Main page > News archive > Progut^® Info Letter 3/2009

11.12.2009

The effect of hydrolysed brewery yeast Progut^® on rumen fermentation characteristics in continuous rumen simulation

1.     Objective

The aim of the study was to investigate the effect of hydrolysed brewery yeast Progut on rumen microbial fermentation using a continuous rumen simulation method.  

2.      Materials and methods

The effect of Progut on rumen microbial fermentation was investigated in a rumen simulation study by Alimetrics Ltd. in Finland in 2009. Fermentation simulation was initiated with 0.5 g (dry wt) of feed, fresh inoculum from a fistulated cow and fermentation buffer mimicking ruminant saliva. Four replicates for each treatment was used to provide desired statistical significance for detected responses. The whole procedure was accomplished under complete anaerobiosis at 37 °C in order to mimic rumen system as closely as possible. The fermentation was continued for 24 hours after initiation and then 20% of fermentation vessel content was transferred to a new simulation vessel that was prepared as described above, except no fresh rumen inoculum was used for re-inoculation. This continuous re-inoculation procedure was continued for 7 days.

The gas production was measured at 6 and 24 hours after the re-inoculation. All gas produced during each 24 hours fermentation period was collected and used for methane analysis. After each 24 hours fermentation period the material (80% of fermentation vessel volume), not used for re-inoculation, was used for the following analyses:

• Microbial biomass production by flow cytometry counting
• Rumen energy production by short chain fatty acid analyses

The feed used in the simulation was a 1:1 mixture of compound feed and grass silage. Dunnett’s post hoc tests and t-tests were performed for every 24 hours period and for all measured parameters to determine which individual treatments differed from the control treatment.

3.      Results

3.1.           Applicability of the method

Data analysis indicated that the first six days of the continuous simulation performed as expected and provided no radical changes in any of the measured parameters. However, the last seventh day behaved strangely and showed a non-linear performance in comparison to earlier re-inoculations. The reason for this is not clear and therefore, the last day results were omitted from the data analyses.

3.2.           Progut stimulated rumen fermentation and reduced methane production

Progut addition, during the whole six day trial period, increased the total number of microbes (figure 1) and propionate production (figure 2). Interestingly, these parameters are among the most important for ruminant health and performance. Concerning propionate production the difference to the control was statistically significant in most of the time points. Progut also increased the production of total short chain fatty acids (figure 3). The results are showing very similar trends than previous rumen simulation trials at Alimetrics (n = 18) and at Hannover Veterinary High School (n = 4).

Figure 1. The effect of Progut on the total number of microbes

Figure 2. The effect of Progut on propionate production

Figure 3. The effect of Progut on SCFA production

Interestingly, Progut addition decreased methane production in the simulation (figure 4). During the first two days of the simulation this effect was small but it increased remarkably in the later phases of the simulation. The difference to the control was statistically significant during the day three to five of the trial. ;

Figure 4. The effect of Progut on methane production

In general propionate and the total number of microbes had an increasing trend and the other parameters a decreasing trend during the six day trial period (figures 1 - 4). In living animal, microbial metabolites are constantly being absorbed through rumen epithelium and rumen content is emptied with certain frequency. Because rumen model lacks the absorption and emptying and refilling is achieved only once in every 24 hours the model is prone to the slow tendencies shown in figures 1 – 4. The further method development will show if these tendencies can be removed by adjusting the feed quantity and re-inoculation frequency.

4.      Conclusions

-          Progut significantly or numerically increased the production of microbial biomass, propionate and SCFA during the six day rumen simulation

-          These results are well in accordance with the results from previous rumen simulation studies and from trials with fistulated cows