• Carbon And Nitrogen Flows In Zero -Water Exchange Shrimp Culture: Inferences Using Stable Isotope Tracers

      Epp, Michelle A.; Schell, Donald M. (2002)
      Nutrient and energy flow in cultures of Pacific White Shrimp, Litopenaeus vannamei, were examined in zero-water exchange, 1200--1300 L mesocosms at the Oceanic Institute (OI), Waimanalo, Hawaii. A technique was developed for monitoring shrimp use of formulated feeds through the addition of stable isotopically labeled nutrients to the feed ingredients. Crystalline amino acid compounds were ineffective as labels due to their rapid dissolution in the tank water with feed pellet break-up. Labels which were 'packaged' as algal cells prior to addition to the feed pellets were more effectively incorporated into shrimp tissues than crystalline label (approximately 27% versus 8% for crystalline label). The 'packaged' label technique was also used to test soluble proteins from pollock processing wastes (stickwater) as a feeding stimulant for Litopenaeus vannamei. Indoor controlled condition experiments and outdoor experiments with natural pond biota compared stickwater amended feed to squid liver powder amended feed for growth and assimilation by the shrimp. Initial results indicated that pollock processing by-products might function as a feeding stimulant in shrimp aquaculture. The addition of 15N-ammonium to outdoor shrimp tanks showed that natural tank production contributed significantly to shrimp growth requirements providing between 17 and 77% of the growth nitrogen. When labeled ammonium was added to black covered tanks, shrimp had slower growth rates (0.5 g/wk as compared to 0.7 g/wk for uncovered ammonium addition tanks) but significant uptake of this label, with a tank biota contributing 23%. This finding supported a bacterial role in shrimp nutrition that will require further study. Isotopic analysis of individual amino acids in shrimp muscle from outdoor tanks with and without added 15N-ammonium further established the role of tank natural populations to shrimp nutrition. Rapid increases in delta 15N for threonine one day after label addition suggested an increased requirement for this essential amino acid. Further identification of the contribution of tank biota to shrimp amino acid profiles will require profiles of the delta 15N of specific amino acids for suspended particulate organic matter.
    • Daily Meal Patterns, Voluntary Food Intake And Fattening Of Reindeer During Winter And Responses To Insulin

      Stimmelmayr, Raphaela; White, R. G.; Drew, K. L. (2001)
      I determined the effect of insulin injections on daily feeding behavior and voluntary food intake (VFI) in reindeer (Rangifer tarandus t. ) fed a concentrate ration during winter. Food intake in the absence of insulin injections was down regulated and characterized by small, regular meals during daylight and irregular and sometimes large nighttime meals. Each large nighttime meal was associated with a long post-meal interval. Daytime meal size could be predicted from an estimate of the energy deficit incurred since the previous meal; however, the occasional oversized nighttime meals were not predicted from energy deficit and suggested that appetite may be deregulated at night. I hypothesized that a low daily dose of long acting insulin (1.0 IU/kg BW, s.c.) would result in regular feeding day and night, which should result in reduced VFI. Changes in serum insulin concentration could not be detected following insulin treatment, however exogenous insulin resulted in a loss of daytime and nighttime differences in meal size and intermeal interval length and a decrease in mean daily meal size. Over a 21 d treatment period, exogenous insulin prevented an increase in VFI during a warming trend and tended to counter a linear decline in body mass and backfat depth (measured by ultra-sound) typified by control animals (given Lactate Ringer 0.005 ml/kg BW, s.c.). The influence of insulin over fat retention suggests that reindeer are capable of lipogenesis in winter. A combination of rhythmic variation in satiety response to meals during daylight and decoupling of meal size and frequency at night is suggested as an endocrine model underlying daily appetite regulation in the reindeer.
    • Diet-induced thermogenesis in a carnivore, the arctic fox, Alopex lagopus

      Tallas, Peter George; White, Robert G. (1986)
      Carnivores consume diets low in carbohydrate and high in protein and fat. The high dietary levels of protein and fat are thought to contribute greatly to diet-induced thermogenesis (DIT), i.e. the increase in metabolic rate associated with feeding. Low dietary levels of carbohydrate cause the carnivore to stress gluconeogenesis. Consequently, a well developed capacity for gluconeogenesis may be an important adaptation in the carnivorous arctic fox (Alopex lagopus), and may participate in DIT. The objectives of this study of the arctic fox were to (i) determine DIT associated with four diets that varied in the proportion of fat, protein, and carbohydrate, and (ii) assess glucose utilization in the fed and fasted arctic fox. Fox were fed four diets (high protein, high fat, high carbohydrate, and high protein/fat) at three levels of energy intake (sub-maintenance, near/above maintenance, and above maintenance). Pre- and postfeeding metabolic rates were measured by open circuit indirect calorimetry. The results indicate that (i) DIT contributes significantly to total heat production of the fox, but is dependent on diet type and energy intake, (ii) DIT is non-existent at sub-maintenance energy intake, regardless of dietary nutrients, and (iii) the high fat diet is associated with the highest prefeeding and postfeeding metabolic rate at sub-maintenance energy intake, although DIT is non-existent at all levels of energy intake. For the assessment of glucose turnover, four arctic fox were fed, over a long term, a low carbohydrate, high protein/fat diet. Fed and fasted fox were injected intravenously with radiolabeled glucose, and their blood assayed over time for disappearance of the labeled glucose. The results indicate that glucose metabolism, i.e. total entry rate and irreversible loss, is high compared to other animals, and may support the high blood glucose concentrations of the arctic fox, but does not participate in DIT.
    • Influence of weather on movements and migrations of caribou

