Phytonutrients as additives in ruminants: the unexpected target organ

Abstract Text:

Plants produce an extensive array of organic compounds derived from secondary metabolism that may be useful in animal nutrition because of their chemical makeup. These plant-derived bio-active compounds, also referred to as phytonutrients or phytobiotics, have been shown to express antimicrobial activities against a wide range of bacteria, yeast, and fungi and have been investigated as rumen modifiers in animal nutrition. Reports have concluded that phytonutrients may inhibit deamination of amino acids and methanogenesis in the rumen and shift fermentation towards propionate and butyrate. Responses, however, have been highly variable. Most of the experiments have been conducted in vitro. Although in vitro data are useful for screening purposes, the true value of phytonutrients for altering rumen microbial fermentation and ultimately enhancing animal production must be assessed in vivo and in long-term experiments. Some phytonutrients, due to their phenolic nature, are likely less susceptible to microbial degradation in the rumen and, similar to observations in monogastric species, may exhibit activities postruminally. For example, depending on dose, 15 to 30% of capsaicin from capsicum oleoresin administered intraruminally was estimated to escape ruminal degradation. Thus, phytonutrients such as garlic, curcumin, and capsicum, which have modulatory effects on both the innate and adaptive immune systems in monogastric animals, may exhibit similar properties in ruminants, if protected from ruminal fermentation. This opens a new area of research on the effects of phytonutrients on the immune system, physiology, and health of ruminant animals. Studies with dairy cows have shown that some phytonutrients delivered postruminally increase a subtype T cells in peripheral blood (CD4+) related to adaptive immunity. More recent reports indicated that capsicum increased energy-corrected milk yield and facilitated immune cells related to acute phase responses in high-producing dairy cows. In another study with dairy cows, a rumen-protected capsicum product tended to increase milk yield and increased feed efficiency. Increased insulin sensitivity during a glucose tolerance test in that study suggested that capsicum may redirect glucose for lactose synthesis and milk production. Data also suggest that capsicum may be enhancing fat mobilization in early lactation. Further research is needed to elucidate the effect and mode of action of phytonutrients on immune function and animal energetics. Overall, the effects of phytonutrients on immunity, health, and productivity of ruminant animals observed in short-term, crossover studies are encouraging, but need to be confirmed in long-term, production experiments.  

Keywords:

phytonutrients, postruminal effect, immune response, insulin sensitivity, dairy cow