Efficacy of the phytogenic feed additive oregano essential oil (OEO) (Origanum vulgare L.) was assessed as an alternative to an antibiotic as a growth promoter (AGP) in broiler diets. Three hundred male broiler chicks were assigned to five treatments, which consisted of diets with different levels of OEO (300, 600, and 900 mg/kg of diet), a negative control, and a positive control. Broiler performance was evaluated from 1 to 21 and 1 to 39 days old. From 1 to 39 days old, the broilers of the negative control group presented lower feed intake than those fed OEO300. No significant effect was observed on weight gain. The greatest feed conversion ratio occurred in the positive control group. Broilers treated with OEO300 had greater carcass yield than those in the positive control group. The haemogram, leukogram, and heterophil/lymphocyte ratio were positively influenced by OEO300. Red blood cell and leukocyte counts increased in a dose-dependent manner in broilers fed OEO-supplemented diets, while broilers in the positive control group had the lowest levels of haematocrit, mean corpuscular haemoglobin concentration, and plasma protein. Differential leukometry revealed lymphocyte numbers were increased with OEO treatment and reduced in the positive control group. For hepatic and renal metabolism, the broilers in the positive control group exhibited the greatest serum activities of aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, and alkaline phosphatase. Although more studies on its efficacy are needed, OEO at 300 mg/kg may be used as a phytogenic additive in broiler diets, especially those without AGP.

Os efeitos da parede celular de Saccharomyces cerevisiae (PCSc) na dieta para frangos foram avaliados com base nos tratamentos: dieta referência com avilamicina (AV); dieta referência (DR); DR com 0,1% de PCSc (PCSc0,1); DR com 0,2% de PCSc (PCSc0,2); DR com 0,3% de PCSc (PCSc0,3). O delineamento foi o de blocos ao acaso, com cinco tratamentos e seis repetições de 10 aves, totalizando 300 frangos, machos. No período de nove a 21 dias de idade, o tratamento PCSc0,3 influenciou negativamente no ganho de peso (631g), e no período de 34 a 39 dias, o tratamento PCSc0,1 proporcionou melhor ganho de peso (461g) em relação ao tratamento com o antimicrobiano. O maior peso vivo ao abate, 2571g, foi obtido no tratamento PCSc0,1. Os pesos absolutos de sobrecoxa e coxa+sobrecoxa foram maiores nos tratamentos PCSc0,1 (290g e 560g) e PCSc0,2 (292g e 561g) e menores no tratamento PCSc0,3 (263g e 515g). Não houve influência na metabolizabilidade da ração e na contagem total de coliformes totais no íleo. Dietas com inclusão de até 0,2% de PCSc resultaram em índices produtivos adequados, podendo ser utilizadas como aditivo em dietas livres de antimicrobiano melhorador de desempenho sem o comprometimento do desempenho, características de carcaça, metabolizabilidade da ração e da contagem total de coliformes totais do íleo.

No abstract