I have read that non veg food are better for proteins while veg food is deficient in either one or other protein. If it is so are herbivores protein deficient always in case of animals as well as humans?
Link from VonBeche is good.
Proteins vary in amino acid content. Humans can make some but we need 9 of them in our diets.
from https://www.ncbi.nlm.nih.gov/books/NBK234922/ Nine amino acids—histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine—are not synthesized by mammals and are therefore dietarily essential or indispensable nutrients.
This guy http://michaelbluejay.com/veg/protein.html is clearly a vegetable enthusiast but he makes a good point (and provides a nice table): just about any vegetable can provide enough amino acids if you eat enough of it. Getting your entire caloric requirement from iceberg lettuce would a project, it is true. But until I did the back reading for this answer I thought it would be impossible to take in the calories it would require to get all necessary amino acids from some of these plant foods. Thanks michaelbluejay.
I here assert that animal foods have more amino acids per calorie than vegetable foods. So, if you wanted to limit calories but meet your amino acid requirement it would be easier to do with animal proteins than with vegetable proteins.
But even all calories from potatoes can get you your amino acids. The people who get into trouble are people who are not getting all the calories they need because they are starving, and the calories they do get are from low protein source foods like yams or bananas. That is protein-calorie malnutrition.