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The effects of social dominance on the production and behavior of grazing dairy cows offered forage supplements.

We examined whether separating dominant and subordinate cows affected production or behavior, and the relationships between dominance and production measures, by using grazing cows, some of which were offered forage supplements. In experiment 1, 80 cows were allocated to either pasture only or pasture and a silage supplement offered indoors overnight. Dominance was principally related to body weight, but was also positively correlated with lactation number and negatively correlated with grazing time. In experiment 2, 72 spring-calving cows were classified as dominant or subordinate, on the basis of aggressive interactions, and were divided by two factors; i.e., dominant and subordinate cows grazed together or apart, and with or without a hay supplement, which was offered indoors for 75 min/d. Dominant cows produced more milk than subordinates, probably because of their faster pasture biting rate and hay chewing rate. The hay-supplemented dominant cows produced more milk when kept apart from subordinates, and both dominant and subordinate cows gained more weight and lay down for longer when kept apart. However, when no hay was offered, dominant cows produced more milk and had a faster pasture biting rate when grazed together with subordinates. Cows high in the dominance order were more likely to enter the parlor first, but not to begin grazing first. The results suggest that production can increase when dominant and subordinate cows that are offered forage in a competitive situation are separated, whereas there is no benefit in separating them if they are at pasture all day.

Aggression↗

The effect of head nurse behaviors on nurse job satisfaction and performance.

Many nursing executives ponder the repeated problems at the unit level and occasionally surmise that effective supervision at that level holds the key to quality patient care. These pragmatic concerns, while commonplace, have yet to be explored empirically. The relationship of head nurse direction and support on subordinate job satisfaction and performance is not clearly understood. This study examines these relationships in the context of three moderating factors--role clarity, job anxiety, and unit size. Additionally, head nurse support is examined as a moderator of relationships between head nurse direction and subordinate satisfaction and job performance. Using a sample of 103 registered nurses in a medium-capacity metropolitan general hospital, the results show some significant correlations between head nurse behavior and job satisfaction and performance, and in moderating the effects of job anxiety, unit size, and support. The study highlights the need for replication in other settings. Additionally, other variables relevant to job satisfaction and performance such as life stressors (death or illness in the family) require investigation. The findings of this study reveal implications for management at the unit level and the importance of understanding subordinate behaviors in the context of head nurse support and direction.

Anxiety↗

Trends of reproductive hormones in male rats during psychosocial stress: role of glucocorticoid metabolism in behavioral dominance.

Stress in socially subordinate male rats, associated with aggressive attacks by dominant males, was studied in a group-housing context called the visible burrow system (VBS). It has been established that subordinate males have reduced serum testosterone (T) and higher corticosterone (CORT) relative to dominant and singly housed control males. The relationship of the decreased circulating T levels in subordinate males to changes in serum LH concentrations has not been evaluated previously. Since decreases in LH during stress may cause reductions in Leydig cell steroidogenic activity, the present study defined the temporal profiles of serum LH, T, and CORT in dominant and subordinate males on Days 4, 7, and 14 of a 14-day housing period in the VBS. The same parameters were followed in serum samples from single-housed control males. Leydig cells express glucocorticoid receptors and may also be targeted for direct inhibition of steroidogenesis by glucocorticoid. We hypothesize that Leydig cells are protected from inhibition by CORT at basal concentrations through oxidative inactivation of glucocorticoid by 11beta-hydroxysteroid dehydrogenase (11betaHSD). However, Leydig cell steroidogenesis is inhibited when 11betaHSD metabolizing capacity is exceeded. Therefore, 11betaHSD enzyme activity levels were measured in Leydig cells of VBS-housed males at the same time points. Significant increases in LH and T relative to control were observed in the dominant animals on Day 4, which were associated with the overt establishment of behavioral dominance as evidenced by victorious agonistic encounters. Serum LH and T were lower in subordinate males on Day 7, but T alone was lower on Day 14, suggesting that lowered LH secretion in subordinates may gradually be reversed by declines in androgen-negative feedback. Serum CORT levels were higher in subordinate males compared to control at all three time points. In contrast, oxidative 11betaHSD activity in Leydig cells of dominant males was higher relative to control and unchanged in subordinates. These results suggest the following: 1) failure of Leydig cells of subordinate males to compensate for increased glucocorticoid action during stress, by increasing 11betaHSD oxidative activity, potentiates stress-mediated reductions in T secretion; and 2) an inhibition of the reproductive axis in subordinate males at the level of the pituitary.

11-beta-Hydroxysteroid Dehydrogenases↗

Social status in zebrafish modulates the behavioral response to 5-HT2C receptor agonists and antagonists.

