The development of agonistic behavior was characterized in outbred Swiss CD-1 male Mus domesticus. At weaning (postnatal day [PND] 21), mice were housed either individually or as male pairs. Social encounters were carried out between dyads of initially unfamiliar same-age and same-housing subjects every 3rd day, from PND 23 to 47. The majority of both offensive and defensive elements had their onset around PND 29. Overall, their expression increased around puberty (i.e., on PND 35), which also represented the peak of an inverted U-shaped profile for the frequency of the "ambivalent" tail rattling behavior. A stability of dominance-submission relationships over development appeared, and early short latencies to display either the first crouched posture (subordinate) or the first attack (dominant) turned out to be possible predictors of adult social status. Ongoing individual housing was associated with a greater expression and an earlier onset of fighting behavior.

Interleukin-6 (IL-6) is a cytokine released by activated immune cells which has been shown to affect brain function. In this experiment aggressive and affiliative behaviour exhibited during agonistic encounters by transgenic male mice either not expressing (IL-6 -/-) or overexpressing (NSE-hIL-6) IL-6 in the central nervous system was investigated. All subjects were isolated for 24 days before the aggressive encounter and were 52 days old at the time of testing. Subjects were placed for 5 consecutive days in a neutral cage for 15 min with an opponent of the Balb/c strain that had been previously isolated for the same amount of time. The first and the last test sessions were videotaped to evaluate the first approach and the establishment of the social role, respectively. A number of behavioural categories were later scored. When compared with wild-type controls, IL-6 -/- mice showed a higher degree of aggressive behaviour as indicated by a higher frequency of Offensive Upright Posture, an effect more pronounced on the fifth encounter. On the contrary, NSE-hIL-6 subjects showed a tendency to be more involved in affiliative-type social interactions, displaying a higher frequency and duration of behaviours such as Anogenital, Nose or Body Sniff. IL-6 -/- mice showed a clear tendency to exhibit less affiliative interactions compared with their controls while dopamine levels were found to be modified in a number of brain regions in these mice. Overall, these data suggest that IL-6 affects both aggressive and affiliative-type interactions, although the behaviour of the NSE-hIL-6 subjects was less affected than that of the IL-6 -/- group. The effects of the genetic background of the animal in screening the outcome of gene manipulations on behaviour are also discussed.

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Dogs with acute diarrhea are often presented to clinical practice and, although this generally represents a self-limiting condition, antibiotics are still frequently used as treatment. The aim of this study was to evaluate the effects in dogs with acute non-hemorrhagic diarrhea of the administration of an antibiotic combination in comparison to a nutraceutical product. Thirty dogs were enrolled and randomly assigned to two groups: 15 dogs (group A) received a nutraceutical commercial product while 15 dogs (group B) received an antimicrobial combination of metronidazole and spiramycin. For each dog, the Canine Acute Diarrhea Severity Index, the fecal microbiota and the Dysbiosis Index were assessed. Both stool consistency and frequency decreased on day 2 in the dogs of group A compared to baseline, while in group B, these parameters significantly decreased at days 3 and 4. The global concern for rising antibiotic resistance associated with indiscriminate use of antimicrobials, in both humans and animals, suggests the necessity of avoiding empirical and injudicious use of these molecules in diarrheic dogs. These results suggest that the nutraceutical treatment had a similar clinical effect compared to the antibiotic formulation, representing a valid antibiotic-sparing therapeutic approach in canine acute diarrhea.

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