Normal behavior and the clinical implications of abnormal behavior in guinea pigs.

Cavies are becoming more popular as pets because they are relatively easy to care for and provide never-ending love and entertainment with their curious but gentle nature. As with other species, the best way to learn about guinea pig behavior is to own guinea pigs. Understanding normal behavior provides the practitioner with the ability to more easily recognize pathology and abnormal behavior. This allows the veterinarian to provide necessary supportive care and pain management more quickly while performing diagnostics and determining the need for therapeutics. Understanding the behavior of cavies allows the clinician to better educate guinea pig-owning clients and to better and more quickly serve the needs of their guinea pig patients.     

Normal and abnormal xylose absorption in the horse.

The D-xylose absorption test was applied to clinically normal horses and to horses with signs of gastrointestinal disease. A dosage of 0.5 grams of xylose per kilogram of bodyweight was useful in detecting horses that absorbed the pentose abnormally. The clinical findings were correlated with gross and microscopic findings by biopsy and at necropsy. Gastrointestinal lesions associated with abnormal xylose absorption were classified as: 1) villous atrophy; 2) edema of the lamina propria or 3) necrosis of the lamina propria.     

Male sexual behavior

This article considers causes of variability in male sexual performance and identifies management techniques that can be used to improve the reproductive success and efficacy of our captive animal populations.     

Reflections on mare behavior: Social and sexual perspectives

Among horse owners “mare-ishness” is easily recognized, if poorly defined, as generally awkward or recalcitrant behavior. In common with other mammals, however, horses do show a range of female-specific behavior patterns concerned particularly with sexual and maternal functions but also encompassing aspects of social peer interaction. Many of these behavior patterns are observed more easily in free living feral populations and are repressed at least partially under standard domestic management regimes. Feral horses form small stable breeding groups within which mares create linear dominance hierarchies based on the outcomes of aggressive encounters and positive social bonding. Rank within the social hierarchy may also influence reproductive success, with dominant mares having shorter foaling intervals and earlier foaling than lower ranking subordinate mares. Advantageous early foaling may reflect preferential mating by the group stallion based either simply on enhanced physical condition leading to earlier reproductive cycling in dominant mares or on an increased attractiveness to dominant mares by the stallion contingent on some aspect of dominance characteristics. The endocrine axis responsible for regulation of sexual behavior in the mare shows a degree of commonality with systems underlying social dominance. Both these behavior patterns are driven by a complex interaction of endocrine and neuro-endocrine factors sensitive to physical and social environmental cues and in feral free-living horses these are interlinked to an extent that may be under appreciated in domestic breeding populations.     

Normal sexual maturation and reproductive function in domestic hens following unilateral adrenalectomy

The ovulation-inducing properties of adrenal hormones and the anatomical juxtaposition of the left adrenal gland and the ovary suggest that a functional relationship exists between these two endocrine organs. To test this hypothesis, the effect of unilateral adrenalectomy on sexual maturation and reproductive function was examined in left and right adrenalectomized SCWL pullets. Between 9 and 13 weeks of age, 24 and 12 pullets were either left or right adrenalectomized, respectively; 12 birds were sham operated and 7 birds served as unoperated controls. Blood samples were obtained immediately before and after surgery, 48h after surgery and at 14, 19 and 23 weeks of age. All samples were analyzed for plasma corticosterone by radioimmunoassay. At 20 weeks of age all birds were weighed and the photoschedule was changed from 8L:16D to 16L:8D. During the first 52 days following photostimulation the age at first egg and the distribution of ovipositions within the 24h photoschedule were recorded.Mean plasma corticosterone levels of the unilaterally adrenalectomized hens were not significantly different (P > .05) from those of control birds 48h after surgery or at 14, 19 and 23 weeks of age. Unilateral adrenalectomy had no effect on body weight at 20 weeks, average age at first egg, or percent hen-day production. In addition, 95% of the eggs laid in the first 52 days after photostimulation were restricted to a 10 hour period of the day regardless of the surgical treatment. These observations indicate that the removal of either the left or the right adrenal gland does not affect plasma levels of corticosterone, sexual maturation, or the open period for LH release as evidenced by the times of oviposition and fail to support the hypothesis of a localized functional relationship between the left adrenal gland and the ovary.     

