Pierre Orgeur

Changes in gonadotrophins and prolactin levels in isolated (seasonally or lactationally) anovular ewes associated with ovulation caused by the introduction of rams

Abstract The response of seasonally or lactationally anovular ewes to ram stimulation (teasing) was investigated in Ile-de-France (IF) and Prealpes (PA) ewes. In the first experiment (seasonally anovular IF and PA ewes) the possible role of prolactin (PRL) in the response to teasing was investigated by selective blockage of the secretion of PRL by CB 154 for 7 days before teasing. In the second experiment (lactationally anovular PA ewes) the role of PRL in the teasing response was investigated by studying ewes suckling one or two lambs, which presented differences in LH and PRL concentrations ( p p p p =0.05). Stimulation by the rams resulted in a rapid increase (

Ontogeny of social awareness in domestic herbivores

Abstract It is now well established that domestic animals construct responses to their environment that depend on experience and on integration of several features of the environment, including social partners. This ability to be aware of the environment is not fully developed at birth but improves and varies through the animals life. This topic is discussed on the basis of social processes in sheep and cattle. Social relationships of an animal with its conspecifics develop with age; they do not merely depend on pre-programmed behaviours but rely at least in part on learning of characteristics of the partners. Soon after birth, a strong preferential bond establishes with the dam then to a lesser extent, the young associates to other members of the flock, especially other young. The attractiveness of the group varies later in life due to external events or to physiological state: the abrupt separation from the dam at artificial weaning strengthens bonds between peers, whereas around parturition, females are less disturbed by isolation from the group. More recently, the awareness of social partners has been described in non-social contexts: the animal modifies its responses to events according to the presence of partners, and also to their emotional state and behaviour. The effects of partners seem to depend on their relationship with the animal and also on the social motivation of that animal, which both vary during its life. We recommend study of the ontogeny of awareness using the model of social influences.

Olfaction mediates the establishment of selective bonding in goats

Nine pregnant goats of the Creole breed were rendered anosmic 3 weeks before parturition by irrigating their olfactory mucosa with zinc sulfate, and nine additional pregnant goats were left intact. At parturition, interactions between all females and their young were observed for 1 h. No differences were found in mother-young relationships between intact and anosmic mothers during this time, except that kids from anosmic females were slower to suck than controls. After 4 h of uninterrupted mother-young, mothers underwent three successive 5-min tests in a predetermined order to study selective bonding: with their own kid, an alien kid of similar coat color and pattern, and an alien kid of dissimilar coat color and pattern. Intact goats readily discriminated between kids, and rejected the two aliens while accepting their own. By contrast, anosmic mothers showed no signs of discrimination and accepted the three types of kids. It is concluded that during the first postpartum hours of contact, mother goats memorize individual olfactory characteristics of their kid that serve as a basis for selective suckling and exclusive bonding. Furthermore, at this early stage, visual characteristics of the young do not appear able to compensate for the loss of olfactory cues.

Neuroendocrine consequences of very early weaning in swine

An experiment was conducted to investigate the consequences of very early weaning of piglets on neuroendocrine variables and growth. Sixty piglets from eight litters were either weaned on Postnatal Day 6 (early weaning, or EW piglets) or left with their dam until normal weaning at Day 28 (control piglets, or C). At Days 5, 7, 11, 14, and 19, urine was collected between 7:00 and 8:00 a.m. for the measurement of catecholamines, glucocorticoids, and creatinine. Compared with C, EW piglets displayed a transient increase in urinary cortisol on the day following separation from their dam (Day 7) (P<.05). Urinary norepinephrine (NE) was three times lower in EW compared to C piglets from Day 7 until Day 14 (P<.01) but there was no difference between the two groups on Day 19. Urinary epinephrine (EPI) did not differ between C and EW piglets on the day after weaning. Thereafter, EW piglets displayed a three times drop in urinary EPI as compared to C piglets until the end of the period (P<.01). Weaning induced an immediate reduction in food intake and growth rate and at Day 28, the body weight of EW piglets was 1.60 kg lower than that of C piglets (P<.0001). In conclusion, weaning of 6-day-old piglets results in a marked and prolonged suppression of the release of catecholamines. This result likely reflects physiological responses to insufficient energy intake after weaning, as reflected also by changes in thermoregulatory behavior. The transient increase in cortisol excretion in weanlings may be caused by both emotional distress and acute food deprivation.

