Genetics and Animal Welfare - Genetics and the Behavior of Domestic Animals - page 442

Canada, has extensive experience of raising both breeding sows and broiler
breeder chickens. She told the first author that “broiler breeders are so highly
selected for appetite that they do not work behaviorally as animals.” For
example, when broiler breeders were fed ad lib., they spent 50% less time
pecking objects ( Sandilands et al., 2005 ). There is also some evidence that
sows that produce large litters have more stereotypic behavior ( von Borell and
Hurnick, 1990 ). D'Eath et al. (2009a) and Lawrence et al. (1989) both warn
that feeding a bulkier, less nutrient-dense diet may not solve all the welfare
problems associated with feeding motivation. Further research is needed on
the effects of “metabolic hunger.” There may be a point where continued
breeding of animals for appetite will cause grave problems.
MOVEMENT RESTRICTION VERSUS FEED RESTRICTION
The general public is often most concerned about movement restriction when
animal welfare is being discussed. Some examples are egg-laying hens
housed in cages, veal calves housed in crates, and gestating cows kept in
stalls where they are unable to turn around. Research clearly shows that ani-
mals are motivated for movement ( Dellmeier et al., 1985; McFarlane et al.,
1988 ). However, movement restriction may be less stressful to the breeding
animals than feed restriction ( Rushen, 1995; Rushen et al., 1993 ). This could
be especially true in animals genetically selected for high appetite. In one
experiment, gilts were housed in crates that made turning around difficult. In
the first treatment, food and water were positioned at opposite ends of the
crates so the gilts had to turn around in order to eat and drink. In the second
treatment, the water and feeder were placed at the same end of the crate.
Gilts that did not have to turn around did so just as many times as gilts that
had to turn in order to eat or drink ( McFarlane et al., 1988 ).
In another experiment, Dellmeier et al. (1985) found that veal calves
housed singly in small stalls for six-and-a-half weeks responded with greater
activity when tested in an open-field arena, compared to calves housed in
groups in a yard. The calves housed in small stalls ran around and kicked up
their heels when turned loose in the test arena. Calves raised in large group
pens did not do this. Pasille et al., (1995) questioned the results of Dellmeier
et al. (1985) , due to the fact that the open field was more novel for the
calves housed in stalls. Pasille et al. (1995) suggest that Dellmeier et al.
(1985) did not control for the novelty factor in the test arena. However, the
first author has observed that cattle kept in a large, open feedlot pens and
cattle housed singly in small “dog run” pens behave differently when
released. Large, fat cattle raised in small “dog runs” ran up and down a
3.5-meter-wide alley when released. The increased activity cannot be
explained by the effects of novelty. Both groups of cattle were raised outside
on the same farm and the alley was visible from their pens. Our informal
observations support the findings of Dellmeier et al. (1985) .