It depends on the type of carnivore "obligate carnivores" such as cats would die of malnutrition while other carnivores such as dogs can survive without meat
Also- carnivorous animals do not have the capacity to break down cellulose like herbivores. Cows for example have a four chambered stomach which allows them to break down the cellulose for use in the body. Youll notice that cows have a longer 'appendix' which is used to breakdown these fibres. This 'appendix' is not present, or is extremely small, in carnivores.
