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Nitrogen and mineral (Fe, Mg, Na, K, and Ca) compositions of foodstuffs consumed by and dung produced by male, pregnant and lactating female adult Icelandic reindeer and calves were determined during May of 1992. Iron levels in foodstuffs are consistently above the reported toxicity level for similar-sized sheep (0.5 ppt) and may lead to iron toxicity when consumed by reindeer during periods of high lean body mass catabolism. Male and female reindeer meet nutrient requirements for all measured elements and nitrogen with the possible exception of calcium for males during antler growth.

The hormonal control of the seasonal antler cycle was investigated over 4 years in four adult female Norwegian reindeer, Rangifer tarandus, maintained in captivity at Tromsø, Norway (69 degrees N). The antlers were fully redeveloped in August, cleaned of velvet in September, and were retained in hard antler throughout the winter before being cast in March or April. The cleaning of the antlers occurred at the seasonal onset of ovarian activity and was associated with an increase in the blood plasma concentrations of testosterone, androstenedione, oestradiol and progesterone. Ovariectomy in October resulted in premature casting of the hard antlers in that year. This was paralleled with a decrease in the plasma concentrations of oestradiol and progesterone, but not of testosterone and androstenedione. Antlers were redeveloped, cleaned of velvet and cast each year in the ovariectomized females, but the antler cycle was abnormal since the cleaning of the antlers began 1-3 months later than in intact females and was often incomplete, and the casting surface of the old antler was deformed. The hardening of the antlers in the ovariectomized animals in autumn was correlated with seasonal increases in the plasma concentrations of androstenedione, but not in the concentrations of other steroid hormones; provocation tests using GnRH and arginine vasopressin (AVP) illustrated that the adrenal gland was a likely source of androgens. The initiation of antler growth in spring always followed the seasonal increase in the secretion of prolactin. The overall conclusion is that a gonadal steroid hormone, possibly oestradiol, normally acts to induce and maintain the hard antler state in female reindeer. This hormonal mechanism acts to synchronize the antler cycle to the seasonal reproductive cycle with the hard antlers functioning as weapons in intrasexual competition in winter.

The threshold body core temperature for selective brain cooling (SBC) as well as the slope of brain cooling were determined in three Norwegian reindeer (Rangifer tarandus tarandus) during rest and during exercise. Brain temperature was measured in the hypothalamus (Thypo) and blood temperature (Tblood) was measured either in the right carotid artery or in a few cases in the right atrium of the heart. During rest the animals were subjected to ramp-like increases of Tblood by means of a thermostatically controlled water circulated heat exchanger (HE) introduced into the rumen via a chronically implanted rumen cannula. During exercise the animals ran on a treadmill at a speed of between 5.5-8.0 km hr-1 and a slope of 13.5 degrees for periods of 30-60 min. The elevation of Tblood during both rest and exercise resulted in significant amounts of SBC. The mean threshold for SBC (Thypo = Tblood) during rest was 38.7 degrees C. The threshold for SBC was elevated significantly to 39.5 degrees C during exercise. The mean slope of SBC (increase of SBC per degree increase of Tblood) was 0.82 both during rest and exercise.

Captive reindeer were fed four different rations which supplied equal energy but varying amount of crude protein: lichens (3%), mixed hay plus lichens (10%) and two feed concentrates with medium (12%) or high (18%) protein content. Kinetics of total body water were measured with tritiated water from February to March 1985, and thermal energy cost of daily water intake was estimated. Biological half-time of water was shorter, and daily water intake significantly higher on the hay plus lichens diet and on the medium- or high-protein concentrates diet than on the lichens diet during March 1985. Similar differences were found between reindeer on medium-protein concentrate and on lichens at the end of the corresponding feeding period during April 1986. Daily water inflow was positively correlated with a dietary supply of digestible crude protein (r = 0.916). Thermal energy costs of daily water intake were highest 1.9 MJ (3.7 l-1) in reindeer on high-protein concentrate during March 1985, and 2.0 MJ (3.9 l-1) in reindeer on medium-protein concentrate during April 1986. The reindeer fed on lichens had minimal and nearly twice as small thermal energy cost of daily water intake (mean 1.1 MJ 2.1 l-1) as on either of the concentrates. Our results show that even a moderate feed protein ration can significantly increase free water intake and its thermal energy cost in reindeer as compared to dominant natural feed (lichens) during winter. Careful protein supplementation is recommended to support body condition with a concomitant addition of easily soluble carbohydrates to compensate for increased thermal costs of water intake.

