The effect of hydrolysed brewery yeast (Progut™)on rumen fermentation

  1. Objective

The aim of the trials was to study the effects of hydrolysed brewery yeast product Progut™ on rumen fermentation parameters in vitro and in vivo. The effect of Progut™ on the milk production of dairy cows has been studied at HelsinkiUniversity and in farm trials in different countries and reported earlier by Progut Info Letter 1/2007.

  1. Rumen simulation studies at Alimetrics Ltd.

The effect of Progut™ on rumen fermentation was investigated in a series of rumen simulation studies by Alimetrics Ltd. in Finland in 2006. An in vitro model imitating the rumen fermentation processes as closely as possible was used. Total gas production, pH and short chain fatty acid production (SCFA) was measured and the total number of microbes was determined by flow cytometry. The effects in vitro were verified later in vivo by a trial with fistulated cow.

2.1.Progut™ enhanced rumen fermentation rate

Rumen fermentation provides energy and protein for the animal. Therefore, a fast increase of microbial fermentation after feeding means more energy and protein. Furthermore, faster fermentation also means better degradation of feed material which enables higher feed intake to support high volumesof milk production. In the rumen simulation study Progut™ enhanced rumen fermentation rate significantly after feeding, the effect being independent from the basic feed raw materials tested (figure 1). The fermentation rate is calculated from microbial gas production and presented as maximum enhancement percentage compared with the control. The effect on gas production was dose dependent and it was most pronounced 4-6 hours after feeding.The tested diets were: Diet 1 - 50 % grass silage and 50 % compound feed A, Diet 2 - 50 % maize silage, 25 % barley meal and 25 % soy meal and Diet 3 - 50 % grass silage and 50 % compound feed B.

The effect of Progut™ on rumen fermentation was also tested in comparison with a competitive pure live yeast product (1 x 10E8 cells per gram) and with an inactivated yeast culture product. The results presented in figure 2 clearly indicate that Progut™ hadat least similar efficacy than the live yeast product and superior efficacy in comparison with the inactivated yeast culture product tested as measured at the same dose levels in the simulation.

Figure 1. The effect of Progut™ on microbial gas production with different diets

Figure 2. The effect of different yeast products on microbial gas production

2.2.Progut™ increased the energy and protein supply

It has been estimated that microbial protein accounts for 70-90 % of the cow's protein requirement and fatty acids account for up to 80 % of the energy requirement. In the rumen simulation study Progut™ increased both the production of energy and protein by increasing the number of rumen microbes and by increasing short chain fatty acid production during the simulation process (figure 3). When converting these effects to microbial protein and energy, it was seen that the addition of Progut™increased the protein and energy supply of ruminants (figure 4) remarkably.

Figure 3. The effect of Progut on rumen fermentation parameters

Figure 4. The effect of Progut™ on the protein and energy supply of ruminants (calculated from the effects on rumen fermentation parameters presented in above)

Progut™ had positive effects on all rumen fermentation parameters studied (table 1). The live yeast product studied had also positive effects on rumen fermentation and on the production of total SCFA and butyrate but its effects on the production of acetate and propionate and on the number of microbes were non-significant. The inactivated yeast culture product had an effect only on butyrate production. None of the tested yeast products was able to increase the pH of the rumenliquor. The proposed positive effect of yeasts on rumen pH in vivo may be due to higher roughage intake and due to possible changes in the composition of rumen microflora. Since the method used in this trial was batch fermentation, these types of effects weren't possible to detect.

Table 1. The effects of different yeast products on the rumen fermentation parameters in vitro

Progut™ / Live yeast product / Inactivated yeast culture product
Fermentation rate 0-6 hours / +++ **** / +++ *** / NS
Total SCFA / +++ ** / ++ * / NS
Acetic acid / ++ ** / NS / NS
Propionate / +++ ** / NS / NS
Butyrate / +++ ** / +++ **** / ++ ****
Microbes / +++ *** / NS / NS
pH / - * / - ** / NS

Symbols used:

