Variation au cours du cycle annuel de l'état nutritionnel du vison mâle adulte. II. - Production de chaleur et besoins d'entretien

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Abstract
During 14 consecutive months, 4 minks of group A, fed ad lib the same pelleted diet stayed together 13 times in respiratory chamber during 3 days (3 .times. 23 h). The level of intake was always lower during the stay in chamber. The respiratory quotients were < 1 (0.76-0.91). The daily heat productions (CN balance) were relatively constant. When calculated on the basis of live weight or metabolic size, heat production was lower in winter, from Nov.-Feb., than in summer from April-Sept. (149 and 167 kcal/Wkg0.75, respectively). An attempt was made to estimate the energy requirement for maintenance: 155 kcal ME/Wkg0.75. Taking into account this value, metabolizable energy for production was calculated individually for 6 periods of the weight cycle observed in part I. The comparison with the live weight change during these periods made evident the accuracy of this value for animals staying in experimental room but showed that in mink farm (group V), requirement was higher (195 kcal/Wkg0.75) probably due to outdoor conditions (larger changes in temperature). The patterns of mean O2 consumption during a day pointed out high differences between short and long day-night. The influence of photoperiodism on these animals was also suggested by evolutions of hormonal plasma concentration (thyroxine, testosterone) shown by several authors.