Daily patterns of pineal function were studied in different seasons in 10 adult semidomesticated female reindeer and 5 prepubertal calves living in a natural arctic environment at latitude 69 degrees 10'N. Serum samples for melatonin RIA were collected every 4 h for 24 h in October (10 h of light, 14 h of darkness and 8 h of light, 16 h of darkness), December (24 h of darkness), March (13 h of light, 11 h of darkness), and June (24 h of light). A significant daily variation in serum melatonin levels was observed in the adult reindeer, with peak values (20-50 ng/liter) occurring during the night in autumn, winter, and spring, but not summer. The daytime values at 13 h (5-10 ng/liter) were constant throughout the year. Total daily amounts of melatonin, the duration of peak levels, and maximal concentrations were significantly lower in spring and summer than before the rut in autumn. The exposure of adult animals to artificial darkness from bright sunlight on August 1 and September 21 resulted in an immediate increase in serum melatonin concentrations. The 2-week-old calves had detectable serum melatonin levels, but no daily rhythm in the spring, whereas a rhythm was detectable by the first autumn, only to disappear unexpectedly during the first winter and return in the spring. At the age of 16 months, the calves had serum melatonin concentrations similar to those in the adults. Our present results show that the continuous illumination experienced during the summer abolished the normal daily melatonin rhythm. This does not seem to be related to organic changes in the pineal gland, since exposure to darkness during the summer increased melatonin levels. The highest melatonin secretion occurred in the autumn and was evidently associated with the rut. Similarly, the daily melatonin rhythm of an adult type observed in the calves at the age of 16 months may be related to the observation that most calves were in rut. Thus, a high rhythmical melatonin secretion appears to relate to puberty and the initiation of heat in female reindeer.

1. The vasomotor responses to neuropeptides of the angular oculi and facial veins of reindeer were examined in vitro and correlated with the neuropeptide distribution in the perivascular nerves, as demonstrated by immunohistochemistry. 2. Nerves displaying calcitonin gene related peptide (CGRP)- or neuropeptide Y (NPY)-like immunoreactivity (-LI) were observed in the media of both veins, while very few fibers were immunoreactive to vasoactive intestinal polypeptide (VIP) or substance P (SP) in either vein. 3. The staining pattern for NPY-LI was largely identical to that of dopamine-beta-hydroxylase, a marker for noradrenaline (NA) producing fibers, indicating coexistence of NPY and NA. 4. Administration of NPY in vitro elicited contractions in both veins in the presence of propranolol, though more conspicuously in the angular oculi vein. 5. The peptide was without any modulating effect on NA-stimulated contractions in the angular oculi vein, whereas a small enhancement of the NA-induced tone was seen in the facial vein. 6. CGRP caused partial relaxation of both veins, whereas atrial natriuretic polypeptide caused relaxation only in the facial vein. VIP and SP had no effect on either vein. 7. The results suggest that in reindeer the sympathetic nerve fibres to both facial and angular oculi veins contain the vasoconstrictor neuropeptide NPY besides NA, even though these fibres exert a vasodilator action on the myogenically active facial vein. 8. The vasodilator neuropeptide CGRP, which is present in other more sparse perivascular nerve fibres mainly in angular oculi vein, is perhaps of afferent nature in which case CGRP might subserve axon reflex functions. 9. If, however, also the CGRP fibres are truly efferent in nature, chances for a central reciprocal control of flow through angular oculi vein might be at hand.

