Influence of Moulded Feed with and without Thiamine Supplementation on Rumen Protozoa in Cattle (in vitro)

The rumen protozoa are anaerob and 4 to 500 μm large. They live facultative in symbioses with the ruminant and take part in the ruminal metabolism (e. g. increase of food digestibility, stabilisation of the ruminal fermentation and the pH, supply of essential amino acids and unsaturated fatty acids). Consecutively, the rumen protozoa influence animal's health (increased growth during energy-limited diets, lower incidence of scours in calves, anti acidic effect, detoxification of nitrate and zear-alenon, lower incidence of copper intoxication on the one hand, but greater incidence of bloat on the other hand). The protozoa population is affected by its environment, e. g. by the pH, carbohydrates, lipids, proteins, vitamins, antibiotics, myco- and phytotoxines. Therefore protozoa were sometimes used as bio sensors in bio assays.

In recent studies, the influence of hay, moulded with Alternaria alternata, Epicoccum nigrum, Mucor racemosus or Ulocladium chartarum were investigated using the long term rumen simulation technique (RUSITEC). The moulds used derived from a Northern German pasture, where cows suffered from CCN probably caused by thiamine deficiency. As the moulds were supposed to have a thiaminolytic effect, the efficiency of thiamine substitution to cope these effects on rumen protozoa was tested, too. Four experiments lasting 25 five days each were carried out. After a control phase of nine days two five day test phases followed. During this time two reaction vessels were charged with moulded hay (moulded with Alternaria, Epicoccum, Mucor or Ulocladium) and two with good hay. In the second test phase all vessels were additionally charged with thiamine. Protozoa were counted by the means of a microscope in daily taken samples and differentiated into small, medium-sized and large types (81 – 93%, 6 – 18% or 0 – 3%, respectively, of the total number of protozoa under usual conditions).

The moulded hays affected medium-sized protozoa to a different extent (Alternaria alternata: -16%, Epicoccum nigrum: -27%, Mucor racemosus: -9%, Ulocladium chartarum: +2%). Thiamine stabilised small protozoa in general and had positive effects on medium-sized protozoa during the influence of Ulocladium chartarum (+26%) as well.

Apparently there exists a specific sensitivity of medium-sized protozoa to certain moulds. Thiamine dependent metabolic pathways seem to get reversibly blocked.

So, while feeding moulded hay or grass to cows for financial reasons, it might be useful to add thiamine (e. g. as yeast) to the feed.