The effects of previous social experiences on social behavior have been demonstrated across species both in cooperative and competitive contexts. In dominance-subordinate hierarchies, differences across social ranks have been observed in many different mechanisms. Dominance hierarchies interfere in defensive behavior, where subordinate animals present a greater defensive behavior, regarding potential threats ("anxiety-like behavior"), than dominant animals. The serotonergic system plays a key role in regulating and mediating threat responses, including 5-HT2 receptors in the types of proximal threat responses modulated by the stress of social defeat. We separated 148 adult zebrafish in pairs and allowed them to interact for five days; after that, the dominant-subordinate rank was determined, and animals were treated with a 5-HT2C receptor agonist (MK-212) or antagonist (RS-102221) before being observed in the novel tank test. While MK-212 increased bottom-dwelling, erratic swimming, and freezing across all statuses, RS-102221 decreased these variables in dominants but increased them in subordinates. Moreover, the effects of MK-212 were larger in subordinates than in controls or dominants, suggesting a sensitization of the 5-HT2C receptor.

Animals↗

Growth depression in socially subordinate rainbow trout Oncorhynchus mykiss: more than a fasting effect.

To assess the effects of subordinate social status on digestive function, metabolism, and enzyme activity in salmonid fish, juvenile rainbow trout Oncorhynchus mykiss were paired with size-matched conspecifics (<1.5% difference in fork length) for 5 d. Fish that were fasted for 5 d and fish sampled directly from the holding tank were used as control groups. Both subordinate and fasted fish experienced significant decreases in intestine mass (P = 0.043), and the gall bladder showed marked and significant changes in both size (P = 0.004) and appearance. These findings suggest that the negative effect of social subordination on digestive function reflects in large part a lack of feeding. Hepatic phosphoenolpyruvate carboxykinase activity was significantly higher in subordinate fish relative to dominants, whereas subordinate hepatic pyruvate kinase activity was significantly lower; activities of both enzymes were significantly correlated with plasma cortisol concentrations and behavior scores. Dominant-subordinate differences in the activities of these enzymes were eliminated by administration of the glucocorticoid receptor antagonist RU486, underlining a role for circulating cortisol in eliciting the differences. Significant increases relative to control fish were also detected in red and white muscles from subordinate fish in the activities of protein catabolic enzymes (aspartate aminotransferase, alanine aminotransferase, glutamate dehydrogenase). These differences occurred in the absence of any change in plasma free amino acid or ammonia concentrations, supporting an enhanced turnover of amino acids in muscle in subordinate fish. The results support the hypothesis that changes in metabolism, beyond those elicited by low food consumption, may be responsible at least in part for the low growth rates typical of subordinate fish and that these changes may be related specifically to circulating cortisol levels in subordinate fish.

Amino Acids↗

Menstrual cycle and social behavior in vervet monkeys.

We assessed the relationship between social behavior and the menstrual cycle in 11 adult female vervet monkeys (Cercopithecus aethiops sabaeus) living in an established, stable social group. The findings indicated that fluctuations in ovarian steroids are accompanied by behavioral changes in vervet monkeys. A significant increase in aggressive action, avoidance of social overtures, and retreats from threat occurred during the late luteal phase. However, the social environment can greatly affect behavior independent of the phase of the menstrual cycle. The 10 nondominant (or subordinate) individuals not only exhibited behavioral changes across their own menstrual cycles, but also were responsive to the dominant female's cycle. During the dominant female's late luteal phase, subordinate females significantly increased aggression and decreased social activity. Some of behavioral patterns in female vervet monkeys are therefore relatively independent of direct hormonal modulation and support the contention of the dominant female as the driving force for behavioral changes related to aggression and social interaction. The differential effect of hormones and social status and other environmental factors on behavior has not been critically evaluated in human studies of the premenstrual syndrome. The present study suggests that it is important to assess which behavioral patterns in women are hormonally mediated and which are dependent on the environment.

Aggression↗

Social status as determinant of alcohol effects on aggressive behavior in squirrel monkeys (Saimiri sciureus).