Male deer reduce food intake and lose weight during the breeding season (rut) in autumn. Growth hormone (GH) is lipolytic in ruminants; therefore, pulsatile GH secretion was measured in three young reindeer (Rangifer tarandus tarandus) bulls during the natural period of weight loss during rut. Blood samples were withdrawn through a jugular cannula every 20 min for 16 hr on 5 occasions from late summer to early winter in unanaesthetised animals. The deer were group fed a pelleted concentrate ration ad libitum, and food intake, body weight, and testicular diameter were recorded. The hormone profiles were analysed by the pulse detection algorithm PULSAR. The bulls showed the normal pattern of rut-associated weight loss and reduced food intake followed by a period of weight increase in late autumn before weight plateaued in early winter. Mean GH was highest (P less than 0.05) at the time of minimum body weight and food intake compared with all other sampling periods. Neither the amplitude nor the frequency of GH pulses, as detected by PULSAR, differed significantly with sampling period, although the high mean GH values were associated with a different pulse shape; pulses were longer, with a large area under the curve, presumably reflecting a longer duration of secretion or reduced clearance. Thus weight loss and low food intake were associated with long, large area pulses of GH. An opioid antagonist, naloxone, was given to reindeer intravenously at hourly intervals for 4 hr and blood sampling was continued for 7 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

A histological and histochemical study of biopsy specimens from the Lapland reindeer antler indicated that the intercellular matrix of the cartilage that forms the partitions of longitudinal channels becomes calcified at virtually the initial stage of formation. The lacunae at the peripheries of the cartilaginous partitions are invaded by osteoblasts in a process comparable to endochondral ossification. The very centres of the partitions evidently become directly converted into bone without the presence of e.g. osteoclasts. The osseous partitions are remodelled by osteoclasts. The antler increases in diameter by periosteal apposition.

Values for Young's modulus of elasticity, ultimate and yield stresses, ultimate and yield strains, work under the stress-strain curve and work of fracture were obtained from tensile and bending tests on specimens of narwhal tusk dentine and cement, femoral bone from young and mature cattle, and reindeer antler. Compared with the cattle bone the narwhal tissues had low Young's moduli, low yield stresses, rather low ultimate stresses and high ultimate strains. In all these properties they were similar to reindeer antler. The calcium content and hardness of the narwhal tissues were compared with those of human and cattle dental tissues. The narwhal dentine was considerably softer and less mineralized than human and cattle dentine. Human cementum was softer and less mineralized than cattle cementum, and was like narwhal cementum. In general, the mechanical properties of the narwhal tusk tissues were as would be expected from their mineral content, except that the stiffness of the cementum was low. It is likely that narwhal dentine is not very similar to human and cattle dentine in its mechanical properties.

The sedative action of medetomidine (-ketamine) was studied in 12 captive Norwegian semidomesticated reindeer (NR), including 4 newborn calves, and in 7 free-living Svalbard reindeer (SR). Medetomidine, with or without ketamine, caused effective, reliable immobilization in NR. Doses of 50-200 micrograms/kg medetomidine alone or 30-125 micrograms/kg medetomidine combined with greater than or equal to 300 micrograms/kg ketamine induced complete immobilization, good muscle relaxation and persistent, deep sedation with little respiratory depression in NR; SR required higher doses. Atipamezole successfully antagonized medetomidine (-ketamine) resulting in rapid and persistent reversal of immobilization in all cases (NR and SR). Both medetomidine and atipamezole had wide safety margins and no conspicuous lasting side effects after reversal.

With the aid of intramural multipolar technique, the sequence of the heart ventricles depolarization was studied in deer. Electric potentials were led from 1500-1700 points in the myocardium. Primary foci of excitation were revealed in the subendocardium of the caudal and cranial areas of the middle third of left and cranial portions of the upper third of right side of the interventricle partition. Within 5-10 msec. the ventricles subendocardium is wholly involved into the wave of depolarization. For 10-20 msec., the main lot of free walls, the central and upper portions of the partition, are excited. This period is characterized by spreading of the depolarization wave from numerous foci of excitation in all directions. Last the upper portions of the pulmonary artery output cone (40-45 msec.) and portions of the interventricle partition adjacent to the ventricles basis (45-50 msec.), become excited.

