The endocannabinoid system in controlling feed intake and energy balance during the transition from late pregnancy to early lactation of dairy cows

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During the transition from late pregnancy to early lactation, high producing dairy cows usually experience a negative energy balance due to insufficient increase in feed intake and the enormous energy requirements for milk production. As a consequence, mothers mobilize their body fat reserves, but as more fat is usually mobilized the lower is the postparturient increase in feed intake. Dams would benefit from an increased level of feed intake and reduced body fat mobilization to minimize deposition of mobilized fat in liver. So far, the effect of numerous metabolites and hormones on the reduction of feed intake has been described in literature, however, until today there is only marginal knowledge on endogenous signals significantly promoting feed intake of ruminants during the early lactation period. Prominent signaling stimulating feed intake while confining lipolysis is triggered through endocannabinoids. Among this substance class, N-arachidonoylethanolamine (AEA) has been described to exert one of the strongest feed intake stimulating effects. Therefore, the objective of the present project is to test the hypotheses that: 1. Endocannabinoids signal to promote feed intake postpartum, but high extent of fat mobilisation stimulate the degradation of endocannabinoids and thus their orexigenic action. 2. Intraperitoneal AEA administration improves energy balance of early lactating dairy cows by increasing feed intake involving increased hypothalamic orexigenic signaling and stimulation of lingual sweat taste receptors. 3. Peripheral AEA administration reduces lipolysis and increases lipogenesis in adipose tissue and mammary gland, thereby reducing liver fat content in early lactation. By pursuing these aims we expect to elucidate the physiological regulation of endocannabinoid-mediated signaling during the transition from late pregnancy to early lactation, and to depict ways of improving energy balance and health status of early lactating dairy cows.