Efeito da monensina no desempenho e saúde de bovinos de corte confinados submetidos ao estresse de transporte

Abstract

The transportation of cattle is a necessary step in beef production and influences the feedlot system, as the adaptation of newly arrived animals represents a major challenge, further aggravated by transport stress. This stress triggers an inflammatory response that reduces dry matter intake (DMI) and influences animal performance during the feedlot period. The use of growth-promoting additives in feedlot cattle diets is a common practice among nutritionists. The most widely used molecule is monensin, due to its ability to increase feed efficiency (FE). However, since monensin may reduce DMI, it was hypothesized that it could exacerbate the inflammatory process caused by transportation, impairing animal adaptation and negatively impacting performance throughout the feedlot period. The objective of this study was to evaluate the effect of monensin in the diet of beef cattle subjected to transport stress in a feedlot system. A total of 84 Nellore cattle were used, undergoing 12 hours of transportation over a distance of 410 km. Blood samples were collected on days 1, 20, 60, and 112 of the feedlot period, along with body weight measurements and carcass evaluation by ultrasonography. The animals were allocated in a randomized block design according to body weight. Upon arrival at the feedlot, the following treatments were applied: Control (without monensin); Monensin (30 mg/kg DM – Rumensin®, Elanco). The adaptation phase lasted 21 days, followed by the final diet for 96 days. Monensin did not aggravate the inflammatory response during the adaptation phase to the feedlot and did not influence DMI or FE, thus not altering average daily gain (ADG). Over the total feedlot period, monensin also did not affect the inflammatory response, but it reduced DMI and maintained ADG, resulting in greater FE. Due to the action of monensin in modulating ruminal fermentation, it was observed that the control treatment showed greater subcutaneous fat thickness. It is concluded that monensin does not influence the inflammatory response caused by transportation and increases feed efficiency.