SUMMARYThe efficiency of utilization of the energy of the food by growing pigs of the Large White breed was measured. Ten diets had a digestible energy varying from 75·3 ± 0·91 to 85·7 + 0·81% and a metabolizable energy from 72·3± ·92 to 83·4±0·64% of the gross energy. Net energy was 85·2±3·20% of the metabolizable energy (ME).Regression calculations resulted in the following estimates: a maintenance requirement of 151 kcal ME for growing pigs weighing 9–58 kg and efficiencies of 66·7 and 100% for the utilization of ME for protein and fat accretion, respectively.Feeding regime (ad libitum or restricted at about 80% ad libitum) did not influence food utilization.
The efficiency of utilization of feed energy as digestible, metabolizable and net energy is similar in pregnant and lactating sows irrespective of the stage of these physiological conditions. This efficiency with the value of about 71% resembles the one found in the growing and fattening pigs, which enables us to use, for this category of animals, the same system offered evaluation and of the energy requirements based on fat nutritive units. The maintenance energy requirement expressed in ME varies from 467 kJ/kg 0.75 in pregnant sows to 512 kJ/kg 0.75 in lactating sows, for the suckling piglets having intermediary value of 498 kJ/kg 0.75. The efficiency of utilization of diets protein for maintenance and for synthesis is also similar for these categories of pigs, varying from 71% in lactating sows to 75-76% in pregnant sows. In suckling piglets we had recorded an efficiency of DCP utilization which varies parabolically with size of the ingesta and therefore with that of weight gain. The DCP maintenance requirement expressed in g N dig./kg 0.75 varies within narrow limits between 0.345 g N in suckling piglets 0.380 g N in pregnant sows; In lactating sows we have detected an intermediary value of 0.355 g N. Based on these experimental data and also using recent experimental results obtained by Schiemann and Beyer (1984) regarding the energy and N content of the foetuses, of the organs of reproductions and of milk, we could calculate the energy and protein requirements. These requirements when compared with the values used in our country show us higher values of energy in pregnant and lactating sows and lower values of protein for the same categories, including the piglets, where we have also found lower values for the energy too.
In a total of 134 experiments concerning the general metabolism of growing pigs in a live weight range of 10 to 30 kg the nutrient and energy retention were investigated under the conditions of ad libitum feeding and feeding on the maintenance level including two fasting days, providing four rations with different protein concentration (16 to 22%). N-utilisation was ascertained as 81.2 +/- 4.2% and N-maintenance requirement as 0.199 g N per kg live weight0.75. The utilisation level of metabolisable energy (ME) was independent of the protein level but dependent on the method of calculation. The utilisation value of 73.8 +/- 3.0% was calculated as the best adaptation to the balance experiments altogether. It corresponds to the energy maintenance requirement of 434 kJ ME/kg live weight0.75. The standards of the energy requirement of growing pigs in the live weight range of 10 to 50 kg are derived from this results and earlier experiments and put up for discussion.
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