Subdermal Fat Determined by Ultrasound and Electrical Conductivity, and Its Relationship to Body Condition Score of Dairy Cows
Body condition score (BCS), a very useful field tool for estimation of changes in body tissue reserves is time consuming and subjective. The relationship between body condition score and subdermal fat (SFAT) was determined biweekly as potential for development of a low cost, portable digital ultrasonic or conductivity sensor for BCS. Digitized scans of subdermal fat were determined from two ultrasonic units equipped with 3.5/5.0 (Pie Medical), and 7.5 (Modified Sonomed) MHZ transducers. Cows were implanted with pacemaker probes at rib, loin, and rump to determine conductivity of subdermal tissue. Conductivity of SFAT measured three times a week read 51.1 +/- 2.5 before and 50.2 +/- 0.6 mS/cm after calving. At BCS of 2.58, least square means of subdermal fat were: rib 6.0; loin 5.5; rump 5.3 mm, obtained with Pie Medical, and rib 5.2; loin 5.6; rump 5.5 mm. obtained with modified Sonomed ultrasound. Regression of BCS from subdermal fat at rib, loin, and rump sites along lactation showed significant R2 values of 0.36, 0.41, 0.33 with Pie Medical, and 0.68, 0.69, 0.59 with Sonomed ultrasound. Due to machine differences in SFAT measurements, echo genic, point targets of known distances apart embedded in a multipurpose phantom of tissue mimicking material were scanned with the two ultrasonic units to determine relative machine errors. The difficulty to diagnose differences in ultrasonic machine resolutions could be attributed to the non tissue-specific coded velocity and density of each ultrasonic unit. Although slight differences existed, all body sites could be used to predict BCS. Digitized cross sections of ultrasonic scans obtained with modified Sonomed, followed by identification and measurement of subdermal fat via on algorithm for analysis of peak values, was a promising method for the development of a sensor for scoring body condition it dairy cattle. The method removed most of the subjectivity of BCS, but substantial development is needed to reduce time required for data collection, before expecting a commercial ultrasonic sensor for scoring cows automatically. Determination of body condition score from electrical conductivity of subdermal fat thickness needs further research at higher frequency ranges.
Agriculture, Food Science and Technology
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign