A feed supplement comprising at least one selected from lactic acid bacterium belonging to Lactobacillus gasseri, a crushed product of the lactic acid bacterium, culture of the lactic acid bacterium, residue of the culture of the lactic acid bacterium and a treated product thereof (a concentrate, a pasted product, a dried product, a liquid product, a diluted product, a sterilized product, etc.) and a feed composition comprising the feed supplement.