Dr. Hernandez recently presented a Real Science Lecture series webinar on this topic. You can find the link at balchem.com/realscience.

Dr. Hernandez begins with an overview of how she came to study calcium metabolism in the mammary gland. Over the past number of years, she has worked on research to manipulate what’s happening in the mammary gland in the prepartum period to ensure adequate endocrine, nutritional, reproductive, and immunological status. (5:55)

The panelists discuss how “normal” has changed when it comes to transition cow health. Dr. Overton reminds listeners that 25 years ago, 6-8% of fresh cows in a herd having clinical milk fever was pretty typical. Now, we accept none of that. Subclinical hypocalcemia was not on the radar then, and we thought we had calcium all figured out. Dr. Hernandez’s work shows that this was not the case. She is pleased that a synergism of producers, veterinarians, and academics have been working together to understand the mechanisms of calcium metabolism to find solutions for individual farms based on their situation. (9:22)

Dr. Hernandez then discusses various interventions used in the industry, including low-potassium diets, negative DCAD diets, and zeolite clays. The clays are new to the US, and it seems that they work primarily through a phosphorus reduction mechanism and are best limited to feeding 10-14 days pre-calving. (18:14)

Dr. Overton asks Dr. Hernandez about a point in her webinar that cows are in negative calcium balance through 150-200 days in milk. She confirms that there are approximately 8.5 kilograms of calcium in the bones of a cow, but we don’t know how much of that she loses each lactation. Her dream scenario would be a CT scanner large enough to fit a dairy cow in to evaluate how her bones change throughout lactation. This leads to a discussion of whether or not we should be including higher rates of calcium in dairy cow diets. Dr. Hernandez would like to learn more about what’s happening with calcium absorption in the gut in real-time with endocrine status and stage of lactation, which is a challenging task. (23:17)

Co-host, Dr. Jeff Elliott, asks if the reason multiparous cows are more prone to milk fever is because they’re not as efficient at calcium resorption to the bone. Dr. Hernandez doesn’t have a definitive answer, but it could be due to less effective gut absorption with age, or it may be related to the influence of estrogen on bone density. She also mentions it could be endocrine-controlled or even stem cell-related.  (28:59)

Dr. Hernandez’s hypothesis has always been that you have to have a calcium decrease to trigger the negative feedback loop involved in calcium metabolism. Her advice is to wait until 48 hours to take a blood sample to analyze calcium. This aligns well with epidemiological research on the veterinarian side regarding delayed, persistent, transient, and normal hypocalcemic animals. (33:04)

Dr. Overton asks about a calcium-chelation study that Dr. Hernandez’s group conducted and whether or not chelating calcium had an impact on colostrum production. It did not in that experiment. Dr. Hernandez was surprised at how much chelating agent was needed to overcome the draw of the mammary gland, but that further underlines how much of a priority lactation is in metabolism. (41:45)

Scott asks both panelists their views on what the priority should be for research in this area. Dr. Hernandez’s ideas include more research on how zeolite clays work biologically, finding out what’s happening in the gut, mammary gland, and bone of a dairy cow at different stages of lactation. She emphasizes that research should be conducted at different stages rather than just extrapolating from one stage to another because lactation is incredibly dynamic. Dr. Overton seconded the idea of a better understanding of zeolite clays and their feeding recommendations, as well as research defining what happens to and where all the calcium is pulled from the bone during lactation. (45:32) 

In closing, Jeff, Tom, and Laura share their take-home thoughts. Jeff is excited to learn more about how zeolite clays work and if other products may come to the forefront to help in calcium metabolism management. Tom commends Laura on her work and how it has dovetailed so well with the epidemiological research from the veterinary side. Laura reminds listeners that the mammary gland is running the show and is thrilled that her work as a basic scientist is having an applied impact on the dairy industry. (51:17)

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