We investigated the behavioral effects of alcohol, especially those on aggression, on members of established groups of squirrel monkeys. A continuous measurement of monkey behavior in groups revealed consistent differences between dominant and subordinate animals. Dominant monkeys aggressed more frequently than subordinate monkeys, and spent less time in stationary postures. Alcohol produced dose-related biphasic changes in the number of threats, grasps, and displacements exhibited by dominant but not subordinate monkeys. Low doses of alcohol (0.1, 0.3, 0.6 g/kg) increased the frequency of aggressive behavior, and high doses (1.0 g/kg) decreased these behaviors. The largest change in behavior was evident in the first 20-40 min after injection, with a return to baseline 60-120 min later. The aggression-enhancing effect of alcohol in dominant monkeys required a stable baseline, which was obtained by daily administration of distilled water. Low levels of aggressive and associative behavior in subordinate monkeys were relatively unaffected at any dose of alcohol. They were associated with and aggressed against more often by untreated members of the group. The status-dependent effects of alcohol may be related to the neuroendocrine and neurotransmitter profiles characteristic of dominant and subordinate monkeys.

Aggression↗

Styles of male social behavior and their endocrine correlates among low-ranking baboons.

We have previously studied the relationship between social subordinance (by approach-avoidance criteria) and physiology among male olive baboons (Papio anubis) living freely in a national park in Africa. In stable hierarchies, subordinate individuals have elevated basal glucocorticoid concentrations and a blunted glucocorticoid response to stress, as well as a prompt suppression of testosterone concentrations during stress. These facets have been interpreted as reflecting the chronic stress of social subordinance. In the present report, we find these endocrine features do not mark all subordinate individuals. Instead, endocrine profiles differed among subordinate males as a function of particular stylistic traits of social behavior. A subset of subordinate males was identified who had significantly high rates of consortships, a behavior usually shown only by high-ranking males. Such behavior predicted the beginning transition to dominance, as these males were significantly more likely than other subordinates to have moved to the dominant half of the hierarchy over the subsequent 3 years. In keeping with this theme of emerging from subordinance, these individuals had also significantly larger glucocorticoid stress-responses, another feature typical of dominant males. However, these subordinate males also had significantly elevated basal glucocorticoid concentrations; it is suggested that this reflects the stressfulness of their overt and precocious strategy of reproductive competition. In support of this, subordinate males with high rates of covert "stolen copulations" did not show elevated basal glucocorticoid concentrations. A second subset of subordinate males were the most likely to initiate fights are to displace aggression onto a third party after losing a fight. these males had significantly or near-significantly elevated testosterone concentrations, compared to the remaining subordinate cohort. Moreover, these males had significantly lower basal glucocorticoid concentrations; this echoes an extensive literature showing that the availability of a displacement behavior (whether aggressive or otherwise) after a stressor decreases glucocorticoid secretion. In support of this interpretation suggesting that it was the initiation of these aggressive acts which attenuated glucocorticoid secretion, there was no association between glucocorticoid concentrations and participation (independent of initiation) in aggressive interactions. Thus, these findings suggest that variables other than rank alone may be associated with distinctive endocrine profiles, and that even in the face of a social stressor (such as subordinance), particular behavioral styles may attenuate the endocrine indices of stress.

Aggression↗

Influence of female's sexual cycle on aggressiveness in male rats.

Two experiments examined the relationship between the female's stage of estrus and agonistic behavior among males. Socially subordinate male albino rats were exposed to an inaccessible female and then given equal numbers of free-choice and forced-choice trials to a more aggressive "target" male or to an empty compartment. The submissive males were more aggressive following exposure to an estrous female than following exposure to a diestrous female. Furthermore, the probability of approaching the more aggressive male increased. This heightened level of aggressiveness was accompanied by a comparable increase in hostile behaviors by the dominant target males of Experiment 1. However, in the second experiment the increase in submissive-male aggressiveness was sufficient to reduce the social distance between the submissive subjects and their moderately aggressive target males.

Aggression↗

A genetic analysis of nicotine effects on open field activity.

The genetics of the effects of nicotine on the open field activity of mice were studied using a 5 by 5 diallel cross. The five inbred strains used were: A, BALB, C57BL, DBA, and C3H. These strains differ both in basal open field activity as well as activity after injection of nicotine. Analysis of the results of baseline activity indicated that both additive and dominance variance affected the activity of the animals. The dominance was non-directional. Likewise, the responses observed after injection of 0.75 mg/kg nicotine displayed both additive and dominance components. However, after correcting the results for differences in basal activity, the dominance item was primarily directional. This directional dominance was towards a more intense response to the effects of the drug, that is, a decrease in open field activity.

Animals↗

Anxiety and ethanol consumption in victorious and defeated mice; effect of kappa-opioid receptor activation.

