The effect of formic acid and 2 plant extracts on performance traits, apparent ileal digestibility (AID), intestine mucosa morphology, and meat yield of broilers was studied in a 49-d experiment. There were 6 treatments: a negative control diet without additives (control); 10 ppm of avilamycin; 5,000 of formic acid; 10,000 ppm of formic acid; 200 ppm of plant extract based on a blend of oregano, cinnamon, and pepper essential oil; and 5,000 ppm of hydroalcoholic plant extract from sage, thyme, and rosemary leaves. A total of 312 Ross chicks were distributed into 24 groups of 13 in each, comprising 4 replicates per treatment. The performance data revealed significantly better FCR in all the supplemented diets except for the 5,000 ppm of hydroalcoholic plant extract diet. All additives improved AID of nutrients. Both acidifier inclusion levels improved villus height, and the group fed the 10,000 ppm of formic acid diet also had the greatest crypt depth; however, villus surface area was not influenced. Meat yield was not affected. It was concluded that the diets with 5,000 and 10,000 ppm of formic acid, and with 200 ppm of plant extract based on a blend of oregano, cinnamon, and pepper essential oils were similar to avilamycin and were beneficial for improving growth traits and nutrient AID. Furthermore, a positive effect of formic acid on intestine mucosa was observed. This experiment involved a small sample, so the additives that showed beneficial effects should be further studied in commercial farms.
