Influence of Northern German Moulds and Anorganic Salts on Ruminal Cellulase Activity (in vitro)

Non ruminants lack cellulolytic enzymes. That's why they 're not able to digest cellulose. Cellulases however are wide spread in microorganisms. Living in symbiosis with ruminal microbes like bacteria, protozoa and fungi, ruminants can metabolize cellulose and use it energetically. Cellulose is build up by glucose elements connected β-glycosically and is metabolized to glucose by exo- and endocellulase and cellobiose. Cellulases can be influenced positively and negatively.

The aim of these experiments was to test the influence of moulded hay on the one hand and that of anorganic salts on the other hand on ruminal cellulolytic activity (CA, in vitro, RUSITEC). The moulds used were harvested from pastures in Northern Germany where several cattle of different herds which showed the clinical signs of CCN and responded well to thiamine application. Since the grass was overgrown with rust and other fungi we tested the influence of those fungi (Alternaria alternata -AA, Epicoccum nigrum -EN, Mucor racemosus -MR, Fusarium graminearum -FG, F. poae -FP, F. culmorum -FC, Cladosporium herbarum -CH or Ulocladium chartarum -UC) on the one hand and that of anorganic salts (MgO, Na₂SO₄ and Na₂SO₃ as constituents of fertiliers) on the other hand on the ruminal cellulases.

Five investigation periods lasting about 23 days each were carried out. After a control period of nine days a five day testphase followed. During this time two vessels were charged normally and two with moulded hay (moulded with AA, EN, MR, FG, FP, FC, CH or UC) or with Na₂SO₄, Na₂SO₃ or MgO respectively. In the second testphase (five days) daily 0.3 mg thiamine were added. The last days served for regeneration with normal hay. Before feeding the system, rumen fluid was daily taken for the determination of CA [1, 2].

The following effects on the CA could be noted: AA: + 22%, FG: + 18%, FP and FC: -38%, EN, MR, UC, CH:+/- 0%; MgO: + 25%, Na₂SO₄: -37%, Na₂SO₃: +/- 0%.

This means that AA, FG obviously have their own CA and FP or FC depending reduction of CA is overcome by thiamine. The latter supports the idea that Fusarium toxins destroy or block a thiamine depending key function of the CA. Furthermore Mg⁺⁺ as cellulase stimulator is known while it was surprising that Na₂SO₃ had no influence. May be that the increased fermentation (4 h) after supplementation destroyed the inhibitory effects.