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Plant/Animal Production
The effects of internal parasites: an experimental trial
This material addresses aspects of the following syllabus outcomes:
H2.1 describes the inputs, processes and interactions of animal production systems
H4.1 Justifies and applies appropriate experimental techniques, technologies, research by methods and data presentation and analysis in relation to agricultural problems and situations.
The work presented in the following section contributes towards understanding the following syllabus content areas:
Students learn about:
Experimental analysis and research in plant/animal systems
- experimental design
- the collection and analysis of data
Extract from Stage 6 Agriculture Syllabus NSW Board of Studies Amended 2009
This section summarises much of the information you have gained about the internal parasites that affect sheep and how correct management can reduce their effects.
Research is constantly being carried out to improve animal production. This piece of work presents you with an experimental trial that was carried out in order to determine the effect of internal parasites on the growth rate of lambs. You need to analyse and interpret the data gained in this experimental trial using your knowledge of internal parasites and experimental analysis.
Internal parasite trial
An experiment was carried out to determine the effect of internal parasites on the growth rate of lambs. When you have read through the aim, method and results of the trial you should complete the questions.
Aim: To determine the effects of no internal parasite control compared with the Wormkill recommended control of internal parasites, on the liveweight gains of two groups of Texel cross lambs.
Method: A mob of 40 first cross ewes were used in the experiment. They were all same age, they all had the same vaccinations, drenches and feed until the start of the experiment. The ewes were all joined in April with the same Texel ram.
- The ewes were yarded and then alternately drafted into two groups after joining was completed. Those ewes drafted to the right were Group A, while those drafted to the left were Group B.
- The groups were then put into separate paddocks. Both of these paddocks had not had sheep in them for the last six months. The paddocks were the same size and had similar pasture species growing in them.
- Group A ewes were treated for internal parasites in accordance with the Wormkill program. The ewes lambed in September. The lambs were drenched in December and February with Seponver and a broad-spectrum drench. The lambs were weaned onto a low worm pasture in December.
- Group B ewes were not drenched at all. The ewes lambed in September. The lambs were weaned but not drenched at all. They were weaned onto pasture that had previously had ewes and lambs on it.
- The pasture types and paddock sizes were the same in both weaning paddocks.
- At 24 weeks the lambs were weighed. The liveweights are shown in the following table.
| Group A (worm control) | Group B (no worm control) |
|---|---|
| 59 | 53 |
| 54 | 47 |
| 47 | 48 |
| 64 | 58 |
| 50 | 48 |
| 52 | 49 |
| 45 | 41 |
| 58 | 53 |
| 52 | 51 |
| 52 | 44 |
| 57 | 50 |
| 66 | 62 |
| 66 | 64 |
| 40 | 34 |
| 39 | 32 |
| 61 | 55 |
| 43 | 43 |
| 51 | 46 |
| 43 | 39 |
| 41 | 35 |
| 61 | 47 |
| 60 | 40 |
| 63 | 53 |
| 49 | 39 |
| 57 | 45 |
| Mean =" | Mean =" |
| Standard Deviation = 8.34 | Standard Deviation = 8.21 |
Activities
- Calculate the mean weights (kg) for each of the groups.
- What conclusion can be drawn from this experimental trial? That is, how does worm control affect the liveweight of lambs?
- Describe how randomisation was carried out in this experiment.
- How was the standardisation of conditions ensured in this experiment?
- What measure of performance was examined in this experiment?
- What was one variable in this experiment?
- What variables were controlled in this experiment? Why is it important to control variables in experiments?
- Describe the role of rotation in livestock grazing systems.
- The standard deviation has been calculated for each of the groups of lambs. What information about this experiment is provided by these standard deviations?
If you would like to find out more about sheep internal parasites you should
investigate the NSW Agriculture 
website.
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