PARASITIC DISEASES OF FARM ANIMALS.

Otago Witness, Issue 1933, 25 February 1892, Page 7

PARASITIC DISEASES OF FARM ANIMALS.

After the escape of the embiyo of the liver fluke from the egg, the minute creature seeks instinctively for an object on which it can exercise its powers of boring by means of a pointed appendage to its head. It is not, however, indiscriminate in its attacks ; on the contrary, in the observations to which we referred in the last article, embryos were seen to make thrusts at various objects, and then leave them to search for others ; and in Mr Thomas' experiments they always finally devoted themselves to the Limneus truncatulus, into the tissues of which they passed, locating themselves near tlie lungs. When once placed in a position of security in the interior of a suitable snail, the fluke embryos lost their activity, curled themselves up, and soon assumed a circular, and lastly an elongated oval form, in which numerous germs are developed. This first stage in the development of the fluke is called the sporocyst. In the interior of the sporocyst further development occurs. The circular germs become oval, and at length acquire a sack-like shape. When fully grown, these organisms, which are called redia? (after the anatomist Redi), pierce a way through the walls of the sporocyst, and get free. Others follow, and each sporoeyst may send forth 10 or 12 redire during its term of life.

From the second generation (redire) a more advanced series of organisms are produced, bearing a general resemblance in structure to the fluke, excepting the presence of a long tail. The third generation of organisms are known as cercuria, indicating the presence of a tail.

Cercuria escape from the parent redije by a spe( i il opening, and having so far gained an independent existence, they next proceed to escape from the snail, and may be found swimming about in the water in which the snails live. Only for a short time is this active life maintained. On coming in contact with the water plants the cercuria curls up, the tail is thrown off, and from the surface of the animal exudes

a gummy substance, which forms a covering or cyst, in which the creature is preserved from injury. In this condition of encystment in the stems of plants the future fluke is most favourably placed for securing a new habitat in the digestive system of herbivorous animals which may be grazing on the infested lands. Free or encysted cercuria which arc swallowed by sheep or other animals may bo, and probably are, to 'some extent digested in the stomach and do no harm, but a certain number escape and find their way into the liver. And here it may be observed that the apparent absence of flukes in the liver ducts oncost mortem inspection does not amount to proof that the organ is free from them. The examiner expects to find the parasites in the liver of a sheep affected with rot in large numbers, of a size which renders their detection easy ; but in the early condition of their development the parasites are microscopic objects, and before it can be determined that they are not present in the liver it; is necessary to examine the bile by the microscope and also to inspect sections of various parts of the suspected organ. This mode of investigation is, of course, only demanded for scientific purposes for the identification of the disease (liver rot) when no signs of disorder arc exhibited by the sheep, although the expert may have reason to suspect infection, owing to the presence of the necessary conditions in the pasture, i. «., dampness of soil, deficient drainage, and the presence of Limneus truncatulus.

Where the climatic conditions and other circumstances are favourable to the development of the fluke, the locality is known as "a rotting district," and the timely detection of the first indications of disease may enable the flockowner to apply preventive measures. There is good reason to believe that when the young fluke reaches the liver its growth is very rapid. Mr Thomas states that from the observation which he has made he is inclined to fix the period of growth, from the microscopic parasite of l-80th of an inch in length to lin or more, at about six weeks, and it is probable that, until the flukes have reached the period of adultism, they do not produce any derailment which can be detected by outward signs ; in fact, it is well known that sheep may be kept in rotting lands for six weeks not only without suffering from auy apparent disease, but with obvious benefit to their condition, although if killed at the end of that time they will be found to be infested with flukes in various stages of growth. This fact is of importance in calculating the date of infection, because it proves that from the time of the appearance of the symptoms of rot it is necessary to date back for at least six or eight weeks in order to arrive at the time of tnc first introduction of the embryo flukes.

