Optimizing Starch Nutrition for Rhythmic Dairy Cattle: The Sustaining Economic and Environmental Challenges of Today's Industry

Starch makes up a considerable portion of dairy diets (up to >30%). Thus, starch utilization efficiency im-mensely affects rumen function, animal performance and health, farm economics, and environmental qual-ity. It is crucial to take into account the ruminal digestion rhythms of different cereals when formulating diets for optimal dry matter intake (DMI), milk production, and animal health. Optimizing the physical processing of cereal grains is required for maximal microbial protein yield and minimal sub-acute rumen acidosis (SARA). Physical processing of barley and corn grains, as the two most popular cereals in dairy diets, needs more contemplation towards synchronizing rhythms of starch and protein fermentation in the rumen. Optimizing the dietary inclusion rates of cereal grains and starch has been a key missing part in improving nutrient efficiency and gastrointestinal health and integrity. Global guidelines need to be devel-oped to precisely address optimal dietary inclusion rates of different cereal grains. Setting such guidelines becomes more important when high-starch corn silage is major forage in the diet. Monitoring circadian rhythms of rumen fermentation when differently processed cereal grains are fed will allow developing feed-ing strategies that minimize the occurrence of SARA. The minimized SARA will enable decreasing nutrient loss across portal drained viscera (PDV) and splanchnic tissues. An innovative global philosophy is being developed to rely more on oil seeds and less on starchy grains in feeding dairy cows. To practically prevent SARA, physical processing can be partly effective, but essentially the dietary inclusion rate of differently processed cereal grains needs to be optimized. Lessons are to be learnt from human nutrition. Although metabolism differs between ruminants and non-ruminants, carbohydrates especially sugars and starch are under scrutiny and need to be limited in human diets to minimize risks from obesity and diabetes. Educa-tion, education and education is the final frontier for success in improving rumen and animal health as far as starch nutrition is concerned. For now, it is recommended to feed dairy cows no more than 25-28% starch (DM based). Future research will focus on establishing optimal dietary inclusion rates of differently proc-essed barley and corn/sorghum grains for cows of different production levels and lactation stages. Rumen fermentation circadian rhythmicity and environmental considerations including decreased methane produc-tion and urinary and fecal nitrogen excretion will be discussed.