This study evaluated the inclusion of concentrate and monensin, salinomycin and flavomycin in sheep diets on intake, digestibility, in situ degradability, ruminal variables and nitrogen balance. Five sheep in a latin square received the treatments: HAY (hay only), CONT (hay + concentrate), MON (hay + concentrate + monensin), SALI (hay + concentrate + salinomycin), and FLAV (hay + concentrate + flavomycin). Hay was offered ad libitum, concentrate, 20 g kg-1 of body weight (BW), and additives, 0.75 mg kg-1 of BW. The treatments with the concentrate (CONT, MON, SALI and FLAV) showed increased (P≤0.05) on intake, digestibility, total VFA, propionate and butyrate proportions, N-NH3, and nitrogen balance, and decreased (P≤0.05) DM and NDF degradability, acetate proportion, acetate:propionate ratio, and rumen pH compared to the HAY. The comparison between the outcome effects from additives with the CONT

RESUMO: Os receptores de agonistas beta-adrenérgicos (β-AA) estão presentes em praticamente todos os tipos de células de mamíferos e são estimulados pelas catecolaminas (adrenalina e noradrenalina) produzidas pelo próprio organismo. Os agonistas β-AA são substâncias sintéticas com estrutura similar a estas aminas. Quando fornecidos na ração alteram a composição corporal dos animais, afetando a repartição dos nutrientes em favor da deposição proteica e diminuindo a lipogênese. Apesar dos mecanismos de ação não serem completamente entendidos, estes podem causar alterações morfofisiológicas, tais como o aumento do fluxo sanguíneo, a diminuição do nível plasmático de insulina, a diminuição da lipogênese e a hipertrofia muscular principalmente nas fibras do tipo II. Observam-se também alterações na motilidade do trato gastrointestinal e secreções, além da influência direta sobre as bactérias do rúmen, podendo alterar a digestibilidade da dieta. Os agonistas β-AA liberados em alguns países para utilização em bovinos de corte são o Cloridrato de Ractopamina e o Cloridrato de Zilpaterol. De acordo com dados de literatura, a inclusão destes aditivos na dieta de bovinos confinados tem sido relacionada com aumento na eficiência alimentar e ganho de peso diário, e igual ou menor consumo de ração. Nas características de carcaça tem sido observado aumento no peso das carcaças, e aumento da área de olho de lombo, porém com possibilidade de diminuição da espessura de gordura subcutânea e de marmoreio. Avaliações em painel sensorial da carne de animais consumindo agonistas β-AA mostraram diminuição na maciez, com igual ou menor suculência. Os agonistas β-AA melhoram o desempenho e as características de carcaça, porém mais estudos são necessários para comprovar se possuem influência negativa nas características organolépticas da carne.Palavras-chaves: novilhos, ractopamina, terminação, zilpaterol. BETA-ADRENERGIC AGONISTS AS ADDITIVE IN BEEF CATTLEABSTRACT: The agonists receptor beta-adrenergic (β-AA) are present in virtually all types of mammalian cells and are stimulated by catecholamines (epinephrine and norepinephrine) produced by the organism itself. The β-AA agonists are synthetic substances with similar structure to these amines. When provided in the diet they alter the body composition of animals, affecting the distribution of nutrients toward to protein deposition, and decreasing lipogenesis. Although the mechanisms of action are not fully understood, these may cause morphological and physiological changes such as increased blood flow decrease in plasma insulin, decreased lipogenesis, and muscle hypertrophy mainly in type II fibers. We also observed changes in motility and secretions grastointestinal tract, beyond the direct influence on the rumen bacteria, altering the digestibility of the diet. The β-AA agonists released in some countries for use in beef cattle are ractopamine hydrochloride and zilpaterol hydrochloride. According to literature data, the inclusion of these additives in the diet of feedlot cattle has bee...

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. How to cite: Vedovatto, M.; Diogo, J. M. S.; Beltrame, J. A. M.; D'Oliveira, M. C.; Silva, C. J.; Mendes, C. Q.; Cabral Filho, S. L. S. and Franco, G. L. 2019. Effects of antibiotic growth promoters mixed with mineral supplement on growth performance, ingestive behavior, and mineral intake of grazing bulls. Revista Brasileira de Zootecnia 48:e20190114.