Electronic Detection of Bolus Swallowing to Measure Forage Intake of Grazing Livestock1
- J. R. Forwood,
- M. M. Hulse and
- J. L. Ortbals2
Understanding forage intake of grazing livestock is critical to understanding their level of performance. Unfortunately, current methods of measuring intake of free-roaming ruminants are laborious and indirect. To overcome these problems, two devices were tested with confined animals to measure passage of boli within the esophagus of cattle (Bos taurus) as an estimate of intake. The first, labeled a conductivity transducing cannula (CTC), consisted of electrodes mounted slightly above the sleeve on a conventional metal sleevetype esophageal cannula so they would contact material passing within the esophagus. A stable current source allowed data to be transmitted to a strip chart recorder via coaxial cable. The second device, a pressure transducing cannula (PTC), involved a flexible water-filled tube mounted on the conventional cannula sleeve. Material passing within the esophagus exerted pressure on the tube. A pressure transducer converted water pressure to an electrical signal which was received by a strip chart recorder. The PTC device was discarded for lack of accuracy and portability. The CTC device was modified and inserted in year-old esophageally fistulated steers fed known amounts of forage in confinement. The cannula accurately signaled forage swallowing events. The CTC device appears to distinguish boli swallowing from eructation and water swallowing. The CTC device also shows a positive relationship between number of swallows and dry matter intake of differing levels of orchardgrass hay (r2 = 0.81) and chopped big bluestem grass (r2 = 0.99).Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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