Metabolizable protein effects on the acute-phase inflammatory response following environmental and dietary changes of finishing beef cattle

Abstract

The acute-phase inflammatory response is an immune process that is activated by different internal and external factors such as stress. During inflammatory responses, protein metabolism is altered to support an increase in nutrient demand of the immune system. Such alteration can negatively affect animal health, wellbeing and performance; however, nutritional strategies arise as alternative tools to overcome it. Therefore, the objectives of the present study will be to evaluate the effects of diet (growing phase: supplementation of Rumen Undegraded Protein (RUP) and finishing phase: supplementation of different protein/RUP sources) on the acutephase inflammatory process and performance of beef cattle undergoing inflammatory response caused by stress associated with environment and dietary changes. In this study 54 Nelore beef steers (averaging an initial BW of 360 kg), coming from a grazing study on the growing phase, will be finished in feedlot where they will be allocated in collective pens in a completely randomized design (3 treatments, 1 pen/treatment and 18 animals/pen). The experiment will last approximately 105 days (first 21 days to diet and environment adaptation followed by 3 experimental periods of 28 days each). Diets will be as follow: A) adaptation diets will be the same for all animals and will consist of decreasing forage: concentrate ratio: 1) 70:30% (A1); 2) 50:60% (A2) and 3) 30:70% (A3). Corn silage will be the forage source and ground corn the concentrate source; B) experimental diets will consist of a 30:70% forage: concentrate ratio (corn silage and ground corn) supplemented with different protein/RUP sources: 1) soybean meal supplementation at 1.6% of the BW (T1); 2) gluten 60 supplementation at 1.6% of the BW (T2) and 3) protected soybean meal supplementation at 1.6% of the BW (T3). For that, 6 animals coming from each treatment during the background phase (pasture + mineral salt 100g/animal/day, pasture + gluten 60 or pasture + protected soybean meal supplementation at 0.3% of the BW) will be used on each treatment, totaling 18 animals/treatment (total n=54). Samples will be collected at different time points (days 0, 7, 8, 10, 14, 21, 49, 77, and 105 relatives to the beginning of the finishing period) and variables such as blood concentration of proteins from the acute-phase inflammatory response (haptoglobin, serum-amyloid A, and ceruloplasmin), total plasma amino acid, blood immune cells count, inflammatory gene expression of blood immune cells, and animal performance will be evaluated. Data will be analyzed using the Mixed Procedure of SAS and the means will be compared using the Tukey test. Statistical significance will be set at P d 0.05. The hypothesis is that the use of RUP supplementation to increase Metabolizable Protein (MP) supply during growing and finishing phases of beef steers can improve animal's immune system and consequently increase animal performance and well-being and reduce feedlot finishing time. The understanding of the link between nutrition and inflammation is essential for the complete evaluation of animal nutritional requirements, health and productivity. It allows nutritionists to better formulate diets and recommend management strategies to be used as tools to prevent or overcome the negative effects of inflammatory response caused by stress associate with dietary and environmental changes on animal performance. (AU)