Sexual differentiation of reproductive behavior in pigs: Defeminizing effects of prepubertal estradiol

The present study sought to determine (1) whether estrogen by itself can defeminize the behavior of pigs during the late juvenile-early pubertal period, and (2) whether the progressive late defeminization reported for pigs is a true organizational effect, as opposed to an artifact of the time between castration and testing. Male pigs were castrated at 19-22 days or left intact and females were ovariectomized at 3 months. Additional males castrated at 19-22 days and females ovariectomized at 3 months were implanted with estradiol benzoate (EB) from 3 to 5.5 months. After castration of the previously intact males at the age of 5.5 months, all subjects were tested beginning at 6.5 months for proceptivity (choice of a male versus a female in a T-maze) and receptivity (immobilization to a mounting male) following an injection of EB. EB administered during development significantly defeminized proceptivity and receptivity in both sexes. The decrease in proceptivity was more pronounced in males than in females and was more pronounced than the decrease in receptivity, as if differentiation ends earlier for proceptivity than for receptivity; the decrease in receptivity was more pronounced in females. To see whether the capacity to display female-typical behavior is a function of time since castration, we castrated additional males at 4 months and tested for receptivity 9 days later following an injection of EB, then tested again with the other subjects at 6.5 months. The proceptivity and receptivity scores for males castrated at 4 months fell between those for intact males and males castrated at 3 weeks, and thus these animals were not completely defeminized. They were more receptive at 6.5 months than at 4 months, but the difference was not significant. These results indicate that in pigs estradiol defeminizes both receptive and proceptive behavior and that this defeminization can occur relatively late in development.

Influence of housing and social changes on growth, behaviour and cortisol in piglets at weaning

The present experiment aimed at evaluating the relative effects of environmental and social changes on behaviour, growth and salivary cortisol of piglets at weaning. On Day 0, 26-day old piglets were weaned and allocated to one of four treatments: neither environmental nor social change (C), environmental change (E), social change (S), and both changes (SE). Overall, 6 replicates of 10-12 animals/pen/treatment were analysed. Piglets were video recorded during the first three days after weaning to observe social behaviour and general activity. Saliva was collected between 07:00 and 09:00 on Day 0 just before weaning (D0H7), on Day 1 (D1H7) and Day 2 (D2H7 and D2H16) to measure cortisol. Saliva cortisol did not change after weaning in C piglets but increased significantly at D1H7 in S and SE piglets, at D2H7 and D2H16 in E and SE piglets. Compared to C piglets, numerous behaviours were altered in SE piglets: more total lying (P<0.08), less lying on the belly, less environmental exploration, less playing, more fighting regardless the day, more lying awake inactive on Day 0 (P<0.05). Compared to C piglets, E piglets displayed more total lying but less environmental exploration whereas S piglets showed less lying on the belly but more fighting (P<0.05). Present results show that moving piglets to a new environment as well as mixing them with unfamiliar conspecifics at weaning have stressful effects which are additive.

Influence of the blood concentration of prolactin on the length of the sensitive period for establishing maternal behavior in sheep at parturition.

Abstract The fading of postpartum maternal interest for the neonate (sensitive period) in ewes separated from their young at lambing is delayed when parturition is induced with 20 mg of estradiol benzoate (EB). An experiment was carried out to investigate the role of prolactin in this phenomenon. The sensitive period was studied in three groups of parturient ewes. In all groups lambs were removed at birth and reintroduced to their mothers 24 hr later. Maternal acceptance was tested at this time. In group 1 (dexamethasone D), ewes were induced to lamb with dexamethasone (15 mg im). In group 2 (EB), ewes were treated with 20 mg of estradiol benzoate (im). In group 3 (EB + CB 154) ewes received 20 mg of EB as in group 2 and 1 mg of CB 154 (sc) every 12 hr to prevent the enhanced secretion of prolactin which normally occurs after EB injection. The concentration of prolactin was highest in group 2 (EB), lowest in group 3 (EB + CB), and intermediate in group 1 (D) (p ⩽ 0.001 between groups). By contrast, the proportion of ewes showing maternal behavior was similar in groups 2 and 3 ( 15 23 and 17 22 ), both of which differed from group 1 ( 3 22 ; p ⩽ 0.005 ). It is concluded that the lengthening of the sensitive period for establishing maternal behavior in sheep following EB induced parturition is not related with high levels of prolactin in the peripheral circulation.