Investigation of III-thrift of Lambs in South Canterbury

New Zealand Journal of Agriculture, Volume 97, Issue 3, 15 September 1958, Page 241

Investigation of III-thrift of Lambs in South Canterbury

By

M. C. ARMSTRONG,

Veterinarian, Department of Agriculture, Timaru

THE economic importance and complexity of unthriftiness in lambs have warranted intensive investigation in various districts of New Zealand to find fundamental causes and reliable methods of control for every circumstance. In this article the terms ill-thrift and unthriftiness are. considered synonymous because the practical farmer applies both terms to animals failing to thrive for different possible causes such as mineral deficiencies, pasture unpalatabilities, internal parasitism, and inadequate quantity or quality of feed.

ILL-THRIFT occurs in different, sometimes contradictory, circumstances in various parts of New Zealand. For example, summer illthrift of unknown cause in Ashburton County in 1956-57 was controlled on short pasture whereas autumn ill-thrift of unknown cause in the North Island was reduced on long pasture. . There was, however, a similarity between the occurrence of ill-thrift on light land . in South Canterbury and on similar land in Ashburton County the previous summer. Outbreaks In the North Island an uthriftiness of lambs known as hogget ill-thrift occurs when autumn rains give vigor-

ous pasture growth after dry conditions in late summer.. This autumn ill-thrift is unrelated to mineral deficiencies, but presents a picture of unpalatable pasture associated with a lower dry-matter intake and a lower digestibility of immature, rapidly growing plants. In this peculiar type of ill-thrift a secondary parasitic attack is a frequent complication. E. A. Clarke and D. B. Film (1956) reported that the incidence of hogget ill-thrift may be reduced by providing long, mature pasture containing, where possible, a high proportion of white clover, and that losses from parasitism may be reduced by the strategic use of phenothiazine. In Ashburton. County during the summer of 1956-57 the occurrence of heavy mortalities and severe unthriftiness of thousands of lambs was associated with the provision of long, rank, and bulky feed produced on large

areas of light shingly soils, particularly Lismore soil types. Unlike the North Island ill-thrift, which is an autumn pasture-complex condition, the Ashburton outbreak was severe from mid November to mid February; that is, a summer setback just as severe on rape crops as on pasture and with no relationship to the species of feed. It was, however, severe on long grazings and reduced on short pasture. The result of a farm management survey by the Department of Agriculture was a recommendation by R. C. Stuart and others (1957) that short feed should be available for all lambs in spring and summer as an aid to the prevention of ill-thrift.

Occurrence in South Canterbury

From November 1957 to March 1958 heavy mortalities and widespread unthriftiness of lambs were experienced under very similar circumstances to those of the Ashburton outbreak the previous season, namely, the middle of summer on long, rank pastures, lucerne, and rape crops growing on light stony soils.

In South Canterbury the Animal Industry Division conducted a detailed veterinary investigation on individual farms over large areas of the Waimate, Geraldine, and Mackenzie Counties. Feed conditions and management were recorded, post-mortems conducted, and specimens sent to the Department of Agriculture’s Wallaceville Animal Research Station for diagnosis.

Lamb deaths reached 50 per cent in some flocks and it was not uncommon for all the survivors to be visibly affected by unthriftiness. On the average farm in February the mortality was z about 15 per cent and 70 per cent of the survivors were unthrifty. Areas Affected 111-thrift occurred on light stony land in three districts: 1. In the Orton district, Geraldine County, between the Orari and Rangitata Rivers. 2. In Waimate County in a large triangle bounded by the Waitaki River to the south, the coast to the east, and a line from Morven through Pikes Point to Ikawai on the north-west.

3. In the Ashwick district of the Fairlie basin, Mackenzie County.

The soils are light stony silt or sandy loams generously topdressed with lime and. superphosphate. Pastures are sown down in high-producing, grasses and clovers, particularly perennial ryegrass and white, red, and subterranean clovers. The districts have favourable records for the fattening of lambs in dry summers, but wet summers have often been troublesome.

