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We used captive caribou (Rangifer tarandus granti) and reindeer (Rangifer tarandus tarandus) to study the effects of energy intake, protein intake, dietary protein:energy ratio, date, and body condition on (i) body fat versus body protein deposition and (ii) maternal tissue deposition versus milk production. Energy intake was the only variable significantly affecting body mass (BM) changes in either breeding or nonbreeding adult females. Lactating and nonlactating females had comparable efficiency coefficients for net energy retention (60 and 65%, respectively), but the daily maintenance requirement for lactating females (457 kJ/BM0.75) was twice that for nonlactating individuals (232 kJ/BM0.75). In both lactating and nonlactating females, the proportion of tissue deposited as fat rather than protein increased between spring and fall but decreased with increasing fatness. Energy intake increased protein deposition in lactating females but increased fat deposition in nonlactating females. Milk water volume increased with maternal energy intake and decreased with calf age. However, production of milk dry matter, milk fat, and milk energy were not affected by maternal energy or protein intake, maternal body condition, or calf age. Production of milk lactose correlated with maternal energy intake, while production of milk protein correlated with the maternal dietary protein:energy ratio.

Growth rates, milk intake, activity patterns, and daily energy expenditures of neonatal caribou (Rangifer tarandus granti) and muskoxen (Ovibos moschatus) were compared over a 100-day period to examine the strategies of two arctic follower species with different life history patterns. Relative growth rates, which reflected milk protein and energy intake, were higher for caribou during the 1st week of age and after 75 days of age than for muskox calves. Daily energy expenditures, estimated with the doubly labeled water technique, were significantly greater for caribou neonates than for muskoxen. Adult female caribou lost body weight during the first 2–3 weeks of lactation, but then increased 15% above postpartum weights during the summer period. Adult female muskoxen maintained weight, with no significant changes throughout the summer. Caribou milk was higher in protein, dry matter, and energy content than that of muskoxen.

A method is given for analyzing particulate digestive marker data in terms of digesta fill, fecal output, and digesta passage times. The method applies the Stewart – Hamilton Principle to data obtained from a single marker dosing followed by feces sampling; it assumes steady-state conditions for the digesta, but makes no assumptions concerning compartmentalization of digesta. Data analyses are presented for an experiment with sheep in which a particle phase marker, cerium-141 chloride, was used. The estimate of fecal output obtained was 1.8 ± 2.2% (mean percent difference ± SE) greater than the actual fecal output; the in vivo estimate of total digesta fill was 3.3 ± 3.4% less than measured digesta fill. For comparison, the present data were also analyzed using two established compartment modeling approaches, namely a time-independent and a time-dependent two-compartment model. The only significant difference between the estimated parameters as obtained from the Stewart – Hamilton method and the compartmental models was a significantly shorter transit time as estimated by the time-dependent model.

Sodium (Na) and potassium (K) concentrations in plasma, saliva, rumen liquor, urine, and feces were measured in reindeer, Rangifer tarandus, given diets high in Na and K (a commercial livestock ration), low in both minerals (lichens), and low in Na and high in K (summer range in interior Alaska). Sodium concentrations in plasma, urine, feces, and saliva were high in reindeer fed the commercial ration and were lower in reindeer grazing summer vegetation. Concentrations of Na and K in saliva were highly correlated with those in plasma. During summer, there was a decrease in saliva Na and an increase in K. The calculated salivary Na:K ratio for reindeer grazing summer vegetation (1.4:1 and 1.6:1) suggested Na insufficiency. Sodium concentrations were higher and within the normal range in saliva of reindeer fed lichens.

Body growth and carcass composition were measured in lean reindeer during the juvenile growth period between birth and 3 years of age. Mean carcass weight in these lean reindeer was 56 ± 4% of body weight and the deposition of body muscle and bone mass was linearly correlated with body weight after the 1st month of age. The weight of the brain relative to body weight and carcass weight declined, while the relative changes in heart, liver, kidneys, parotid glands, and tissues of the gastrointestinal tract were small after the neonatal period. The extractable fat content in carcasses increased from 4.4 to 11.4% of wet weight or approximately 100 g fat at birth and 3.5 kg fat in adult reindeer. Fat-free dry matter represented a constant percentage (18–20%) of wet carcass weight independent of body weight after the neonatal period, while a significant inverse relationship between carcass fat and body water was found.

