Effect of Feeding Isoquinoline Alkaloids on Biomarkers of Inflammation and Inflammatory Cells in Feedlot Finishing Bulls Fed a High-Grain Diet

Feeding high-grain rations in feedlots has improved feed efficiency, allowing feedlot cattle to achieve finishing weights faster. However, high-grain diets can lead to metabolic and digestive disorders, as well as to the suppression of the immune system. An impaired immune function predisposes the animals to infectious diseases. In poultry and swine, supplementation with isoquinoline alkaloids (IQs) has demonstrated to modulate the immune response and improve performance. The objectives of this study were to assess the effects of an IQs containing supplementation product on the circulating concentrations of an inflammation biomarker (haptoglobin) and inflammatory cells (leukocytes and neutrophils) in feedlot yearling bulls fed a high-grain diet. Animals were randomly allocated to 2 treatment groups with 16 replicates: (1) no supplementation (CON, n=16), and (2) supplementation with 4 g/head/d of an IQ containing product (Sangrovit^® RS, Phytobiotics Futterzusatzstoffe GmbH, Eltville, Germany; SAN, n=16) top-dressed at the time of feed delivery. During the study period, all animals were fed the same high-grain diet containing a mixture of 85% whole corn and 15% protein-vitamin-mineral mix as a total mixed ration. Animals received the experimental diet ad libitum for 42 d with an initial adaptation period of 14 d. From study d 21 to 42 daily examination of animals for identification of nasal secretions was performed. On study d 42, blood samples were collected for assessment of serum haptoglobin concentrations and leukocyte and neutrophil counts. Haptoglobin concentrations did not differ (P=0.25) between treatments (CON= 230.1±40 ug/mL; SAN=181.7±21 ug/mL). Similarly, no differences (P=0.45) in circulating leukocyte count was observed between SAN (12.76±1.42 x 10⁶/mL) and CON (11.42±1.1 x 10⁶/mL) groups. However, circulating neutrophils were elevated (P=0.0006) in the SAN (3.25±0.05 x 10⁶/mL) compared to the CON (1.18±0.01 x 10⁶/mL) group. In addition, less animals (P=0,006) in the SAN group (4.2 animals) presented nasal discharge when compared to the CON group (6.2 animals). Results from this study suggest that supplementation with IQs reduced the negative effects associated with feeding high-grain diets on immune cells. Animals fed IQs had increased circulating neutrophils counts which may help improve the animal response to infectious diseases.