REDUCE CRESS TAINT IN CREAM

New Zealand Journal of Agriculture, Volume 63, Issue 1, 15 July 1941, Page 31

REDUCE CRESS TAINT IN CREAM

By

A. V. ALLO,

Instructor in Agriculture, Tauranga, and F. H.

McDOWELL, Chemist, Dairy Research Institute, Department of Scientific and Industrial Research, Palmerston North.

Cress tainting of cream is one of the biggest problems facing the dairy industry. Recent experiments show that control methods must come from the farm, and ways and means by which the

farmer can avoid a great deal of trouble from cress taint are described in this article. It is pointed out that, while controlled grazing is effective, it will not prove a complete remedy.

IN spite of all that has been written, the tainting of cream by land cress is becoming more widespread every year. The taint was first noticed as being very prevalent in the South Auckland district, but in recent years reports of its occurrence have been received from districts all over the North Island. The subject is thus serious — fact, one of the biggest problems facing our dairying industry. It is one meriting the serious attention of the farmer, because in the first place cress-tainted cream, if detected on the grading stage, will be given a low grade or may even be rejected altogether. Also, and of far greater moment to both dairy farmers and factory managers, such a loss of cream grade is reflected in the grade of the butter, with consequent financial loss to all the suppliers of the factory. In the' factory itself the taint is troublesome because it is difficult to detect in cold cream, and because a small quantity of tainted cream can affect a large volume of clean cream with which it may be mixed in the holding vat before churning. Tainted cream from one or two farms on one day can thus lower the returns to the factory for the whole of that day’s make of butter. Unfortunately, experience shows that the cress taint cannot be removed completely by treatment in the factory.

Careful experimental work carried out by the Dairy Research Institute at the Tauranga factory substantiates the evidence, although such investigations are still being continued, and will .be reported on elsewhere. In this article it is sufficient to state that, with the knowledge at present at our disposal, control measures must come from the. farm. It is our purpose ‘to indicate to the dairy farmer ways and means by which he can avoid a great deal of -trouble from cress taint. What Can Be Done On the Farm? ' • During the past two. seasons a series of careful field trials have been conducted at Tauranga and Te Puke and in the Manawatu district, and the recommendations which are made in this article are based on the results of these trials. The farmer who desires to keep his cream free from land cress taint has a twofold task— (a) To do his utmost to prevent the growth of cress in his dairy pasture by a carefully planned system of pasture management, and (b) if, in spite of his efforts, or through any other cause outside his control, cress invasion occurs, he must be prepared to institute a system of controlled grazing on the infested areas. Prevention of Land Cress Growth Land cress, Coronopus didymus, is an annual with trailing stems, finely divided leaves, and small, clustered, white, inconspicuous flowers. It appears in the early spring, and in a normal season may last until after Christmas.

- When the leaves are crushed one can smell the pungent mustardy odour so characteristic of the plant. As the plant is an annual, making its growth when the principal pasture species are making their main growth, it does not usually cause much concern in a pasture containing a dense sward of grasses and clovers. The seeds in such a sward get little chance to germinate and grow before • the smothering grasses get away. . It is in a weak thin sward that the weed shows up at its worst.

Factors favouring the appearance of cress in a pasture are:— (1) Heavy stocking or trampling of a pasture during winter, with consequent overgrazing and pugging leading to a deterioration and opening up of the sward. (2) The practice of leaving old stack bottoms and ensilage pits unfenced from stock. Cress grows very freely in such places and may cause trouble, even though the areas are small. All such areas should be shut off from stock until the end of December. (3) Heavy tramping around gateways, and bare ground around' cowyards, stockyards, and under hedges give conditions where cress is likely to appear.and thrive. . It is not always possible to fence off these areas, but they should be f watched and any cress plants destroyed by hand cultivation. ' (4) Even in a dense sward cress may ■ sometimes occur if chain harrowing has been neglected. The writers have often seen cress growing strongly around old cow pads. Similarly, the bare ground around the base of a thistle may be found to provide conditions suitable for cress growth. (5) Grass grub attack, which weakens the pasture growth and leaves bare patches in the sward. (6) Paddocks lying uncultivated after a crop such as maize usually have a high cress population, and should not be grazed by milking cows. (7) Spring sowing of pastures, particularly after a maize crop, gives rise to conditions suiting cress development, and such a practice has been responsible . for conlsidjerable loss to certain farmers. The danger is accentuated if cheap seed is sown, or if the mixture of seed contains a high preponderance of slow-establishing pasture species. The sowing of a suitable pas-