The purpose of this study was to determine whether a convenient relationship could be found between heart rate (HR) and energy expenditure at rest and during running in the high arctic Svalbard reindeer (SR) and the subarctic Norwegian reindeer (NR). Measurements of HR and energy expenditure (O2 consumption) were made at different ambient temperatures, at rest, and during running at different speeds during both summer and winter. Cost of transportation (Science 177: 222-228, 1972) was 3.56 and 2.67 J X g-1 X km-1 in SR and NR, respectively. The y-intercept value obtained for NR was close to the predicted value (J. Exp. Biol. 97: 1-22, 1982), whereas that of SR was much lower. In NR the relationship between HR and energy expenditure at running speeds from 0 to 9.2 km X h-1 is, regardless of ambient temperature (in the -30 to +10 degrees C range), described by the following equations: y = 8.04x + 48.70, r = 0.92, n = 27 (summer); and y = 7.48x + 31.20, r = 0.95, n = 52 (winter). In SR, the corresponding equations were y = 7.60x + 49.20, r = 0.94, n = 29 (summer); and y = 8.90x + 32.10, r = 0.96, n = 44 (winter), where y is HR (beats X min-1) and x is metabolic rate (W X kg-1).

Exhaled air temperature (Te), respiratory frequency (f), and rectal temperature (Tb) were measured in two reindeer before, during and after running for 45 min at a constant speed of 9.2 km X hr-1 on a level treadmill at different ambient temperatures (Ta), in summer with fur insulation at a minimum and in winter with fur insulation at its prime. Before and immediately after the 45-min running period, skin temperature (Tsk) and radiative surface temperature (Tr) were also measured. Te, Tsk and Tr decreased at rest with decreasing Ta both summer and winter Tb was elevated during running except at low Ta in summer. During running Tsk, Te and f were higher in winter than in summer, while Tr was higher in summer than in winter. The changes in Tr and Tsk in response to running were more pronounced on the legs than on the trunk. It is suggested that in the running reindeer the body surface is an effective avenue of heat loss during summer, while heat dissipation by way of the respiratory tract attains increased importance in winter, when fur insulation is at its best.

Previous results [(1988) Arct. Med. Res. 47, 83-88] have shown that hemoglobin from reindeer is characterized by a low overall heat of oxygenation. This particular aspect has been investigated further in a series of precise oxygen equilibrium experiments. The results obtained show a peculiar dependence of the temperature effect on the fractional saturation of hemoglobin with oxygen, which could be regarded as a very interesting case of molecular adaptation to extreme environmental conditions.

Partition of heat loss was performed in resting (standing) and exercising (running; 9.2 km . h-1 for 40 min) winter- (W) and summer- (S) insulated conscious reindeer (Rangifer tarandus tarandus) in a climatic chamber set to an ambient temperature (Ta) of -30, 0, or 25 degrees C. Heat loss and production were determined using indirect calorimetry. The relative importance of radiant heat loss was greatest during rest at low Ta's, both during winter and summer (44-58% at Ta's -30 and 0 degrees C). At high Ta's, especially during exercise, a large proportion of total heat loss occurred through evaporation [45% at Ta 25 degrees C during rest and 47% at Ta 0 degrees C during exercise (W); 38% at Ta 25 degrees C during exercise (S)]. The proportion of heat lost through convection during rest and exercise was 38-52 and 46-72%, respectively, depending on Ta and season. The legs were found to represent an important avenue for radiant heat loss, particularly in heat stress situations. Their importance for convective heat loss was even greater, especially during exercise.

Left ventricular volumes were measured by cineangiocardiography in 56 sessions on 25 reindeer, together with determinations of arterial pressure and blood oxygen saturation. The heart rate with the animal kept lying on the sternum at rest was 50 b/min, the aortic blood oxygen saturation 94 to 98% and the aortic blood pressure 153/130/115 mm Hg. The left ventricular end-diastolic volume was 3.4 ml/kg of b.w., stroke volume 2.6 ml/kg, cardiac output 133 ml/kg . min, and ejection fraction 76%. If the animal was placed on its side the aortic blood oxygen saturation decreased by 2 to 3 per cent, end-diastolic volume rose 10%, stroke volume 25%, cardiac output nearly 30% and ejection fraction 14%. The heart rate and cardiac output increased in hypoxemia, but the end-diastolic and stroke volumes simultaneously decreased. If the aortic blood pressure rose during hypoxia, the end-diastolic and stroke volumes increased, while the ejection fraction first increased and then decreased again. In normoxia a rise in aortic blood pressure was associated with decreased end-diastolic and stroke volumes and ejection fraction. An increased heart rate at rest was followed by increased cardiac output, but decreased end-diastolic and stroke volumes and ejection fraction.

