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Renco lean indicator
All hogs have a genetic potential for three layers of fat. As the hog grows, fat is deposited in the top two layers. The third
layer will not have a fat deposit until later in the hog's life. When the third layer fills with fat, you can measure the dept of
the three layers of fat. Do not attempt to measure three layers of fat over the shoulder or the ham. The resulting
measurements may not be accurate.
1. How to use the Renco lean indicator
1.
Use the Renco charger supplied to charge the lean indicator battery for about 12 hours before the first use.
Charging the battery after each day's use for three times longer than the time it was used will insure long battery life. When
the battery becomes discharged the display will either begin flashing, or remain off.
2.
The most accurate spot in which to measure backfat can be found by walking your fingers forward along the hog's
flank until you can feel the last rib, then place the probe on this site B, 65mm (2.6 inches) from either side of the backbone.
Saturate the skin with a light oil, like scan gel or paraffin oil on the spot where apply the lean indicator. Insufficient amount
of fluids is the most common cause for inaccurate readings. Good skin contact with the probe and skin must be made for
the ultrasound to enter the hog and reflect back to the lean indicator.
To make a measurement, turn the instrument on by pressing the POWER push bottun. Apply the probe to the test site, and
using a gentle pressing/twisting action, move the probe slightly to force out any air bubbles between the skin and probe. It
is very important that the probe be kept perpendicular to the back. Errors may result if probe is at an angle. Many have found
that probe is most easily managed if held between the index and middle fingers.
When the READ light, to the left of the main display, lights the reading is complete. If the READ light does not come on, then
skin contact is poor. Use more oil. Make a greater effort to remove air bubbles. Be sure probe is flat against the skin and
perpendicular to the animal's back. Consistency of probe placement is of great importance in obtaining comparative
measurements.
3.
Turn the instrument on. The red READ indicator will light when the lean indicator detects and measures, the total
of the fat layers. The lean indicator attempts a new measurement several times each second. A reading will remain until a
new, different reading is detected.
Small irregularities in the fat may sometimes block the beam of sound, causing the lean indicator to give low readings.
Moving the probe slightly will allow the beam to bypass, and the correct reading to appear. (Always keep the probe
perpendicular to the animal's back)
Fat layers are not uniformly thick. Thus, averaging two or three readings at adjacent sites insures greatest accuracy. The
initial reading that occurs when the POWER button is pressed has no meaning. Measurement occurs only when the READ
indicator is lit. Accuracy of the reading is ±1mm. Usable range is from 5mm to 35 mm.
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Older animals with tough dead skin will require extra effort to obtain a good clean probe contact with the
underlying live tissue. If necessary, remove the hair at the site. Then wet the skin with hot water. Next, apply light oil and
allow it to penetrate the skin a minute or two before measuring. Young hogs, with softer skin, generally do not require
much site preparation.
2. Why only measure the last rib?
Only site B (the last rib) will give an accurate reading of the three layers of fat. The lean indicator measures the skin and the
first two or three layers of fat. Many hogs have the thin layer of third layer fat at an early age. As they increase in weight
and age, the third layers become thicker and more wide spread over the body. Site B is the location normally used in metal
ruler probing, and shows the best correlation with overall carcass yield. Because of the trapezius muscle at the shoulder
(false lean), measurement at site C is more diffcult and inconsistent. (True for both ruler and ultrasound devices.) Site A will
give accurate measurement for two layers of fat but may not give an accurate measurement for three layers of fat due to
the muscle tissue below the fat layers.
Values obtained using ultrasonic devices on live animals will generally measure 10% less than those measured at slaughter
because measurement sites are somewhat different and the slaughtered carcass is disorted.
For comparison of backfat values between animals of different weights, the readings should be adjusted to a "standard"
100kg (220 lb.) hog. Tables of adjustment factors are readily available from most extension services. A convenient formula
for the adjustment which is valid for a 100kg ±15kg hog: FAT READING x FACTOR
FACTOR = 1.275 + ((.0033(weight)) – (.0000605(weight)²))
Renco lean indicator
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