Alcohol consumption and addiction have been related to anxiety and the anxiolytic effect of ethanol. It has been shown in mice that losers with repeated experience of social defeats are more anxious than winners with repeated experience of victories. Mice with a different social status were tested for their oral ethanol consumption using a free two bottle choice paradigm and for their social approach behaviour after ethanol consumption using the partition test, in which anxiety is an important component. In addition, the sensitivity of the animals for the kappa-opioid receptor agonist U-50,488H (2.5 mg/kg, s.c.) was assessed using the partition test, in which this drug has been shown to induce anxiolytic-like effects. Further, the effect of daily treatment with U-50,488H for 8 days on ethanol consumption was tested in animals that had consumed ethanol and were subjected during these 8 days to a period of 5 days of interruption of ethanol supply and subsequently to a period of 3 days of renewed access to ethanol. Losers consumed more ethanol than winners. Consumption of ethanol was accompanied by a decrease of anxiety level, as evidenced by an increased approach behaviour in the partition test. U-50,488H stimulated ethanol consumption after a period of 5 days of interruption of ethanol supply and drug treatment in the losers, but not in the winners. U-50,488H increased approach behaviour in the losers not consuming ethanol and decreased this behaviour in the winners, especially in those that had consumed ethanol. It is postulated that U-50,488H acts as a partial agonist in this respect. The increased anxiety may be related to the enhanced ethanol consumption in the losers, which may be of relevance for the etiology of alcohol addiction.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

A reevaluation of the electrophysiological correlates of expert object processing.

Subordinate-level object processing is regarded as a hallmark of perceptual expertise. However, the relative contribution of subordinate- and basic-level category experience in the acquisition of perceptual expertise has not been clearly delineated. In this study, participants learned to classify wading birds and owls at either the basic (e.g., wading bird, owl) or the subordinate (e.g., egret, snowy owl) level. After 6 days of training, behavioral results showed that subordinate-level but not basic-level training improved subordinate discrimination of trained exemplars, novel exemplars, and exemplars from novel species. Event-related potentials indicated that both basic- and subordinate-level training enhanced the early N170 component, but only subordinate-level training amplified the later N250 component. These results are consistent with models positing separate basic and subordinate learning mechanisms, and, contrary to perspectives attempting to explain visual expertise solely in terms of subordinate-level processing, suggest that expertise enhances neural responses of both basic and subordinate processing.

Adult↗

Long-term impairment of autonomic circadian rhythms after brief intermittent social stress.

This experiment was designed to examine the short- and long-term behavioral, cardiovascular, and thermoregulatory responses to brief intermittent agonistic confrontation in rats. The experimental procedure involves resident-intruder confrontations consisting of a 10-min period during which both animals are separated in the home cage of the resident, followed by a brief physical encounter leading to defeat of the intruder and a 10-min period, when the intruder was alone in the home cage of the resident. These 30-min-long confrontations were repeated on 5 consecutive days. Before the first confrontation with a resident, an intruder rat's telemetered heart rate and core temperature show a stable circadian rhythm that is entrained by the light cycle. Acutely, the confrontations produce immediate and large tachycardia and hyperthermia in intruders. A decrease in amplitude of the circadian rhythms for heart rate and core temperature, as detected by cosinor analysis, persists for at least 10 days after the last of five daily brief confrontations with the resident. The defensive upright posture is nearly absent during the first exploration of the resident's home cage, but is displayed by the intruder for one-third of the available time before and after the fifth defeat. Intermittent brief social stress is sufficient to induce profound changes in defensive behavior and long-lasting depression of circadian rhythmicity that persist for weeks.

Agonistic Behavior↗

Modulation of aggression in male mice: influence of group size and cage size.

Aggression in group-housed male mice is known to be influenced by both cage size and group size. However, the interdependency of these two parameters has not been studied yet. In this study, the level of aggression in groups of three, five, or eight male BALB/c mice housed in cages with a floor size of either 80 or 125 cm(2)/animal was estimated weekly after cage cleaning for a period of 14 weeks. Furthermore, urine corticosterone levels, food and water intake, body weight, and number of wounds were measured weekly. At the end of the experiment, tyrosine hydroxylase (TH) activity, testosterone levels, and weight of spleen, thymus, testes, and seminal vesicles were determined. Results indicate a moderate increase of intermale aggression in larger cages when compared to the smaller cages. Aggression in groups of eight animals was considerably higher than in groups of three animals. The increase of agonistic behavior was observed both in dominant and subordinate animals. Physiological parameters indicate differences in stress levels between dominant and subordinate animals. It is concluded that aggressive behavior in group-housed male BALB/c mice is best prevented by housing the animals in small groups of three to five animals, while decreasing floor size per animal may be used as a temporary solution to decrease high levels of aggression in an existing social group.

Aggression↗