Ultrasound Results: Unanalyzed Data

The lambs were scanned on August 6 to determine carcass characteristics.The short-scrotum lambs (n=17) scanned with slightly larger rib eye areas (1.88 in²) than the ram (n=19) or wether (n=23) lambs (1.85 and 1.70 in², respectively) but when rib eye area was adjusted to a common weight (100 lbs), they had slightly smaller rib eye areas (1.54 in²⁾, and there were no differences between the ram and wether lambs (1.58 in²⁾. The ram and short-scrotum lambs had deeper loins compared to the wether lambs (0.99 vs. 0.93 inches).

For the 59 lambs scanned, the average rib eye measurement was 1.8 in² or 1.59 in² per 100-lb. live weight. It is worth noting that the actual carcass measurements were considerably higher.  For the 51 carcasses measured, the average rib eye measurement was 3.04 in² or 2.70 in² 100-lb. live weight.

Group	No.	Live Wt., lbs.	REA, in2	REA per cwt	Loin depth, in.	Backfat, in.
Ram	19	117.5	1.85	1.58	0.99	0.086
Short-scrotum	17	116.5	1.88	1.54	0.99	0.088
Wether	23	104.4	1.70	1.58	0.93	0.102
ALL	59	113.3	1.80	1.59	1.00	0.090

It is not yet known if any of the differences are statistically significant.

According to scanning, the wether lambs had a little more backfat (0.102 inches) than the ram and short-scrotum lambs (0.086 and 0.088 inches, respectively). Average backfat for the 59 lambs scanned was 0.09 inches, compared to 0.128 for the actual carcass measurements (n=51). All carcass measurements (ultrasound and actual) were taken between the 12th and 13th ribs. Rib eye was measured on the carcass using a plastic grid (Iowa State University), where 20 dots are equal to 1 in².

The moderate level of nutrition (pasture, plus some grain) provided did not result in the majority of lambs reaching market readiness. Lambs with less than 0.8 inches of backfat fail to qualify for the USDA Choice grade. The yield grade of a lamb with 0.9 inches of backfat is only 1.3 Yield grade 1 lambs are considered too thin and generally do not receive the price premiums than yield grade 2 and 3 lambs receive.