Seasonal Conditions and Management On this occasion ill-thrift became apparent and severe before weaning, which is done in January on the farms investigated. Lambs, born after the first week in September had not done well from November onward and some heavy losses were experienced by the end of January. From early November to March there were long periods of dull, changeable,- wet weather which promoted a prolific growth of pasture, especially clovers. Pastures were continually wet and rank and set stocking was common practice. With limited numbers of sheep it was impossible to control the abundant pasture growth, because cattle are not usually kept on this light country and topping of pastures is not practised because of the vagaries of climate. In . ordinary seasons very little drenching against worms is done, but on this occasion nearly all farmers dosed their lambs with phenothiazine when the unthriftiness became severe. Post-mortems On 22 farms post-mortems were conducted on freshly killed ill-thrift lambs. There was a consistent picture of very low blood volume and a heavy infestation of small stomach worms. Digestion and the assimilation of

nourishment appeared to be at a standstill and the only contents of the fourth stomach were parasites in a watery fluid containing lumps of catarrhal mucus. The majority of stomachs showed evidence of ulceration or irritation by the worms. There were no other postmortem appearances. Livers were submitted to Wallaceville for copper and cobalt estimates and viscera for parasite counts and diagnosis. Scouring was not a feature. Ostertagia Parasitism Heavy infestations of Ostertagia species of small stomach worms were a consistent finding and very high counts (up to 22,000 Ostertagia) ■ were recorded for individual lambs. Ordinary dose rates of phenothiazine and copper sulphate-nicotine sulphate were not effective against Ostertagia species, which are very resistant to anthelmintics. Increased dose rates of fineparticle phenothiazine were tried. Trials on affected farms indicated that control of Ostertagia and improvement in lambs were obtained by giving 23 gm. of very fine phenothiazine (particles under 5 microns). This is equivalent to 1| fl. oz. of a phenothiazine containing at least 60 per cent of particles under 5 microns. Confirmation under field conditions was given the report of P. L. Thomas and D. C. Elliot (1957) at Wallaceville

that the finest preparation of phenothiazine used was the only one to give a highly significant reduction against Ostertagia spp. Cobalt Deficiency Trials The investigators considered that an incipient cobalt deficiency could be an important predisposing cause of the parasite problem because it was limited to the leached gravel soil types and because of the unusually abundant pasture growth. Symptoms of depressed appetite and poor digestion are early effects of cobalt deficiency.

Accordingly in January the Animal Industry Division started seven cobaltsupplement trials in three of which the value of additional copper and iron was tested. All these trials were over 8 weeks and with typical ill-thrift lambs with initial average liveweights of about 40 lb. The standard cobalt drench used was 1 fl. oz. each week of a mixture containing 1 oz. of cobalt sulphate in 5 gallons of water. The standard cobalt, copper, and iron drench used was 1 fl. oz. each week of a mixture containing 1 oz. of cobalt sulphate, 1 lb. of copper sulphate, and

2 lb. of iron sulphate in 5 gallons of water. Significance of Cobalt The results of trials 1,2, 3, 4, 5, and 8 have established the existence of cobalt deficiencies on five light land soils (Pukeuri, Ashwick, Lismore, Steward, and Eyre silt loams). Liver estimates of lambs affected by illthrift on vigorous pastures on other farms confirmed that cobalt deficiencies occur on these soils and exposed

DETAILS OF COBALT DEFICIENCY TRIALS

TRIAL 1 (20/1/58 to 20/3/58) Location: Morven, on Pukeuri shallow silt loam and on Steward very stony silt loam. Management: All lambs were grazed on long, rank, clover-dominant pasture. They were given 14 fl. oz. of fine-particle phenothiazine every 3 weeks. Results 20 lambs cobalt drench each week 21.4 lb. av. gain 20 lambs cobalt, copper, iron 1 each week 19.6 lb. av. gain 20 lambs control 7.3 lb. av. gain Comments: Cobalt very highly significant; copper and iron of no extra value; controls responded to worm treatments. . TRIAL 2 (26/1/58 to 28/3/58) Location: Fairlie, on Ashwick very stony silt loam. Management: All lambs grazed on long, rank pasture and given 14 fl. oz. of fine-particle phenothiazine every 3 weeks. Results 30 lambs cobalt drench each week 9.7 lb. av. gain 30 lambs cobalt, copper, iron each week 8.8 lb. av. gain--30 lambs control 4.5 lb. av. gain Comments: Cobalt very highly significant; copper and iron of no extra value; controls responded to worm treatments. TRIAL 3 (26/1/58 to 26/3/58) Location: Orton, on Lismore very stony silt loam. Management: All lambs grazed on long, rank, cloverdominant pasture and given 14 fl. oz. fine-particle phenothiazine every 3 weeks. Results 30 lambs cobalt drench each week 11.7 lb. av. gain 30 lambs cobalt, copper, iron each week 9.7 lb. av. gain 30 lambs control 6.5 lb. av. gain Comments: Cobalt highly significant; copper and iron of no extra value; controls responded to worm treatments. TRIAL 4 (20/1/58 to 20/3/58) Location: Morven, on Steward very stony silt loam. Management: All lambs set stocked on long, rank cocksfoot and subterranean and red clover pasture. No worm treatments given. Results 20 lambs cobalt drench each week 3.5 lb. av. gain 20 lambs control 9.4 lb. av. loss Comments: Cobalt very highly significant; control lambs without cobalt and no worm treatments were in bad state.

