ARTICLE 74 FEED & ADDITIVE MAGAZINE November 2025 Freeze/thaw Stability A less obvious and often overlooked issue is freezethaw stability of lipid encapsulates. When lipid encapsulates are frozen and then thawed, the coating can expand and contract. This allows water to penetrate during storage or in the rumen, resulting in a loss of nutrient protection. Some lipid encapsulates are not freeze/thaw stable. Temperature Another often-overlooked factor that can affect coating integrity is temperature. Feed encapsulates are not robust enough to withstand the temperatures and pressures associated with pelleting. High temperatures designed to gelatinize starch and deliver a harder pellet will damage encapsulates, adversely affecting nutrient payload protection. In addition, the pressure associated with pelleting can crack or fracture encapsulates, further degrading nutrient protection. RUMEN PROTECTION Nutrients in unprotected form such as choline, niacin, lysine and methionine are almost completely degraded in the rumen via microbial fermentation (>87%), potentially leaving very little nutrient available for intestinal digestion and absorption. Rumen protection refers to the encapsulation system’s ability to protect a nutrient from degradation in the rumen so that it can pass into the abomasum and small intestine for utilization by the animal. Ruminal degradation is often determined in situ or in vitro. In situ studies suspend dacron bags containing the rumen protected products inside the rumen of a cannulated cow to measure stability of the encapsulate. In vitro studies use lab-based procedures with either collected rumen fluid or solutions that mimic the rumen environment to determine degradation. In either case, digestibility of the encapsulates can be measured at a single time point or at multiple points in time. INTESTINAL RELEASE/BIOAVAILABILITY The key to making an efficacious encapsulate is to create a product that not only resists ruminal and environmental degradation, but can then be released and digested in the abomasum and small intestine. Developing an encapsulated product with a high level of durability and resists microbial degradation in the rumen may come at the expense of intestinal digestibility. Depending on the nutrient of interest, in vivo and in vitro methodologies can be utilized to test an encapsulate for intestinal release. In general, in vitro methodologies that mimic the digestive system of an animal are relatively quick and inexpensive but only provide relative rankings in terms of bioavailability. However, in vivo methodologies performed within the animal, such as stable isotope and selenomethionine, provide more accurate and precise bioavailability estimates for encapsulated nutrients. BIOLOGICAL PERFORMANCE Biological performance observed in the animal once the encapsulate is fed becomes the ultimate and final test of efficacy. Responses observed may be related, but not limited, to milk and components, health and reproduction as well as offspring health and growth. These responses will also vary depending on the nutrient that was encapsulated. Positive biological responses are observed when all three components of a well-made encapsulate are met (durability, rumen stability and intestinal release). SUMMARY Encapsulated nutrients can provide consistent, reliable and cost-effective alternatives to traditional feedstuffs. However, how well these products perform in terms of durability, rumen stability, intestinal release and, ultimately, cow performance vary depending on the encapsulation and manufacturing process utilized. Thus, it is critical that in situ, in vitro and in vivo research be used to evaluate an encapsulate’s performance in each of these metrics. The ultimate measure of an encapsulated nutrient is the cost per unit of bioavailable nutrient. This is a function of the cost, durability, rumen protection and intestinal digestibility. To get the best value, just ask a few simple questions: • Is the product durable enough to withstand feed/ mineral mixing, time in a TMR, manufacturing and
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