Biology Reference
In-Depth Information
Merriam-Webster, Inc. (1983) defines welfare as “the state of doing well
esp. in respect to good fortune, happiness, well-being, or prosperity” and
well-being is defined as “the state of being happy, healthy, or prosperous.”
To animal researchers, prosperity and happiness are unlikely to be meant,
but rather absence of chronic pain and suffering, good health, ability to
respond to stressors, and components of fitness (including productivity in
some contexts) are likely to be included. There is a tendency, especially
among Western Europeans, to place emphasis on mental conditions such as
fear, frustration, anxiety, anger, and similar emotional states ( Barnett and
Hemsworth, 2003; Duncan and Dawkins, 1983; Duncan and Petherick, 1991;
Green and Mellor, 2011; Mellor, 2012; Yeates and Main, 2008 ). Although
most agree that emotional states should be included, it needs to be recog-
nized that certain temporary stressors, likely to be associated with unpleasant
mental states, prepare chickens to cope better with more severe stressors later
in life ( Gross, 1983; Zulkifli and Siegel, 1995 ). Life in general is a series of
stressors, for humans and animals, in the quest for food, shelter, security, and
reproduction. In each of these basic quests, even in natural conditions, most
animals experience periods of food deprivation, disease, predation, competi-
tion, and stress. Our quest should not be to provide as natural conditions as
possible, lest we expose animals to the undesirable aspects of nature as well,
but rather to protect animals from such natural stressors, while ensuring a safe
healthy food supply, free of disease, for human consumption.
Criteria of Welfare
Having defined, in very general terms, what is meant by well-being, it is
then necessary to examine how it may be evaluated. In what follows we
adopt the general categories of evidence suggested in the review of Craig
and Adams (1984) . More detailed descriptions may be found in other
reviews ( Craig and Swanson, 1994; Duncan, 2005; Mench, 1992; Webster,
2001; Yeates and Main, 2008 ).
Overt Signs
Bodily injury, morbidity, extreme weight loss, heavy feather loss (not associ-
ated with natural molting), and death of individuals are widely accepted as
indicators that welfare is impaired. When the well-being of groups in produc-
tion settings is considered, longevity, i.e. days' survival over the production
period, can be used as an overt indicator. This measure takes into account all
aspects of stress ( Hurnik, 1990; Muir and Craig, 1998; Quinteiro-Filho et al.,
2012 ). Lifetime stress as the result of adverse environments will increase
susceptibility to diseases and will result in other physiological manifestations
which shorten the life-span. Vices such as feather and cannibalistic pecking
also increase exposure to disease or cause death. Thus, longevity, if measured
over a long period, is a direct measure of welfare.
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