 4 trained Standardbreds. PROCEDURE: Horses performed a 40-minute exercise test at 65 to 70% maximal heart rate (HRmax; no incline) and a 12-minute test at approximately 90% HRmax (3.5 degrees incline). The 40-minute test was performed with ad libitum access to drinking water (normohydration), after water had been withheld for 24 hours (dehydration), and 30 minutes after 12 L of water at body temperature had been given via nasogastric tube (hyperhydration). The 12-minute test was only performed with normohydrated horses. RESULTS: Plasma ANP concentration was higher toward the end of exercise during hyperhydration than during the other 2 hydration states, and the area under the plasma ANP concentration curve was significantly greater during hyperhydration than during dehydration. The maximal plasma ANP value induced during the 12-minute test was similar to that of the 40-minute test. After the 12-minute test, plasma ANP concentration did not decrease during the first 30 minutes of recovery, whereas after the 40-minute test, plasma ANP concentration decreased by approximately 30% during the same period. CONCLUSIONS: Hydration status can affect plasma ANP concentration in horses during submaximal exercise. Maximal plasma ANP concentration was similar at the 2 exercise intensities studied, but the postexercise return to baseline values differed. CLINICAL RELEVANCE: Changes in hydration status can cause alterations in plasma concentration of ANP, one of the hormones involved in the control of cardiovascular functions during exercise.

Localization of carbonic anhydrase in the goat mammary gland during involution and lactogenesis.

The aim of this study was to determine whether carbonic anhydrase (CA) activity in goat mammary capillaries is regulated mainly by local or systemic mechanisms. One gland was dried before the contralateral gland, and after parturition only one gland was milked. Biopsies were taken from the mammary glands of three goats at 14 d intervals during involution and the start of the following lactation. A histochemical method was used to visualize sites of CA activity. To follow the involution process, milk (liquid) samples were taken from both teats each week and analysed for pH and composition. The time course of CA activity disappearance and reappearance in the capillaries was related to changes in milk composition and alveolar area. A dense network of capillaries showing membrane-bound staining for CA was found surrounding the alveoli in the lactating gland. CA activity gradually decreased in the drying gland, although the other gland was being milked. After 8 weeks involution the dried gland had a significantly lower number of stained capillaries than the milked gland. Almost no stained capillaries were found during late pregnancy, when both glands were dried and the tissue growth maximal. During lactation milk pH was 6.6 +/- 0.3 and this increased to 7.0 +/- 0.1 in the course of involution. In the last trimester of pregnancy the pH returned to its lower value, while the mammary gland was devoid of stained capillaries. Therefore, the capillary CA could not have been directly involved in the pH regulation of milk. The CA activity reappeared in the capillaries directly after delivery, but only in the milked gland. Clearly the regulation of CA activity is influenced more by local than by systemic factors and is associated with the metabolic activity of milk secretion.

Elemental composition of muscle at rest and potassium levels in muscle, plasma and sweat of horses exercising at 20 degrees C and 35 degrees C.

In this study, 4 Standardbred geldings were exercised at 20 and 35 degrees C. The exercise test (ET) consisted of 2 exercise bouts separated by 2 h of rest in their boxes. Blood samples were taken before, during and after the second exercise bout and muscle (m. gluteus medius) biopsies were taken before the first exercise bout and after an intensive trot over 2600 m in the second exercise bout. The blood samples were analysed for plasma potassium and total plasma protein concentration (TPP) and the muscle fibres were analysed for elemental composition by x-ray microanalysis. The intracellular content was as follows: sodium (Na) = 40 +/- 7; magnesium (Mg) = 32 +/- 4; phosphorus (P) = 282 +/- 15; sulphur (S) = 222 +/- 13; chloride (Cl) = 119 +/- 31; potassium (K) = 304 +/- 21 and calcium (Ca) = 8 +/- 2 mmol/kg dry weight under resting conditions. Intracellular potassium content increased after exercise compared to resting values. There was a good correlation between exercise intensity, plasma potassium concentration and shifts in plasma volume, indicated by alterations in TPP. This probably reflects the very fast shift of potassium and fluid between muscle and plasma. Plasma potassium concentrations decreased below resting values post exercise. The higher dehydration degree and potassium sweat loss after exercise at 35 degrees C was not reflected in lower muscular potassium content, but by a lower plasma potassium/total plasma protein ratio after exercise, indicating less circulating potassium.

