Submitted to: American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2002
Publication Date: July 21, 2002
Citation: MARCHANT FORDE, J.N., LAY JR, D.C., RICHERT, B.T., PAJOR, E.A. THE EFFECTS OF RACTOPAMINE ON BEHAVIOR AND PHYSIOLOGY OF FINISHING PIGS. AMERICAN SOCIETY OF ANIMAL SCIENCE. 2002. Technical Abstract: This study aimed to examine the effects of ractopamine (RAC) on behavior and physiology of pigs during handling and transport. Twenty-four groups of 3 finishing pigs were randomly assigned to one of two treatments, four weeks prior to slaughter; 1) finishing feed plus RAC (9ppm), 2) finishing feed alone. Pigs were housed in adjacent pens with fully-slatted floors and access to feed and water ad lib. Behavioral time budgets were determined in half the pens over a single 24-hour period during each week. Behavioral responses to routine handling and weighing were determined at the start of the trial and weekly. Heart-rate (HR) responses to unfamiliar human presence were measured in all pigs and blood samples were taken from a single pig in each pen on different days during week 4. At the end of week 4, pigs were transported for 20 min to slaughter. HR was recorded from at least one pig per pen during transport and a further post-slaughter blood sample was taken from pigs previously sampled. During weeks 1 and 2, RAC pigs spent less time inactive (week 1, 75 2% vs 81 1%, p<0.05; week 2, 76 1% vs 81 1%, p<0.01) and less time lying laterally (week 1, 55 2% vs 65 2%, p<0.01; week 2, 58 3% vs 68 1%, p<0.05). There were no differences in time budgets during weeks 3 and 4. Initially, there were no differences in responses to handling. However, over each of the next 4 weeks, fewer RAC pigs exited the home pen voluntarily, they took longer to be removed from the home pen, longer to handle into the weighing scale and needed more interactions from the handler to enter the scales. At the end of week 4, RAC pigs had higher HR in the presence of an unfamiliar human (144.6 3.2 bpm vs 136.4 2.7 bpm, p<0.05) and during transport (151.6 4.1 bpm vs 140.7 3.3 bpm, p<0.05), but not during loading and unloading, and had higher circulating epinephrine (253.0 55.0 pg/ml vs 101.5 15.0 pg/ml, p<0.05) and norepinephrine (991 150 pg/ml vs 480 58 pg/ml, p<0.01) than control pigs. Circulating cortisol concentrations and cortisol responses to transport did not differ between treatments. The results show that, at the dose administered in this experiment, ractopamine does affect the behavior and physiology of finishing pigs and may make them more difficult to handle and more susceptible to handling and transport stress.