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This article was published in 1975
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Report on Trials to Determine the Value of Treating Sucker Lambs for Cestodes
W.B. Harding, B.V.Sc., M.A.C.V.Sc., A.R. Jackson, B.V.Sc., Ph.D., A.K, Bell, H.D.A.
INTRODUCTION
There is a widespread belief held by the breeders of fat lambs that cestodes cause harmful effects and retard weight gains. The evidence available in this country did not indicate that treatment was of any value. However, benefit following treatment has been reported by some overseas workers. Stampa (1967) in South Africa, Helle (1971) in Norway and Katiyar and Garg (1966) in India.
It is common practice to treat lambs and older sheep that are not 'doing' with costly drenches in the belief that cestodes are responsible. These trials were designed to ascertain if this management procedure had any economic value, and the pattern of natural cestode infestation.
We were fortunate in selecting a property for these trials where the owner had, for many years, treated his sucker lambs for cestodes and believed treatment was of value.
MATERIALS AND METHODS
Two trials were conducted. The first with spring drop prime lambs, the second with autumn drop prime lambs.
The procedures in both trials were exactly the same and this paper is a précis of papers to be published.
In each trial 100 sucker lambs, having a mean age of six weeks, were divided into two groups of 50 (Groups A and B), according to weight and sex, For slaughter purposes an additional group of 15 lambs was selected, having the same weight and sex distribution (Group S).
All lambs at marking time and at the commencement of the trial were vaccinated for enterotoxaemia. On four occasions at three week intervals Group B was treated with 'Mansonil' (Bayer) at the recommended dosage. Also on the same occasions both Groups A and B were treated with a broad spectrum anthelmintic 'Nilverm' (I.C.I.). Group S were not dosed with anthelmintics.
The following observations were recorded:
Body weights on five occasions at three week intervals.
Cestode ova counts on 20 lambs randomly selected from each of the Groups A and B at each weighing.
From each of three lambs from Group S cestode volumes, number of cestode heads, cestode ova counts and strongyle worm and ova counts at commencement and end of 3rd and 6th week of trial were made in the first trial with the spring drop lambs. In the second trial with the autumn drop lambs these observations were also made at the 9th and 12th weeks of the trial. On two occasions in both trials similar observations were made at time of abattoir slaughter of animals.
RESULTS
Body Weights
In papers to be published full details of the results are set out in tables, but for the purpose of this précis the results are summarised.
In the first trial with the spring drop lambs there was practically no difference between the performance of the treated and untreated groups. The mean weight gain of the treated Group B Was 33.0 lbs. compared with 31.9. lbs. in untreated Group A over a period of 12 weeks. This result is considered insignificant. The mean weight at the end of this period in Group A (untreated) was 66.8 lbs, against in Group B (treated) 68.0 lbs.
In the second trial with autumn drop lambs there was no difference between the performance of the treated and untreated groups. Group B (treated) gained 39.75 lbs, compared with 40 lbs. in Group A (untreated), over a period of 12 weeks. The mean weight in Group A was 74.2 lbs. against 74.1 lbs. in Group B.
Cestode Infection
This is recorded in detail in tables and graphs in papers to be published. The cestode populations in spring and autumn lambs are shown in the graph in Figure 1.
In both trials treatment completely suppressed tapeworm ova. Further, in the first trial opportunity was taken at the 13th week of the trial to examine 7 lambs from Group B (treated) at Abattoir slaughter and no tapeworms were present, confirming the effectiveness of the 'Mansonil' treatment.
In the spring lambs observations on slaughtered lambs showed there was a rapid rise in cestode infestation measured by strobila volume to reach a peak at 9 weeks of age followed by a rapid decline to reach a low volume at 21 weeks of age. Cestode ova in the untreated Group A parallels the infestation but reached a peak three weeks later.
In the autumn lambs no tapeworms were present in slaughtered lambs at 9 weeks of age then the number rose to a maximum at 15 weeks of age and thereafter declined to a steady level by 21 weeks. The number of cestode heads bore a constant relation to their strobila volume.
Incidence of Scouring
In the autumn drop lambs at the 12 weeks of age observation scouring was seen in both groups and was associated with the soft green condition of the feed. At the next observation at 15 weeks of age all but one of the lambs in the treated group had dried up while eight in the untreated group were still scouring. At 18 weeks of age two in both the treated and untreated groups were scouring.
DISCUSSION
In neither trials was a weight gain advantage obtained by keeping the lambs cestode free and this confirms previous Australian work. The infestation in the autumn drop lambs reached its peak six weeks later than the spring drop and at half the level but in both trials dropped to a constant lower level at about the 21st week.
The literature does not suggest any precise information on levels of infestation. We suggest that the strobila volume of 100 mls. of tapeworms constitutes a moderate infestation and 200 mls. a heavy infestation. In the slaughter lambs in the first trial the infestation at its peak was heavy and in the second trial was never greater than moderate.
The reason for the persistence of scouring in the untreated Lambs in the second trial (autumn drop) is not clear. It is not considered to be related to nematode infestation as all lambs (except Group S) were drenched at three weekly intervals with 'Nilverm'. Scouring is an important problem in lambs as they cannot be accepted at abattoirs whilst so affected or without crutching. However, it did not affect the economics of the trial because crutching of about an equal number was required in both the treated and untreated groups.
The rapid rise and fall in the level of infestation in both trials was interesting. It does strongly suggest that treatment of lambs over about 18 weeks of age is valueless.
SUMMARY
The trials were conducted to determine the value of treatment of cestodes in spring and autumn drop prime lambs.
There was no weight advantage demonstrated in continually controlling cestode infestations in both trials. The natural level of infestation of lambs with tapeworms reached a peak in the spring drop at 9 weeks and in the autumn drop at 15 weeks. It then declined and had reached a low level in both drops by 21 weeks of age.