ARTICLE FEED & ADDITIVE MAGAZINE November 2022 75 have increased incidence of metabolic diseases (retained fetal membranes, milk fever, and displaced abomasum) as well as poorer reproductive performance. It is not surprising therefore that fatty liver has a significant economic impact on dairies. It is very important to recognize that NEFA mobilization is essential. Around parturition, all cows experience negative energy balance and mobilize lipids, resulting in increase NEFA in the blood. Without increase blood NEFA there would be less glucose available to the udder for lactose synthesis and milk production would suffer. The key to a smooth transition and high peak milks is to effectively manage the ability of the liver to handle the NEFA surge at parturition, not to prevent mobilization. Feeding and management strategies exist to help mediate declines in prepartum DMI and minimize postpartum negative energy balance and NEFA mobilization during transition, but, these are beyond the scope of this paper. Regardless of those strategies one clearly effective tool is to feed Rumen Protected Choline. A major functionality of choline is as a precursor for phosphatidylcholine which in turn is a key structural component of VLDL. The rate of VLDL export (and therefore fat export from the liver) depends on the rate of phosphatidylcholine synthesis (Cole et al. 2011). The classic symptom of choline deficiency in many species is fatty liver. It is not surprising then that supplementation of rumen protected choline to cows can help alleviate the degree of fat accumulation in the liver (Cooke et al., 2007; Zom et al., 2011; Zenobi et al., 2018a). Figure 1 shows the results of supplementation of rumen protected choline (ReaShure) at graded levels on liver fat accumulation in restricted fed dry cows (Zenobi et al., 2018a). As choline ion increased liver fat accumulation decreased linearly. Lima et al. (2012) reported on two studies conducted on large commercial dairies. In the first study 369 animals (primiparous and multiparous) were utilized. Rumen protected choline was fed for 25 days prepartum to 80 days postpartum. Clinical ketosis, mastitis (cases/cow), morbidity, IV dextrose treatments and oral propylene glycol and calcium propionate treatments were all significantly reduced and there was a strong tendency for a decrease in mastitis incidence when choline was supplemented. There was no interaction between parity and treatment. In the second study with heifers, rumen protected choline was only fed for 22 days prepartum. Choline supplemented heifers had significantly lower incidence rate of retained fetal membrane (RP) and fewer mastitis cases per heifer. Metritis and fever incidence rates were actually higher in heifers fed choline. It is important to remember supplementation with choline stopped at calving in the heifer study and potential added health benefits of extended supplementation postpartum cannot be assessed.
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