ARTICLE 80 FEED & ADDITIVE MAGAZINE September 2023 the transition period greatly influences the success of the remainder of the lactation of a cow. An obstacle frequently encountered by dairy cows during the initial stages of lactation is the excessive mobilization of fat tissue, which can lead to an amplified deposition of triacylglycerol within the liver. This condition is commonly referred to as hepatic lipidosis or fatty liver. While minor increments in hepatic triacylglycerol may not necessarily yield detrimental effects on subsequent performance, cows displaying a more pronounced lipidosis, ranging from moderate to excessive levels, experience compromised productivity and well-being. This situation also heightens the likelihood of premature culling. Approximately 40 to 45% of dairy cows develop moderate to severe hepatic lipidosis in the first 3 weeks of lactation. Recent research from the University of Florida published in the Journal of Dairy Science sheds new light on hepatic lipidosis and its impact on dairy cow performance2. In that specific cohort study, the authors examined a group of 329 cows to establish a connection between the concentration of hepatic triacylglycerol within the first week postpartum and its subsequent impact on health, production, and survival outcomes. The study's results demonstrated that once concentrations of hepatic triacylglycerol surpassed the range of 4 to 7%, the risk of disease occurrence escalated while productive performance declined. Though not establishing causality, these associations suggest that identification of strategies to reduce the accumulation of triacylglycerol in hepatic tissue may benefit dairy cows. One potential solution to alleviate fatty liver is to increase the export of triacylglycerols from the liver, requiring increased synthesis and assembly of very-low-density lipoproteins (VLDL). Choline, a nutrient identified in the 1850s, has subsequently been recognized as a required dietary component for mammals due to its pivotal role in facilitating the synthesis of various compounds. These include phospholipids, sphingolipids, and neurotransmitters. As it turns out, the synthesis and secretion of VLDL by the liver necessitates the presence of phospholipids, many of which fall under the category of phosphatidylcholines. Coincidentally, during the early 1920s when Canadian scientist Frederick Banting was in the process of discovering insulin, his experimental model involved dogs that had their pancreases removed. Remarkably, these dogs developed hepatic lipidosis, a phenomenon observed by one of Banting's students named Charles Best. Best, who later gained international recognition as a scientist, conducted further research and demonstrated that adding phosphatidylcholine to the diets of these depancreatized dogs mitigated the severity of lipidosis in their livers. These groundbreaking findings prompted an exploration of choline as an essential nutrient within the human diet.
RkJQdWJsaXNoZXIy MTUxNjkxNQ==