      Eastland, Warren George (1991)
      Caribou (Rangifer tarandus granti) are typified by use of calving grounds and by making twice-annual migrations between summer and winter ranges. This study used satellite technology to examine the influence of weather on calving site selection, autumn and spring movements, and timing and directionality of migrations of the Porcupine Caribou Herd (PCH) that calves in northeast Alaska and northwestern Canada adjacent to the Beaufort Sea. The reigning hypothesis that females select areas that become free of snow early for calving sites was rejected because females selected areas of $>$75% snowcover ($P=0.02$) preferentially for calving. Benefits from use of mottled snow for calving were access to vegetation in its early phenological stages and protection for their calves from predators. Access to nutritious forage and predator avoidance appeared to be the main reasons for calving site selection. Multiple linear regression models were used to examine rate and direction of autumn and spring migrations using weather data from U.S. and Canadian sources. Weather was found to be both an ultimate and an approximate influence on the rate and direction of autumn migration ($P<0.05$). Explanatory power of the equations was low ($R\sb{a}\sp2<0.41$). Proximal causes of movement were best explained by caribou tracking of vegetation phenology. Pre-rut movements in September lacked concurrence between rate and direction whereas rate and direction were related in October. Models of spring migration of parturient females indicated a common timing among years, late April and early May, and movements were significantly affected by weather ($P<0.02$), in particular snow depths and conditions that would affect foraging and traveling conditions. This study suggests that: (1) females preferentially use areas of delayed snow melt for calving, and (2) weather influences both spring and autumn migration of caribou, although the effect of weather may be more indirect than direct.
    • The effect of diet on energy partitioning in moose

      Hubbert, Michael Everett; White, Robert G. (1987)
      Moose (Alces alces) have dynamic seasonal patterns of food intake and body weight changes. Body weight may vary by 35% from winter lows to summer highs. Food intake levels during summer may exceed winter levels by up to a factor of 5. Forage quality and availability are thought to drive the seasonal patterns of food intake and weight loss. Changes in digestive strategy of moose in winter and spring were analyzed in this thesis. During December, the total mean retention time (TMRT) of food in the alimentary tract increased as dry matter intake decreased, while alimentary fill remained constant. In contrast, during April TMRT did not increase with increased intake; rather, alimentary fill increased. There appeared to be a seasonal digestive strategy for optimizing nutrient intake. True basal metabolic rate (TBM) was estimated using regression analysis of heat production on metabolizable energy intake. TBM was estimated at 68.8, close to the interspecies mean of 70 (kcal/kg BW$\sp{0.75}$/d). However, differences in TBM noted during December, February, and April were not significant. Paper birch (Betula papyrifera) twigs were collected during winter and cut from the tip to 8 specific diameters (2-9 mm), and analyzed for neutral detergent fiber, acid detergent fiber, crude protein, acid detergent lignin, ash, and in vitro dry matter disappearance. Results indicated that dietary quality decreased with increasing diameter. Moose subjected to 4 different stocking rates (23, 31, 41, and 66% utilization of paper birch) showed no difference in the diameter of paper birch (mean = 2.66 mm) harvested. A simulation model was presented in which food intake by moose was controlled by both physiological demands and alimentary capacity. Seasonal estimates of food intake changed with energy demands. The model proved useful in estimating seasonal energy requirements of moose.
    • The Turnover Of 75-Selenium - Selenomethionine As An Indicator Of The Status Of Protein Metabolism In Reindeer (Rangifer Tarandus) (Degradation Rate, Reincorporation, Reutilization)

      Blanchard, John Michael (1983)
      The turnover of a single injection of ('75)Se-selenomethionine (('75)SeM), a radio-labeled seleno-analog of the amino acid methionine was used to estimate protein turnover, the irreversible loss of protein nitrogen, in reindeer. ('75)Se-selenomethionine turnover was measured in nine adult female reindeer grazing on natural forage during winter (November-April) and summer (July-August). ('75)Se-selenomethionine turnover was two to four times higher during summer than during the winter months. Seasonal changes in ('75)SeM turnover were believed to be due primarily to seasonal changes in protein and/or methionine intake. The relationship between the intakes of protein and methionine and the turnover of ('75)SeM was determined in ten pen-fed reindeer. Reindeer consumed one of three rations containing 3, 11, or 18 percent crude protein. This resulted in daily crude protein intakes of 1.6, 5.1, or 8.2 g per kg ('0.75) b.w. and daily methionine intakes of 0.01, 0.06, or 0.12 g per kg ('0.75) b.w. ('75)Se-selenomethionine turnover was four times higher for reindeer with high protein and methionine intakes than those reindeer consuming low levels of these nutrients. High positive correlations were found between ('75)SeM turnover and the intake of crude protein and methionine. The method of using ('75)SeM as an indicator of protein turnover showed a good empirical relation, but application to other biological conditions should be accompanied by calibration trials.