C Terlouw | PubMed Health

PubMed1998

Presence of cues from stressed conspecifics increases reactivity to aversive events in cattle: evidence for the existence of alarm substances in urine.

In gregarious species like cattle, the presence of partners often affects fear-related reactions. The first experiment investigated whether behavioral and physiological responses to stress depend on the emotional state of the partner. Aubrac heifers were presented with food in a novel environment. Compared to heifers in the presence of a companion that had been previously habituated to the environment without receiving shocks, those in the presence of a companion animal that had previously received electric shocks in that environment had a stronger increase of cortisol response (11.2+/-1.1 vs. 7.4+/-0.9 ng/mL), showed a significantly longer latency to feed (60.1+/-12.3 vs. 17.8+/-5.9 s), and fed more slowly (54.5+/-11.4 vs. 110+/-7.3 s). After repeated exposure to the test conditions, when heifers of both treatments fed rapidly after entrance, response to an unexpected air blast from the feeding bucket was measured. Heifers in the presence of a stressed companion showed an increased latency to feed again compared to those with a nonstressed companion (44.5+/-5.1 vs. 22.8+/-4.3 s). Stressed companions urinated during tests; therefore the second experiment investigated whether heifers respond differently to urine collected from stressed and nonstressed conspecifics. In a first test, heifers were presented with food on a grid in a bucket in a novel environment. They had a longer latency to feed when the bucket contained urine from stressed rather than from nonstressed conspecifics underneath the grid (128.1+/-9.6 vs. 108.2+/-4.9 s). In a second test, heifers were presented with a novel object in a familiar environment. Heifers showed a longer latency to explore the object when it had been sprayed with urine from stressed compared to urine from nonstressed conspecifics (215.2+/-45.0 vs. 25.8+/-8.6 s). The results show that heifers perceive the state of increased stress of conspecifics and become more fearful as a result. They further show that this perception is at least partly mediated by olfactory cues in the urine.

Animals↗

PubMed1988

The propensity for schedule-induced polydipsia is related to differences in conditioned avoidance behaviour and in defense reactions in a defeat test.

In line with previous research showing that animals predisposed to develop schedule-induced polydipsia when submitted to intermittent distribution of food show differential behavioural and neurochemical characteristics, the present experiments investigated the nature of defense reactions to aversive situations in rats that do or do not develop schedule-induced polydipsia. It was found that rats that engage in excessive drinking during intermittent feeding display more rapid active avoidance learning in a 2-way shuttle-box and show less freezing when confronted with an aggressive resident male in a defeat test than those that do not develop schedule-induced polydipsia. These results are consistent with the hypothesis that individual differences in the propensity to exhibit oral consummatory activities in conditions of mild stress are related to the ability to shift behavioural programmes in response to external stimulation.

Aggression↗

PubMed1988

Schedule-induced polydipsia experience decreases plasma corticosterone levels but increases plasma prolactin levels.

To determine the neuroendocrine pattern of response to excessive drinking induced by exposure of rats to an intermittent distribution of food (schedule-induced polydipsia, SIP), the present experiment investigated changes in plasma corticosterone, prolactin and catecholamines in chronically catheterized rats that had developed or not this form of adjunctive behaviour. It was found that rats that engage in excessive drinking displayed decreased plasma levels of corticosterone and increased levels of prolactin during the course of a SIP session. There was, however, no differences between groups in plasma catecholamine levels. The difference observed between SIP-pos and SIP-neg rats were entirely condition-specific, since they disappeared in the absence of access to water.

Animals↗