Behavioral and endocrine response of sows to prostaglandins F(2α) and cloprostenol

Abstract

Behavioral and endocrine changes in the sow following injection with prostaglandin F(2α) (PGF(2α)) or its analogue, cloprostenol (CLO), were monitored to identify endocrine correlates of prepartum activity (nest-building). On Day 112 postcoitum, within 15 min after injection with 10 mg PGF(2α), sows offered straw in pens engaged in intense prepartum activity, but few behavioral changes occurred during the first 2 h following administration of 175 μg CLO. The temporal pattern of prepartum activity, however, was affected by both prostaglandins. In control sows, most prepartum activity came during Hours 16-0 before delivery of first piglet (delivery). After CLO, sows engaged in nest-building more during Hours 32-17 and less during Hours 16-0. In another experiment, sows in farrowing crates were injected with saline, 175 μg CLO, or 10 mg PGF(2α) on Day 112 and blood was collected 0, 15, 30, 60, and 90 min later. Another sample was collected when spontaneous prepartum activity was first observed. For approximately 90 min after PGF(2α) treatment, sows rooted, pawed, and bit and rubbed faces on crate bars; after saline and CLO, this behavior was rarely observed. After prostaglandin treatment, plasma progesterone tended to decline, a 10-fold rise in relaxin came within 15 min, but estrone did not change. Plasma prolactin rose 10-fold within 30 min after PGF(2α) treatment, and rose more gradually after CLO treatment. When sows exhibited spontaneous prepartum activity (approximately 7 h before delivery), endocrine status was characterized by low progesterone, high estrone:progesterone ratio, and high prolactin. Similar profiles of progesterone and relaxin after either PGF(2α) or CLO treatment indicated that changes in luteal hormones were not directly responsible for behavioral differences. Only prolactin was associated with both PGF(2α)-induced and spontaneous prepartum activity.