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The effects of internal parasites: an experimental trial - Answers
- Calculate the mean weights (kg) for each of the groups.
Group A mean = 53.2 kg Group B mean = 47 kg
- What conclusion can be drawn from this experimental trial? That is, how does worm control affect the liveweight of lambs?
In this experimental trial it can be seen that worm control affects the liveweight of lambs. Those lambs that underwent the Wormkill program had a mean liveweight of 53.2 kg, while those lambs that had no internal parasite control had a mean liveweight of 47 kg. It can be concluded that internal parasite control results in larger liveweight gains compared with no internal parasite control.
- Describe how randomisation was carried out in this experiment.
Randomisation was carried out by the ewes being drafted alternately into two groups.
- How was the standardisation of conditions ensured in this experiment?
Standardisation of conditions was ensured in this experiment by the following:- the mob of ewes were all first cross, the same age and had all had the same vaccinations and feed
- the ewes were all joined with the same ram at the same time
- the ewes were all kept in similar paddocks.
- What measure of performance was examined in this experiment?
The measure of performance examined in this experiment was liveweight.
- What was one variable in this experiment?
The one variable in this experiment was the drenching program. Group A followed a Wormkill program, while Group B followed no worm control program.
- What variables were controlled in this experiment? Why is it important to control variables in experiments?
The variables controlled in this experiment include:- the breed of sheep
- the age of the ewes
- the nutrition provided for the ewes and subsequently for the lambs
- vaccinations for all sheep.
- Describe the role of rotation in livestock grazing systems.
Rotation in livestock grazing systems helps in the control of internal parasites. Sheep and cattle are largely susceptible to different parasites. Ewes with lambs tend to carry heavier burdens of worms than do wethers and dry ewes. Therefore, putting weaners onto pastures that have recently been grazed by cattle or older sheep without lambs, is likely to reduce the worm infestation in those weaners. Hence, the rotation of pastures in grazing systems is a useful tool for controlling internal parasites.
- The standard deviation
has been calculated for each of the groups of lambs. What
information about this experiment is provided by these standard deviations?
The standard deviation indicates how closely around the mean the weights were clustered. In this experiment, the weights were clustered around each respective mean weight to the same extent. This helps you accept the results with greater confidence.
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