INCREASING EFFICIENCY OF MILK SYNTHESIS BY UNDERSTANDING THE REGULATION OF THE CIRCADIAN RHYTHM OF THE MAMMARY GLAND

Most physiological processes exhibit daily or "circadian" rhythms that improve fitness by synchronizing processes so that they occur at the optimum time of day and by allowing anticipation of changes over the day. Disruption of these rhythms has significant implications for metabolism and health in rodents and humans. We hypothesize that circadian rhythms in the cow are entrained by cues such as feeding time and nutrient absorption. However, we expect that many feeding and management schedules disrupt circadian rhythms in the cow, resulting in reduced milk yield and feed efficiency. Specifically we will focus on: 1) the flexibility of mammary circadian timekeepers and their responsiveness to the timing of feed intake and 2) what nutritional and hormonal cues regulate the daily rhythms of milk synthesis in the whole animal and directly in mammary epithelial cells. We expect to elucidate the nutritional factors regulating the daily rhythm of milk synthesis and the mammary biological clock to understand the impact of nutrition on the rhythms of the mammary gland. Our long-term goal is to develop a complete understanding of the circadian regulation of intake and milk synthesis and apply this knowledge to develop management strategies that improve productivity and animal well-being while simultaneously optimizing economic return and sustainability to producers. These investigations provide the foundation to develop nutrition and management strategies considering circadian rhythms for managing dairy cows and provide opportunities for new gains in productivity and efficiency.