THE EFFECT OF ANTHELMINTIC TREATMENT OF MAIDEN EWES IN THE PERIPARTURIENT PERIOD ON PASTURE CONTAMINATION AND PRODUCTION OF PRIME LAMBS F. M . DAKVlLl*, J . H. ARUNDELt and P . B. BROWNS SUMMARY: A replicated experiment using first cross Border Leicester/Merino maiden ewes set stocked at the rate of 9.9 per hectare was conducted to examine the effects of treatment of the ewes in the periparturient period (PPP) and treatment of lambs at about 12 weeks of age on the production of prime lambs. All treatments given were thiabendazole. Four groups each of 100 ewes ( 4 replicates x 25) were treated either pre-lambing, 2 weeks before lambing commenced and again post-lambing, 8 weeks later when lambing was almost complete (DD), pre-lambing only (DO), post-lambing only (OD) or not treated during the lambing period (00). Lambing commenced 24 July 1972 with the bulk of lambing (98%) occuring within the first 4 weeks of a 6 weeks lambing period. The effectiveness of the drenching regimes was judged by observing bodyweight gains per day during four overlapping intervals between birth and 18 weeks of age. The bodyweight gain of lambs up to 18 weeks and the number of lambs exceeding a target weight of 33 kg at 18 weeks of age were considered to be critical measurements of production efficiency. Significant bodyweight differences were observed within 30 days from birth, favouring DD and DO over OD and 00 lambs (p < 0.01). These differences continued until 12 weeks of age at a reduced level of significance ( p < 0.05). By 18 weeks of age the results favoured DD over DO ( p < 0.05) over both OD and 00 lambs (p < 0.05). Further differences were created by the treatment of lambs at 12 weeks of age (p < 0.01). At no time during the entire experiment were any significant differences observed between OD and 00 lambs. The periparturient rise (PPR) in faecal nematode egg output was monitored throughout the experiment. Anthelmintic treatment of the ewes in the PPP did not eliminate the PPR but did affect the onset, magnitude and duration of the PPR which was either delayed by the prelambing treatment or truncated by the post-lambing treatment; treatments both before and after lambing delayed and depressed the PPR and reduced total pasture contamination by 29%. An effect on bodyweight of ewes was also observed with ewes being treated pre-lambing (Groups DD, DO) being significantly heavier at 18 weeks post-lambing than OD and 00 ewes ( p < 0.05). The observed effects on lamb production have been attributed in the main to an apparent, though not s ecifically measured, effect on lactation in those ewes being treated Dre-lambing. The effect ordelayed (Groups DD, DO) andlor reduced (Group DD) pasture contamination was considered to be additive to the earlier lactation response. Treatment of lambs at 12 weeks did not obscure these responses.

Introduction

I t has been shown by a number of workers (Nunns ef a1 1965; Brunsdon 1966; Connan 1967) that when ewes were treated, either pre- or post-' lambing and then moved to clean' pasture, the periparturient rise ( P P R ) was eliminated. Conversely it was shown by Dunsmore (1965), Connan (1967), Arundel a n d Ford (1969) and Arundel (1971) that i f ewes were not moved to clean pastures following those treatments the ewe became reinfected and the PPR resumed a normal but delayed course. However, the provision of pastures substantiall y free of parasitic infection has become increas*b.(mcL W a r p h I h l i i i i c l A L i \ i r a l t : t l PI). 1 id.. I' 0 I l o x 79. ( ~ r ~ ~ ~ ~~Y Ci Nl S l co u, ~ l l M;ile\. 2142

t l l n i \ e r u i ) o f Zlclbouriic. \ CICI ~ i i n r )Clinical C m i r e . \ \ ' c r r ~ h ~ c\. I C I O T I ~ ~3 0 3 0 t P . 0 . Box IIJh. \4 cllinglor~.Nca S u i i l h M a l e \ . 2x20

