A Study of nitrogen metabolism, with special reference to mink
Creators: name: Oldfield, James Edmund
Publisher: name: University of British Columbia
Year: 2012

description: Experimental studies with mink at the University of British Columbia had their origin with the acquisition by the University of a mink colony in 1947. In September of that year various local mink ranchers donated some 60 animals to the University with a view to establishing an experimental unit on which research might be carried out. The ultimate object of such research was to be the formulation of definite feeding standards for mink, such as are already available for other species. This project was recognized as a long-term proposition, and initial experiments were designed to investigate the protein requirements, of mink. Preparatory to the experimental project, a survey of the literature concerning general nitrogen metabolism, and more particularly the concept of so-called "endogenous" nitrogen metabolism was carried out. This survey constitutes the opening portion of this Thesis. The actual experimental work undertaken was divided into two phases: 1. Investigation of the endogenous nitrogen excretion of mature animals maintained in a fasting condition, or on a nitrogen-free diet. 2. Conventional nitrogen balance trials, involving the establishment of nitrogen equilibrium at the lowest possible level, using certain specified sources of dietary protein. The method followed involved the collection and analysis of urine samples from adult animals maintained under different stated conditions of nutrition. Total nitrogen was determined by the Kjeldahl-Gunning procedure, and creatinine content was estimated by the Folin-Jaffe alkaline picrate reaction. Various supplementary procedures were instigated to guard against possible interference by abnormal urinary constituents. The results obtained would appear to have extensive implications regarding future investigations into the nutritive requirements of mink. First, at the expense of a great deal of time and effort, equipment has been built which has proven satisfactory for the laboratory investigation of this newly domesticated animal. Second, the close correlation of actual data with figures cited in the literature for other species of similar bodily dimensions suggests that the mink is not physiologically abnormal, and that predictions as to its nutritive behaviour may be made in comparison with other species with reasonable accuracy. Third, the experiments dealing with protein requirements suggest that considerable overfeeding of proteins may be common practice, especially in cases of mere maintenance of mature animals. A very strong suggestion is put forward for future studies into the biological values of different native proteins for mink. Detailed descriptions of analytical procedures and experimental equipment, and discussion of additional topics regarding mink nutrition are appended to the main body of the Thesis, in the hope that they may serve as a useful reference for future investigations along this theme. These latter include figures representative of time of passage and basal metabolism; reference to the natural diet of the mink in the wild state; correlations between organ size and body weight in mature animals, and weight changes exhibited by growing mink kits.