LAMB UNTHRIFTINESS STUDIED

Press, Volume XCVII, Issue 28559, 12 April 1958, Page 9

LAMB UNTHRIFTINESS STUDIED

Worm Infestation And Cobalt Deficiency

During the current lamb fattening season the Animal Industry Division of the Department of Agriculture has been studying severe lamb losses and outbreaks of unthriftiness in lambs on both heavy rind light land in South Canterbury. These investigations, which are discussed today by Mr M. C. Armstrong, Government veterinarian in Timaru, indicate that there is a link between heavy worm infestations (which have been noted in lambs) and a cobalt deficiency and it is recommended that action be taken to counter both the worm infestations and a possible cobalt deficiency.

The studies described by Mr Armstrong cover 32 properties in the Waimate, Levels and Geraldine counties, and in the Fairlie area of the Mackenzie county. Deaths of lambs were as high as 500 on individual properties, and on the 32 farms they totalled about 5000. Two types of unthriftiness have been investigated—the first in the spring and suirimer on light land, and the other in the late summer and autumn on downlands and foothills.

On the lighter land, Mr Armstrong says, the areas affected were mainly those which had been generously topdressed with lime and superphosphate and. sown down in high-producing grasses and clovers—particularly perennial ryegrass, white, red and subterranean clovers. This land has had a good record for fattening lambs in previous seasons, but on this occasion the younger lambs had not done well since November, and by the end of January some- severe losses had been experienced. The long periods of changeable, dull, wet weather from early November .to March had promoted a prolific growth of pasture, especially white and red clovers, on all the affected farms. These pastures were continually wet and rank and farmers had grazed paddocks continually for long periods at a time to try to hold the growth. .No quantity of cattle was kept on affected farms. Parasitic Infestation On all the 22 farms on the light land a heavy parasitic infestation was a very important contributing factor, and the weather and the lack of effective worm control measures on all these properties had further accentuated the trouble. Heavy infestation of Ostertagia, a species of small stomach worms, were a consistent finding and very high counts of up to 22.000 Ostertagia were confirmed laboratol> aminations of individual lambs. The presence of 4000 Ostertagia would be sufficient to interfere with the health of a lamb.

It was found by trials that heavy infestations of Ostertagia could be immediately reduced only by giving 23 grammes of phenothiazine particles under five microns in size. This is equivalent to 1$ fluid ounces of a phenothiazirie -containing at least 60 per cent, of particles under five microns in size.

Mr Armstrong says that it was apparent that an incipient cobalt deficiency could be an important predisposing factor in the parasitic problem because of the leachable gravel soil type and the unusual pasture growth. Accordingly, in January, seven cobalt supplement trials had been started. In these trials 60 lambs were weighed, numbered and divided into two equal groups. One group was marked and given a cobalt supplement each week for eight weeks, and the other group was left as a control for comparison. It was arranged that in three of the trials a third group should be given copper, cobalt and iron supplements, all together, to study the value of the additional copper and iron. In six of the seven trials there were cobalt responses, but in the three trials where additional copper and iron were used the results were no better than where cobalt was used alone. In one trial at Glenavy there was no effect from the addition of cobalt, and both groups gained the same average weight after parasites were controlled by fine particle phenothiazine. Weight Gains

In five trials an average weight gain of 13.51 b a head was recorded for the cobalt group, whereas there ~ was an average gain of 6.81 b in the control groups. In these trials the parasite position was well controlled by fineparticle phenothiazine, and it should be noted that in all cases where this was done the control lafribs gained weight. In one trial where no worm control measures were used the cobait ’group gained only 3.31 b in average weight, while the control group lost an average of 9.41 b and were in a dreadful state.

Mr Armstrong states that most of the light-land farms under investigation had been liberally topdressed with lime and superphosphate and of pasture growth was rapid and lush under the weather conditions experienced. There was evidence from trace mineral investigations in New Zealand that heavy applications of lime could induce cobalt deficiencies, and other observations indicated that seasons favouring lush growth tended to cause the appearance of cobalt deficiencies. As well, the cobalt content of pastures tended to decrease in spring and summer and increase in the late autumn and winter. It had, however, also been stated before that there was no good reason why the normal practice of using lime and fertilisers should be avoided because of its possible effect on cobalt status. On the other hand, more knowledge of the way in which these factors worked would increase the ease with which cobalt deficiency could be recognised and' prevented. On light land farms where there were ill-thrift problems, Mr Armstrong said that at present the following advice was given to farmers:

(1) Avoid excessive liming but rather use lime and fertilisers as recommended by the district in-

structors in agriculture. (2) Use cobalt by annual spraying or topdressing at the rate of 5 ounces an acre for preference in early spring of each year. Where pasture application was not possible, cobalt could be administered direct to the sheep by bullets or drenches. Cobalt bullets could be given to young lambs and would remain active in the paunch for two. or more years. A disadvantage was that at least 5 per cent, of the bullets were not retained. A cobalt drench for best results had to be given every week and the usual mixture recommended was a dose of one fluid ounce of a mixture of one ounce of cobalt sulphate in five gallons of water. Monthly drenches were more convenient in practice and in this case it was necessary to dissolve four ounces of cobalt sulphate in one gallon of water and administer one fluid ounce. This might be useful to give to lambs in doubtful cases of deficiency. (3) To control internal parasites it was needful to take precautions during and just after periods of dull wet weather. It was advisable to adopt a seven-day shift on to clean, spelled feed during “wormy” weather so as to reduce the intake of infective larvae. s The cleaning up of pastures by grazing cattle before shifting lambs on was also very effective for worm and pasture palatability control. Good results would generally follow the strategic use of a phenothiazine containing a high percentage of fine particles under five microns in size. If trouble had set in the dose should be increased to 1| fluid ounces and drenching repeated in three weeks for all unthrifty lambs. On Heavier Land 111-thrift and deaths of lambs in the late summer and autumn had also been investigated on 10 farms on the heavier downlands and foothills of South Canterbury- In these there had also been a consistent picture of heavy worm infestation and in some cases the deadly Haemonchus contortus or Barber’s Pole worm had been very active. In other cases on the heavier land Ostertagia, Trichostrongylus and Cooperia parasites had been found in large numbers.

In addition to the possibility of predisposing cobalt deficiencies, Mr Armstrong said, it .was important to consider the palatabilities of different species of pasture plants and variations at various stages of growth. It was known also that plants differed in their ability to take up minerals from soils. For example legumes took up more cobalt, copper and calcium than grasses. Significant difference among grass species had also been recorded, especially for iodine, which was much lower in short-rotation ryegrass than in perennial and Italian.

It had been shown that fresh autumn growth of pasture after drought was less palatable than mature growth; that immature white clover was less palatable than mature while clover; and that mature white clover was more palatable than perennial ryegrass. With proper control of cobalt and parasites good results had been obtained by fattening lambs on mature clover pastures. On heavier land a cobalt supplement should be given immediately, in addition to worm control, where there was trouble in lambs, and where possible a cobalt’ bullet trial should be arranged to test for a deficiency. The weight gains of 30 lambs dosed with cobalt bullets could be compared by the farmer with the individual weight performance of 30 control lambs which had had no cobalt supply for an eight week period.