TRIAL 5 (20/1/58 to 20/3/58) Location: Glenavy, on Steward very stony silt loam. Management: All lambs grazed extensively on 6 acres of rape and given one dose of 14 fl. oz. of fine-particle phenothiazine at the start. Results 20 lambs cobalt bullet .' 7.0 lb. av. gain 20 lambs control . . . 1.3 lb. av. gain Comments: Cobalt very highly significant. Rape failed to provide sufficient cobalt. This is the first recorded instance- of cobalt deficiency on a brassica crop. TRIAL 6 (26/1/58 to 26/3/58) Location: Fairlie, on Ashwick very stony silt loam. Management: All lambs on very short grazing on halfploughed. paddock, weeds, and soil and given 14 fl. oz. of fine-particle phenothiazine every 2 weeks. Results 30 lambs cobalt drench each week 16.1 lb. av. gain 30 lambs control 15.0 lb. av. gain Comments: All lambs responded very well to short grazing and phenothiazine. The intake of soil cobalt is considered to have masked the true assessment of the cobalt drench. TRIAL 7 (20/1/58 to 20/3/58) Location: Morven, on Steward very stony silt loam. Management: All lambs were shifted each week on short unimproved pasture, weeds, and access to soil and given phenothiazine every 3 weeks. Results 20 lambs cobalt drench each week .;.... 3.5 lb. av. gain 20 lambs control 3.5 lb. av. gain Comments: The intake of soil cobalt and possibly a higher cobalt level in slow-growing unimproved pasture concealed a deficiency. Liveweight gains were limited by the poor feed. Before this trial started a liver from a lamb that had been on rank improved pasture showed a low cobalt content of 0.02 parts per million. TRIAL 8 (24/12/57 to 28/2/58) Location: Glenavy, on Eyre very stony sandy silt loam. Management: All lambs were grazed on long, rank pasture and no worm-control measures were applied. The lambs, which averaged 70 lb., were in fair order at the start of the trial, which was conducted by the Waimate Farmers’ Veterinary Club. This farm had a history of trouble after weaning. Results 20 lambs cobalt drench each week 8.7 lb. av. gain 20 lambs control 5.0 lb. av. loss Comments: Cobalt highly significant; decline of control lambs aggravated by the ravages of parasites.

a deficiency on Paparua stony sandy silt loam near the Waitaki River. Liver estimates from all these soils were low (0.02 and 0.03 parts per million of cobalt).

Though in trial 6 the beneficial effect of cobalt was small and in trial 7 there was no difference in the groups, a liver from a lamb on rank pasture obtained before trial 7 began had a low (0.02 p.p.m.) cobalt content. The lambs in both these trials were managed on very short pasture with easy access to soil.

Cobalt in Soil Eaten with Short

Experiments by the Department of Agriculture in Southland by E. D. Andrews and others (1958) have indicated that cobalt deficiency disease in lambs is likely to be more severe on long pasture than on short pasture at the same time. This confirms observations by J. K. Dixon (1936), who noticed that short pastures were beneficial in controlling mild cobalt deficiency disease in lambs at Morton Mains, Southland.

