BLOAT PROBLEM UNDER REVIEW

Press, Volume CIII, Issue 30342, 18 January 1964, Page 8

BLOAT PROBLEM UNDER REVIEW

Bloat is one of the most serious problems of the New Zealand dairy industry'. Cloverrich pastures give high production, but they carry with them this grim penalty; that something like 15,000 cows a year die of bloat. The total cost of bloat to the industry can only be guessed at, though it may be revealed more clearly by a survey the Dairy Board has been conducting. But there is no lack of pointers to the scale of the problem. In the Waikato alone, bloat losses as high as £480,000 through animal mortality and reduced production have been recorded in a single year.

The national loss from bloat must be prodigious. In terms of individual farm experience it can be little short of disastrous. Take the case of a farmer at Shannon who runs a herd of 120 cows. He lost an average of 20 cows, worth £7OO, a year from bloat. When bloat hit his herd in the spring of 1960, his daily cream production dropped from 350 lb to less than 2001 b—a production loss of £lB a day. Cases like that, or worse, are multiplied by the hundreds of thousands whenever severe bloat conditions arise, and when they do there is generally a clamour for more research into bloat

There is irony in this. Most of the loss through bloat occurs because the knowledge research ha? already made available to farmers is not applied. Spraying of pastures may be a troublesome chore, involving immediate costs some farmers are reluctant to face, but it does give protection when properly carried out, and the savings are out of all proportion to the small cost entailed; Take the Shannon farmer again. In October, 1960, with half of His herd bloated, he sought expert advice. Acting promptly on what he was told, be began spraying his pastures with a paraffin emulsion the next day. Within two weeks, his daily cream production was up to 3751 b and since then he has not lost a single cow from bloat. For him, the complete answer to bloat was a capital expenditure of £6O and a daily cost of 257- plus about an. hour of his time while bloat conditions lasted. The same answer is available to every farmer who cares to use it..

It is not the perfect or final answer, That is still being sought, and the search is the major activity of the Plant Chemistry Division of ’the Department of Scientific and Industrial Research. New Zealand has led the world in bloat research, and still does. It was as a result of work initiated at the Plant Chemistry Division 11 years ago that the immediate cause of bloat—formation of a stable foam in the animal’s If ore stomachs during fermentation of feed —was determined and the practical method of control by spraying pastures with anti-foam-ing agents was worked out. Though research has shown in broad terms what happens in the bloated animal and what the farmer can do about it, there remain unanswered many basic questions concerning the factors contributing to foaming in the. cow’s stomach: It is improbable that any further advances can be made on the practical front until more is known about these factors.

The present work of the Plant Chemistry Division’s

bloat research team Is aimed at providing this necessary background •of knowledge. There are four main lines in this research—an effort to find out just what plant factors are involved in the foaming; an effort to determine what conditions in the animal favour production of foam; a continuing investigation of ’ the effects of bloat in the animal; and further studies of the anti-foaming agents used in control.

Oh the plant side, one of the first baffling facts to emerge was that there is no major change in plant composition which can be correlated with the- onset, of bloat. Analyses showed that the composition of clover remained to all intents and purposes constant through both bloating and non-bloat-ing conditions. Clovers contain both foaming and anti-foaming agents —protein material which tends to promote foaming, and fatty substances which tend to inhibit it. It is suspected that minor changes in the balance between these substances, either in the amounts present in the plant or in the rate of their release in the stomach, may bring about the condition which results in bloat. Evidence is still being sought as to whether this is so. Some recent work has been directed toward the study of particular plant fats (or lipids) which may have a connexion by virtue of their possible properties as foaming or anti-foaming agentsWork in this field has been hampered by the difficulty of measuring the relevant compounds. The most important fatty component of clover from the point of view of anti-foaming properties is extremely difficult to isolate as a pure compound in sufficient amounts for experimental work, and only very small amounts of it have ever been available for study. A method of measuring its concentration in the growing plant and in the animal’s stomach is now in the process of being developed. Animals differ greatly in their susceptibility to bloat. K towledge of what makes one animal susceptible and another resistant might provide clues to the basic cause of bloat. Hence, a considerable proportion of the research effort is devoted to investigation of conditions in the animal which may contribute to the bloat situation. In these studies, identical twin cows with rumen fistulae are extremely useful, and the Plant Chemistry Division has several pairs of these animals. A rumen fistula is a kind of- porthole, surgically inserted in the cow’s side, giving access to the rumen—the major section of the fore stomachs. It can

be opened at will for the taking of samples from the! rumen; for study of the micro-organisms involved in the animal’s digestive pro-, cess; for direct observation of the effects of anti-foaming agents; for the insertion of instruments to measure the activity of the rumen, and so on. Without this device, much of the investigation into bloat would be impossible. The cows live quite happily with the fistulae. The can have calves, and they can live as long as ordinary cows. One animal in the United States lived 15 years with a fistula, and some of those at the Plant Chemistry Division have had fistulae in them for seven years. Not that it is exactly normal life. Odd things happen—like eating a box full of clover and never getting any fuller, because some scientist’s hand is waiting to catch each wad of chewed food as it drops into the rumen. One reason for . variation in cows’ susceptibility to Moat could be differences in the flow and composition of saliva. Saliva contains viscous components of types which are known to stabilise foam; and since it also contains sodium bicarbonate, its reaction with the acids created by fermentation in the rumen liberates a lot of carbon dioxide gas. But on the other hand, foaming agents are most active in acid condition, and saliva tends to neutralise acids in the rumen. Saliva can thus both promote foaming and help to control it. Studies are being made of the composition and flow of saliva. A special difficulty in these is that any attempt at direct measurement of the salivary flow tends to Upset the flow. In some experiments analyses have been made of the chewed and salivated feed actually delivered to the stomach. However, it is difficult to .obtain any positive measure of all the salivary components in this material, because certain Substances in saliva also occur jn clover. This material is also used to study the extent to which plant substances are released by chewing.

Another possible explanation of the variation in susceptibility to bloat could be related to the fate of plant fat or other anti-foaming agents in the rumen, where

they may be destroyed, or even converted into foaming agents. This aspect is being investigated although the study of these fats in the rumen is even more difficult than in plant. tissue. A cow's rumen has a huge population of bacteria and protozoa, which digest the animal’s feed. Large quantities of gas are given off through the activities of these micro-organisms, and without this gas there could be no bloat. Differences in the micro-organism populations in the rumens- of different animals may account for the variations in susceptibility Likewise, changes in the population may help to account for the unpredictable spasmodic nature of bloat. Present studies are aimed at, ascertaining what microorganisms are present in New Zealand cows; the relative gas-producing ability of protozoa and bacteria; and the part played by individual types. in the breakdown of foodstuffs. They are slow and difficult studies because these micro-organisms can live only in the absence of oxygen; and < are very hard to grow outside the rumen. The environment provided in the stomach for the microorganisms is also being investigated. At the same time, a more detailed study of the way in which anti-foaming agents act in the rumen is being undertaken in the hope that the useful properties of these materials can be identified. Such knowledge would help in the search for more effective foam-breaking substances. An eye is also being kept on the techniques of spraying and the effectiveness of spray materials. New treatments which may be of value are being continually tested.

■ In bloat, scientists are tackling no simple problem, but one whose answer must be sought among a complex of factors, in plants, animals and micro-organisms, the inter-relationships of which are not yet fully defined. Somewhere in this complex may lie the final answer to the problem of bloat, but in searching for it, scientists must explore one possibility after ' another in a patient process of elimination. They cannot be looked to for quick results, but they are accumulating knowledge out of which, some day, practical results may be achieved.