Genetics and Behavior During Handling, Restraint, and Herding - Genetics and the Behavior of Domestic Animals - page 130

squealed; and (5) animal attempted to escape. Lawrence et al. (1991) con-
cluded that the temperament differences between individuals were
stable over time. Yoder et al. (2010) divided pigs into vocal, or not vocal
categories while loading on a single animal scale. Landrace pigs vocalized
compared to Chester Whites, Durocs, or Yorkshires. Yorkshire pigs were
also more difficult to load onto the scale.
Lean, Rapid-Growing Pigs are More Excitable
Ultra-lean hybrid pigs with very little back fat became popular in the United
States during the mid-1990s. The first author has observed some genetic
lines of lean hybrid pigs are much more excitable during handling compared
to fatter breeds of pigs. She speculates this effect cannot be attributed
entirely to early rearing environments. Striking differences in pig behavior
occur in lean hybrids of different genetic backgrounds raised in the same
building operated by the same people. Many pork producers have commen-
ted that some genetic lines of lean hybrids are more excitable than older
crossbred pigs with large amounts of back fat. The differences in behavior
were first noticed when producers changed breeding stocks. Lean hybrids are
more reactive and more likely to squeal when touched. Research by Holl et al.
(2010) helps confirm these observations. They found pigs with a docile calm
temperament and more backfat grew more quickly. Leaner pigs in a composite
population of Duroc, Large White, and Landrace became more agitated on a
single animal scale. Pigs with a very excitable temperament are much more
difficult to handle. Grandin (1994) observed that excitable pigs can be moved
easily if the handler moves slowly and avoids sudden movements. Sudden
movements cause excitable pigs to bunch together and pile up.
Lean hybrid pigs cause serious handling problems in slaughter plants
which process 1000 pigs per hour on a single line. The reactive pigs balk
more and are difficult to drive. Most large slaughter plants were forced to
install a second complete handling and stunning systems in order to handle
the lean hybrids at a rate of 500 pigs per hour in each system.
Behavior Problems in Crossbred Beef Cattle During the 1990s
Behavior problems with crossbred cattle have been observed by breeders.
Bonsma (1975a, b) stated that Brahman crossbreds have more temperament
problems than purebred Brahman. The first author has made similar observa-
tions in crossbreeds of Brahman and Hereford cattle. Compared to the pure-
bred parents, crossbred calves are more difficult to halter break. The authors
speculate that when Brahman are crossed with Hereford or Angus, emotional
traits of either separation distress (PANIC) or CARING is reduced. In the
early 1990s, there were problems with very excitable beef cattle in the U.S.
that were likely to become extremely agitated when suddenly confronted