Amino acids and the regulation of oxidative stress and immune function in dairy cattle

The periparturient period is one of the most challenging periods in dairy cows and encompasses the 3 wk prior to and 3 wk after parturition. The nutrient requirements of dairy cows change greatly during this time, largely due to the exponential growth of the gravid uterus and fetus, followed by the demands of lactation (NRC, 2001). Inflammation, oxidative stress, and adipose tissue mobilization lead to a reduction in dry matter intake (DMI) during the periparturient period. This reduction in DMI leads to a negative nutrient balance (NNB), with a shortfall in the nutrient availability for the cow and fetus (Ingvartsen and Andersen, 2000). Additionally, this reduction in DMI also increases the risk of metabolic (ketosis, fatty liver, milk fever) and immune- related disorders. The risk of these diseases, poor reproduction, and low efficiency is greatly impacted by the degree and length of time during which these systems (metabolism and immune response) remain out of balance (Loor et al., 2013a). Much of the research over the last decade have examined these biological interactions to identify the mechanisms behind the metabolic, physiologic, and immune adaptations that occur during the periparturient period (Loor et al., 2013a, 2013b; Roche et al., 2013; Bradford et al., 2015). It is now known that nutrients, such as amino acids (AA), serve functional roles outside of their use as building blocks for proteins and have immunomodulatory properties and interact through common biochemical pathways (e.g., 1-carbon metabolism; Figure 1). This concept has been well explored in nonruminant species (Li et al., 2007; Sikalidis, 2015). With nutritional management during the periparturient period continuing to be an active area of research, it is important to develop a system understanding the potential immunometabolic role that dietary AA may play during this period. Thus, the objective of this review is to provide an overview of physiological adaptations during the periparturient period, the immune system, and methods to assess immune function and oxidative stress. This will be followed by a more specific discussion of the immunometabolic roles of specific AA and their potential effects in dairy cow during the periparturient period. The potential effects of enhanced AA supply during the preweaning period will also be discussed briefly.