A greater amount of soil would be eaten with short pasture than with long, cleaner pasture. Because soil contains about 30 times as much cobalt as pasture, it is considered that the ingestion of soil with short or heavily grazed pasture provides sufficient cobalt for lambs on mild deficiency areas. This was demonstrated in experiments on mild deficiency land at the Winton Experimental Farm in 1952 and 1953, when the only variable was the length of pasture grazed. Lambs showed cobalt deficiency on pastures over 3 in. long, but were protected on pastures about 1 in. long.

J. K. Dixon (1936) reported that oral doses of soil would prevent cobalt deficiency disease in sheep. Since then there have been many anomalies in experiences with lambs on country on the borderline of deficiency. These can be explained by the different amounts of soil consumed with the feed under various climates and grazing systems.

Cobalt Variations in Pasture

In ordinary dry summers on light land, when plant growth is slower and pastures short, almost all lambs in most years have apparently been able to obtain adequate supplies of cobalt. On soils on the borderline of deficiency under climatic conditions favouring rapid, lush growth plants may contain insufficient cobalt to maintain • the animals’ health and resistance to disease. Under conditions less favourable for growth on the same soils the slower growing plants take up a little more cobalt — enough for the animals’ health.

Seasonal variations indicate that the cobalt content of pasture tends to decrease in spring and summer and

increase in late autumn and winter. New Zealand observations are' that /. . _ 1 . 4.1 4. seasons favouring lush th! develop' pastures tend to cause the develop"D of cobalt deficiency disease n? n Andrews 19561 The effect is E - D - i Andrew s> iy&b L , 1 ee . c t s probably a double one due to longer, cleaner pasture with less soil contammatron and to a lower cobalt uptake by rapidly growing plants. . Effect of Fertilisers Tl , ... . , , ... ~ ~ 111-thrift was associated with light land which had been liberally topdressed with lime and superphosphate and where pasture growth was rapid because of enhanced fertility and dull, wet weather. There is evidence from trace element investigations in New Zealand (E. B. Davies, 1957) that heavy applications of lime can induce cobalt deficiencies. On the light land farms in this investigation there was no correlation between incidence of ill-thrift and the quantity of lime used per acre during the previous 6 years. Some areas had received 6 tons per acre, but others with more ill-thrift had received 2 tons per acre. Nevertheless, farmers are recommended to avoid excessive lime applications and to use lime and fertiUsers at rates recommended by local Instructors in Agriculture. Consideration of the cobalt variations in pasture growing at different rates, the direct and indirect effects of fertilisers on cobalt uptake by plants, and the effects of soil intake with short pasture will help toward an explanation of the increasing incidence of cobalt deficiencies under improvedfertility, high-foliage-producing conditions, especially in the wetter seasons of abundant, clean growth.

Significance of Internal Parasites The most consistent post . morlem ine most consistent post-mortem findi were h WOl P m burd which had the severest effects on animals retarded coba “ animals aheady retarded by cobalt deficiency. In the cobalt trials where of lambs were . given worm treatment only there as a good response in improved vigour and liveweight gains. The great advantage in weight gains by controlling parasites in addition to correcting any cobalt deficiency has emphasised that the effects on health of so-called secondary parasites, particularly Ostertagia species, should not be lightly brushed aside. The degree to which these parasites are harmful depends on the relationship of the numbers present to the resistance of the host. During this investigation in South Canterbury the infective potential of parasites has been greatly favoured by long periods of dull, warm, wet weather resulting in mass hatchings of eggs and great activity and survival of infective larvae on wet grazings, Copper and Iron Tested Representative livers were forwarded to Wallaceville for copper estimations and satisfactory figures were obtained. Furthermore no benefit was obtained in three trials wc h tested the value of additional copper and iron given as a drench e V.° St f dieS ~ 0 lvers an P as ure s ... + -n/r ,If as . ° s eS^ Wn - Molybdenum has ” I S ° concerned 3 - .. CL . c i n r- • r 0 showing seasonal Deficiency As a result of this survey by the Animal Industry Division in South Canterbury the soil types known to

be affected by seasonal cobalt deficiency are the following free-draining, and therefore easily leached, soils:

Ashwick stony silt loams in the Fairlie district; Lismore stony silt loams in the Orton district; and Steward stony silt loams, Paparua stony silt and sandy loams, Eyre stony silt and sandy loams, and Pukeuri shallow silt loams from Morven to the Waitaki River extending, as far as Ikawai in the form of a large triangular district including Pikes Point.

