Advances With Bloat Problem

Press, Volume CVI, Issue 31262, 7 January 1967, Page 9

Advances With Bloat Problem

TJSEFUL advances toward determination of the basic cause of bloat have been made by an Australian scientist working in New Zealand.

Dr. R. H. Laby, a chemist from Melbourne, has spent the last 14 months at the Plant Chemistry Division of the D.S.I.R. in Palmerston North, studying the concentrations of surface-active chemicals in pre-bloat rumen foams.

The surface-activity of a material is a measure of its ability to compete for space on a gas-liquid surface, as on a bubble of foam. Different compounds possess this ability in different degree. Thus, When a foam is formed from a liquor such as rumen liquor, the relative proportions of the compounds which attach themselves to the foam bubbles are not necessarily the same as in the rumen liquor itself. Differences Surface-active compounds present in the rumen include fatty acids, other fats, and some carbohydrate materials. Dr. Laby’s studies have shown that the ratios of certain of these compounds in the foams differ markedly between rumen samples from animals which, on feeding, develop bloat, and those which do not bloat when fed. Such differences are not apparent in the rumen liquor.

A factor which may have an important bearing on this differentiation is the existence of yellow bubbles, so thickwalled as to be almost solid, in the rumen liquor. These have been present in all samples of rumen liquor Dr. Laby has examined, and they have always been more numerous in cases where subsequent feeding produced bloat.

What he thinks at the moment is that foam-breaking materials may be concen-

trated on these yellow bubbles, and that this reduces the availability of these materials to break foam when it forms.

Foams are continually forming in the rumen in the course of digestive fermentation. In normal conditions they break down fairly rapidly, and the animal gets rid of the released gas by belching. Bloat occurs when the foams do not break down but become stabilised and accumulate in the rumen. Next Stage Dr. Laby has now returned to Australia to carry on with the next stage of his work. This will be to investigate, by surface-chemical techniques, the significance of the findings made in New Zealand. At the same time, New Zealand workers in the Plant Chemistry and Food Research Divisions are investigating the chemistry of the yellow bubbles and of anti-foamlng agents normally produced in the rumen.

“So far,” said Dr. Laby in Palmerston North before he 'left, “we have been collecting facts. The next thing is to find out what these facts mean in terms of foam formation in the rumen, and this will involve study of the physical chemistry of the compounds in rumen foams.

“The final goal, which may be years away, is control of bloat through control of the surface-active compounds involved, whether they are foam-forming or foam-break-ing compounds. “If, say, a particularly active foam-breaking compound was one that occurred in clover, attempts could be made to breed varieties of clover which contained it in high quantity. Or if an active foam-breaker was of microbial origin, it might be possible to develop methods of encouraging growth of the microbes concerned in the rumen.” ...