Zusammenfassung Maßgeblich für die Proteinversorgung von Wiederkäuern ist die Menge an nutzbarem Rohprotein (nXP) am Duodenum. Um diese aus Rationsparametern abschätzen zu können, wurden anhand von 532 Einzeltiermessungen aus Braunschweig‐Völkenrode und Dummerstorf‐Rostock an fistulierten Milchkühen Regressionsgleichungen zur Bestimmung des nutzbaren Rohproteins am Duodenum abgeleitet. Als wichtigste Einflußfaktoren auf den Fluß an nutzbarem Rohprotein bestätigte sich die Aufnahme an umsetzbarer Energie (ME) oder verdaulicher organischer Substanz (DOS) und an nativem Futterrohprotein. Eine gewisse Verbesserung der Schätzgenauigkeit ergab sich durch Einbeziehung der in 335 Messungen bestimmten Menge an ruminal nicht abgebautem Futterrohprotein (UDP). Noch etwas geringer wurde der Schätzfehler bei Berücksichtigung der Wechselbeziehung zwischen mikrobieller Proteinsynthese und Abbaubarkeit des Futterrohproteins (XP) im Pansen. Die Schätzgleichungen mit dem höchsten Bestimmtheitsmaß (r2 = 0,91) und dem geringsten Variationskoeffizienten (cv = 8,9) lauteten: g nXP = [11,93 ‐ (6,82 (UDP/XP))]ME + 1,03 UDP, und g nXP = [187,7 ‐ (115,4 (UDP/XP))]DOS + 1,03 UDP

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Experiments were carried out to examine the effects of a Fusarium contaminated wheat (10 mg deoxynivalenol and 0.76 mg zearalenone, ZON, per kg dry matter) and of a detoxifying agent (Mycofix Plus, Biomin GmbH, Herzogenburg, Austria) on the growing performance of bulls, carry-over of ZON and its metabolites into body fluids and tissues, and on nutrient digestibility in wethers. The experiments were designed according to a complete two by two factorial approach which meant that both the uncontaminated control wheat and the Fusarium toxin contaminated wheat were tested both in the absence and presence of Mycofix Plus. The growing experiment with bulls (n = 14 per treatment) covered the live weight range between 244 kg and 460 kg. The respective wheat batches were included in the concentrate portion at 65%. Concentrates were fed according to plan whereas maize silage was offered for ad libitum consumption. Daily dry matter intake and live weight gain [kg per animal and day] were 7.40, 7.52, 7.51 and 7.49 and 1.367, 1.296, 1.380 and 1.307 for bulls fed the unsupplemented control wheat, the supplemented control wheat, the unsupplemented and Fusarium toxin contaminated wheat and the supplemented Fusarium toxin contaminated wheat, respectively. ZON and its metabolites were not detected in edible tissues. The most striking effects of feeding the Fusarium toxin contaminated wheat on carcass characteristics were a reduced dressing percentage, an increased weight of the emptied gastro-intestinal tract and a reduced weight of the testicles. No effect of the detoxifying agent was seen for these parameters whereas heart weight increased independently of Fusarium toxin contamination of the concentrates. Nutrient digestibility of the two wheat batches, unsupplemented or supplemented with Mycofix Plus was evaluated according to the difference method using wethers. Presence of Fusarium toxins in wheat did not influence its feeding value. The effects of the addition of the detoxifying agent were mycotoxin unspecific and resulted in an increase in apparent digestibility of crude protein and a decrease in crude fiber digestibility. It is concluded that feeding of Fusarium toxin contaminated wheat did not adversely affect performance of growing bulls (approximately 2.2 mg DON and 0.1 mg ZON per kg complete ration at a reference dry matter content of 88%) or nutrient digestibility in wethers. The effects of the detoxifying agent Mycofix Plus on growing performance and on nutrient digestibility were rather Fusarium toxin unspecific. The slightly negative effects on growing performance needs to be examined further.

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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.