Anything that is formed without the act of fertilization is biologically called “vegetative”. The term “vegetative” is more appropriate to the plants but not for animals. But it has become customary to term the unfertilized eggs of hens as vegetarian eggs since they are formed without the fusion of sperm.
Country breed birds lay fertilized eggs. Such eggs are laid a week or more after the cock has mated the hens, but white leghorns which are suitable for egg production lay only unfertilized eggs as they are not allowed to mate with cocks. The leghorns are genetically improved birds which produce through successive generations under improved breeding methods.
Nutritionally there is no difference between a vegetarian egg and an ordinary egg, but in certain physiological characteristics they differ. Leghorn eggs cannot be incubated, but eggs of country breed can be incubated. Such hatching eggs deteriorate with storage and therefore should not be stored beyond seven days, while leghorn eggs can be stored for several days.
The eggs of poultry bred leghorn birds are larger in size, with more amount of albumin and always white in colour. The eggs of country bred birds are smaller in size and have less amount of albumin and the shell colour may vary from white to pale straw yellow colour. The natural feeding habit of these birds is the only reason for these characteristics.