Plaizier, J.C. and Kennedy, A.D., Department of Animal Science, University of Manitoba (Winnipeg, MB).
In order to ensure high productivity and the good health of dairy cows, daily feed intake and the utilization of ingested nutrients need to be optimized. This is of special significance during early lactation when increases in feed intake lag behind increases in nutrient requirements. On most Canadian dairy farms, the herd manager determines the timing of feeding. Feeding time affects eating patterns, as eating is stimulated by the provision of fresh feed. Circadian rhythms, which are entrained by environmental cues such as light, liver function, metabolic hormones, nutrient metabolism and glucose tolerance have been identified in many animal species and humans. Such rhythms are expected to also occur in cattle. Circadian rhythms are difficult to manipulate. It is possible that some feeding practices result in a sub-optimal relationship between exogenous rhythms that are determined by time of feeding and circadian rhythms. This will have a negative impact on animal productivity and health. The proposed project will investigate diurnal rhythms and patterns in feed intake, rumen fluid composition, blood composition, metabolic hormones and liver function. By varying the time of feeding (morning vs. evening) and diet composition (inclusion rates of concentrated and rumen degradable protein), the project will determine if these rhythms and patterns are circadian or exogenous, and how they are affected by exogenous factors. The results will be used for the development of feeding strategies that increase feed intake and the utilization of ingested nutrients, and thereby improve the health and productivity of Canadian dairy cows.