The pattern of protein and energy retention and the chemical composition of the body in White Leghorn pullets.

The change of body composition, energy content and energy and protein balance was studied in White Leghorn pullets from hatching to 140 days of age. The animals received corn, soybean meal and fish meal based diets ensuring maximal growth. Correlations were established between ingested feed and body weight gain both from the point of view of quantity and quality, determining the content of protein, fat, ash, water and energy in the total body and in feathers, separately. On the basis of digestibility and comparative slaughtering the energy and protein requirements for maintenance and for protein and fat retention were calculated. The obtained results can be utilised to develop a mathematical model for energy and protein retention in growing White Leghorn pullets.

The pattern of nutrient and energy utilization, retention and the chemical composition of the body in broilers from hatching to maturity.

The change of the body composition, of the energy content, and of the energy and protein balances was studied in male and female broiler chicks from hatching to maturity (about 140 days). The animals received corn, soybean meal and fish meal based diets which ensured maximal growth. Correlation were established between the ingested feed and the body evolution both from the point of view of quantity and quality, determining the content of protein, fat, ash, water and energy. By experiments of digestibility and by comparative slaughterings the energy and protein requirements both for maintenance and for protein and fat synthesis were determined.

Study on the energy and protein requirements in goats.

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%.

Study on the energy and protein metabolism in horses.

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.

Mathematical model for energy and protein balance simulation in broilers.

The authors used the empirical equations of mathematical modelling for the energy and protein balance simulation, with the view of calculating the body weight gain in broilers fed various diets. The results found by using the model were compared with the experimental data obtained by several authors. A standard deviation of +/- 1.20% and a mean error of +/- 0.28% and a mean error of +/- 0.28% which proved that the model average was a sufficient estimate of the experimental average were found. Furthermore, using the regression method, a significant correlation of variables was evidentiated.

Feeding value of corn and corn silage fed at different levels in the diets for young cattle.

4 heifers (268 to 400 kg live weight) were fed with four rations containing corn silage and corn flour in ratios of 82:18 (I), 65:35 (II), 45:55 (III) and 25:75 (IV). Urea was added to achieve an N balance. The rations were aimed at a daily weight gain of 700-800 g. The digestibility of the rations, their metabolizable energy, heat production and retained energy were determined. The digestibility of the organic matter was, in the sequence of I-IV = 73.2, 74.3, 75.4 and 75.8%. In the same sequence the energy intake per animal and day in MJ was = 95.9, 92.8, 91.3 and 89,7; the digestibility of the energy was 71.5, 72.2, 73.8 and 74.8%. In urine 3.1, 2.5, 2.7 and 2.9% and in methane 7.6, 7.8, 7.6 and 7.2% of the energy intake were excreted. Metabolizable energy was 60.8, 62.0, 63.5 and 64.7%, heat production 48.7, 48,7, 48.2 and 49.8% of the energy intake. 12.2, 13.2, 14.4 and 14.9% of the energy intake were retained. 51.6, 48.8, 42.4 and 40.1% of the retained energy was protein energy. The energetic feed value of both ration components has been calculated and stated according to various mathematical methods.

Efficiency of food utilization by pregnant and lactating sows. 2. The influence of isocaloric diets with different protein levels on pregnancy and lactation.

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.

Efficiency of utilisations of food energy by female growing minks.

The efficiency of utilisation of food energy by female growing minks, from weaning to adult age, was studied. The food given, pelleted according to an original technology, has the following chemical composition on a DM basis: 87.0% organic matter, 37.1% crude protein, 11.7% crude fat, 2.6% crude fiber, 35.6% nitrogen-free extractives and 13.0 per cent ash. Young minks had a feed intake, in relation to body weight, warying from 11.6 g to 58.6 g DM/d. Maximum feed intake related to kg0.75 was recorded at 700 g body weight (approximately 98 g DM/kg0.65). Digestibility of the given food expressed in DE, averaged 87.7 +/- 1.2%, while metabolizability, 82.3 +/- 1.1%. Total heat production related to the intaked gross energy, was 48.0 +/- 3.0%, and the retained energy, 34.3 +/- 4.0 per cent. The net efficiency of the metabolizable energy used for maintenance and production could not be accurately determined. However, taking to account the calculated values required for maintenance, of 649 kJ/kg0.75 in 300 to 600 g young minks, and of 607 kJ/kg0.75 in 600 to 1100 g young minks and also the maintenance efficiency, Km = 0.75, the coefficient for ME utilisation in protein and fat synthesis, of 0.50 and 0.75, respectively, it was able to determine the average ME efficiency used as net energy for maintenance and production: 70%. The highest values of nictemeral metabolism were recorded in the evening, and the lowest ones, at noon; the difference between the maximal and the minimal value did not exceed 6 per cent.

[Utilization of feed rations of varying protein content by growing pigs]. / Die Verwertung von Futterrationen mit verschiedenem Proteingehalt in der Ferkelaufzucht.

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.

[Feed conversion and the energy requirement of pregnant heifers]. / Die Verwertung des Futters und der Energiebedarf trächtiger Färsen.

Eight Holstein heifers were subjected to experiments running over the entire pregnancy period to investigate the conversion of rations mainly made up of maize silage (85% of the ration's dry matter) by the experimental animals. Both digestible and metabolizable energy (ME) and the energy requirement were studied. The live weight (LW) of the heifers was found to rise linearly during the entire pregnancy period being 422 kg at service and reaching 565 kg at calving. Feed intake, referred to 1 kg live weight0.75, was almost constant until the 7th month of gestation and declined gradually until parturition. The degree of digestibility and metabolizability of the energy contained in the silage-bases rations prove equal over the whole gestation period. The energy required for maintenance and gravidity (y) was found to rise exponentially as pregnancy advance (t). This relationship is reflected by the equation: ME, kcal/kg LW0.75y=135+0.2590.0206t range of significance=+/-0.07 During the last two months of gestation, a negative energy balance was found. This negative energy balance corresponds with a negative fat balance and a reduction, of the respiratory quotient, a fact suggesting to the mobilisation of body fat reserves by the mother to cover the increased energy requirement during pregnancy. The protein balance was found continuously positive during the entire gestation period. The conversion of metabolizable energy for fetus development was found to be 8.13%.