Circadian Patterns of Feed Intake and Milk Composition Variability

The dairy cow has a well-recognized natural daily pattern of feed intake and milk synthesis, but regulation of these circadian rhythms has not been well described in the literature or well considered in current dairy management. Even when a total mixed ration (TMR) is fed, ruminal fermentation varies due to circadian variation in feed consumption, resulting in more fermentable substrate in the rumen during the high intake period of the day. We propose that “circadian feeding and management strategies” can improve milk yield and efficiency by stabilizing rumen fermentation and temporally matching nutrient absorption and mammary requirements, thereby altering the interactions between central and peripheral circadian clocks. Although we are early in our research efforts, we have demonstrated that there is a daily pattern to milk fat and protein synthesis that is dependent on the timing of nutrient intake.