Browsing by Person "Zuber, Karin Helga Renate"

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Fermentations- und Syntheseleistung der mikrobiellen Gemeinschaft des Pansens in vitro bei Variation der Grobfutter- und Stickstoffquellen
(2017) Zuber, Karin Helga Renate; Rodehutscord, Markus
In the first part of this doctoral thesis five batches of maize silage (MS), five batches of grass silage (GS) and three batches of alfalfa silage were incubated in the Hohenheim gas test. The variation of silages based on in vitro gas production kinetics and ammonia-nitrogen-concentration (NH3-N-concentration) in the mixture of rumen liquid and buffer solution over time was determined. For this purpose, 10 glass syringes per silage batch were used per experimental run. 3 glass syringes were used to determine the gas volume over 72 hours. The remaining 7 glass syringes were removed from the incubator at 7 time points and the NH3-N-concentration in the mixture of rumen liquid and buffer solution was determined. Upon the incubation of the 13 silages both silage species and batch had an influence on the potential gas production and on the rate constant of gas production. The determined potential gas production was between 62.5–74.2, 56.0–64.9 and 39.9–59.6 mL/200 mg organic matter (OM) for MS, GS and alfalfa silages. The rate constant of gas production amounted to 5.5–7.3, 3.8–7.1 and 5.0–7.7 %/h for MS, GS and alfalfa silages. Both silage species and batch as well as the time point and their interactions had an influence on the NH3-N-concentration in the mixture of rumen liquid and buffer solution. In the second part of this work one MS and one GS were incubated in the rumen simulation Rusitec. The influence of the forage source without supplementation of concentrates on the NH3-N-concentration in fermenter liquids over time and the fermentation and synthesis characteristics of the ruminal microbial community were investigated in vitro. Degradation of nutrients, gas, methane and short chain fatty acid (SCFA) production as well as NH3-N in effluent and microbial protein synthesis (MPS) were measured. The NH3-N-concentration in fermenter liquids was determined at different time points within two periods. Upon the incubation of GS, degradation of OM and fibre fractions, amount of NH3-N in the effluent as well as MPS and its efficiency (EMPS) was higher than with incubation of MS. Degradation of crude protein (CP) and total amount of SCFA were unaffected by silage. N-efficiency was higher with incubation of MS than with incubation of GS. During period 1, NH3-N-concentration in fermenter liquids increased for all treatments within the first 24 hours and was not different between the treatments. For GS, NH3-N-concentration subsequently continued to rise up to a maximum value at the last time point of measurement in period 1. NH3-N-concentrations in fermenter liquids in period 2 remained on a relatively constant level for MS and GS, differing between the two silages at all five time points of measurement. Mean NH3-N-concentration in fermenter liquids measured in period 2 corresponded in level with NH3-N-concentration determined in the effluent of both silages. In the third part of this work, the influence of different N-supplements to MS compared to GS on fermentation and synthesis characteristics of the ruminal microbial community in vitro was investigated. GS and MS were incubated in a Rusitec, the latter being either unsupplemented or supplemented with urea, pea protein, pea peptone or a mixture of amino acids to adjust N-content of MS to that of GS. The NH3-N-concentration in fermenter liquids was determined 0, 2, 4, 12 and 24 hours after changing the feed bag on day 12. Results concerning degradation of OM, CP and N-free extracts showed a positive influence of N-supplementations except for MS+pea protein. Furthermore, degradation of detergent fibres were partially improved through N-supplementations. The values of MPS and EMPS were enhanced through all N-supplementations. Thereby supplementation of urea and pea peptone to MS resulted in the largest increase in EMPS. However, through none of the N-supplements the level of GS in EMPS could be achieved. The determined course of NH3-N-concentration in fermenter liquids was largely similar between the treatments. Variation in nutrient composition of MS, GS and alfalfa silages were reflected in a large variation both in gas production kinetics and curve shape of NH3-N-concentration in the mixture of rumen liquid and buffer solution. Upon the sole incubation of MS and GS in the Rusitec, GS promoted MPS and EMPS stronger than MS. Supplementation of MS with different N-sources resulted in an increase in MPS and EMPS compared to MS without N-supplementation. Thus the assumption of an insufficient N-supply of ruminal microbes during the sole incubation of MS in vitro was confirmed. However, through none of the N-supplementations level of GS in EMPS could be achieved.