Australian Veterinary Journal, Vol. 54. December, 1978

ingly difficult in many farming situations because of economic pressures demanding high stocking rates and the growing acceptance of set stocking as an alternative management system. The situation is worsened in solely sheep enterprises and particularly where late winterlspring lambing is practised. In these situations the longevity of larvae on pasture makes i t almost impossible to provide the clean pastures necessary for the control of the PPR (Donald a n d Waller 1973). This situation demands that an alternative approach be devised that is both practical and financially acceptable to the grazier wishing to implement a n effective parasite control program. O n e such approach is the weaning of lambs at 10 t o 12 weeks of age. This has been discussed by Southcott and Corbett (1966), Thomas and Boag (1968), Arundel (1971) and Lewis ef af (1972) and 575

shown to decrease worm burdens significantly and increase growth rates providing weaning was not done too early. However, this too is dependent upon the provision of clean pastures onto which the lambs may be weaned and would not be acceptable to many prime lamb producers as it involves the weaning of lambs of 20 to 25 kg liveweight; this could induce a check in production that would preclude the acceptance of those lambs in early summer markets and require that they be carried over the summer period into the following autumn. Connan (1968) considered that where reinfection was inevitable, treatment of the ewes should be delayed for as long as possible or repeated at regular intervals. However, deferment of the treatment until post-lambing may not avoid significant levels of pasture contamination, as O'Sullivan and Donald (1970) have shown that the rise frequently commences pre-lambing. Others (Salisbury and Arundel 1970; Brunsdon 1967; F. L. Bowen, personal communication 1975) have shown the intensity of the rise to be greater in early lambing ewes than those lambing late. Thus, in flocks with an extended lambing, the early lambing ewes may have caused considerable pasture contamination before the flock is treated. Few experiments appear to have been conducted that measure the production implications of attempts to control the PPR. The experiment reported in this paper was designed to measure the effects of pre-lambing and post-lambing anthelmintic treatments of maiden ewes on pasture contamination by the ewe and on the bodyweights of both ewes and lambs. Further data applicable to the second and third years of this experiment will be reported separately. Materials and Methods The experiment was conducted on 'Clover Park', situated 35 k i n south-west of Hamilton in the Western District of Victoria. Climatic conditions of the area are characterised by predominantly winter rainfall with hot dry summers typical of that experienced in a large portion of south-eastern Australia. Paddocks Sixteen 2.53 ha paddocks of uniform topography and soil type were created within an area of established Perennial Rye Grass (Ldiurn perenne) and Subterranean Clover (Trifoliurn subterraneurn cv. MI Barker) pasture. The area was mown prior to subdivision and then not grazed by sheep until the introduction of the experimental stock, 5 months later, on 27 April 1972. Experimental Siock Five hundred maiden, 10 to I2 months old, Border LeicesterMerino cross ewes were run with vasectomised rams for 4 weeks before mating, in an attempt to consolidate the lambing interval. On 1 March 1972, all ewes were treated with thiabendazole*, at recornmended dose rates, and Darset Horn rams introduced for a 6-week mating period. Ram harnessest were ' "Thibcnzolr" - Merck Sharp & Dohine (Auslralia) Ply. Lld.. Sydney. New Souih Wale\. f "Sire 5iiie" - Horlico Lsd. Sydney.

576

New South Wales.

changed at 7-day intervals. All ewes marked by the rams in each interval were recorded for randomisation purposes. At the completion of mating 400 ewes within a body weight range of 36 to 55 kg were randomly allocated after stratification according to bodyweight and the duration of pregnancy into 16 equal groups, then to one of the 16 individual paddocks and one of 4 treatments. The ewes then remained set-stocked on those paddocks until the experiment was completed on 20 December 1972. Lambing Lambing commenced o n 24 July and continued over the followling 45-day period. The mean birth date of all lambs born was 6 August and this dale is used throughout this paper as an age reference; 98Oh of the lambs were born in the 4-week period ending 22 August. 7'rearrneiir Groups Table 1 shows the design of the experiment where the 4 groups of ewes ( x 4 replicates) were given either both pre- and post-lambing (DD), pre-lambing (DO), post-lambing (OD) or neither pre-nor post-lambing (00) treatments. The prelambing treatment was given o n 12 July, 2 weeks before the anticipated commencement of lambing, whilst the post-lambing treatment was given 8 weeks later on 3 September. O n I November, when the lambs averaged 12 weeks of age, each ewe group was divided into 2 sub-groups (x 2 replicates) and the lambs in one of these sub-groups treated, while those in the other remained untreated. T h e treatment on each of those occasions was thiabendazole, at the dose rate recommended by the manufacturer. I n all other respects, both ewes and lambs in all groups were treated similarly. Observa rioiis Hodyweight of all ewes was recorded at approximately 4weekly intervals from mating to weaning. Ten ewes were randomly selected from each replicate and from these rectal faecal samples were regularly collected for faecal nematode egg counts (epg) and individual faecal culture and larval differentiation; these samples were initially collected at 4-weekly intervals ( I March to I July), then weekly ( 8 July to 6 October) and then fortnightly (19 October to 30 November). Faecal egg counts were determined by the McMaster slide technique modified by Whitlock (1948) with a sensitivity of 100 epg. Larvae were cultured by the method described by Whitlock (1956) and differentiated on the criteria adopted by Dikmans and Andrews (1933). As the purpose of this faecal sampling was to observe pasture contamination derived from the PPR and the generic composition of the rise, any data from ewes that subsequently failed to rear a b m b were excluded from analysis. Shortly after birth, each lamb wab weighed and permanently identified by a numbered ear tag. At the same time, sex, whether single or twin, and the number of the dam were recorded. Bodyweights of each lamb were again recorded when lambing was completed a n d thereafter at 4-weekly intervals. Commencing 2 October, faecal samples were collected at 2weekly intervals, from 10 lambs within each replicate, and examined for faecal epg and larval differentiation, using the same techniques as described above. Disposal of'Lanibs