ture mixture in the early autumn, combined with thorough preparation

of the seed bed and adequate phosphate manuring, will help to ensure

that the new pasture will contain little or: no cress in the following spring. If bpring sowing cannot be avoided, the mixture should be dominantly ryegrass and white clover. \ From the foregoing, it is obvious that cress control will be a matter 'of pasture management, the aim being to graze the pastures in such a way that conditions favouring the establishment of the cress will not arise.

Control Grazing of Cressy Pastures It will be generally accepted that, where possible, cress-infested pastures should be grazed with dry stock, but this is not always practicable. In many instances farmers have not the necessary area of non-infested pasture available, and in other cases the number of dry stock is not large enough to deal with the cressy pasture. Moreover,

the badly infested pastures are sometimes young grass of great value for milk production, and the loss of this grazing is definitely a serious matter for the dairy farmer. It is therefore of paramount importance that the possibilities of reducing land cress taint in cream by controlled grazing of the infected pastures should be fully explored. Last season detailed experiments were carried out in the Tauranga and

Te Puke districts by the writers, using commercial dairy herds turned’on to cress at various times before milking, and at the Dairy Research Institute-the feeding of specified quantities of cress to individual cows at different times before , milking was studied. The following remarks are based on the evidence afforded by these trials. Time Taken for Taint ; To Appear in Milk Cress-flavoured milk, cream and butter have a characteristic flavour, rather harsh to the palate, and with a burning mustard-like quality. The taint is difficult to detect in cold milk or cream unless it is fairly strong, but it becomes much, more evident when the milk or cream is heated. This introduces a very great difficulty for the factory grader, who may allow a tainted cream to pass as clean, while the cress taint becomes evident in the pasteurised cream and in the butter. Many cases have come ' to . our notice where a can of tainted cream which has been pasteurised and mixed with a large bulk of clean cream in a 3,000-gallon vat has tainted the .whole day’s make of butter. . It has been shown that with most cows cress taint appears in the milk within a few minutes after the plant is eaten. Apart, also, from the state of health of the cows, it has been found that some animals give a tainted milk more rapidly than others. It does not take much cress to produce a taint in the milk, and strong cress taint has been reported in the- milk of a cow that had consumed 11 oz. of cress. How Effective Is Controlled Grazing? Much has been ..written on the system of controlled grazing for the prevention of feed taints. The usual recommendation is to graze the cows on the “weedy” paddock to within three

or four hours of milking, and then to transfer them to a clean paddock until milking time. Unfortunately, experiments have proved conclusively that with cressy pastures this control is not absolute and will not always give the desired results. The indications are that, if the amount , of cress in a field is small, such a system of controlled grazing will give satisfaction. If the feed is badly infested with cress, controlled. grazing will not result in the production of a cress-free cream. It will undoubtedly, result in a better cream being produced than would have been the case had the cows been on the cress all day, but the cress taint will not - always be completely eliminated. In last season’s experiments cows were grazed on a very cressy paddock until noon and were then run into a concrete yard until milking time. The resultant cream still had a, cress taint. In another trial cows were grazed between 9 and 10 a.m. on a paddock badly infested with cress and were .then taken to a clean paddock for. the rest of the day. The evening’s cream was strongly tainted. In several instances cress taint had been noted in cream

