Marie-France Bouissou

Effects of early handling on heifers' subsequent reactivity to humans and to unfamiliar situations

Abstract The influence of early handling on the behavioural and physiological responses of Friesian heifers to unfamiliar situations and human manipulation was studied. Forty abimals were used. The animals were reared in 4 groups of 10, under standard artificial husbandry conditions. Animals of one group (control animals) were handled only in respect of the demands of normal husbandry. Experimental animals were subjected to additional handling, which consisted of brushing twice a day and leading with a halter. All handled animals received the same amount of handling (30 days) but at different periods in life: 3 days/week from 0 to 3 months of age (Group 0–3); 3 days/week from 6 to 9 months of age (Group 6–9); or 3 days/month from 0 to 9 months of age (Group –9). When the animals were 15 months old, each heifer, from each treatment group, was tested individually and once only in a set of behavioural tests designed to investigate fearfulness (in the presence or absence of human contact) and the ease with which the animal could be handled. Animals from Group 0–9, and to a lesser extent those from Group 6–9, were less reactive than controls in tests involving the presence of a human. However, in most cases Group 0–3 animals did not differ significantly from controls. Thus, it would appear that only prolonged handling during early life substantially influences man-animal relationships. In the fear-eliciting tests, which did not involve human contact, only the responses of Group 0–9 animals differed significantly from those of the controls. It is suggested that temporary prolonged handling influences the expression of fear responses in heifers.

Effects of androgen treatment on behavioral and physiological responses of heifers to fear-eliciting situations.

Sex steroids are known to influence dominance relationships in cattle. This effect seems due to a reduction of fear in response to conspecifics. In order to determine if gonadal steroid can also modulate fear reactions in nonsocial situations, testosterone-treated heifers were exposed to various events reported to elicit fear in cattle. The experimental subjects received daily im injections of testosterone propionate (0.60 mg/kg body wt) for 100 days while controls received the same volume of the vehicle. In a first experiment, the influence of testosterone treatment on behavioral reactions of animals was studied. Treated heifers were much less fearful than controls: they were less reactive to an unfamiliar environment or to a novel object, and they were also less disturbed by a surprising event. In a second experiment, the effects of androgen treatment on cardiac and adrenal responses were evaluated in another group of subjects placed in the same situations. Whereas heart rates after the fear-eliciting events never differed between groups, the increase in cortisol levels was always lower in treated heifers than that in controls in response to human approach, to a surprising event, and to fear conditioning. Furthermore, after stimulation of the adrenal cortex by ACTH administration, the increase in cortisol levels was twice as great in controls than in treated heifers. Thus, prolonged androgen treatment reduces fearfulness in cattle, at least in some situations. Possible mechanisms by which testosterone influences fear-related behaviors are proposed.

Assessment of fear reactions in domestic sheep, and influence of breed and rearing conditions

Abstract The aim of this study was: (1) to design a series of tests to measure fear reactions of domestic sheep placed in different fear-inducing situations; (2) to interpret the observed behaviour in terms of the presence or absence of fear; (3) to test the hypothesis that fear is a unitary phenomenon; (4) to investigate the effects of breed and rearing conditions before weaning as possible factors causing variation in fear reactions. Four tests, based on the presence of stimuli classically reported to induce fear, were designed to measure fear reactions. They involved: (1) a surprise effect; (2) the presence of a human; (3) the presence of a novel object; (4) an unfamiliar environment (open-field test). In each of these tests food was present, so a conflict between food-motivation and fear arose. Eighty-eight sheep were individually submitted to the first three tests on subsequent afternoons having been exposed to the control situation (same surroundings without the fear-inducing stimulus) each morning. The open-field test was conducted on the fifth day. The behaviour of sheep was observed when in control or frightening situations. The results indicate that high values for the following parameters reflect the expression of fear: latency to enter the testroom, latency to feeding, time spent away from the stimulus, immobilization, high-pitch bleats, defecation, locomotory activity (number of squares entered), attempts to escape, trotting, glances at the stimulus and latency to sniff the stimulus. On the other hand high values for feeding time, latency to bleat for the first time, sniffings of the trough and sniffings of the stimulus are expressions of a low level or an absence of fear. The correlations between measurements of fear from different fear-inducing situations suggest that fear is a unitary phenomenon. Fear reactions were influenced by; (a) breed—Romanov sheep were more fearful than Ile-de-France sheep; (b) rearing conditions before weaning—for Romanov but not Ile-de-France sheep, dam-reared animals were more fearful than artificially reared ones.

Sex differences in fear reactions in sheep

Abstract In order to assess potential sex differences in fear reactions, 40 rams and 40 ewes were studied using a battery of tests previously designed and validated. Animals were individually confronted with situations classically reported to induce fear in sheep: i.e. isolation from conspecifics, surprise effect and presence of a human. Eight groups were studied, each comprising ten animals of the same sex, breed (Romanov or Ile de-France) and rearing condition (artificially or dam-reared). Males and females of the same breed and rearing condition were tested alternately during the same week (4 days of habituation plus 3 days of tests) in order to prevent fear reactions from being biased by differences in the environment (such as noises, ambient light, etc.) which could influence fear reactions. Twenty-six behavioural items related to fear were recorded. Furthermore, an overall score, based upon those items and reflecting the fear level of each subject in each of the test situations, was calculated. All the significant differences between sexes ( P P P P = 0.06) in the human test (higher scores reflect heighthened fearfulness). When subjected to non-social fear-eliciting situations, rams were seen to be less fearful than ewes. This conclusion could serve as an impetus for more general behavioural studies of factors influencing fearfulness and thus adaptability of farm animals to intensive housing conditions.