L.ambs were sold in 2 drafts. O n 28 November, when lambs were 16 weeks of age, all lambs i n excess of 33 kg were removed; these &ere then divided into 3 grades and each grade valued by an experienced stock buyer. On 12 December. all remaining lambs were again weighed, drafted into 3 grades and valued by the same stock buyer. Siarisiical Aiialysis Lamb birth weight and bodyweight gain data were analysed, using standard analysis of variance techniques, for a randomised block design. The significance of treatment mean differences were determined using least significant differences.

Australian Veterinary Journal, Vol. 54, Deceniber, 1978

TABLE 1 Design of a Replicated Experiment where Ewes were Treated both Pre- and Post-Lambing (DO), Pre-Lambing (DO), PostLambing (OD) or not at all (00)and where Lambs were either Treated or not Treated at I 2 Weeks of Age

3c

25

Ewe Treatment Group

2c

-

15

u 0

;1c a

Ewes Treated Ewes Treated Lambs Treated Post at 12 Prelambing* Lambing? Weeks

DD DO OD

X X 0

X

X X X X

00

0

DD DO OD

X X 0

0

0 0

00

0

0

0 0

0

X 0

c

q. Y I

n

5

Y

c

X

X

~~~~~

0

X 0

*

-5

801

t

n

j: Lambs treated 14 weeks following commencement of lambing.

I

Figure 1 Mean 5 day maximum and minimum temperature ("C) and serial 10 day precipitation (mm) recorded in the Hamilton district during 1972

Results

Climatic Conditions Figure 1 shows rainfall and temperature data recorded in the district during 1972. Rainfall was recorded daily from a point within the experimental paddocks and in the figure is shown as serial 10-day precipitations. Temperature records from the experimental site were incomplete and the data shown in the figure were recorded 40 k m away at the Hamilton Pastoral Research Institute; these are shown in the figure as mean 5-day maximum and minimum temperatures. The data show 1972 to have been generally a mild and relatively dry year. A total of 650 mm of rain was recorded, representing 85% of the 21 year average annual rainfall for the district. Rainfall during the 4-month periods ending 30 April, 31 August and 31 December, accounted for 36, 44 and 20% respectively of the recorded annual rainfall. These latter figures represented 141, 82 and 52% respectively, of the average rainfall recorded in the same 4-month periods during the preceding 21 years. Only in 4 months (January, February, Ausfr-ahan Verer;narj/Jourrial, Vol. 54,December, 1978

Treatments with thiabendazole 44 t o 6 6 mg/kg liveweight Not treated Pre-lambing 2 weeks prior to commencement of lambing Post lambing 6 weeksfollowing commencement of lambing

April and July) did the recorded monthly rainfall exceed the average monthly figures of the previous 21 years. During the period from mid May until mid October, the mean 5-day maximum temperature was generally below 17"C, while the similarly derived minimum temperature was regurarly below 5°C. Numbers of Lambs Born and Reared No significant differences were observed in the numbers of lambs born in each of the 4 ewe groups. Twinning rates, dry ewe persentages and ewe mortalities were similar in all 4 groups and independent of treatment. Similarly, no significant differences existed in the number of lambs reared within each group and lamb deaths did not significantly affect the composition of the lamb groups in relation to the balance between age, single or twin a n d male o r female lambs (Table 2). TABLE 2

