FEED Business Worldwide March, 2012
How Bonsilage Plus increases ruminant's crude protein availability
by Dr. Ewald KRAMER, ISF GmbH Pinneberg
Protein evaluation system for ruminants
The German protein evaluation system for ruminants is based on the principle of usable crude protein in the small intestine (nXP), which is composed of microbial protein (MP) formed in the rumen and bypass protein (UDP). In addition, it is generally known that the amount of UDP in the ration of a high-yielding cow needs to be increased compared with an average-performing cow, in order to meet its nXP requirements (see Figure 1).
Protein quality of grass as a basic fodder
During silaging, vegetable protein undergoes extensive degradation and conversion processes (proteolysis). The amount of UDP is reduced and non-protein nitrogen (NPN) compounds are produced, including NH3-N, free amino acids (AAs), peptides and biogenic amines.
If present in large quantities, these lead to a considerable surplus of nitrogen (N) in the rumen which has to be detoxified to some extent via urea in the liver. This is often at the expense of the animal's health.
Test laboratories do not record the conversion processes undergone by the vegetable protein: routine silage analysis determines only the crude protein (XP) and does not provide any further information on UDP content, for example.
Recently, an extensive test method has made it possible to calculate the UDP content of silage. To do so, it is necessary to assign the vegetable protein by means of wet-chemical heating processes to certain fractions depending on their speed and extent of release in the rumen ('CNCPS' system - see Figure 2).
The other main advantage of this method - besides its capacity to calculate bypass protein (UDP) content– is the ability to use the determination of protein fractions to document the extent of the changes occurring in the vegetable protein as it develops from fresh grass into silage.
Proteolytic activity in the silaging process is unavoidable to a certain extent and attributable to the activity of plant enzymes. In addition, protein is broken down by clostridia and enterobacteria, which in turn are suppressed by highly competitive lactic acid bacteria.
This information also explains why some proteolysis is pH independent, and why its extent can be reduced considerably by means of a rapid and lasting pH reduction at the start of silaging.
Figure 3 shows the protein fractions according to the CNCPS system for fresh grass, a silage with good fermentation quality and a silage with poorer fermentation quality. The differences are clear: In the silage with poorer fermentation quality, the proportion of fraction A is much higher and the proportion of fraction B2 much lower compared with fresh grass and the good-quality silage.
It is an established fact that the targeted use of specialised lactic acid bacteria can improve the fermentation of grass silage. That this also leads to less protein degradation during silaging could previously only be inferred from the proportion of NH3-N in total nitrogen. With the use of special lactic acid bacteria, that proportion is much lower than in an untreated variant.
Protein quality test results
As part of a large-scale trial, first-cut grass from permanent grassland was silaged by the field trial station in three dry matter ranges (20-30 %; 30-40 %; 40-50 %) and two fertiliser variants (25 m3 slurry + 100 kg CAN; 25 m3 slurry + 250 kg CAN).
Each sample type was divided into test groups that were either treated or not treated with Bonsilage Plus. The LWK (Chamber of Agriculture for Lower Saxony) investigated basic nutrients and fermentation quality, while the University of Hohenheim carried out the protein fractioning using the above mentioned system.
Fermentation quality results
Across all the DM ranges and fertiliser variants, Bonsilage Plus showed a clear effect - documented by an average number of DLG (German Agricultural Society) points for fermentation quality of 99.5 out of a possible 100 compared with an average of 71.3 points for the untreated variant.
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