PSXI-18 - Effects of different fiber levels on rumination and inflammatory markers in feedlot cattle

Abstract: Adding fiber to feedlot diets is essential to maximize performance, optimize feed conversion and maintain animal health. Monitoring blood inflammatory markers and rumination behavior can help to identify fiber levels that maximize performance and animal well-being. We aimed to evaluate the effect of fiber levels on inflammatory markers, lactate dehydrogenase and haptoglobin and rumination of Nellore cattle in confinement fed with diets containing 12% and 7% forage NDF, over a period of 50 days. Diets included corn silage as the source of forage fiber with 23.3% and 13.6% corn silage in the dry matter 64% and 73.5% ground corn, and 0.2 and 0.5% potassium chloride, respectively for the 12% and 7% fNDF. Soybean meal (1.5%); cottonseed (7%), urea (1.2%), and mineral mixture (2.7%) containing 25 ppm of monensin were present in both treatments. Average initial weight was 460±38 kg and average age 20 months. Twenty bulls were randomly distributed for each treatment with animal being the experimental unit. The feeding behavior was monitored on days 21 and 42, with observations at each 10-minute interval, over 24 hours and data obtained were averaged for analysis and blood samples were collected immediately after behavior analysis. Blood samples were obtained by puncturing the jugular vein, centrifuged to separate the serum, stored at -20°C and subsequently analyzed. Lactate dehydrogenase was analyzed in an automatic biochemistry system using cattle specific cattle kits (LABTEST Diagnóstica SA). Haptoglobin analyses were carried out by ELISA (Vidavet- Veterinary Lab). Data were evaluated by PROC GLIMMIX from SAS. A significant interaction was observed between minutes of rumination and fNDF levels in relation to the concentration of lactate dehydrogenase (p< 0.0001), expressed by the solution: Lactate = 1272.12 + 908.86 * (tract=7) + 1, 1427 -3.3170 * (treat= 7) *rumination. For animals receiving the 7% fNDF diet, the concentration of lactate dehydrogenase decreased as the minutes of rumination increased, with a significant linear effect (p< 0.001). On the other hand, for animals treated with 12% fNDF, no significant correlation was observed (p=0.34) with increasing rumination time. There was also an interaction between minutes of rumination and fNDF levels for haptoglobin concentration (p< 0.01), expressed by the solution: Haptoglobin = 0.1901 + 0.4865 * (treat=7) + 0.000828 - 0.00163 * (treat=7) * rumination. In animals treated with 7% fNDF, haptoglobin concentration decreased with increasing minutes of rumination, with a significant linear effect (p=0.02). Our data demonstrates that, for the low forage diet, as bulls increased rumination time there was an improvement (a decrease) in inflammatory markers concentrations.