from cows the following morning—that is, 14 to 18 hours after the ingestion of the cress. There is evidence to indicate that cress taint is more pronounced during wet weather, and that controlled grazing is more effective in dry weather than in wet weather. The position should not be misunderstood. Controlled grazing for three to four hours before milking in all cases will result in a better 1 cream being produced than if the cows were on the cress paddock all day, but in cases of fairly heavy cress infestation, the controlled grazing system will not remove the taint from the milk completely. Pasture Management Important The whole scheme of control must hinge on the method of pasture management. It has been proved conclusively that the paddocks most likely to be affected, other than paddocks of young grass, are those which are heavily overstocked ' during the winter. Consequently, control depends upon better provision of winter .supplementary feed, combined with winter spell-

ing of pastures. By the latter, is meant the closing of a few ryegfass-dominant paddocks in the autumn, and lightly grazing them during the winter so that they will be in good strong grassy growth in the following spring, Such paddocks should contain little or no cress. Cows can be grazed on them for one and two hours daily, and can then be turned into a clean 1 run-off paddock. Cressy paddocks should be grazed by dry stock, wherever possible. Remember, always, that prevention is better than cure. The farmer who has ample supplies of winter feed and who winter-spells part of his farm is not likely to encounter trouble with cress taint on an uncontrollable scale, and at the same time he gets the best out of his: cows, as they are being fully fed at the period of the year when they are producing their maximum. Even on the most carefully controlled farm cress plants may appear in places. All farmers in their own interest should learn to recognise the plant'/ by sight, and all plants seen should be hoed out immediately. ,

Other Feed Taints Many other weeds can give taints in Cream,, for example, pennyroyal, camomile, sweet vernal, and water cress. Control measures on the farm should be based on the methods advocated for cress. . ’ Unfortunately, certain plants of vital importance in a sward, more particularly the clovers, can in certain circumstances give just as much trouble as weeds. The chief offenders are subterranean clover, suckling clover, and white clover, in that order of import-

ance. Trouble is usually experienced when a pasture contains a high percentage of one or more of these clovers, especially in the period of their rapid growth and before the pasture has had a chance to harden off. Such clovery pastures usually follow close grazing in late autumn and winter, and control measures to be adopted are similar to those advocated for cress. Winter spelling, of pastures will encourage grassy rather than clovery swards, thus helping to ensure a better quality cream. Also, controlled

grazing of clover swards with a runoff into a grassy paddock three or four hours before milking, gives far better taint control than is obtained when adopting such measures with cress, and should be practised in all cases where a farmer is getting “feedy” cream. - ■

Many farmers have a defeatist complex on the whole taint question, and are inclined to take the view that the trouble is just seasonal and is “just one of those things.” This is definitely not the case, and examples can be quoted of many farmers who have made a material improvement in the grading of their cream by adopting the various measures suggested in this article. . ' ,

Answers to Correspondents

Burning Out Stumps F.J.8., (WANGANUI):— Will you please let me know whether you are aware of any treatment that can be applied to old macrocarpa stumps in order to burn them out? FIELDS DIVISION:— The idea that tough tree stumps can be treated with chemicals to make them burn easly or to rot them quickly has persisted for many years. It has often been stated that saltpetre put into large auger holes in such stumps will, after a few weeks, cause the stump to burn readily right into the ground, getting rid of the roots 'as well as the stump. Another suggestion is . that strong acids, such as nitric or sulphuric acid, poured into auger holes will rapidly rot both green and dead stumps so that they will readily bum in a few weeks. • There is no foundation whatever in these statements. Careful trials with both acids and saltpetre have shown that the method is quite ineffective. If , explosives can be used without danger to buildings, etc., the burning out of tough stumps such as those referred to can be speeded up by using blasting powder or gelignite to loosen the ground under and round the stump and also to split and shatter the stump. By shattering the stump the fire can work much more freely and effectively, while the loose soil round the roots allows the fire to penetrate more deeply, thus getting rid of more of the. roots than would otherwise be the case. The use of explosives as stated'is the only effective method which can be of assistance in burning out such stumps.