ROUND THE RESEARCH STATIONS

New Zealand Journal of Agriculture, Volume 100, Issue 5, 16 May 1960, Page 476

ROUND THE RESEARCH STATIONS

Current Work and Findings in Department of Agriculture Trials and Experiments

Wallaceville

Diagnosis of Cobalt Deficiency in Sheep

The best way of diagnosing cobalt deficiency, as previously pointed out in

"Journal” articles, is by a trial on the farm with two groups of animals, one of which receives no special treatment and the other receives cobalt. Cobalt bullets are useful for this purpose. If both groups are weighed at the beginning and the end of the trial, an average weight change difference of about 5 lb in favour of the cobalt group is usually indicative of cobalt deficiency. However, it is not always convenient or practicable to run trials on the farm, and laboratory examinations of livers from suspected deficient animals are carried out at . Wallaceville Animal Research Station to assist diagnosis. Formerly livers were analysed for cobalt content, but it has been found that cobalt is active in the form of vitamin 812,B 12 , to which it is converted in the paunch, and that cobalt deficiency is,. in effect, a deficiency of vitamin 812.B 12 . On the basis of this information Wallaceville.trials have shown that the vitamin 812B 12 content of liver gives a better indication of the presence or absence of cobalt deficiency than does the cobalt content. Provisional vitamin 812B 12 diagnostic criteria for fresh liver have been worked out and are as follows: Very low: Less than 0.07 parts per million 812.B 12 . Low: From 0.07 to 0.10 parts per million 812.B 12 . Borderline: From 0.11 to 0.19 parts per million 812Normal: More than 0.19 parts per million 812.B 12 .

Wallaceville

Escherichia coli Septicaemia in Lambs

An Escherichia coli septicaemia has been found to be responsible for the sudden deaths of about 100 lambs from a flock of 1,400 in the South Island

and for a number of lamb deaths in other flocks. The affected lambs were three to eight weeks old and had been docked, and though they were observed twice daily by the farmer, they were almost invariably found dead at the rate of three or four a day without any premonitory signs. Deaths were at first thought to be due to enterotoxaemia, but administration of enterotoxaemia antiserum failed to check losses. The most characteristic finding on post-mortem examination was the presence of large amounts of straw-coloured fluid and fibrin strands in the thoracic cavity, with fibrin in the abdominal cavity. Other evidence of septicaemia, such as small hemorrhages throughout the carcass, was usually lacking. Some lambs showed all the features of enterotoxaemia, while in others there were no significant changes. Some lambs survived the initial septicaemia, and infection localised in the central nervous system, leading to meningitis and symptoms of a central nervous disorder, and in the joints, leading to arthritis and severe lameness. E. coli has been regularly isolated in pure culture from all organs, ribs, and arthritic joint fluid of affected lambs. In transmission experiments lambs were readily infected by intravenous inoculation of thoracic fluid from affected lambs or a pure broth culture of E. coli,

and died in seven to 23 hours. . Post-mortem findings were similar to the most characteristic field cases and E. coll was recovered from all organs and ribs.

Rukuhia

Method of Cutting Pasture for Silage

The normal practice in silage making is to close a field as it becomes surplus

to requirements and when the pasture has attained silage stage, commonly 15 in. to 18 in. high, it is cut with the mower. Pasture research suggests that the mower normally cuts closer to the ground than is desirable and that a succession of cuts when the pasture is at an optimum stage might yield more material of better quality than if one cut is taken at the normal silage stage. With the advent of the forage harvester it is possible, if it is shown to be worth while, to modify general practice by cutting higher above the ground and by taking several cuts, say, when the pasture reaches 6 in. to 8 in. high. To get more precise information on these particular aspects of silage making a preliminary trial was carried out at Rukuhia Soil Research Station last spring in which the effect of cutting at two heights (1 to IJ4 in. and 3 in.) above the ground and. of cutting at various stages of growth was studied. Yield records from the variously treated swards are being continued to assess the effect of the cutting methods on subsequent pasture growth. . Results cannot be evaluated until this latter phase of the trial is completed, but the data so far obtained are of sufficient interest to justify a larger trial which is being planned for next spring.

Wallaceville

lodine and Goitre in Lambs

A method of preventing goitre in new-born lambs by giving ewes doses of iodine during the last two months before

lambing has been described in “Care of Livestock” notes in June issues of “The Journal”. Support for this practice comes from studies using radioactive iodine which have shown that the amount of iodine accumulated by the thyroid gland of the developing foetus increases sharply at the beginning of the fourth month of pregnancy and remains at a high level throughout the fourth and fifth months until the lamb is born. Some preliminary work suggests that injections of a poppyseed oil compound containing 40 per cent of iodine given once only two months before lambing may also be effective in preventing goitre, but more trials are required before this practice can be

recommended.

Wallaceville

Avian Encephalomyelitis

A number of cases of avian encephalomyelitis (“epidemic tremor”) have been reported this year, all involv-

ing White Leghorn-Australorp cross chickens. The disease has not been seen in purebred chickens. This is a virus disease and, as the name suggests, it produces nervous signs. In a proportion of affected chickens there is a very fine tremor which may not be seen but is readily felt if the chicken is held in the hand. Some • chicks will nod their heads and become staggery and weak in the legs. They rapidly decline until they cannot walk and death results from their inability to feed.

The numbers affected have varied from 5 to 40 per cent and losses have sometimes been confined to certain hatches. This virus is egg borne and the disease cannot be diagnosed with certainty without microscopic examination of the brain or transmission tests. It has been intensively investigated overseas and a summary of these results will be published later.

Wallaceville

Cobalt Deficiency on Kaitoke Farm

Recent research has shown that cobalt deficiency sufficiently severe to cause death can occur in ewes and lambs

at Wallaceville’s Kaitoke farm. The importance of this finding is that the farm consists mainly of two soil types, Kopua silt loam and Dannevirke silt loam, which together cover more than 100,000 acres and occur mainly in the Wairarapa district. While it cannot be said that all farms on these soil types are necessarily cobalt deficient, this disease must be considered as a possible cause of unthriftiness, particularly in lambs, on farms located on Kopua and Dannevirke silt loam soils and on similar soils elsewhere.