PLASMA PROTEINS IN MILK REPLACERS: WHAT DAIRY FARMERS SHOULD KNOW
- Marcos Marcondes
- 6 hours ago
- 2 min read
Choosing a milk replacer is one of the earliest and most important nutritional decisions made on a dairy farm. Because pre-weaned calves have an immature digestive system and limited immune defenses, both the type of protein and how that protein functions in the gut can influence calf health, treatment rates, and overall program success.
Most milk replacers rely on milk-derived proteins such as whey or milk protein concentrate. These ingredients are highly digestible and nutritionally consistent, but they have become increasingly expensive due to competition with the human food industry. As a result, some commercial milk replacers now include spray-dried plasma proteins in their protein blend.
Plasma proteins are derived from blood collected from healthy, inspected animals and processed under strict conditions to ensure safety while preserving functional components. Depending on the source, milk replacers may contain porcine plasma (SDPP) or bovine plasma (SDBP), typically as a partial replacement for whey rather than a complete substitute.
One reason plasma proteins differ from milk proteins is their amino acid profile, shown in the figure above. Compared with whole milk or whey protein, plasma proteins contain higher concentrations of amino acids such as arginine, glycine, and cysteine, which are involved in immune signaling, antioxidant defenses, and gut integrity. At the same time, plasma proteins contain lower levels of certain essential amino acids, particularly methionine and lysine, which are critical for tissue growth. For this reason, plasma-containing milk replacers must be carefully formulated and supplemented to avoid limiting growth.
Research in dairy calves suggests that milk replacers containing plasma proteins can improve health outcomes, including reductions in diarrhea, morbidity, and in some cases mortality. However, it is important to recognize that only a limited number of well-controlled calf studies are available, and responses have not been consistent across all trials. Some studies show clear health benefits, while others report minimal or no differences compared with whey-based formulations. This means plasma proteins should be viewed as a potential health-support tool, not a guaranteed solution.
Growth performance also varies. When amino acid balance is properly addressed, average daily gain is often similar to whey-based milk replacers. When formulations are not balanced, growth can be constrained. This reinforces the importance of evaluating the entire formulation, not just the presence or absence of plasma protein.
From a farm perspective, plasma proteins are not handled directly. The key decision is selecting a commercial milk replacer that aligns with farm challenges and goals. Products containing plasma proteins may be most useful under higher disease pressure or when reducing treatment rates is a priority.
Bottom line: Milk replacers containing plasma proteins offer a promising but still evolving nutritional strategy. While there is evidence of health benefits in calves, the current data set is limited, and more controlled research is needed. Farmers should view these products as part of a broader calf health program and continue to ask manufacturers and researchers for additional, transparent research to guide on-farm decisions.
̶ Marcos Marcondes
̶ Kyan Zamaniyan
SUNY Plattsburgh student intern
