ISSUE FOCUS FEED & ADDITIVE MAGAZINE May 2024 39 ed with rumen-protected choline and fed colostrum from similarly treated dams displayed improved immunoglobulin absorption. These same calves exhibited reduced inflammatory responses when exposed to bacterial compounds simulating infectious diseases." The University of Florida research also showed that calves from supplemented dams grew faster than calves not exposed to choline in utero. Researchers saw an improvement in growth of about 0,05 kg per day, resulting in heifers being 36 kg heavier at first calving (see Figure 1). This initial growth also resulted in heifers that produced 524 kg more milk during their first lactation. He adds that the effects of specific nutrients, like choline, on calves are still emerging, with considerable room for further exploration compared to other well-established research areas. Dr. Heather White from the University of Wisconsin – Madison, who recently concluded a research project on prepartum feeding rates of rumen-protected choline, provides insights into the methylation process. Methylation involves the attachment of a methyl group to DNA's histone, the structural component around which DNA is wound, determining its level of compaction. "In essence, if the DNA is tightly wound, it remains unread at a specific moment," White explains. "Methylation can activate or deactivate genes, and some methylation modifications endure throughout the offspring's lifetime." The process of DNA methylation, along with other aspects of epigenetics, can be significantly influenced by the dam's nutrition during gestation, shaping the calf's gene expression. In the context of dairy cattle, rumen-protected choline supplementation has been studied for more than 25 years, primarily during the prepartum and early postpartum phases. Cows consistently respond positively to this supplementation, resulting in increased milk production, energy-corrected milk production, and dry matter intake. Furthermore, the latest research demonstrates that calves born to these choline supplemented cows also experience enduring benefits in terms of growth and overall health. Due to choline's sensitivity to the rumen environment, it necessitates protective measures to avoid degradation within the cow's rumen. Encapsulation is a method that shields the nutrient from the harsh rumen microbial environment, enabling it to pass through the rumen intact and ultimately be absorbed and utilized in the small intestine. In the absence of supplemental choline, many cows fall short in choline levels. White emphasizes, "Choline acts as a methyl donor. We understand its role as a methyl donor in adult animals. When we provide it during pregnancy, it may contribute to the methylation of fetal DNA, potentially explaining its lasting influence on calf growth beyond birth." White also highlights that several choline studies have extended their observation period to 100 days or more postpartum, as opposed to the typical 21-day window, consistently revealing positive responses in milk production that endure well into the distant postpartum period. 2018 Study Zenobi et al., 2018a Zenobi et al., 2022 (personal communication) P = 0,06 Average Daily Gain, kg/day 0,85 0,80 0,75 0,70 0,65 0,60 2022 Study 0,80 0,85 0,77 0,82 Dams not fed ReaShure Dams fed ReaShure Figure 1. Summary of average daily gains for Holstein heifers through 350 days from two independent studies
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