Studies of weaner sheep during and after a period of weight stasis. I. Energy and nitrogen utilization

Abstract

Wether sheep (4 months old) were held at 20 kg liveweight for either 4 or 6 months by restricting their food intake, and then fed ad libitum to recover weight for age.

Voluntary food intake during recovery was recorded for several months in 20 penned animals. Basal metabolic rate was estimated in eight other sheep at intervals during weight stasis and once after a month of recovery. Complete balances of energy, carbon and nitrogen were measured continuously in the latter sheep during the first month of recovery and in immediately preceding and succeeding short periods at 'maintenance'. Control data were derived from an earlier experiment.

Voluntary food intake was greater during rehabilitation than in controls of the same weight.

Basal metabolic rate per kg¾ tended to fall during the period of weight stasis. It rose in the first month of recovery but by a smaller amount than predicted for controls growing at the same rate.

Net energetic efficiency was probably higher than normal, and maintenance requirement lower, in the first week of recovery, but otherwise was the same as for the controls. Hence, apart from this first week, gross efficiency was unusually high solely because voluntary food intake was high relative to maintenance requirement. Nitrogen utilization was also more efficient in the first week or two of compensation than predicted for control sheep of the particular body weights and energy intakes.