[The exactness of nitrogen balance in long-term metabolic studies]. / Uber die Exaktheit von Stickstoffbilanzen bei langfristigen Stoffwechselversuchen.

The N-retention calculated by balance experiments should, theoretically, be identical with the results obtained by chemical analysis of the animals. Experimental comparisons of both methods being reported in the literature are contradictory. To scrutinize this problem measurements of N-retention were conducted with 22 pigs by continuous balance experiments from 20-40 kg LW up to 110 kg LW (n = 16) or up to 160 kg LW (n = 6), respectively. At the end of the experimental period the animals were slaughtered and the N-content was determined quantitatively by chemical analysis of the whole bodies of the pigs. To calculate the N-content of the pigs at the beginning of the balance experiments 19 pigs were slaughtered and analysed quantitatively at 25 kg LW (n = 11) and 40 kg LW (n = 8), respectively. In all animals N deposits as determined by slaughter investigations were less as compared to balance experiments, the differences amounting to 6.7% of the calculated N-retention being equivalent to 93.3% analytical recovering of the N-retention as measured in balance experiments. The differences between both methods increased slightly with longer duration of the experiments resulting in 6.2% and 8.1% with the pigs of 110 kg and 160 kg final live weight, respectively. The differences must be regarded as being caused by accumulation of small errors completely coinciding into the same direction. Thus a certain overestimation of N-deposits by balance experiments might be looked at as being unavoidable irrespective considering any meticulous care in conducting the experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

[Energy requirement for the maintenance and utilization of energy convertible to protein and fat deposits in piglets]. / Untersuchungen zum energetischen Erhaltungsbedarf und zur Verwertung der umsetzbaren Energie für den Protein- und Fettansatz bei Ferkeln.

In respiration experiments with 16 piglets the effect of feeding level on energy metabolism was studied with the aim of estimating energy requirement and costs of protein and fat deposition. Four groups of 4 animals each were fed on different levels of digestible protein and metabolisable energy (ME). Group 1 was fed intensively, whereas the piglets of group 2, 3 and 4 received 92, 76 and 55% respectively of the amounts given to group 1. In the group 1-4 mean daily weight gain was 457, 437, 360 and 205 g respectively. As a consequence the rearing period increased from 44 days to 46, 56 and 98 days. The variation in feed intake affected not only significant differences in energy deposition but also changes in gain composition. In the groups 1-4 the average energy deposition was 4.2 MJ, 4.0 MJ, 3.0 MJ and 1.4 MJ per day and protein gain exceeded fat gain in all groups. Estimations of energy requirement for maintenance were carried out by means of multiple regression analysis using different models. As a result a value of 428 MJ ME per kg live weight 0.75 was obtained and the models used have hardly shown any influence. It seems that higher values for maintenance requirement, as formerly published, are due to different conditions of livestock management, such as temperature. For all groups the average efficiency of ME-utilisation for growth was 0.77, ranging from 0.73 to 0.82. The variation can be attributed to the changes in protein and fat formation. The groups with a higher proportion of protein in the accretion utilised metabolisable energy more efficiently than the intensively fed group 1 with the highest proportion of fat, the difference between the groups being in the range from 0.73 to 0.82. The efficiency of ME-utilisation for protein deposition was calculated to be 0.83 and for fat deposition 0.73. As a higher coefficient for fat formation may be expected in the light of the high fat content in the ration, calculations with an assumed coefficient from 0.75 and 0.80 had been carried out, showing that the efficiency of ME-utilisation for protein gain would only decrease to 0.79 and 0.73 respectively. According to these results the statement must be called in question, that the energetic efficiency of protein deposition of about 50 to 55% - as measured in numerous experiments mainly with older pigs - can generally be accepted.

[Dependence of rumen fatty acid production on the composition of rations]. / Untersuchungen über die Abhängigkeit der Fettsäureproduktion im Pansen von der Rationszusammensetzung.

In three experiments with two Black-and-White dairy cows the influence of soybean oil and coconut fat as well as that of rations rich in roughage and concentrated feed on the production of fatty acids were determined with the isotope dilution method. A change in the method of sampling from the rumen in the course of the investigations resulted in distinctly different absolute production quotas, which can presumably be traced back to the disproportionate mixing in of the isotope and/or different production quotas in various regions of the rumen. The relative differences between the production quotas dependent on the rations, however were approximately the same with both sampling methods, so that they make the comparison of the rations concerning rumen fermentation possible. The production of acetic acid and the total production of fatty acids (C2--C4) correlated closely both with the intake of digestible energy and the intake of digestible organic matter. There was also a highly significant correlation o that they make the comparison of the rations concerning rumen fermentation possible. The production of acetic acid and the total production of fatty acids (C2--C4) correlated closely both with the intake of digestible energy and the intake of digestible organic matter. There was also a highly significant correlation o that they make the comparison of the rations concerning rumen fermentation possible. The production of acetic acid and the total production of fatty acids (C2--C4) correlated closely both with the intake of digestible energy and the intake of digestible organic matter. There was also a highly significant correlation between the relation of acetic and propionic acid in the rumen fluid and the quotient from acetic and propionic acid produced. In contrast to this, a significant relation between the concentration of fatty acids and the production of fatty acids could not be ascertained. Soybean oil and coconut fat brought about a slightly better utilisation of the fat-free organic matter for the production of fatty acids in the rumen. This could mainly be traced back to the increased production of propionic acid. The production of acetic acid per kg fat-free organic matter was insignificantly reduced. A reduced quota of roughage in the ration as well as the use of feed fats resulted in a decrease in the production of acetic acid and an increase in the production of propionic acid. The influence of the quota of roughage, however, was bigger than that of the use of fats. When rations rich in roughage were given, the share the energy contained in the total fatty acids has in the total of the digested energy was, on an average of both animals, slightly lower in comparison to rations rich in concentrated feed. However, the reason for this is not to be found in a lower share the energy digested in the stomachs has in the total of digested energy but in a higher amount of fermentation losses with a nutrition rich in roughage.