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Selected Publication:

Type of publication: Journal Article
Type of document: Review
Presentation type: Presentation

Year: 2020

Authors: Arnold, W

Title: Review: Seasonal differences in the physiology of wild northern ruminants.

Source: XIIIth International Symposium on Ruminant Physiology (ISRP 2019), Leipzig, Germany, SEP 3-6, 2019. Animal (14), S1 s124-s132.



Authors Vetmeduni Vienna:

Arnold Walter

Vetmed Research Units
Research Institute of Wildlife Ecology


Project(s): Polyunsaturated fatty acids and seasonal acclimatizatioin


Abstract:
Ruminants living in seasonal environments face a two-fold challenge during winter. The energetic cost of maintaining a high body temperature is higher at lower ambient temperatures, and this is compounded by poor availability and quality of feed. Wild ruminants acclimatize to this energetic challenge by hypothermia, that is, reduced endogenous heat production and abandoning the maintenance of a high body temperature, particularly in peripheral body parts. Further but lesser contributions to lower energy expenditure during winter are reduced foraging activity; lower heat increment of feeding; and reduced maintenance cost of size-reduced organs. Altogether, metabolic rate, estimated by the continuous measurement of heart rate, during winter is downregulated to more than half of the summer level, as is voluntary food intake, even in animals fed ad libitum. The transformation from the summer into the thrifty winter phenotype is also evident in the physiology of digestion. Microbial protein synthesis is less facilitated by diminished phosphorus secretion into the shrunk rumen during winter. In line with this result, the concentration of ammonia, the end-product of protein digestion in the rumen, peaks in rumen liquid in spring, whereas the molar proportion of acetate, an indicator of fermentation of a diet rich in fiber, peaks in winter. In contrast to reduced stimulation of growth of ruminal microbes during winter, active transport of nutrients across the intestinal epithelium is increased, resulting in more efficient exploitation of the lower amount and quality of ingested winter feed. Nevertheless, the energy balance remains negative during winter. This is compensated by using fat reserves accumulated during summer, which become a major metabolic fuel during winter.

Keywords Pubmed: Acclimatization
Ammoniametabolism
Animal Feed
Animals
Body Temperature Regulation
Dietary Fibermetabolism
Digestion
Eating
Energy Metabolism
Fermentation
Hot Temperature
Rumenmetabolism
Ruminantsphysiology
Seasons
Thermogenesis

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