Haematological Profile of Broiler Chickens under Acute Stress Due to Shackling

Abstract

The aim of our experiment was to assess the stress response of broilers to different periods of shackling when conditions similar to practice at slaughterhouses were simulated. In this study, heterophil to lymphocyte (H/L) ratios were used as an index of stress status. Also total erythrocyte and leukocyte counts, haematocrit, haemoglobin, mean cell volume (MCV), mean cell haemoglobin (MCH) and mean cell haemoglobin concentration (MCHC) values were monitored and differential leukocyte count was assessed. At 42 days of age, 10 broilers were subjected to a 2-min shackling period (S2 group) and other 10 broilers were subjected to a 5-min shackling period (S5 group). Broilers were suspended from shackles placed in an experimental processing line and other stress factors (e.g. preslaughter transport, crating and ambient disturbances) were eliminated in order to assess the stress response to shackling particularly. When compared with an unshackled control, both S2 and S5 groups exhibited a highly significant increase in heterophil counts and H/L ratio 20 h following shackling. When compared, the mean value of the H/L ratio of S2 and S5 chickens was higher due to the longer shackling period. The difference, however, was not statistically significant. In addition, S5 broilers exhibited a statistically significant elevation in the number of basophils in comparison with the control. When compared with the control, S2 broilers exhibited a significant decrease in haemoglobin level, a highly significant decrease in erythrocyte cell count and MCHC values due to shackling. Both S2 and S5 groups of broilers manifested a highly significant increase in MCV values and markedly depressed erythrocyte count and MCHC values in comparison with unshackled broilers. When S2 and S5 broilers were compared, none of the monitored haematological indices of the erythrocyte count manifested any significant changes due to the different periods of shackling. Results of our experiment proved that the preslaughter shackling induced considerable changes in haematological indices of both leukocyte and erythrocyte count in broilers and indicated a markedly increased level of stress effects. In conclusion, using a method that eliminates the stress associated with the shackling of live birds before electrical stunning should be considered as a better option as far as bird welfare is concerned.