Valutazione di diversi marker temporali in alcune specie di ruminanti domestici sottoposti a differenti condizioni sperimentali

The aim of the study was to investigate some rhythmic markers in three different ruminants species. For this purpose, three different experiments were conducted. The aim of the first experiment was to investigate clock gene expression in Bos taurus and the alteration occurring during pathological conditions, through the evaluation of the daily expression pattern of four clock genes (Per2, Cry2, Bmal1, Clock) in peripheral blood cells. Five healthy cows, five affected by Brucellosis (BR) and five affected by Bovine Viral Diarrhoea- Mucosal Disease (BVD-MD) were housed in indoor stalls under natural spring conditions, blood samples were collected at 4 h intervals over a 24 h period. Statistical analysis showed rhythmic expression of clock genes mRNAs in healthy cows. Cows affected by BR did not show any rhythmic expression of clock genes mRNAs while in cows affected by BDV mRNA levels of Bmal1, Clock and Cry2 changed during the day. These findings highlighted that circadian system could be involved in homeostasis alteration and that clock genes could be considerate as regulatory genes or early response genes during inflammation, so their regulation should be evaluated in health research and treatment. The second experiment of this study was to evaluate the circadian rhythm of melatonin in sheep and in goats and to compare the rhythmicity under the same conditions. Five female Sarda sheep and five female Sarda goats were housed in boxes equipped with an opening window. Animals were kept under a natural photoperiod and in indoor ambient temperature (16–20 °C). Blood samples were collected every 2 h over 48 h period. Results showed a circadian melatonin rhythm with a nocturnal acrophase in both species and a high robustness between rhythm 61.20 ± 7.57 and 83.60 ± 7.26, denoting a high percentage of stationarity of melatonin circadian rhythm. No significant differences were found on melatonin levels in sheep and goats. Our finding demonstrates the similarity between the two species in the secretion and rhythmicity of melatonin. The third experimental study evaluates the pattern of plasma melatonin during the trough and the peak of its daily rhythm. Blood samples from 8 ewes were collected every 3 h for a 48-h period. On the third day, blood samples were collected from 10:00 to 13:00 (trough) and from 20:00 to 23:00 (peak) every 20 min. Our results showed a robust daily rhythm of melatonin in both days of monitoring, with nocturnal acrophase. During the trough, a significant decrease was observed starting from the 10:40 with a progressive decrease about every 40 min. During the peak of the plasma melatonin daily rhythm, an increase was observed starting from the 20:40 with a progressive increase about every 40 min. These data could be taken into consideration to monitor the plasma melatonin variations during the 24 h, and for the administration of melatonin for breeding in ewes. In conclusion, the circadian rhythms in domestic ruminants appear to be modulated by exogenous factors that not change the normal homeostasis of the organism, for example the photoperiod, and by exogenous noxae, for example infectious diseases, that can produce an alteration of the normal expression of clock genes