BACK TO QUEBEC CITY 2002 TITLES
The effect of ACTH on
pigs’ attraction to salt or blood flavoured tail-models
M.L. Jankevicius and T.M.
Widowski
University of Guelph,
Guelph, Canada
Adrenocorticotrophic hormone
(ACTH) leads to a marked increase in salt appetite in mice, rats, rabbits
and sheep. In a previous study, pigs treated with ACTH did not increase
their ingestion of salt solutions. However, pigs may prefer to chew on
salty objects rather than drinking salt solutions. In the first of two
experiments, the effect of ACTH on chewing behaviour directed at rope tail-models
flavoured with whole pig’s blood or a salt solution having the same salt
content as blood were examined. Sixteen individually housed pigs (45 kg)
were divided into two groups: an ACTH-treatment group, receiving intramuscular
injections of long-acting ACTH (50 IU twice daily for 5 days) and a control
group, receiving no injections. Chewing behaviour directed at water-soaked,
salt-flavoured or blood-flavoured tail-models was observed during two 30-minute
periods. Overall, chewing of tail-models tended to decrease in ACTH-treated
pigs during the injection period with a significant reduction in chewing
directed at blood-flavoured models (P<0.05). A decrease in standing
(P<0.05), sitting (P<0.05) and rooting the pen (P<0.05) were also
observed in ACTH-treated pigs during the injection period. The incidence
of chewing directed at blood-flavoured models was greater than that directed
at models soaked in water or salt for all pigs, regardless of treatment
or period (P<0.05). In the second experiment, the effect of colour on
the preference for different flavoured tail-models was determined. The
chewing behaviour of sixteen individually housed pigs was observed twice
daily. Water-soaked, salt-flavoured or blood-flavoured tail-models were
dyed with a red food colouring agent to appear similar in colour. Pigs
still preferred to chew on those tail-models soaked in blood to either
of the ones soaked in just red food dye or salt solution plus red dye (P<0.05).
Growing pigs do not appear
to develop an increased salt appetite or attraction to blood when given
exogenous ACTH. It appears that pigs are using olfactory or taste cues
to discriminate among the different models. It does not appear that salt
content is what is attracting pigs to blood, at least not when they are
fed diets that meet their nutrient requirements.