Ninety six pigs of Polish Large White x Pietrain crossbreed (48 gilts and 48 barrows) were allotted to three feeding treatments: 1 – control, where the animals were fed with the control mixtures for growing (25–65 kg body weight) and finishing period (65–105 kg BW); treatment 2 and 3, where the control group mixtures were supplemented with 20 mg antibiotic "Avotan" or with 50 g herb mixture per 1 kg diet, respectively. The herb mixture components were: herb of great nettle (Urtica dioica), lyophilized garlic (Allium sativum) bulbs and rhizomes of wheat-grass (Agropyron repens). The pigs were housed in pens (four gilts or four barrows per pen). Feed and water were available ad libitum and individual liveweights and pen feed consumption were recorded on days 30, 60, 90 and 110 (at slaughter) of the trial. Herb mixture supplementation of the diets improved the average daily gains and feed utilization ratio by about 5 and 10%, respectively. The antibiotic "Avotan" additive had approximately half the influence on pig performance. Backfat thickness (an average of 5 measurements) was increased significantly after treatment with either additive. Both additives also increased the percent of subcutaneous fat in the ham. Leanness of the ham increased significantly in both experimental groups. No significant changes in physico-chemical or sensorial characteristics of the meat were noted.