Strategies for voluntary rehydration in horses during endurance exercise.

To avoid dehydration and a decrease in performance capacity in horses, fluid and electrolyte losses need to be compensated for during long distance rides as well as on other occasions when sweat losses are high during exercise. Thirteen endurance-trained horses, age 5-14 years, were used to compare 3 strategies of voluntary rehydration during prolonged exercise, offering 1) water, 2) water after administering salt paste (3 x 30 g of NaCl) per os and 3) 0.9% saline. The ride covered 62 km and consisted of 3 rounds, of 20, 22 and 20 km, respectively. During the first 20 km, no fluid was offered to any of the horses. Thereafter, fluid was repeatedly offered from buckets at the 'vet gates' and at fluid stations situated in the middle of the rounds. Fluid intake and bodyweight were measured during the ride and up until 3 b after the ride. The low heart rates and unchanged plasma glucose concentration indicated that the work load was moderate. Total fluid intake was significantly higher in the saline group than in the water group or the salt paste group. The total plasma protein concentration (TPP) fell below resting values in the saline group post exercise, indicating an increase in plasma volume. No changes in TPP were seen in the other groups. Plasma sodium concentration during the ride increased in the salt paste group but not in the saline drinking horses despite their higher NaCl intake. The water group had an increased plasma aldosterone concentration post exercise, indicating that sodium-conserving mechanisms had been activated. Plasma potassium concentration decreased in all treatments from pre- to post ride. It was concluded, that drinking saline solution during and after exercise is a good strategy for rehydration since this group showed the fastest recovery of their bodyweight losses. The persistently elevated plasma sodium concentration in the salt paste group during the ride, is indicative of a disturbance in the fluid distribution between the body fluid compartments, which can be exacerbated by the low water intake. To give salt paste immediately before or during exercise is, therefore, not recommended.

Reproductive period affects water intake in heat-stressed dehydrated goats.

Water intake following dehydration was studied in pregnant (N = 5), lactating (N = 4) and nonpregnant, nonlactating (N = 5) Swedish domestic goats (Capra hircus) to investigate if reproductive period affected drinking. Plasma cortisol concentration and the hematocrit value were measured to evaluate stress. The goats were water deprived from 9.00 h until 15.05 h the next day. They were fed at 7.00 and 15.20 h. On the second day, ambient temperature was increased from 20 degrees C to 38-39.5 degrees C for 5.15 h to accelerate water losses. Water temperature during rehydration was 35 +/- 1 degree C. Plasma Na concentration and osmolality increased most in dehydrated and heat-stressed pregnant and lactating goats. Pregnant goats lost 2.2 kg of their body weight. They drank 3.5 l immediately, followed by 2.5 l during afternoon eating. Lactating goats lost 4.9 kg and drank 6.3 l at once, and 3.9 l during feeding. Nonpregnant, nonlactating goats lost 1.7 kg and drank 2.6 l followed by 0.6 l. The large water consumption in pregnant and lactating goats caused hyponatremia and hemodilution, but they continued to drink during the night (0.5 +/- 0.2 l and 0.8 +/- 0.5 l, respectively). Renal free water clearance increased in all periods, with a long-lasting water diuresis during pregnancy. Plasma cortisol concentrations and the hematocrit values rose in connection with water intake. These results imply that the thirst center became less sensitive to inhibitory signals from the oropharyngeal tract and the diluted blood plasma during pregnancy and lactation. Catching sight of water was the most exciting procedure during these experiments.