| Abstract: | In 3 experiments young broiler chickens were supplied on various feeding levels in the growth range between 200 and 2500 g live weight (2.8 and 2.0 in experiment 1, 2.8, 2.3 and 1.8 in experiments 2 and 4, maintenance = feeding level 1.0). In experiments 1 and 2 short-time measurings (30 min) of heat production by means of gas exchange were made at 500, 1000, 1500 and 2000 g live weight in the post-absorptive state and on the maintenance level of feeding. In experiment 1 the heat production of the restrictively fed chickens was in 3 out of the 4 stages of development studied significantly lower by 10-14% than that of the intensively fed ones. In experiment 2 such an effect could not be observed. Fed on the level of energy maintenance, broilers weighing approximately 2000 g (experiment 3) did not show a significant influence of the sex on heat production as a result of 30-minute gas exchange measurings in the post-absorptive state. In experiment 4 24-hour measurings of the energy metabolism were carried out in the growth development in periods of feeding on the maintenance level by means of indirect calorimetry. In the live weight range between 0.9 and 1.3 kg there was only a low, non-significant decrease of the energy maintenance requirement of 4-6% of the highly restrictively fed chickens in comparison to the intensively fed ones. After continued feed restriction (live weight range 1.7-2.2 kg) an energy maintenance requirement reduced by 17% was measured. In an analogously arranged experiment with 24-hour energy metabolism measurings (experiment 5) male Wistar rats in the growth range between 70 and 280 g were supplied on the feeding levels 1.8 and 1.4 resp. In all three periods studied on the feeding level maintenance--beginning at 140-150 g live weight--the highly restrictively fed animals showed a slightly reduced energy maintenance requirement by 8%, 3% (non-significant) and 6% in comparison with the intensively fed animals. |
