"Additional supplementation" means adding something extra to what is already there in order to provide additional support, improve something, or enhance it further. Full definition
Additional supplementation of omega 3 fatty acids works to improve the health of the skin. (jeffreyspets.com)
If you feed a commercial diet, additional supplementation with vitamins is not necessary for a healthy pet. (vetbabble.com)
Because many women often don't eat enough fish during pregnancy, getting this nutrient from additional supplementation is often critical. (mindbodygreen.com)