The Effect of Social Interaction on Physiologic Response in Cats Fed Two Levels of Dietary Sodium as Compared To Potassium
The purpose of this study was to examine the interaction between a change of social interactions and different concentrations of dietary sodium (n=2) compared to potassium (n=1) on physiologic response in cats. Thirty, healthy adult DSH cats (15 M, 15 F), were randomly assigned to one of three groups for a three phase feeding trial. Average age for each group was 4.7, 4.9 and 4.7 years of age respectively. During the two weeks of Phase I, all cats were housed individually and received a dry food containing 1.1% sodium (Higher Sodium=HS) dry matter basis (DMB) as an initial adaptation period. During Phase II all cats remained individually housed but were randomly assigned into 3 dietary groups. Ten cats remained on HS, ten cats were fed a food with 0.35% sodium (Lower Sodium=LS) DMB and ten cats were fed a food with 2.0% potassium (P) DMB. In Phase III, cats remained on the same foods as in Phase II but were housed in a group by dietary group instead of housed as individuals. Individual housing units allowed for cats to view other cats through windows but not interact, however some time each day was allotted for daily physical interactions with people. During group housing, cats were grouped together, by diet, in separate large rooms, and allowed to jump to resting boards or cubbies, daily physical interaction with people as before, as well as unlimited interaction with cohorts. Urine and blood samples were collected on the last day of Phase I and II and on days 1, 5 and 12 of Phase III. Urine was analyzed for cortisol:creatinine ratio (UCC), and specific gravity. Blood samples were analyzed for aldosterone, cortisol, and osmolality. Data were analyzed using SAS, PROC MIXED methods. UCC showed no difference among groups in response to food fed. However, UCC and serum cortisol were significantly increased in Phase III for all groups on days 1 and 5 compared to Phase II. Urine specific gravity was significantly higher on day 1 of Phase III compared to Phase II. In contrast, serum osmolality displayed a significant group by period interaction between Phase II and Phase III. This was probably attributable to the HS and P dietary groups having a decrease in serum osmolality at day 5 of Phase III. Curiously, there was no significant increase in serum osmolality during day 1 of Phase III to reflect the increased urine specific gravity response. Finally, aldosterone displayed a highly significant group by period interaction. During the individual housing period the response was as anticipated with cats transitioning from HS to LS foods having an increased aldosterone secretion. However, during Phase III, the HS food group had a significant increase in aldosterone secretion in spite of no change in serum osmolality on day 1 and a lower serum osmolality on day 5. The LS and P did not display increased aldosterone during Phase III. Aldosterone response to social adaptation appeared to be dependent on sodium content of the food with higher sodium foods having a paradoxical increase in the face of normal to decreased serum osmolality.