ISSUE FOCUS 28 FEED & ADDITIVE MAGAZINE March 2022 ENHANCING EARLY LACTATION IN COWS THROUGH PLANT EXTRACTS "Milk production can be improved by promoting the “glucose sparing” effect and limiting gluconeogenesis inhibition. We started with the hypothesis that lower insulin levels could lead to a change in glucose distribution, directing more towards the mammary gland and thus improving milk production." Glucose metabolism fuels vital functions by regulating energy supply to cells and tissues. This process in ruminants is characterized by low glucose concentrations–and low insulin response– in peripheral tissues (Bell, Bauman, 1997; Sasaki 2002). Dairy cows have an even more challenging, and extremely intensive, physiological process: they require huge amounts of glucose for milk production and have only a short transition between pregnancy and lactation. GLUCOSE SUPPLY In monogastric species, the main glucose supply is absorbed in the intestines from ingested food, while ruminants depend mainly on glucose produced by liver gluconeogenesis. The primary glucogenic precursor is propionate, representing over 60% of the substrates, followed by lactate, with approximately 20%, then amino acids, minor volatile fatty acids (valerate, isobutyrate) and glycerol (Drackley et al., 2001). GLUCOSE UPTAKE: TISSUES VS. MAMMARY GLAND In order for glucose to be effectively absorbed by cells, it needs to be carried by glucose transporter (GLUT) molecules. There are 13 different types of GLUTs, each with a specific role and operating mode. GLUT1 molecules respond to basal glucose concentration and are found in all tissues throughout the body (De Koster and Opsomer, 2013). Among the various GLUT molecules, only GLUT4 respond to insulin stimulation, facilitating glucose uptake by skeletal muscle, adipose and heart tissues. Glucose uptake in the mammary gland is a special case: it is driven essentially by GLUT1 and GLUT8, and characterized by an absence of GLUT4. In other words, here, the glucose metabolism process is not regulated by insulin. In terms of quantity, the mammary gland absorbs over 50% of available glucose and this number can climb as high as 85% when production peaks. GLUCOSE SPARING At the end of gestation and into early lactation, dairy cows exhibit insulin resistance. In fact, the cow’s internal processes change tack to ensure a sufficient glucose supply to the calf by directing glucose to milk production and, at the same time, limiting glucose absorption in peripheral tissue (De Koster and Opsomer, 2013). This phenomenon is known as “glucose sparing”. Sebastien Constantin Business Development Manager Phytogenic Bioactives Pancosma
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