Long-term use of narasin, salinomycin and flavomycin for Nellore steers fed with high-forage diets: ruminal parameters, apparent nutrient digestibility, and performance

• Ano de defesa: 2020
• Autor(a) principal: Limede, Arnaldo Cintra
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Aditivos alimentares; Desempenho; Digestibilidade; Digestibility; Feed additives; Parâmetros ruminais; Performance; Ruminal parameters
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/10/10135/tde-21082020-142248/

Experiement 1: Thirty-two rumen-fistulated steers Nellore steers (Bos indicus) were assigned to a randomized complete block design, according to their initial shrunk BW (220 ± 12.6 kg). Steers were fed daily and diets were composed of 99% of coastcross haylage and 1% of concentrate, used as a delivery vehicle for the additives. The experimental diets consisted of 1) CON - a forage-based diet without additives, 2) NAR - CON diet plus 13 ppm of narasin, 3) SAL - CON diet plus 20 ppm of salinomycin, or 4) FLA - CON diet plus 3 ppm of flavomycin. The experimental period lasted 140 d, divided into 5 periods of 28 d each. There was no interaction treatment × day for parameters of intake and digestibility. The inclusion of feed additives did not affect the DMI (P = 0.20), and consequently, did not affect the nutrients intake (P > 0.17). In addition, there was no difference in nutrient digestibility among diets (P > 0.40). There is an interaction between treatment x day (P < 0.01) for AcBut:Prop ratio where the NAR treatment had the lowest values from the 56 day (P < 0.01). In addition, animals receiving narasin showed greatest values to acetate (P < 0.01) and higher values to propionate (P < 0.01), butyrate (P = 0.01) and Ac:Prop (P < 0.01). The Volatile Fatty Acids Total was lowest to SAL and FLA treatments (P = 0.02). Experiment 2: one hundred and sixty- four Nellore bulls (Bos indicus) were blocked by initial shrunk BW (298.95 ± 2.5) in a 140-d feedlot trial, divided into 5 periods of 28 d each. Bulls were fed daily and diets were composed of 96% of coastcross haylage and 4% of concentrate, used as a delivery vehicle for the additives. The treatments used were the same as in the previous experiment. There was an interaction between treatment x day for BW (P < 0.01) and Dry Matter Intake (DMI; P = 0.03). Animals of treatment NAR showed greatest BW from 84th day of the experiment (P = 0.03) and had higher DMI in the second, fourth, and fifth period of study (P < 0.05). In conclusion, the inclusion of 13 ppm of NAR improves the ruminal fermentation parameters and the performance of bulls in forage-based diets. There were no evidence that SAL and FLA are effective to forage-based diets.