Acetate Tolerance Test
by Tasha King and Joslyn Beard, PhD Students
Sometimes research procedures and production-based research don’t seem to go hand-in-hand. This summer one of the research protocols we used was an acetate tolerance test. Many of you are nodding your head and saying, “Cool, but what is an acetate tolerance test? And how does it affect me?”
What is an acetate tolerance test?
To conduct an acetate tolerance test, we insert a catheter into the jugular of a cow. A 20% acetic acid solution is then infused through the catheter at 2.75 mL/lb of cow body weight (BW). Blood samples are then taken from the jugular catheter at -1, 0, 1, 3, 5, 7, 10, 15, 30, 60, and 90 minutes relative to infusion. Blood samples are analyzed for acetate concentration level. Blood samples at -1 and 0 tell us the cow’s normal acetate concentration. Blood draws taken at the various time points after infusion determines the rate acetate is the leaving the bloodstream. Samples are analyzed to measure acetate concentration at various time points, which are entered into a calculation to see the rate acetate concentration decreases over time after infusion.
What does this tell us?
Acetate clearance rate can indicate oxidative metabolism, the process of converting food energy to energy utilized by the body. Therefore, a faster clearance rate represents a diet that is more balanced with nutrients (acetate to propionate or amino acids).
Cattle consuming forage-based diets produce a greater concentration of acetate to propionate. Acetate and propionate are volatile fatty acids (VFAs) produced by microorganisms in the rumen utilized by cattle as a source of energy. These VFAs are absorbed through the rumen wall to provide a large proportion of the cow’s energy requirements. Propionate is the only VFA that contributes to glucose production, providing between 27 and 54% of a cow’s glucose. Therefore, a shift in production to a greater concentration of acetate when consuming a forage-based diet, can affect how the cow synthesizes glucose.
How does this affect producers?
When acetate is abundant and glucose is insufficient , the efficiency of acetate utilization can decrease. Cows are either not getting enough energy from their diets or not utilizing the nutrients to the fullest potential. Supplementation strategies can facilitate this nutrient imbalance from the diet to improve cow grazing performance. For instance, this spring we conducted an acetate tolerance test on 3-year-old March calving cows receiving different supplementation treatments. Results will allow us to evaluate how supplementing varying levels of glucose precursors affects efficiency. Previous studies reported an increase in acetate clearance rate with supplementation of protein and propionate in sheep consuming forage-based diets. This provides the opportunity to develop supplementation strategies that will improve efficiency in forage utilization.
Conducting acetate tolerance tests in cows in different production settings allows us to evaluate the efficiency of nutrient utilization in cow-calf systems. Specifically in forage diets, acetate tolerance tests can determine the efficacy of those animals grazing different quality of forages along with implemented supplementation strategies. With the cow contributing 60 to 70% of energy costs of cattle from gestation to slaughter, efficiency and supplementation strategies will continue to be an important research focus.
