Improving Animal Welfare: A Practical Approach

Edited by Dr. Temple Grandin
Colorado State University, USA

ISBN: 978-1-84593-541-2
c. 336 pages
131 figures/illustrations

Subject Classifcation: KNAC, PSVP, TVH, TW
Territorial Market Rights: World
Published by CABI

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Chapter 15: Why are behavioral needs important?

by Tina Widowski, University of Guelph, Canada

This chapter describes how behavioral needs are measured. Ethologists and behavior scientists have developed tests for measuring motivation in many farm animals such as pigs, cattle, and chickens. Some of the most common behavioral tests for determining the animal welfare implications of many on farm conditions are aversion tests, preference tests, strength of motivation tests, and assessments of aggression, such as lesion scoring.

Below is an excerpt from Chapter 15...

Scientific Approaches to Measuring Animalís Feelings

Animal welfare Scientists have developed a number of different approaches for assessing how animals feel about specific aspects of housing and handling. There are two general approaches that are used and these have recently been reviewed (Kirkden and Pajor, 2006). The first general approach is to offer animals some control over specific resources or specific experiences, either by offering them choices or by providing opportunities to get to or get away from some option, and then observing what decisions the animals make. Basically these are methods of asking animals what they want and how much they want (or donít want) it. Examples of the sorts of options that can be tested are types of flooring or stall design, different substrates such as straw, wood shavings or sand, items such as nest boxes, perches or social companions and different types of handling and restraint. Three types of standardized tests are used: preference tests, tests for strength of motivation and aversion tests, which will be explained in more detail. The second general approach to measuring an animalís feelings is to keep it in a particular environment (e.g. a wire cage) or expose it to a specific type of experience (e.g. freeze branding) and then carefully observe and measure the animalís responses in order to identify indications of negative feelings such as frustration, fear or distress. Behavioral responses might include things such as trying to escape (Schwartzkopf-Genswein et al., 1998), behavior that appears out of context to the situation or stereotypic pacing (Yue and Duncan, 2003).

Preference Tests

In standardized preference tests scientists use either a Y-maze or a T-maze with different options offered at the ends of the maze. Animals are trained to use the maze, they learn what options are available at the ends of the maze, and then their choices of going to the different options are counted over a series of tests. Alternatively, the animal may be given continuous access to different options over a longer period of time and the frequency of accessing the options and amount of time spent with the different options is measured by live observation or by video recording. Preference tests have been used to study a whole variety of different design features of housing in all species including environmental temperature for sows (Phillips et al., 2000), different types and intensities of lighting for poultry (Widowski et al., 1992; Davis et al., 1999), different types of bedding and flooring for dairy cows (Tucker et al., 2003) and even different levels of ammonia in the air (Wathes et al., 2002). Preference tests can provide good information about housing alternatives, but the tests have to be carefully designed to ensure that the animals are making choices for the options of interest; for example, not just always choosing the left side. They also have to be carefully interpreted because a number of factors can affect the results, such as the previous experience of the animals (they might be hesitant to enter an area with a novel type of flooring, even motivational state that the animal is in during the test (a pig might choose straw to lie on when it is cold but choose bare concrete when it is hot). Another concern with preference tests is that animals do not always make choices that are best for their long-term health and welfare and this has to be considered when using the results to make housing recommendations. One example may be choosing a floor type that may be comfortable to lie on but may be bad for long-term foot health.

Aversion Tests

Aversion tests are based on the idea that unpleasant feelings or negative emotions evolved to help animals learn to avoid situations that may cause them harm. When an animal experiences something that causes fear, pain or discomfort, it usually behaves in ways that serve to remove the source of those feelings (avoid and escape). If an animal repeatedly experiences something unpleasant, painful or distressing it will learn to avoid the place or the situation associated with those unpleasant feelings. A number of studies have shown that cattle will learn to avoid rough handling either by hesitating or refusing to go down a runway where hitting and prodding have been experienced (Pajor et al., 2000) or by choosing the arm of a maze associated with gentle handling rather than rough (Pajor et al., 2003). Similar tests have shown that sheep quickly learn to avoid an arm of a maze in which they were subjected to electro immobilization as a means of restraint (Grand in et al., 1986). These tests indicate that cattle and sheep do, in fact, distinguish between different types of handling and restraint and that they find some types more aversive than others.

Strength of Motivation Tests

Although preference tests do provide us with good information about the relative merits of different choices to the animal, they do not give us any indication how important those choices are. When given the option, a hen may prefer to dust bathe in peat moss over wood shavings, so if we were going to offer them a substrate we know the one that she values more. However, the results of the preference test tell us nothing about how much she wants a dust-bathing substrate. This information is particularly important when we consider the more difficult questions regarding whether animals suffer from behavioral deprivation. Dawkins (1983) pioneered the concept of using another type of test, the demand test, to gauge the strength of motivation an animal has for a particular resource. Demand tests are based on techniques used by economists to determine what types of things people view as needs or luxury items based on their purchasing behavior. Demand tests used for animals are designed to ask animals to pay for a resource through their behavior. They may have to incur a cost to obtain a resource, for example, forgoing an Opportunity to feed in order to spend time in a larger cage or with a social companion. More often the animal is asked to perform an operant technique ó peck at a key, press a lever with their hoof or snout ó in order to obtain the reward.

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