No abstract

1. The nature of the non-conjugated metabolites of the Eucalyptus oil terpenoid components alpha-pinene, beta-pinene, p-cymene and 1,8-cineole in the urine and faeces of the brushtail possum was investigated. 2. alpha-Pinene was metabolized to myrtenic acid and trans-verbenol, beta-pinene to myrtenic acid, p-cymene to p-cresol and cumic acid, and 1,8-cineole to p-cresol, 9-hydroxycineole and cineol-9-oic acid.

SummaryThis experiment compared changes in complex behaviour patterns, adrenal corticosteroid secretion and the numbers of various types of lymphocytes in sheep that were subjected to the stress of confinement. Grazing Merino ewes (n = 80 in five replicated experiments) were confined either in groups of four per pen or in total isolation from other sheep. The percentage of CD4 + lymphocytes increased while the percentage of CD8 + lymphocytes decreased over the experimental period. This result was more pronounced in isolated sheep than in grouped sheep. The increase in CD4:CD8 was greater for isolated sheep than for grouped sheep and greater for 2 week sheep than for 3 week sheep. The percentage of CD5 + cells also increased, less so in isolated than in grouped animals. Interpreting these changes as a recovery of immune competence following introduction of a stressor, it is apparent that isolation impaired immune system recovery more severely than group confinement. Physiological and behavioural adaptation over the period were characterized by a decline in the adrenocortical response, resumption of the normal pattern of flocking behaviour and a reduction in motor activity during the test. These findings add to the evidence pointing to the possible correspondence between critical features of the psychoneural, neuroendocrine and immune systems.

The disparity between the distribution and abundance of the koala (Phascolarctos cinereus) and its major food trees (Eucalyptus spp.) is examined in terms of the essential oil content of the leaves, the influence of weather, social behaviour, and the level of available nitrogenous food.The essential oils are considered to be relatively unimportant since the koala has the ability to detoxify them. It is proposed that the level of available nitrogenous food is the major limiting influence on the abundance of the koala. Social behaviour enables a few koalas to acquire sufficient food while the majority of the population is subject to a relative shortage of food. The weather varies the local availability of adequate nitrogenous food by its influence on leaf growth in the eucalypts.Unusually favourable weather or inappropriate management which lead to a local increase in the availability of young growing leaves (flush growth) may result in outbreaks in koala numbers.

The dimensions of different regions of the digestive tract and digestive efficiency were determined in koalas maintained on leaves from the grey gum, Eucalyptus punctata, in summer and winter trials. Intakes of wet and dry matter, and apparent digestibility of dry matter, compared favourably with values reported for various other herbivorous mammals. Seasonal differences were marginal. A low but positive nitrogen balance was generally maintained in both seasons, although the apparent digestibility of nitrogen was lower in winter. This was reflected in the values for dietary and apparent digestible nitrogen intakes required for the maintenance of similar levels of nitrogen equilibrium in summer and winter. Mean nitrogen balances in summer and winter were not significantly different at 0.040 and 0.034 g/kg W*0.75 per day respectively. Daily dietary nitrogen intakes were significantly different, however, at 0.426 and 0.493 g/kg W*0.75 in summer and winter respectively, while the apparent digestible nitrogen intakes were not significantly different at 0.180 and 0.127 g/kg W*0.75 per day respectively. This is discussed in relation to the quality of the food offered. It is concluded that the digestive tract of the koala, presumably aided by the relatively large caecum, is well suited to the fibrous dietary matter on which the animal feeds.