It is well-known that variations in the environment have given a certain biorhythm to all functions of animal bodies. In this context, it is important to find the correlation between biorhythmic variations and the most favourable moments in a nychthemeron for applying treatments and performing prevention activities through vaccination. The experiment studies nychthemeral variations of white formed elements, especially the variation of lymphocyte count in broiler chickens. The chickens were observed weekly, since they were one day old until they were 21 days old, before and after being vaccinated against Newcastle disease. The experiment involved 10 broiler chickens, since they were one day old until they were 21 days old. When the chickens were one day, 7 days, 14 days and 21 days old, blood samples were taken for the preparation of smears (at 7 o’clock, 1 pm, 7 pm and 1 am) which were stained through the Diff Quick method. The smears were examined by reading 200 leucocytes/smear. The chickens were vaccinated when they were one day old and then again when they were 14 days old, with La Sota live attenuated vaccine. Blood samples were taken from 6 chickens at 21 days, for the determination of vaccine antibodies. The experimental data were processed statistically with the help of the non-parametric Mann Whitney U Test. When the broiler chickens were one day old, the highest value of lymphocyte count during a nychthemeron was recorded at 7 o’clock in the morning (40.45±3.36%). Statistically, this value was insignificantly bigger than the values obtained at 1 pm, 7 pm and 1 am. When the chickens were 7 days old, statistically significant differences were recorded in the lymphocyte count, with bigger values in the morning than at night (p<0.05). In the same way, the values were bigger at noon than in the evening (p<0.05) and at night (p<0.001), respectively. When the chickens were 14 and 21 days old, no statistically significant differences were found among the values recorded during a nychthemeron. The average proportion of lymphocytes in one day-old chickens during one nychthemeron is significantly lower (p<0.0001) than the average values of 7, 14 and 21 days, after the vaccination against Newcastle disease. The statistically significant increase of the lymphocyte count in broiler chickens until 14 days old is the effect of the vaccination they received when they were one day old. The booster vaccination received at 14 days does not statistically change the nychthemeral average proportion of lymphocytes. Similarly, from a statistical point of view it changes nothing in the average lymphocyte count in the different sampling hours when the chickens were 14 and 21 days old.

biorhythm, nychthemeron, broiler chicken, leucocytes, lymphocytes

Presentation: oral