+(-)Significant increase (decrease) by 0-5 %

++Significant increase by 5-10 %

+++ Significant increase by > 10 %

* 0.05 < p-value 0.01

** 0.01 < p-value 0.001

*** 0.001 < p-value 0.0001

**** p-value < 0.0001

  1. Rumen simulation studies at HannoverVeterinaryUniversity

In the rumen simulation studies at Hannover Veterinary University 2006, the rumen simulation technique (Rusitec) as described by Czerkawski and Breckenridge (1977) was used. In the first experiment standard Progut™ was tested and in the second experiment less hydrolyzed brewery yeast of the same raw material was used. The roughage to concentrate ratio in the trials was 55:45, the duration of the control period was 6 days and the duration of the trial period was 10 days. The results in figure 5are presented as a % from the control. The addition of Progut™ with both inclusion rates tested increased the production of total SCFA, acetic acid and propionate. The effect of the less hydrolyzed brewery yeast on rumen microbial metabolism was negligible. This indicates that the degree of hydrolysis is important for the efficacy of this type of yeast in the rumen.

Figure 5. The effects of Progut™ and less hydrolyzed brewery yeast on in vitro rumen microbial metabolism. Hannover Veterinary University 2006

  1. The effects of Progut™ on rumen fermentation measured with fistulated cow

A rumen fistulated cow received (6am and 3pm) 1 kg dose of compound feedtwice a day. Grass silage and water was available for the cow ab libitum. Progut, at a levelof 15grams per day, was mixed to the 6am compound feed diet to ensure homogenous mixing and rapid ingestion of the active ingredient. The sampling was done by aspiring rumen fluid with a vacuum pump. To reduce data variation the sampling was done every day three hours after the cow had fully consumed the morning compound feed dose.

The feeding protocol for Progut was as follows

  • Day 0 No Progut, a control sample
  • Day 1-7 Progut 15g per day
  • Day 8-14 No Progut, a washout period

In order toquantitatively analyze the effects of Progut™(15g per day) on rumen fermentation parameters, the data requires a mathematical model that has a statistically significant fit with the experimentally measured data. Therefore, many dynamic models were fitted to the data, and the best fit was reached with a model that assumes a linear increase for four days after the start of Progut feeding, a steady state until four days after Progut feeding was stopped and linear decrease after that. All rumen parameters were thereafter modeled by using the assumptions described above.

Results:

Progut™ increased all the studied rumen fermentation parameters compared with the control sample (table 2). The number of rumen microbes showed and increasing trend, but the high variation prevented the accurate modeling of the data.

Table 2. Summary of responses for Progut™ addition (ND = no accurate model due to high variation)

Maximum increase in %
SCFA / 40 %
Volatile fatty acids (VFA) / 39 %
Acetate / 35 %
Propionate / 40 %
Butyrate / 71 %
Microbes / ND

All the measured rumen fermentation parameters followed a similar pattern. A linear increase during the first four days of Progut™ feeding, a steady state until four days after Progut™ feeding was stopped and a linear decrease after that.For example, the volatile fatty acid (VFA) concentration increased from the control level during the first four days of Progut™ feeding, then stabilized and started to decrease after the feeding of Progut™ was stopped (figure 6). The same phenomenon was seen also with all the separate fatty acids, like propionate (figure 7).

Figure 6. The effect of Progut™ on the concentration of VFA with fistulated cow (r² = 0,54, p < 0.0001)

Figure 7. The effect of Progut™ on the concentration of propionate with fistulated cow (r² = 0.34, p < 0.0001)

  1. Conclusions

Alimetrics:

-Progut™ enhanced the rumen fermentation rate measured as microbial gas production. The effect on rumen fermentation was independent from the basic raw materials tested.

-Progut™ had significant positive effects on all of the rumen fermentation parameters studied. The live yeast product studied had similar positive effects on rumen fermentation rate and on production of total SCFA and butyrate while the inactivated yeast culture product had an effect only on butyrate production.

-Progut™ increased the production of protein and energy by increasing the number of rumen microbes and by increasing the production of SCFA. The extra protein and energy supply calculated from the simulation results corresponds well with the improvements of the milk production seen in the performance trials

Hannover:

-In the rumen simulation study at Hannover Veterinary High School Progut increased the production of total SCFA, acetic acid and propionate

Fistulated cow:

-15 grams of Progut per cow per day significantly increased the concentrations of VFA, acetic acid, propionate and butyrate

-Concentration of all the volatile fatty acids increased from the control level during the first four days of Progut™ feeding, then stabilized and started to decrease after the feeding of Progut™ was stopped

-The number of microbes showed an increasing trend but the high variation prevented the accurate modeling of the data

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