Cineangiographic examination of reindeer exposed to local (hypothalamic) or general heating and cooling revealed that the angular oculi veins are constricted during cold stress but dilated during heat stress. Moreover, during heat stress a segment of the facial vein appeared to be occluded, causing the cold venous return from the nasal mucosa to be routed directly to the cavernous sinus for selective cooling of the brain. Histological examination of the vasoactive segment of the facial vein showed unusually thick longitudinal and circular layers of smooth muscle cells. Obstruction of angular oculi blood flow by clamping of the veins in the heat-stressed animal resulted in an immediate rise in brain temperature. When reindeer under heat stress shift from closed- to open-mouth panting, only the expiratory phase of the respiratory cycle takes place through the mouth, whereas inspiration through the nose is continued. In this way, cooling of the nasal mucosa and, hence, cooling of the brain, is maintained.

The cold venous effluent returning from the nose of the heat-stressed reindeer may be distributed through angular oculi veins for selective cooling of the brain and through facial veins for general body cooling. In vitro experiments indicate that adrenergic receptors of the angular oculi vein are exclusively of the alpha-adrenergic type, whereas facial veins contain mainly beta-adrenergic receptors. We suggest that the antagonistic adrenergic neuroeffector organization of these veins plays a major role in control of brain cooling. Thus simultaneous sympathetic stimulation results in constriction of angular oculi veins and release of a preexisting stretch-induced tone in facial veins. In this situation cold venous blood is directed via facial veins and used for general body cooling. Reduction of sympathetic activity, on the other hand, results in dilatation of angular oculi veins and constriction of facial veins, due to development of myogenic tone in the latter vessels. In this situation cold venous blood is distributed via angular oculi veins and used for selective cooling of the brain.

1. In connection with a study of hormonal effects on food consumption in reindeer, weight changes during treatment were compared with weight changes during a 3-week period following treatment. 2. Rates of weight change during the post-treatment period were inversely proportional to induced weight changes. 3. This inverse relationship is interpreted as evidence for a functional set-point for body weight in reindeer.

A total of 301 female reindeer of various ages was shot on South Georgia in all months of the year to study seasonal and age-related changes in ovarian structures, and to undertake an intraspecific comparison with North American caribou. Ovarian weights and follicle numbers did not change in reindeer calves, and it is concluded that the South Georgia population do not attain physiological puberty in their first year. Compared with caribou, reindeer showed an earlier onset of ovarian activity, and had twice as many follicles greater than 2 mm diameter and secondary corpora lutea. The relationship between luteal scars and age was significant (P less than 0.001), despite an overcount of scars relative to age in some individuals, and indicated a fecundity rate of 0.93. The left and right ovaries of reindeer were equally productive. It remains unclear whether the differences in reproductive performance between reindeer and caribou are of genetic origin.

A simplified single-plane angiocardiographic method for the measurement of the left ventricular volumes in the reindeer heart has been developed, on the assumption that the left ventricle forms half a revolution ellipsoid. On the basis of a study of 30 ventricular casts the following formulae were constructed for the calculation of the left ventricular volume (VLV) in end-diastole (D) and end-systole (S): VLVD = 0.60 k3a2l - 3.9 and VVLS = 0.40 k3a2l - 12 where k = magnification factor of the x-ray system, a = cross-sectional diameter of the ventricle and 1 = longitudinal diameter of the ventricle. The method was tested on the casts by comparison with biplane integration and with the single-plane ellipsoid method. In addition to this, a comparison was made in vivo by simultaneous stroke volume determination by angiocardiography and the oxygen Fick, and a good agreement was observed.