Seasonal cobalt deficiency could probably occur on all light stony soils when climate and pasture improvement give lush growth. The findings of this investigation could be of importance to other areas of similar stony soils belonging to the Lismore, Steward, Paparua, Eyre, and Pukeuri soil types, which occur over extensive areas of the plains of Canterbury and to the foothills. Recommendations Farmers on the light stony soils are recommended to: 1. Provide additional cobalt for sheep by either: (a) Applying cobalt sulphate at 5 oz. per acre annually as a solution or in topdressing in early spring for preference. (b) Giving cobalt- bullets to all lambs at 6 weeks old or to newly purchased store lambs and replacement lambs. (c) Arranging a cobalt bullet trial in doubtful cases and testing for a deficiency when unthriftiness is apparent or retarded growth suspected. The weight gains of 20 ear tag numbered lambs dosed with cobalt bullets can be compared over 8 weeks with the individual weight performances of 20 ear tag numbered lambs that have no cobalt supplied. ■

2. Control internal parasites: Good results should follow the strategic use of a fine-particle phenothiazine containing a high percentage of particles under 5 microns. If trouble sets in, the ordinary dose should be increased to 1J times and drenching repeated at intervals of 3 weeks for - all unthrifty lambs. Take precautions during and just after periods of dull, wet weather. It is advisable to adopt a 7-day shift on to clean, spelled feed during “wormy” weather and to prevent lambs from continually foraging over previously used breaks of feed crops to reduce intake of parasites.' Acknowledgment

Diagnostic work and information supplied by the Wallaceville Animal Research Station and access to the result of a cobalt trial supervised by the Waimate Veterinary Club are acknow-

lodged. The author is indebted to E. D. Andrews, Principal Scientific Officer, Wallaceville, for statistical analyses and communications. References E. D. Andrews (1958), personal communication. E. D. Andrews (1956), “Cobalt Deficiency”, “The New Zealand Journal of Agriculture”, vol. 92, pp. 239-244. E. D. Andrews, B. J. Stephenson, J. ,P. Anderson, and W. C. Faithful (1957), “The Effects of Length of Pastures on Cobalt-defici-ency in Lambs”, “New Zealand Journal of Agricultural Research”, vol. 1, pp. 125-139.

. E. A... Clarke and D. B. Hilmer (1956), “Hogget Rearing”, “The New Zealand Journal of Agriculture”, vol. 92, pp. 115-120. E. B. Davies (1957), “Trace Elements in Plant Nutrition”, “Proceedings of the Ruakura Farmers’ Conference 1957”, pp. 85-95. J. K. Dixon (1936), ■ “Investigations on a Sheep Ailment in Southland”, “New Zealand Journal of Science and Technology”, vol. 17, pp. 609-619. R. C. Stuart, H. H. Tocker, E. Stonyer, and H. Evans (1957), “Lamb 111-thrift in Ashburton County”, "The New Zealand Journal of Agriculture”, vol. 95, pp. 449-456. Thomas, P. L„ and Elliott, D. C. (1957), “New Zealand Veterinary Journal”, 5 : 66.

Causes and Remedies

© Severe unthriftiness and heavy losses of lambs on light stony soils of South Canterbury between November 1957 and March 1958 were the result of cobalt deficiency and parasitism induced by continued dull, wet, warm weather and a vigorous growth of foliage.

© Investigations and mineral feeding trials by the Animal Industry Division have shown the importance of controlling both cobalt and parasitism. There was no acceptable evidence that supplements of copper and iron were helpful.

Q The existence of seasonal cobalt deficiency has been established in several light land soil types which comprise large areas of leached soils on the plains and foothills of Canterbury where ill-thrift of lambs can arise. The significance of the benefits of short pastures and of slowgrowing pastures in relation to cobalt contents is discussed in this article.

@ Recommendations , are given for the provision of cobalt by topdressing or by direct administration and for the control of parasitism.

® It is not suggested that any one formula will apply for the control of ill-thrift on all soil types and the results of this investigation may apply only to light stony soils. 111-thrift on other soils requires individual investigation for causes such as primary parasitism, unpalatable or toxic feed, or other feed conditions leading to loss of appetite.