Recorded as part of the Real Science Lecture Series, this webinar features Dr. Bill Weiss, The Ohio State University. He discusses one of the most important—and often misunderstood—aspects of dairy nutrition: trace mineral requirements and practical formulation strategies for dairy cows.
The webinar opens with an overview of the key trace minerals discussed in modern dairy nutrition—copper, manganese, selenium, and zinc. It also introduces a practical framework for balancing mineral requirements, antagonisms, safety factors, and risk management. Dr. Weiss explains why simply meeting published requirements may not be enough. Moreover, he explains why nutritionists must account for biological variation, feed variation, and toxicity risk. (00:00 – 08:32)
The discussion then explores the strengths and limitations of the current NASEM factorial system for determining trace mineral requirements. Dr. Weiss reviews how maintenance, lactation, growth, and pregnancy demands contribute to mineral requirements. He also highlights the challenges associated with estimating absorption coefficients and translating requirements into practical feeding recommendations. (03:42 – 08:32)
Attention then turns to risk management and safety factors, including how nutritionists can balance the risk of deficiency against the risk of overfeeding. The presentation examines variation in mineral concentrations among feedstuffs and uncertainty in animal requirements. In addition, it covers practical strategies for incorporating safety margins into ration formulation. (08:32 – 16:24)
The webinar also addresses the often-overlooked issue of trace mineral variability in forages. Dr. Weiss discusses how soil contamination affects mineral analyses, and how to interpret unusually high trace mineral values. Furthermore, he explains why ash and iron concentrations can help distinguish between plant-derived minerals and soil contamination. (13:32 – 19:50)
A major focus of the presentation is mineral bioavailability and antagonism. Dr. Weiss reviews current knowledge surrounding absorption coefficients and relative availability studies. He covers sulfur antagonism, molybdenum interactions, and practical adjustments that nutritionists can make when sulfur concentrations are elevated in feed or water. (19:50 – 28:38)
The discussion then expands beyond traditional requirement models to examine emerging evidence. Trace minerals may influence rumen function, fiber digestion, intestinal health, and immunity independent of absorption. Thus, these non-factorial responses may help explain some of the performance benefits observed with different mineral sources. (28:39 – 32:21)
The webinar concludes with practical feeding recommendations for copper, manganese, selenium, and zinc. These include guidance on source selection, safety factors, sulfur adjustments, and why the dairy industry may need to reconsider heavy reliance on traditional sulfate mineral sources. (32:21 – 39:07)
A live audience Q&A follows, covering sulfur management, copper toxicity, selenium regulations, injectable trace minerals, trace mineral binders, mineral source selection, and practical troubleshooting on dairy operations. (41:35 – 1:08:03)