A total of 111 male reindeer of various ages was shot in all months of the year to study the relationship between the seasonal changes in testicular activity and the antler cycle. From the changes in testis weight, seminiferous tubular tissue area and plasma testosterone values and the occurrence of spermatogenesis, it is concluded that calves attain physiological puberty in their first year, during which they also complete an antler cycle. The amplitude of the cyclical change in testis weight and plasma testosterone values increases with age and can be correlated with the earlier onset of events in the spermatogenic and antler cycles of older animals. The duration of the spermatogenic and testosterone cycles of reindeer is short, and is inversely related to the long period spent without antlers. It is suggested that testosterone strongly influences the antler cycle of reindeer males.

At birth reindeer calves often are exposed to sub-zero ambient temperatures (Ta) sometimes even combined with wind and precipitation. The resting metabolism was measured in three different age groups (1, 7 and 14 days old) at Ta's of -20, -5, 10 and 20 degrees C. Resting metabolism in the thermoneutral zone decreased from 5.1 W X kg-1 at day 1 and 7 to 4.8 W X kg-1 at day 14. At day 1 apparent lower critical temperature (Tlc) was 11 degrees C, while at day 7 it was 7.7 degrees C and at day 14 7.3 degrees C, but total body conductance continued to decrease below apparent Tlc. At Ta's of -5 and -20 degrees C total body conductance was: 0.77 and 0.72 W X degrees C-1 at day 1, 0.98 and 0.92 W X degrees C-1 at day 7, 1.08 and 0.91 W X degrees C-1 at day 14, respectively. Thermal conductance of pelt samples from the trunk was determined in vitro at different combinations of windspeed, Ta and wetness. The conductance of dry fur increased from 5.9 to 11.8 W X m-2 X degrees C-1 at a windspeed of 0 and 10 m X s-1, respectively, as compared to 28.7 W X m-2 X degrees C-1 when wetted without wind. Newborn reindeer calves seem to be heavily dependent on non-shivering thermogenesis in brown adipose tissue for their cold defence since deep body temperature in a calf subjected to propranolol infusion when exposed to a Ta of -25 degrees C in combination with a 10 m X s-1 windspeed increased its cooling rate five times.

A hypothesis for the operation and control of nasal heat exchange in reindeer is presented that originated from studies of the nasal vascular anatomy and has been supported by physiological measurements as well as test experiments on a physical prototype model of the reindeer nose. A central theme of our hypothesis is that the nasal mucosa possesses arterial and venous retia that communicate by way of capillaries and arteriovenous anastomoses. During heat conservation the blood runs countercurrent in these retia, whereby a temperature gradient along the nasal mucosa can be maintained. During heat dissipation, however, the retia are perfused unidirectionally in the anterior direction, whereby the temperature gradient along the nasal mucosa is reduced and heat loss facilitated. In this situation cooled venous blood, routed by way of the dorsal nasal vein, may be distributed either to the caval veins directly, for general body cooling, or, by way of the cavernous sinus that encases the carotid rete, for selective cooling of the brain.

Antler blood flow was studied in a 2 year old male reindeer during the last half of the antler growth period using an electromagnetic flow probe chronically implanted around the superficial temporal artery. Arteriovenous (a-v) differences of calcium were measured on antler blood. The blood flow increased from 60--90 ml/min when the antler was half-grown to 100--120 ml/min when fully developed. Subsequently a reduction was observed towards shedding. Positive a-v plasma calcium differences (on average 0.2 mM) were recorded during the period of active growth. Two bulls maintained positive a-v calcium differences after a 48 hour starvation period, in spite of reduced arterial calcium concentrations. Exercise to near exhaustion caused a 2 degrees C rise in the rectal temperature. Antler blood flow was decreased immediately after exercise and returned to pre-exercise values usually within 5--10 min. Since no overshoot in antler blood flow was recorded during the hyperthermia it is concluded that variations in blood perfusion of the antlers are without importance in the defence against hyperthermia during and after exercise.

