Royal Canin Nutritional Information

5. Nutritional Information

Focus on: Taurine

Taurine is a sulfur-containing amino acid (H2N – CH2 – CH2 – SO3H). It is found in most animal tissues but not in plants. Seventy-five percent of the taurine is found as free forms within striated muscle cells (Dillon, 1991).

In cats, taurine deficiency leads to central retinal degeneration within a few months. (© J.-P. Lenfant/RC/Norwegian Forest Cat).

Physiological Essentials

By conjugating with cholic acid, taurine facilitates the hepatic synthesis of biliary salts. This is its best-known role, but taurine also acts as an osmoregulator by influencing the flow of calcium between the inside and outside of the cell (Schaffer & Kramer, 1980). This mechanism explains the role of taurine in:

• Platelet aggregation
• Neuron excitability
• Myocardium function ( Freeman, 1998).

The key roles of taurine are summarized in the table.

Consequences of Taurine Deficiency in Cats

Numerous studies have confirmed the essentiality of taurine in cats since 1975. In cats, taurine deficiency is associated with many disorders including:

• Blindness and retinal degeneration (Hayes et al., 1975)
• Reproductive problems and stunted growth (Sturman et al., 1986)
• Dilated cardiomyopathy (DCM) (Pion et al., 1987)
• Nervous problems (Sturman et al., 1985)
• Skeletal deformations (Sturman et al., 1985)
• Platelet hyperaggregation (Hayes et al., 1989)
• Immune system disruptions (Schuller-Levis et al., 1988)

Several factors explain the essentiality of taurine in cats.

• Cats synthesize little taurine due to the very low enzyme activity of the decarboxylase needed to convert cysteine into taurine (cysteine sulfinic acid decarboxylase). Its activity is around a hundred times inferior to the one observed in dogs.
• A lot of taurine is lost through the enteral cycle of bile acids.

At least 0.10% of dry matter (DM) in a dry food or 0.17% DM in a canned food helps prevent taurine deficiency (NRC, 2006). The difference is explained by the higher catabolism of taurine by the digestive flora when canned foods are consumed.

Consequences of Taurine Deficiency on the Cat’s Eyesight

In cats, normal retinal function depends on a sufficient intake of taurine (Hayes et al., 1975). An absolute deficiency of taurine for 25 weeks reduced taurine concentration to 16 - 25% of normal retinal concentration in the retina (Pasantes-Morales et al., 1986). This decrease induces alterations in the integrity of cellular photoreceptors and the underlying structure of the tapetum lucidum. Without rapid correction of the taurine status the photoreceptors will atrophy, leading to gradual but irreversible blindness. This is independent of the level of retinal stimulation by incoming light.

Consequences of Taurine Deficiency for the Cat’s Reproductive Function and Kitten Growth

Several studies have attempted to measure the impact of dietary taurine on reproductive function. The performances of queens fed with a taurine-deficient diet for six months prior to breeding are clearly inferior to those of the control group. The kittens from taurine-deficient mothers have motility problems of neurological origin (Sturman et al., 1986).

Taurine deficiency affects reproductive function and may lead to developmental abnormalities in kittens. (© Y. Lanceau/RC/British Shorthair).

Kittens with mothers that receive a “normal” level of taurine grow best (0.2%) (Sturman et al., 1992).

A high level of taurine (1%) has no apparent secondary effect on reproduction or the health of kittens born during the trial (Sturman et al., 1992).

Effect of Taurine Supplementation in Cats with Taurine Deficiency Cardiomyopathy

DCM caused by taurine deficiency is associated with faulty myocardial contractility (see above). Clinical signs of the disease may be reversed by adequate taurine supplementation, provided treatment is started soon and the disease is not already too advanced. The recommended dose is 250 mg of taurine per cat, twice daily (per os). This supplementation will achieve remission within 2 - 4 months in 65% of cats (Pion et al., 1987).

The results of 37 cases supplemented by taurine have been reviewed by Pion et al. (1992):

• Early death (within the first 30 days of supplementation) was recorded in 14 cats (38%).
• Clear improvement of the clinical and ultrasound signs was observed in 22 cats (59%). Survival was longer than 240 days. The clinical state of these cats remained stable in spite of cessation of all medical treatments (except taurine supplementation).

Conclusion

DCM caused by taurine deficiency illustrates the link that may exist between nutritional balance and heart function. DCM has become rare in cats, as the overwhelming majority of prepared foods for cats does now contain an adequate level of taurine.