By Selby Boerman, M.S. Graduate Student
One essential prerequisite to making supplement decisions is obtaining an accurate forage quality analysis that cattle are consuming. Forage quality testing provides an understanding of what nutritional deficiencies are present as well as when they occur. At Gudmundsen Sandhills Lab, we regularly use esophageal fistulated cows to collect samples for forage analysis.
What is esophageal fistulation?
An esophageal fistula is a similar concept to a rumen cannula. It provides an access point into the animal’s digestive tract, permitting researchers to collect a diet sample. For esophageal fistulation, a surgical procedure provides an access point to the animal’s esophagus through the neck. This allows the diet to be diverted and collected rather than swallowed into the rumen. When the cow is not being used for diet collections, a plug fitted across the opening permits the animal to maintain normal functions like eating, drinking, and ruminating. On the day of diet collections, the plug is removed, and canvas bags are strapped around the cow’s neck. The cow grazes for about 20 - 30 minutes or until an adequate sample quantity has been collected in the bag. The sample is then freeze dried and can be analyzed for forage quality. Our cows are halter broken at a young age and adjust to the routine due to frequent handling.
How does this collection technique relate to producers?
In a producer setting, forage quality is commonly assessed from hand-clipped samples in the pasture. However, these samples represent the quality that is available for consumption, not necessarily what the cattle are selecting. Esophageal diet samples are unique because they provide an accurate picture of what is actually being consumed. Another available forage assessment technique uses NIRS (near infrared spectroscopy) predictions based on fecal samples. While it may be convenient to grab fecal samples to send in for analysis, there are numerous factors associated with this method that can lead to variable and misleading results. To compare result difference of forage quality estimation, see: https://beef.unl.edu/documents/2019-beef-report/MP106_pg053_Johnston_et_al.pdf.
How can this information be applied by producers?
Animal selection preferences will vary depending on available forage quality. Under low quality conditions, cattle will select a higher quality diet than the average hand-clipped sample. The opposite is true in high forage quality environments, with cattle selecting for a lower quality average. By understanding how selection preferences change in different quality environments, producers can more effectively match supplementation programs to fill nutritional deficiencies.
Esophageal-fistulated cow collects a diet sample at GSL