Valuation of immune response by using phagocytosis index and parameters associated as markers of animal stress in fattening lambs

•Different parameters of stress were evaluated in fattening period in lambs.•Immune response was evaluated in lambs by using phagocytosis index.•A high value in red blood cell and haematocrit was found.•A decrease of the above mentioned parameters between two moments has been recorded.•The study of these parameters can be a right method in order to evaluate stress.

The aim of this study was to evaluate immune response function by using neutrophils phagocytic index and parameters associated to stress in order to analyse the effect of feedlot in the fattening lambs classification center (CC). Thirty six Merino lambs were randomly chosen with a live weight about 18–20 kg with 70–90 days of life. Two blood samples were taken in two moments of their period in CC, after the classification processes at the beginning of feedlot and one day before slaughter. High values compared to the reference values were found in red blood cell count (RBC) and haematocrit value, with statistically significant differences (P = 0.003, P = 0.004, respectively) between two moments. However, the increase in the neutrophil/lymphocyte ratio (N/L ratio), the decrease in phagocytosis index and high cortisol values point to stress conditions and a predisposition to develop diseases.