ABSTRACT The objective was to evaluate the addition of antibiotic growth promoters to free-choice mineral supplement on ingestive behavior, mineral intake, and growth performance of grazing bulls. Sixty Nellore bulls [initial body weight (BW) of 219±17.8 kg and 15±2 months of age] were divided in 12 marandu grass paddocks. The treatments were: mineral supplement (control), mineral supplement + virginiamycin (VIRG), mineral supplement + lasalocid sodium (LASA) and mineral supplement + salinomycin sodium (SALI). Mineral supplements were formulated with target intake of 60 g d−1 and the growth promoters of 75 mg 100 kg−1 of BW. The experimental design was the completely randomized blocks. There was no treatment effect on ingestive behavior or mineral intake; however, the active ingredient intake differed between treatments. In the last experimental period, the intake of active ingredient LASA and SALI were higher than VIRG (0.66, 0.54, and 0.39 mg kg−1 of BW, respectively). Treatments also did not affect BW and average daily gain, which were 0.63, 0.60, 0.64, and 0.62 kg d−1 for control, VIRG, LASA, and SALI, respectively. Free-choice mineral supplementation intake by bulls has a high variability, and this impairs the regulation of the intake of antibiotic growth promoter additives. Therefore, the addition of antibiotic growth promoters to the mineral supplement does not affect ingestive behavior, mineral intake, and growth performance of grazing bulls.

RESUMO Objetivou-se com este trabalho comparar o valor forrageiro do milheto e trigo-mourisco, sob irrigação, em diferentes idades de corte. Utilizou-se delineamento experimental em blocos ao acaso, com os tratamentos arranjados em modelo de parcelas subdivididas. As plantas foram cultivadas durante a estação seca, sob irrigação e colhidas em três idades de corte, 47, 57 e 67 dias (tratamentos). Foram determinados os teores de matéria seca (MS), proteína bruta (PB), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), matéria mineral e produção de gases in vitro e a produção de matéria seca. A produção do trigo-mourisco (2301, 3144 e 4471 kg MS/ha) foi superior à do milheto (437, 592 e 2224 kg MS/ha) nas três idades de corte. Os teores de PB do milheto foram, em média, 22,3% nas três idades de corte, mas no trigo-mourisco reduziu de 23,8% no primeiro corte, para 14% nos demais cortes. O trigo mourisco apresentou maior teor de FDN no primeiro corte 57,6% contra 52,1% do milheto, entretanto diminuiu no segundo e terceiro cortes, 46,8% e 41,2%, respectivamente, enquanto que no milheto mantiveram-se em 55,1% e 52,7% no segundo e terceiro corte. Os teores de FDA forma mais elevados para o trigo mourisco em comparação com o milheto nas três idades de corte estudadas. A produção de gases foi maior para o trigo mourisco em comparação ao milheto, com exceção do primeiro corte, quando o trigo apresentou maiores taxas de fermentação. O trigo mourisco apresentou qualidade como forrageira, sendo mais produtivo e nutritivo do que o milheto durante o período seco, sob irrigação.

SUMMARY This trial compared forage production and quality of Pearl Millet and Buckwheat in three cutting age on irrigation conditions during dry season, evaluated in a randomized block split plot design with tree replications. Was determined content of Dry Matter (DM), Crude Protein (CP), Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF), Mineral Matter (MM) and in vitro gas production. Forage production of Buckwheat was higher than Pearl Millet in all the cutting ages. Pearl Millet CP content was similar to all three cuts but Buckwheat CP content was higher in the first cut and reduced in the others. The NDF content of Buckwheat was higher in the first cut and reduced in the others, meanwhile Pearl Millet presented low NDF value in the first cut but increased in the second and third cut. The Buckwheat presented high ADF content than Pearl Millet in all the cuts. In vitro gas production from Pearl Millet was higher in the first cut but more high for Buckwheat in the second and third cuts. Buckwheat produced more forage with high quality than Pearl Millet during dry season.