THE EFFECTS OF HOUSING ON HEART-RATE OF GESTATING SOWS DURING SPECIFIC BEHAVIORS

The heart rates of 21 sows in three different dry sow housing systems were measured during feeding, drinking, rooting and lying with eyes op en. Measurements were made on sows kept in: (1) a large group of 37 wi th an electronic sow feeder (n = 7); (2) small groups of five, with in dividual feeders (n = 7); (3) individual stalls (n = 7). For all three systems, heart rate was highest during feeding and lowest during lyin g, with rooting and drinking intermediate. When comparing between syst ems, stall-housed sows had significantly higher basal heart rates (54. 1 b.p.m.) and average feeding heart rates (118.5 b.p.m.) than sows fro m large-group (45.9 b.p.m. and 105.9 b.p.m.) and small-group housing s ystems (46.7 b.p.m. and 102.5 b.p.m.). The variability of heart rate d uring feeding and the difference between average feeding heart rate an d basal heart rate was also highest in stall-housed sows. Sows housed in the small group had higher mean peak heart rates during feeding tha n sows housed in the large group with stall-housed sows intermediate. Long-term confinement in stalls may induce a greater sympathetic nervo us response to important stimuli such as feeding. However, a feeding e nvironment in which there can be contact between sows results in highe r mean peak feeding heart rates and heart rate variability probably du e to short-term adrenal responses to agonistic interactions. (C) 1997 Elsevier Science B.V.