Sodium pool size and transfer rate was estimated in reindeer (Rangifer tarandus L.) using intravenous and intraluminal injections of 22NaCl. Body water pool size and water transfer rate was estimated with 3HOH. Reindeer were consuming diets high in sodium (Na) and potassium (K) (commercial livestock ration), low in Na and high in K (summer grazing), and low in Na and K (lichens). The exchangeable Na pool size (milliequivalents per kilogram body weight) in reindeer given the high sodium diet (61 ± 2) was similar to other mammalian species. A marked decline in the pool (to 36 ± 3) was noted when reindeer were grazing summer vegetation in central Alaska and the Na pool was also low (46 ± 5) when they were fed lichens. Concentrations of Na in plasma, saliva, urine, and feces were directly correlated with the exchangeable Na pool size. Sodium transfer rates for reindeer given the high Na diet or grazing were two- to three-fold higher than daily Na intake rates. Loss of Na in feces and urine were of roughly equal importance in reindeer fed lichens or at pasture. Signs of Na insufficiency indicated by a salivary Na:K ratio of less than 2:1 were noted when the Na pool size declined below 40 mequiv./kg body weight. Evidence is presented for an extremely rapid replenishment of the Na pool following Na supplement of the diet.

The applicability of using individual bones and muscles as "indicator" tissues for the estimation of body composition in reindeer of various age groups from newborn to maturity was studied. In lean reindeer of both sexes, weights of selected muscles and bones were highly correlated with carcass weight. Total muscle weight was predicted accurately from the weight of each muscle, as was total bone weight from the weight of each indicator bone. Crude chemical composition of carcass was reflected accurately from analyses of indicator muscles. Bone marrow weights and fat contents, on the other hand, were not reliable indicators of body condition in lean reindeer. The use of specific muscles and bones represents an easy and reliable method for estimating body weight and crude chemical composition in reindeer, and opens the possibility through the biopsy sampling of muscle, of continuous monitoring of body condition in free-ranging animals.

Seasonal patterns of body weight, fat, protein, milk quality (dry matter content), and milk production rate were determined for three sexually mature female muskoxen (Ovibos moschatus) over three consecutive lactation periods. Females were allowed to graze in summer and had access to hay year-round. A high-protein pelleted ration supplemented this diet. Following calving in early May (1984, 1986) or June (1985), body weight remained constant throughout the summer, body fat declined for 3–5 weeks after calving, and body protein declined transiently during the latter period. Almost all annual gains in body weight and body fat occurred during the 6- to 8-week rutting period from mid-August to mid-October. High milk production (1.3–2.4 L/d) occurred 3 weeks post-calving, generally remained high for another month, and declined to 1.2 ± 0.15 L/d (mean ± SEM) just before the rut. A major decline in milk production, to 0.44 ± 0.050 L/d, occurred during the rut. Although milk dry matter increased 33% ± 4.3% during the rut, this increase was offset by the 60% ± 6.4% decline in milk production. All females successfully reproduced each year of the study and no evidence was found for a lactational anestrum. The hypothesis that gains in body weight must be made before the rutting period to maximize conception rate was rejected. This study highlighted the importance to lactating muskoxen of the late summer – early winter period for annual regain in body weight and body fat, which occurred concurrently with ovulation and conception.

The total body water of 27 rodents (live weights less than 100 g) were estimated by a tritiated water method and by direct analysis. There was no significant difference between the values as estimated by the two methods. The 95% confidence interval for total body water as estimated by the tritiated water method was ±10% of the value estimated from direct analysis. The accuracy of the method is acceptable for most applications, however, investigators should be cognizant of the estimate error, especially when calculating other components of body composition from total body water, e.g. body fat.

A radiotelemetry system for locating reindeer during both clear and overcast weather conditions was tested using reindeer fitted with transmitters and a light aircraft equipped with a directional receiver. The aircraft was guided to the reindeer by the transmitter signal and subsequently the position of the aircraft was determined by aviation navigational aids. Under simulated overcast weather conditions, reindeer were located within a circle of 3000 m radius. This accuracy was more than adequate to locate members of a herd so that a herder could be directed to his reindeer.

This study involved a group of horses that were snowbound during winter in the Alaska Mountain Range. The severe nutritional and environmental stresses offered a unique opportunity to study the effects of these stressors on the physiology of the horse. The horses were characterized for their basic hematologic, biochemical, and physical condition. Body water contents, body water kinetics, blood volumes, and plasma iron clearance rates were determined using radioisotope methods. These analyses were repeated after the horses were given liquid water, as opposed to snow, and once again after they were given liquid water and feed ad libitum. No significant differences in the measured physiological parameters were found between groups of horses on liquid water versus snow or limited feed versus ad libitum feed except that body water kinetics were directly related to feed intake. Physiological values obtained in this study were compared with literature values for non-stressed horses and no deviation from the normal ranges were found. The results may be interpreted as indicating a remarkable physical stamina for the horse.

The preference by reindeer for five species of lichens commonly found on Central Alaska rangelands was tested under controlled laboratory conditions. Results indicate that reindeer are strongly species selective in their lichen grazing habits. The five tested species ranged as follows in order of decreasing acceptibility: Caldonia alpestris, C. rangiferina, Stereocaulon paschale, Cetraria richardsonii, and Peltigera aphthosa.