The effect of the protein solubility of fish meal and the roughage content of the supplemented diet on its digestion by sheep

No Abstract

Environment, Migratory Tendency, Phylogeny and Basal Metabolic Rate in Birds

Basal metabolic rate (BMR) represents the minimum maintenance energy requirement of an endotherm and has far-reaching consequences for interactions between animals and their environments. Avian BMR exhibits considerable variation that is independent of body mass. Some long-distance migrants have been found to exhibit particularly high BMR, traditionally interpreted as being related to the energetic demands of long-distance migration. Here we use a global dataset to evaluate differences in BMR between migrants and non-migrants, and to examine the effects of environmental variables. The BMR of migrant species is significantly higher than that of non-migrants. Intriguingly, while the elevated BMR of migrants on their breeding grounds may reflect the metabolic machinery required for long-distance movements, an alternative (and statistically stronger) explanation is their occupation of predominantly cold high-latitude breeding areas. Among several environmental predictors, average annual temperature has the strongest effect on BMR, with a 50% reduction associated with a 20°C gradient. The negative effects of temperature variables on BMR hold separately for migrants and non-migrants and are not due their different climatic associations. BMR in migrants shows a much lower degree of phylogenetic inertia. Our findings indicate that migratory tendency need not necessarily be invoked to explain the higher BMR of migrants. A weaker phylogenetic signal observed in migrants supports the notion of strong phenotypic flexibility in this group which facilitates migration-related BMR adjustments that occur above and beyond environmental conditions. In contrast to the findings of previous analyses of mammalian BMR, primary productivity, aridity or precipitation variability do not appear to be important environmental correlates of avian BMR. The strong effects of temperature-related variables and varying phylogenetic effects reiterate the importance of addressing both broad-scale and individual-scale variation for understanding the determinants of BMR

Thermolability, Heat Tolerance and Renal Function In the Dassie or Hyrax, Procavia Capensis

In a series of experiments, designed to examine renal function and thermoregulation in the dassie, the following observations were made: The dassie is unable to exist indefinitely on a dry diet without water. After 8 days without water, feed intake ceases. Water consumption is relatively low, amounting to 45,7 mllkg, which suggests efficient renal function. Faecal water loss is minimal wh.en the animals are dehydrated. A faecal moisture value as low as 35 per cent was obtained after nine days of dehydration. The capacity of the dassie kidney to concentrate electrolytes and urea is very high. The maximum recorded osmolality of the urine was 3 088 mOsm/kg, which is comparable to that of the camel. The most unusual feature of renal function in the dassie is the excretion of large amounts of undissolved calcium carbonate in the urine. The body temperature at comfortable ambient temperatures (2OC) was lower than expected for a mammal of this size and may be implicated in spermatogenesis in the intra-abdominally situated testes of these animals. The dassie appears to be very thermolabile and has surprisingly low heat tolerance. Above 35C (ambient) the animals develop hyperthermia and exhibit fairly profuse nasal sweating. The upper incipient lethal temperature appears to be above 35C but less than 4OC

Thyrocalcitonin studies in elasmobranch fish

Zoologica Africana 4(1): 95-9