Effects of dietary lysine supplementation in cats with enzootic upper respiratory disease

Abstract

To determine the effectiveness of dietary lysine supplementation in cats with enzootic upper respiratory disease (URD), 50 cats were fed a ration containing 11 or 51 g lysine/kg diet for 52 days. Food intake, body weight, clinical signs, plasma amino acid concentrations and presence of Chlamydophila felis or feline herpesvirus (FHV)-1 DNA within the conjunctival fornix were assessed. Food and lysine intake of both dietary groups decreased between days 17 and 22, coinciding with peak disease and viral presence. Mean disease score for cats fed the supplemented ration (0.94) was higher than for those fed the basal diet (0.21); however, this could be attributed to a small subset of male cats which demonstrated fighting behavior that may have contributed to stress within that cage. FHV-1 DNA was detected on 12 occasions in six cats receiving the supplemented diet and on one occasion in one cat fed the basal diet. C felis DNA was never detected. Mean plasma arginine concentration was lower and plasma lysine concentration was higher in supplemented cats. Mean plasma arginine concentration declined throughout the study in both dietary groups. Data from the present study raise important questions but do not permit a definitive conclusion regarding the efficacy of dietary lysine supplementation in cats with enzootic URD.

Fig 1

Cats were assigned to one of four cages and one of two dietary groups according to gender and lysine content of diet fed.

Fig 2

Daily food intake for all cats. Line represents median group food intake per cage; boxes represent 5th and 95th percentiles.

Fig 3

Daily lysine intake for cats fed a basal ration (▪) containing 11 g lysine/kg diet or a supplemented ration (□) containing 51 g lysine/kg diet. Data represent total daily lysine intake for each dietary group.

Fig 4

Total group disease scores for female (groups 1 and 2; circles) or male (groups 3 and 4; triangles) cats fed a basal ration containing 11 g lysine/kg diet (groups 1 and 3; filled symbols) or a supplemented ration containing 51 g lysine/kg diet (groups 2 and 4; open symbols).

Fig 5

(A) Mean (±SD) plasma lysine concentration for cats fed a basal ration (▪) containing 11 g lysine/kg diet or a supplemented ration (□) containing 51 g lysine/kg diet. *P<0.0001. (B) Mean (±SD) plasma arginine concentration for cats fed a basal ration (▪) containing 11 g lysine/kg diet or a supplemented ration (□) containing 51 g lysine/kg diet. §P=0.0011; *P=0.0030.