ARTICLE FEED & ADDITIVE MAGAZINE September 2023 79 Dairy cows are truly remarkable creatures. Consider the rapid transformation of a modern Holstein cow, going from zero to producing as many as 50 kilograms of energy-corrected milk per day in just 3 to 4 weeks of lactation. Such incredible production demands dynamic and integrated adaptations in multiple tissues to cope with the nutrient shifts during lactation onset. Research conducted by Chris Reynolds at the University of Reading in the United Kingdom revealed that during the initial 3 weeks of lactation, there is a notable augmentation in hepatic blood flow. This flow rate rises from around 1.100 liters per hour to 2.220 liters per hour. Remarkably, this shift occurs in conjunction with a twofold elevation in oxygen consumption by the splanchnic tissues over the same period1. These alterations mirror the escalation in both dry matter intake and nutrient absorption within the gastrointestinal tract. This transformation parallels the heightened demand for essential components like glucose, amino acids, and fatty acids. These elements are crucial for the synthesis of milk by the mammary gland. During the first 4 to 8 weeks of lactation, dairy cows experience negative nutrient balance, concurrent with increased susceptibility to diseases. Approximately 30 to 35% of the dairy cows are anticipated to experience a clinical disease event in the first month or two postpartum, and success during “Substantial progress has been made on our understanding of choline as a nutrient for dairy cows. The introduction of rumen-protected products containing choline chloride has facilitated research into various aspects of choline's mode of action within intermediary lipid metabolism in dairy cows. This advancement has also enabled the exploration of crucial questions regarding choline's role in maintaining hepatic health and enhancing productive performance during the critical transition period for cows.” CHOLINE: A REQUIRED NUTRIENT FOR TRANSITION DAIRY COWS Dr José E.P. Santos Department of Animal Sciences University of Florida Usman Arshad Department of Animal & Dairy Sciences University of Wisconsin-Madison
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