Two female reindeer were hydrated by administration of (10% of b.wt.) water into the rumen. The diuretic response was very fast and strong but the urea and electrolyte excretion were little affected. Dehydration was carried out by not giving the reindeer water for 48 h. This water deprivation caused a loss of up to 20% of their body weight. The urine osmolality did not exceed 840 mosm/kg H2O, although the plasma osmolality rose from 300 to 346 and 368 mosm/kg H2O respectively. The plasma and urine urea concentrations were elevated during dehydration, while the urine urea excretion did not increase. Urine sodium concentration did not increase. When the urine flow rate, after two days of water deprivation, decreased to half of the original, the urine Na+ concentrations, instead of increasing, went down to half of the original. So did the potassium excretion. When ADH was injected intravenously into hydrated animals a dose of 30 mU of ADH was needed to induce antidiuresis or increased excretion of potassium. The resistance to ADH and the low relative thickness of the medulla confirm the limited capacity of reindeer kidney to concentrate urine or to excrete a solute load. On the other hand, reindeer is able rapidly to excrete surplus water without affecting the electrolyte or nitrogen balance.

Red deer, sheep and reindeer grazing on their normal hill ranges were examined at intervals over a period of four years. Samples from the digestive tract were taken at different seasons and processed in the field. The Red deer and reindeer were killed before samples were taken; rumen samples from the sheep were taken by stomach tube, but a number of animals were also killed at different seasons to correlate stomach tube and whole rumen samples. The animals sampled were representative of the general condition of the herds. Examinations were made for parasites and any pathological conditions. In most instances parasitic infections were slight. Apparent seasonal changes were found in the compositions of the diets. The Red deer and sheep ate principally heather and grass, the proportion of heather increasing in the winter. The reindeer ate mainly grass in the summer, with lichens and grass forming the winter diet, and these animals seemed to have a higher nutritional status in the winter than did the other two species. The weights of the animals and of their rumen contents, the concentrations of rumen ammonia and volatile fatty acid, and the rates at which different dietary components were fermented are recorded. Rumen fermentation was low in winter and the diets were generally inadequate for the animals. A lack of nitrogen seemed to be a major factor. Some data on caecal contents are also given.

When reindeer were exposed to low ambient temperatures, heat and water were recovered from the exhaled air by a nasal counter-current heat exchanger. Measurements of respiratory frequency, minute volume, exhaled air temperature and metabolic rate were made over a range of ambient air temperatures extending from -5.5 degrees C to 27.2 degrees C. At ambient air temperatures less than 10 degrees C the exhaled air temperatures were an average of 21 degrees C less than body temperature. The reduction of the exhaled air temperature at the lowest ambient air temperatures used in this study resulted in the recovery of 75% of the heat added and 80% of the water added to the inspired air on its way to the lungs. The heat and water recovered by the nasal temporal counter-current heat exchanger in reindeer significantly reduced the metabolic cost of survival during cold exposure.

Total respiratory heat loss (t.r.h.l.) in resting reindeer has been calculated from exhaled air temperature (Te) and respiratory minute volume (V) obtained during heat and cold stress in both summer and winter. Exhaled air temperature decreased with decreasing ambient temperature (Ta) in both summer and winter. The lowest Te recorded was +6 degrees C at a Ta of -45 degrees C in winter and the highest +38 degrees C at a Ta of + 29 degrees C in summer. At any Ta, Te was higher in winter than in summer. V was constant with increasing Ta up to +25 degrees C and -10 degrees C in summer and winter, respectively. Further increase in Ta resulted in thermal tachypnea. During summer t.r.h.l. did not change significantly in the ambient temperature range from -25 to +25 degrees C. In winter, however, t.r.h.l. increased linearly with increasing ambient temperature from -30 to +15 degrees C. Minimum t.r.h.l. was found to coincide with the animals' lower critical temperature. We suggest that the heat exchange in the upper respiratory tract of resting reindeer is actively regulated to attain fine tuning of thermal balance in this high arctic mammal undergoing great seasonal changes in fur insulation.

