TAURINE’S INFLUENCE ON PHOTOPERIODIC ENTRAINMENT OF CIRCADIAN RHYTHMS OF HETEROPHIL, LYMPHOCYTE, AND IMMUNE ORGAN RESPONSES IN BROILER CHICKS DURING BROODING

Résumé

The effect of taurine on circadian rhythm of immune cells/organs of brooded broiler chicks under continuous lighting was studied. Ninety-six (96) clinically healthy day-old broiler chicks were assigned to groups; continuous lighting (CL), restricted lighting (RL), with plain drinking water, while CL+ T and RL + T groups, had 0.1 % taurine added to their drinking water, all served ad libitum. Light emitting diode (LED) bulbs extended lighting hours at dawn (18.00 h) till dusk. On day-15 of brooding, four broiler chicks from each group on 5 – hourly basis were randomly selected, weighed, humanely slaughtered and 3.5mL of blood collected over a 24 h period. The bursae of Fabricius and spleens were harvested and weighed. The statistics applied to the data obtained were the Student T-Test and the Single cosinor application®. The results did not show any significant (P > 0.05) differences in measured parameters in all groups. However, the Single cosinor application® showed the mesors, amplitudes and acrophases in the CL group for heterophil and lymphocyte to be; (28.2 ± 3.50 %, 7.3 %, 09.10 h); (68.3 ± 4.0 %, 6.0 %, 19.7 h) and for RL group as (26.0 ± 1.06 %, 0.4 %, 02.30 h); (68.3 ± 3.80 %, 9.7 %, 13.20 h), and for CL + T group as (30.3 ± 1.10%. 1.4 %, 4.5 h); (68.7 ± 0.91%, 1.3 %, 23.3 h) and for RL + T group as, (30.3 ± 0.69 %, 1.2 %, 22.0 h); (68.4 ± 3.80 %, 1.3 %, 11.4 h), respectively. It was concluded that continuous lighting disrupted the rhythm of immune cells, however, taurine maintained the rhythmicity of the heterophils only in chicks under RL, but did not modulate that of lymphocytes in brooded broiler chicks under continuous lighting.