The research has been conducted on “Ross-308” broiler chickens in the vivarium of Animal Science and Animal Products Processing Chair of the Velikiye Luki State Agricultural Academy in the Pskov Region. The experimental groups have been formed of ten 13-day-old chickens each. The first experimental group has been given mixed fodder and fresh water with a 1% sapropel extract additive (on a volume basis). The second and the third groups have been fed with mixed fodder partially substituted with experimental additives: the second group has received 2.5% of chilled sapropel (on a mass basis), the third group - 10% of sapropel-based green fodder. The chickens have been grown up to the age of 56 days. The most noticeable and regular differences appeared to be between the hens of experimental groups that exceeded the control group in live weight and average daily gains. The comparison of experimental hen groups has revealed some advantage of the second experimental group of broilers. Cock groups are substantially similar, which has considerably influenced the broiler chickens’ total figures.