Population Profile of Groups of Lambs Born to Ewes Treated Pre- and Post-Lambing (OD), Pre-Lambing (DO), Post-Lambing (OD) or not Treated (00) Observation

DD

DO

OD

00

No. ewes lambed No. Iambs born No. ewes rearing lambs No. lambs reared Single lambs Twin lambs - o n e surviving Twin lambs - t w o surviving

97 120 80 87 67 6 14

93 116 81 89 69 4 16

96 119 77 81 65 8 8

94 119 82 88 67 9 12 577

Birfh Weight a n d Lambs Reared N o significant differences were observed in the birth weights of those lambs that were reared until weaning. Twin lambs, however, were significantly lighter at birth than single lambs and this appeared to influence the survival of lambs; 43% of lambs with birth weights less than 3.5 kg died and this accounted for 62% of a n overall mortality of 27% (Tables 2, 3). Bodyweight Gains of Lambs Daily bodyweight gains were calculated in each of 4 overlapping periods for each of single lambs (SS), twin lambs with 1 lamb surviving (TS), and twin lambs with 2 lambs surviving (TT), so as to enable an evaluation of each of the pre- and postlambing treatments of the ewe and the treatment of the lambs at 12 weeks of age. However, because

of the low numbers of lambs in the TS and T T categories, statistical analyses of these d a t a usuall y proved unsatisfactory. Consequently, much of the discussion is centred upon the performance of the SS lambs. These d a t a are summarised in Table 3. Birth fo 12 Weeks: Single (SS) lambs from ewes given a pre-lambing treatment with thiabendazole (Groups DD, DO) and which were at least 20 days old on 5 September, showed highly significant differences (p < 0.001) in bodyweight gain compared with comparable lambs from ewes that did not receive the pre-lambing treatment (Groups OD, 00).This effect remained until the lambs were 12 weeks old (p < 0.05). Twin (TS) lambs showed a similar result at 30 days (p < 0.05) but not at 12 weeks. With twin (TT) lambs the differences were

TABLE 3 Mean Bkth Weights and Mean Bodyweight Gains Per Day of Single and Twin Lambs from Ewes which were Treated either h e - and Post-Lambing (DO). Re-Lambing (DO), Post-Lambing (OD) or not Treated (00)and which were either Treated or not Treated at 12 Weeks of Age DD

DO

OD

00

Statistical Significance

4.57 3.28 3.33 4.28

4.45 3.13 3.65 4.25

4.33 3.40 3.35 4.14

4.5 1 3.43 3.42 4.25

N.S. N.S. N.S. N.S.

0.236 0.209 0.166 0.226

0.243 0.210 0.165 0.228

DD, DO>OD, 00 (pOD. 00 ( ~ < 0 . 0 5 ) NIS. '. DD, DO>OD, 00 (pOD. 00 (0OD, 00 (pDO, OD, 00 (pOD (pDO>OD, 00 (pDO, OD, 00 (pDO, OD, 00 (pDO, OD, 00 (pcontrol

Observation

Mean birth weights (kg) single lambs twin lambs - one surviving twin lambs - two surviving all lambs

Mean bodyweight gain per day (kg) - birth to 30 days* single lambs 0.257 0.270 twin lambs - one survivine. 0.264 0.243 twin lambs - t w o surviving 0.172 0.153 all lambs 0.245 0.249

-

I

.

twin lambs - o n e surviving twin lambs - two surviving all lambs

* t

j: 578

0.248 0.203 0.252

0.253 0.185 0.236

(pOD, 00 (pDO>OD, 00 (p

The effect of anthelmintic treatment of maiden ewes in the periparturient period on pasture contamination and production of prime lambs.

THE EFFECT OF ANTHELMINTIC TREATMENT OF MAIDEN EWES IN THE PERIPARTURIENT PERIOD ON PASTURE CONTAMINATION AND PRODUCTION OF PRIME LAMBS F. M . DAKVlLl...
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