Flukes, like many other parasites, quit their habitat in the liver after some months of residence. The general opinion is that something less than a year is the usual time for the fluke to remain in the organism of its host ; but there are certainly exceptions to this rule, and in some well authenticated cases the parasites have maintained their places for considerably over a year. It has been stated that certain pastures are well known to be capable of causing rot, and are in consequence known as rotting lands. But in the great outbreaks which have occurred at intervals in the country, sheep have become affected with rot on grounds which were habitually healthy, and practical men have no doubt of the fact that excessive rainfall in the summer is an essential cause of rot, even on sound pastures ; and it has been suggested that this circumstance leads to the conclusion that rot is not necessarily caused by flukes, because lands which are free from the germs of these parasites cannot become infected with them merely on account of the quantity of rain which has fallen. It is, however, to be noted that the eggs of flukes are constantly being expelled from sheep which harbour only a few parasites, and also from hares and rabbits, and probably from other mammalian animals. These eggs, falling on ground which is habitually dry, either from the nature or situation of the soil, or because thoroughly draiued, do not undergo development ; but in a wet season the indispensvble conditions— moisture and moderate) heat — are supplied, the embryos are hatched, and if Limneus truncatulus is present to afford the embryo a temporary refuge, all the conditions for the development of the fluke exist. In different districts the time when the danger of infection is greatest varies, but the range of variation is not very extensive. June is the earliest time for the occurrence of the disease, and it is rarely the case that instances of rot are seen in this month. During July and August rot h more frequent, and in some of the northern districts it does not appear until SeiJtember and October. It must, however ._ be remembered that in every case the parasites must have been taken up some weeks before the disease was detected.

Means for the prevention of rot are very easily suggested, but are not always possible in the circumstances of the case. For example, to keep sheep off wet land is an essential part of a preventive system ; but to give such advice in a wet season, or when all the pastures on a farm are equally wet, would be to mock at the misfortunes of the farmer, who certainly would not keep his sheep on wot lend if he could help it. Mr Thomns lays great stress upon the extermination of the Limn.'cus truncations ; in the absence of which, he believos, the embryo

of the fluke would fail to secure a habitat ; and this is a point worth the farmer's attention. Dressings of lime and salt in the spring aid early summer, while the eggs are being hatched, is an important thing to be done, and sd also is drainage ; even on well-drained lind there are wet spots in which the small snail, which forms the temporary resting place for the embryo fluke, may nourish, and such boggy places should receive special attention. And in rotting seasons it is very important to supply sheep with dry food mixed with salt, which will have the double effect of taking the keen edge oft" their appetites, and thus preventing them from grazing closely, and assisting in the destruction of the embryos which may be taken into the stomach along with the salted food.— Field.