The structure of the fur of the reindeer (6 adults, 4 calves) was studied with light and scanning electron microscopy and skin and rectal temperatures were measured in 216 living animals at varying ambient temperatures (-28 to +15 degrees C) and also on excised skin samples in the laboratory (temperature range -20 to +20 degrees C, wind 0 or 10 m/sec, 5 different directions). Guard hair count and length varied according to the site of excision and were on average 2000/cm2 and 12 mm on the foreleg, 1000/cm2 and 30 mm on the abdomen and 1700/cm2 and 30 mm on the back. The corresponding counts in the calves were higher but the hairs were shorter. The rectal temperatures ranged from 38 to 40 degrees C independently of the ambient temperature. The dependence of the skin temperature on the ambient temperature was complex in living animals. The dependence was strongest in the legs. The skin temperature of the excised samples depended rather linearly on the ambient temperature. It is concluded that the reindeer can maintain its body temperature also in severe cold although the extremities show characteristics of heterothermia.

Using radiotelemetric technique, extraordinary changes have been found in cardiac activity of the elk and reindeer during spontaneous emotional stress under natural conditions. Cardiac reaction is characterized by rapid 2--3-fold increase in the heart rate and by 3--4-fold increase in the amplitude of T-wave. It was suggested that these changes are associated with abnormalities of metabolic processes in the heart.

Haemodynamics of two reindeer (18 h and 4 days old) and one elk (1 week old) calves were studied by catheterization and angiography. Early closure of foetal shunts, high cardiac output and large ejection fractions were observed in all three animals. Pulmonary arterial blood pressure decreased to the full-grown level during the first days of life in the reindeer. Electrocardiography showed cranial-orientated QRS vector in both species. The cardiovascular system of the Cervidae is well developed at birth and adapts rapidly during the neonatal period.

Norwegian reindeer (Rangifer tarandus tarandus) were provided with chronically implanted hypothalamic perfusion thermodes to determine to what extent expired air temperature (Tex) is centrally controlled. The effects that alterations of hypothalamic temperature (Thy) had on metabolic heat production, respiratory frequency, respiratory evaporative heat loss, and rectal and leg-skin temperature were simultaneously recorded. Experiments were conducted in conscious animals exposed to ambient temperatures (Ta) of -20, 0, and 20 degrees C in summer, when fur insulation was minimal, and in winter, when it was prime. Altering Thy induced changes in Tex, the degree and direction of which depended on the prevailing Ta, season, and intensity of hypothalamic thermal stimulation. These results indicate that Tex, and hence nasal heat exchange, is under central control. The Thy-induced changes in the other measured parameters confirm that hypothalamic thermosensitivity in these animals is similar to that previously found in other mammalian species.

Right heart catheterizations were performed in 56 sessions on 25 reindeer with determinations of blood pressure and oxygen saturation. Cardiac output was calculated from cineangiocardiograms. When the animals were placed in prone position, heart rate was about 50/min, mixed venous blood oxygen saturation 68 to 72%, right ventricular systolic pressure 27 mmHg, pulmonary arterial pressure 25/16/11 mmHg, pulmonary arterial wedge pressure 6--8 mmHg and pulmonary transfer time 4 to 5 cardiac cycles. When the animals were placed on their side, the heart rate rose to 90 b/min, mixed venous blood oxygen saturation decreased by about 4% and the right ventricular and pulmonary arterial pressures increased by about 10 mmHg; pulmonary arterial wedge pressure did not change. Hypoxemia led to an increase in heart rate, cardiac output and pulmonary arterial pressure; the latter two measures tended to increase whenever the heart rate increased. Under the conditions stated here, an increased pulmonary vascular resistance was calculated when pulmonary arterial pressure was increased.

Electrocardiograms were recorded for 50 Finnish reindeer of age 1 day to 9 years, using standard and unipolar extremity leads in the frontal plane. The range of heart rate was 40-250 beats per minute. Atrial and ventricular depolarization times were 5-10 ms shorter in newborn calves than in other reindeer, and showed only minor variance with respect to heart rate. The duration of depolarization was dependant on heart rate, and was more rapid in young calves. A-V conduction time decreased with increasing heart rate. The mode of the QRS vector was 280-290 degrees, and the mode of the T vector 200-230 degrees in the older animals, but 100-120 degrees in young calves. The main deflection in the QRS complex was S in the leads II, III and aVF.R was dominant in aVL and I.