SummaryThe efficiency of utilization of the energy of food by weaned pigs of the Large White breed was measured. Three diets based on maize (40–60%) had a metabolizable energy of 75·8±1·2% of the gross energy, and 78·2 ±3·4% of the metabolizable energy was present as net energy.The maintenance requirement of metabolizable energy of pigs weighing 14·3 ± 2·1 kg was 143·6 kcal/kg°0·75/24 h (601 kJ/kg0·75/24 h).The energy cost per g protein and fat synthesized by piglets was estimated to be 7·43 and 12·05 kcal (31·1 and 50·4 kJ) metabolizable energy, respectively.Equations for calculation of metabolizable energy (Yl, kcal) and of the net energy (Y2, kcal), based on digested nutrients, were:Y1 = 4·64×1 + 9·12×2 + 4·25×3'CV = ± 1·2%,Y2 = 3·84×1 + 7·09×2 + 3·28×3'CV = ± 1·4%,where X1 = g protein digested, X2 = g fat digested, X3= g carbohydrate digested (crude fibre × N-free extracts).

The present study focused on energy and protein metabolism in pregnant and lactating mares, including the suckling and weaned growing horses, in order to determine feed availability, as also the energy and protein requirements. The authors found that the feeding diets, consisting of alfalfa hay, oats and compounds, had different availability values in terms of energy and protein, according to animal physiological conditions and age. Thus, the pregnant mares utilized the metabolizable energy (ME) and digestible crude protein (DCP) intake in average proportions of 64.5 +/- 3.2%, 54.6 +/- 3.0%, respectively, while in the lactating mares the values were 60.1 +/- 2.8%, respectively, 50.1 +/- 4.0%. However the amount of energy and protein required for maintenance was similar in these two animal physiological conditions: 531 kJ, ME/kg0.75, 529 KJ, ME/kg0.75 and 3 g DCP/kg0.75, respectively. The suckling colts had a daily average gain between 1405 and 891 g and the young horses after weaning up to 2 years of age between 773 and 447 g. The net efficiency of ME and of DCP for growth in the suckling colts was of 40.6 +/- 2.1% and 46.1 +/- 3.2%, respectively and in young horses after weaning had similar values of 40.3 +/- 4.0%, respectively 44.4 +/- 2.2%, but the maintenance requirement of energy and protein differed from 506 kJ, ME/kg0.75 and 4.51 g DCP/kg0.75 respectively to 587 kJ, ME/kg0.75 and 3.51 g DCP/kg0.75, respectively.

SUMMARYThe efficiency of utilization of the energy of food in White Leghorn laying hens for egg production was measured. A ration with a gross energy of 4469 kcal/kg dry matter and 19·4% crude protein had a metabolizable energy of 80·1±1·7% of the gross energy, and 78·5±5·3% of the metabolizable energy was present as net energy.The maintenance requirement of metabolizable energy of White Leghorn hens weighing 1·723±48·5 kg and a production of 19·3±0–49 eggs per month was 125·8 kcal/kg0·75/24 hr.The energy cost per g of protein and fat synthesized by laying White Leghorn hens was estimated to be 7·20 and 12·13 kcal metabolizable energy respectively.

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 present study focussed on the energy and protein metabolism in pregnant and lactating goats, including young female goats up to 8 months of age, in order to determine feed availability, as also the energy and protein requirements. It was found that the diets consisting of alfalfa hay, oats hay, maize, wheat bran and mixed feeds (fed to suckling females) had different availabilities in terms of energy and protein, according to animal physiological condition and age. Thus, in pregnant goats, 21% of the metabolizable energy (ME) was used as net energy for pregnancy (foetus plus foetal membranes); the amount of energy required for maintenance was 0.400 MJ/kg 0.75. The availability of digestible protein in the intestines (PDI) for pregnancy was 41.2 +/- 3.1%, while the amount of protein required for maintenance was 2.32 g PDI/kg 0.75. In lactating goats 60.7% of the ME of the diets is used as milk net energy, and 58.9 of the PDI as milk protein. Young female goats had a daily net gain ranging between 173 g and 60 g; the amount of protein in the gain varied between 23 g (month 2) and 12 g (month 8); and that of fat, between 8 g (month 1) and 24 g (month 6). The energy and protein requirements for maintenance were found to be 0.450 MJ ME/kg 0.75 and 2.43 g PDI/kg 0.75, respectively. The net efficiency of ME for growth was of 46.2 +/- 3% and of PDI for protein retention, of 50.1 +/- 2%.