Normal and abnormal ultrasonographic findings that mimic small intestinal intussusception in the dog

On ultrasonographic examination of the abdomen, the appearance of healthy intestine, enteritis secondary to an intestinal foreign body, and postpartum involution of the uterus may be visualized in some imaging planes as a target-like structure that is subsequently misinterpreted as intestinal intussusception. To avoid misdiagnosis, the ultrasonographer should ensure multi-plane scanning of the lesion, paying particular attention to the completeness of the lesion's peripheral ring structure and the overall width of the concentric rings of the target-like lesion. The presence of a semilunar or G-shaped hyperechoic center and the visualization of the inner intussusceptum (extending into the intussusception lumen) can be useful ultrasonographic findings that distinguish an intussusception from other lesions or from healthy tissues. These principles are illustrated through the following case presentations.     

Differentiation of sexual behavior in cattle, sheep and swine

Gonadal steroid hormones influence an animal's sexual behavior through two primary means. During development they affect differentiation of the brain (primarily in males), and after puberty, circulating concentrations of steroids influence expression of sexual behaviors. In mammals, sexual behaviors of females are regarded as inherent (independent of steroids secreted by the developing ovary). Males, on the other hand, must undergo active differentiation that is brought about by actions of testicular steroids on the brain during discrete sensitive periods of early development. Sexual differentiation in mammals is referred to as processes of defeminization and masculinization. Defeminization is loss of behavioral traits inherent to females and occurs prenatally in sheep but postnatally in swine. Comparative data are lacking for cattle, but preliminary evidence indicates prenatal defeminization of sexual behaviors. Masculinization is acquisition of behavioral traits characteristic of males. Adult females of all three species show mounting behavior after prolonged treatment with testosterone, and in cattle and swine, there is, as yet, no strong evidence that males undergo masculinization of sexual behaviors. In sheep, limited observations are suggestive of two sensitive periods for masculinization; one prenatally and one postnatally. The earlier concept that differentiation of sexual behaviors in mammals occurs prenatally in species with a long gestation and postnatally in species with a short gestation must now be modified in view of recent findings in swine, in which defeminization occurs postnatally. Further studies will likely identify additional species differences with respect to differentiation of sexual behaviors.     

Effect of cortisol on luteinizing hormone release during sexual behavior in the boar.

The effect of inhibiting the rise in cortisol concentrations that occurs at copulation upon luteinizing hormone release was studied in seven adult boars. Plasma samples were collected for assay of luteinizing hormone, testosterone and cortisol on a control day and before, during and after exposure to an estrous sow. The area under the curve was used to evaluate hormone production and treatment effects were evaluated by a paired Student's t-test. The 11 beta-hydroxylase inhibitor, metyrapone, was used to suppress glucocorticoid hormone production. Cortisol concentrations increased significantly (p less than 0.05) after breeding compared to values on the control day while treatment with metyrapone prior to breeding prevented the cortisol increase (p greater than 0.05). Although luteinizing hormone production increased significantly after copulation in both breeding experiments, metyrapone pretreatment resulted in a reduction of luteinizing hormone secretion (p less than 0.05). Testosterone production was also reduced in boars pretreated with metyrapone. The results suggest that the increased levels of cortisol occurring at copulation may enhance luteinizing hormone release in boars.     

Investigating equine ingestive, maternal, and sexual behavior in the field and in the laboratory.

Some of the techniques that may be used to study social, reproductive, and ingestive behavior in horses are described in this paper. One of the aspects of equine social behavior is the dominance hierarchy or patterns of agonistic behavior. Paired or group feeding from a single food source may be used to determine dominance hierarchies quickly. Focal animal studies of undisturbed groups of horses may also be used; this method takes longer, but may reveal affiliative as well as agonistic relationships among the horses. Reproductive behavior includes flehmen, the functional significance of which can be determined using combinations of field observations of harem groups and laboratory studies of stallions exposed to female urine or feces in the absence of the donor mare. Ingestive behavior may include food, salt, or water intake. Direct and indirect measurements of intake can be made and used to answer questions regarding the ability of horses to control their energy intake when the diet is diluted, the effect of feral equids on the ecology of an area, and the abilities of horses to compensate for dehydration and hypovolemia.