Abstract

"Deportation of darkness" in the urban and rural environment constitutes a real health hazard for man and may also adversely affect the health and production of farm animals. In nurseries, dairy farms and feedlots artificial lighting interface at night is a common practice to motivate feed consumption. The basis for the health and industrial threat lies in the fact that artificial lighting at night violates the normal functioning of the biological clock that synchronizes various biological activities. The period between the last trimester of pregnancy and the withdrawal of the mammal from milk is the period in which the biological clock system is constructed and ripens. Melatonin, which is produced in the pineal gland and secreted at night, is the mediator of the darkness signal to tissues, and night lighting interferes with its secretion and the rhythm of physiological activities.

The purpose of the study was to examine the effect of artificial lighting at night on the production of suckling calves. The calves were individually sized in two different lighting regimens until weaning, natural lighting (darkness at night) and artificial lighting at night. During this period, and for two consecutive years, in independent experiments, dry food intake, growth rate, heart rate rhythm, energy expenditure, and blood metabolites were monitored for biochemical analysis of metabolic activity. In addition, in order to examine the feasibility of a critical time window for long-term metabolic programming, we followed the production indices of experimental calves during the advanced stages of fattening.

The results show that artificial night lighting reduces the metabolic efficiency, which is reflected in the efficiency of food utilization which was lower than the natural lighting system. This trend was also maintained during the various stages of fattening, several months after the cessation of the lighting trigger at night, hinting that there is a critical period for metabolic programming. The metabolic profile of the plasma suggests that the lower metabolic efficiency of calves exposed to artificial lighting at night may result, at least in part, from a failure to channel energy into the Krebs cycle. Furthermore, we found in the metabolic profile evidence of peripheral interaction between metabolic tissues (muscle, fat) via "local" metabolites, which could eliminate (or at least affect) the synchronization between the low metabolic rate and the high energy expenditure of the calves exposed to artificial lighting at night.