pings " or portion of the milk taken from the cow jusfc before she is milked dry are much richer than that which comes at the beginning, has been turned to practical advantage by a correspondent of the Dumfries Courier, who so manages as to give new milk to his calves, and yet, by reducing the proportion of butter fat in the natural food Supplied to them, to have a large proportion of that constituent of the milk available for the manufacture of butter. The flan adopted is as follows :— At milking time two large vessels are put outside the byre door, one marked " Dairy" and the other " Calves." One-half of the milk given by each cow— viz., that first drawn— is put into the vessel marked k « Calves," and the other half— viz., that last drawn— is put into the vessel marked "Dairy." This latter half is found on being tested to contain from two-thirds to three-fourths of the cream. The calves have the advantage of being fed with milk warm from the cow at the same time that they are reared at a moderate cost, as their allowance of the milk does not contain much cream. When the number of calves is so large as to require more than one half of the milk, the proportion from each cow and emptied into the calves' vessel is increased, and of course the quantity available for butter-making is to that extent diminished. When the calves grow to some age— say, in the second month of their existence— they are fed on boiled skimmed milk, eight to 10 quarts per day. To prevent the milk being burned, the vessel in which it is heated is suspended in a copper of water. From the end of the second month the calf gets a mixture consisting of twothirds of meal and one-third crushed linseed made into porridge and mixed hot with skim milk. The quantity of mixed meal is gradually increased from lib to 21b per day. The correspondent maintains there is nothing in calfrearing equal to new milk warm from the cow. He believes that calves reared largely on other foods lose constitutional vigour, though to appearance they maybe full of bloom. Value op Salt in Feeding Stock.— A series of interesting experiments to test the value of salt in feeding stock has lately been concluded in Switzerland. Twenty-five sheep of nearly the same weight were selected, and divided into lots of five ; each pen received the same rations, but a different quantity of salt. The food was given at a regular hour every day, and the result at the end of a month was as follows :— Pen 1, which had no salt, gained 14 kilos ; pen 2, which received 24 grammes of salt per head, gained 16 kilos ; pen 3, which had 12 grammes of salt, gained 18 kilos; pen 4, to which six grammes of salt were given, gained 21£ kilos ; while pen 5 only received three grammes of salt, and increased 31£ kilos. Thus three grammes of salt per head per day would seem to give the best result. Prison Farming. — The prison farm at Princetown, Dartmoor, comprises about 2000 acres, which until the year 1850 was waste land. A report in the Journal of the Royal Agricultural Society says this is a notable example of the results of skill and capital. High stone walls built of granite boulders raised in the prison quarries or from the land as the work of reclamation proceeds, divide the land into fields of 15 or 20 acres. Excellent roads have been made where needed, and are extended as required. Swed.es are followed by barley, with which are sown the seeds for permanent grass. No cleaver or purer pastures are to be found anywhere than those laid down on this farm within' the last few years. All kinds of vegetables are grown. A dairy herd and a flock of sheep are kept, and all the calves reared. Annual auotions of surplus live stock are held, at which LI4OO or LISOO worth are often sold. Private sales of ponies, sheep, and pigs are also made. The whole of the work is done by the convicts without the aid of horses, except for carting. Ewe-milking. — Few consumers of Roquefort cheese are aware of the fact that cheege made from ewe's milk was formerly an English product. An interesting article on " Ewemilking " in the Field gives some details as to the old practice, as carried out on the Cheviot Hills in the days of Sir Walter Scott. In 1791 Scott spent a holiday on the Cheviots, and ewemilking was then general in the district. Cheese was made from the milk, and was esteemed as a stomachic and for its peculiar pungent flavour. The whey, too, was greatly in request for invalids. Miss Jean Elliot, in her song " The flowers of the forest," sings : I've heard them lilting at the ewe-milking, Lasses a' lilting before dawn of day. Readers of the " Ettrick Shepherd " may understand the first two lines of the next stanza : At bughts in the morning nae blythe lads are scorning, Lasses are lonely, and dowie, and wae. The "bught" was an enclosure in the corner of a field, where the ewes were milked, and it was a favourite resort for the young shepherds, who delighted in playfully "scorning" or jeering at y the lasses who did the milking. The fun often led up to courtship, and it may be imagined that the maids were "lonely, and dowie, and wae " after the Battle of Flodden, when many of the young men had been killed. At the present time the milking of ewes on the Border hills is quite unknown.

Swiss Cream Cheese. — Miss Jessie Blackshaw, principal teacher at the Eastern Counties Dairy Institute, gave the following recipo for Swiss cream cheese in a lecture delivered in Norfolk recently: — "Take Igal of sweet cream in a glazed earthenware jar ; bring it to a temperature of 65deg, and add sufficient rennet to thicken the cream in 24- hours. The strength of the rennet should be previously tested, and it should be diluted with a wineglassful of water before using it. Stir the cream for a few minutes, and then cover the jar, and keep it in a warm place, as near 65deg as possible, for 24 hours. By this time it should be of the consistency of clotted cream, and -ready for tho straining cloth, which must be sufficiently close in texture to retain the curd ', while allowing the whey to drain off. Now hang it up to drain for 12 hours, taking it down occasionally and breaking the curd, so as to allow the whey to leave the centre. Afterwards place it between two boards under slight pressure for 12 hours. It will then be ready to be pressed into moulds and used." There is such a vast difference in cream cheeses that this recipe may prove useful to many farmers' wives or dairymaids who have not had much experience, or much success, in making these dainty productions.