Androgens, Aggressive Behaviour and Social Relationships in Higher Mammals

This paper reviews the relationships between androgen levels, aggressive behaviour and social relationships in ungulates and primates. In these and most other mammalian species, aggressive behaviour is sexually dimorphic with males being generally more aggressive than females. This difference is evident very early in play behaviour. In males, and sometimes also in females, aggressive behaviour varies in relation with reproductive cycles and the hormonal changes which are involved in these cycles. The experimental manipulation of hormonal levels by castration or administration of exogenous hormones gives results that vary according to the species, sex, type of hormone (e.g. aromatizable or non-aromatizable androgens), and other factors (e.g. antlers state in stags). Nevertheless, it has generally been shown that aggressive behaviour in male ungulates depends largely on androgens and that in female ungulates androgen treatment consistently raises social rank, with or without modification in aggressiveness. Primates, on the other hand, seem to be less dependent on androgens for the expression of aggressive behaviour and social status.

Effect of injections of testosterone propionate on dominance relationships in a group of cows.

Abstract In a group of eight heifers, four animals whose social ranks were 2, 4, 6, and 8 were injected with testosterone propionate for 70 days. They all became dominant over controls and did not modify their own relationships among themselves. This experiment was replicated 3 months after the end of the first treatment with the same group; animals whose ranks were 2, 4, 6, and 8 at the beginning of the second experiment were treated. Again they all became dominant over controls and did not modify their relationships among themselves. Eighty percent of relationships modified by the first or the second treatment remain unchanged without any hormonal support for 4 to 10 months. A first analysis of social interactions does not seem to indicate a higher increase in the frequency of aggressive interactions in treated animals.

Effect of androgen treatment on fear reactions in ewes.

The effects of prolonged androgen treatment (testosterone propionate, 10 mg/day for 56 days) on fear reactions in ewes were studied using a battery of tests previously designed and validated. These tests involved situations classically reported to induce fear in sheep: isolation from conspecifics, surprise, and presence of a human. Testosterone-treated ewes differed from controls in a number of behavioral characteristics which indicate that they are less fearful in the various test situations. Their overall scores were respectively 9.5 vs 11.5 (P < 0.05) in the isolation test, 7.9 vs 13.1 (P < 0.001) in the surprise test, and 7.8 vs 13.2 (P < 0.001) in the human test. Testosterone treatment thus clearly reduces fear reactions in ewes subjected to nonsocial situations that are typically fear-eliciting.

Effect of early androgen treatment on subsequent social behavior in heifers

Abstract Two groups of four heifers received daily injections of 0.30 mg/kg of testosterone propionate in oil for 100 days, between 3 and 6 months of age. Two other groups of four heifers of the same age received only oil and served as controls. Three to five months after the end of treatment, a series of experiments was designed to compare dominance ability, aggressiveness, and reactions associated with fear, between treated and control animals. Dominance ability, when faced with animals of the same age and social experience, is higher for treated animals than controls, 85% of them being dominant. Treated animals established dominance relationships between themselves more slowly than did control animals or mixed pairs. In all experiments treated animals fought more often than controls. Those which became subordinate fought more than those which became dominant. When subordinate, treated animals withdrew less often than control animals and frequently did not react to aggression. When dominant, treated animals were never more, and sometimes less, aggressive than controls. It is proposed that changes in social structure of organized groups and the capacity to become dominant at first encounter are due to a reduction of fear of other animals induced by androgens. The acquisition of social rank in cattle may be principally due to differences in fear or “emotionality” rather than in aggressiveness.

Long-term effects of androgen treatment on fear reactions in ewes.

We have previously demonstrated that testosterone treatment reduces fear reactions of ewes subjected to daily injections of testosterone propionate (10 mg/day) for 56 days. The long-term effects of this treatment were studied in the same ewes and using the same battery of fear-eliciting tests (isolation from conspecifics, surprise, and presence of a human) 4 and 8 months after the injections were terminated. Twenty-six behavioral items related to fear were recorded. A number of differences in the behavior of treated vs control animals indicate that the former are still less fearful, especially in the surprise and human tests. Overall fearfulness scores of treated and control ewes (the higher the score, the more fearful the animals) were 7.3 +/- 1.7 vs 9.7 +/- 1.9, (P < 0.05) for the surprise test, and 7.0 +/- 1.4 vs 10.0 +/- 2.0 (P < 0.01) for the human test at 4 months, and 6.8 +/- 1.4 vs 8.2 +/- 1.1 (P < 0.05) for the human test at 8 months. Thus, not only does testosterone treatment reduce fear reactions in ewes but it also has a long lasting effect on such reactions.

Fear reactions of domestic sheep confronted with either a human or a human-like model

Fear reactions of ewes towards a human, a human-like model or a control (plastic cylinder 1.95 m high) were studied using a test previously designed and validated, in which 16 behavioural parameters have been interpreted as indicators of fear (e.g. a relatively long time spent away from the stimulus) or absence of fear (e.g. a relatively long time spent eating near the stimulus). In a first experiment, 18 animals were individually confronted with each of the 3 stimuli for 4 min (in a counter-balanced order). The results indicated that both the human and the human-like model elicited greater fear reactions than did the control, and that the former two stimuli did not differ in their fear-eliciting properties. In a second experiment designed to determine if the animals become aware of a difference between the human and the model over time, 32 animals were confronted successively with each of the two stimuli for 8 min. Although there was some habituation towards both stimuli, there was no difference between them even at the end of the test period. These results suggest that a model could be appropriate in experiments involving human presence (at least for a short duration) and would allow for better standardization. It can also be hypothetized that exposing animals to a model would lead to familiarization which might in turn help reduce fear of human beings and thus improve ease of handling and welfare.