Final Results: Growth & Carcass

Data from the 2018 comparison study of ram, wether, and short-scrotum lambs were statistically analyzed by Dr. Dahlia O'Brien at Virginia State University.

The short-scrotum rams had heavier final weights than the wether lambs: 117.7  ± 2.0 vs. 110.4 ± 1.7 lbs. Ram lambs were intermediate:  113.4 ± 2.0 lbs. Short scrotum lambs had greater average daily gain (ADG) than wether lambs: 0.549 ± 0.02 lb/d vs. 0.482 ± 0.02 lb/d. Ram lambs were intermediate: 0.510 ± 0.02 lb/d.

There was a tendency for sex to influence rib eye area (REA), as determined by ultrasound. Wether lambs tended to have smaller REA compared to ram and short-scrotum lambs. However, when REA was adjusted to a common weight (100 lbs.), there was no difference between the sexes. Sex did not influence other ultrasonic measurements: backfat (BF) and loin depth.

Actual carcass measurements showed wethers to be fatter, having greater BF (0.15 ± 0.01 in.), thus yield grade (1.9 ± 0.1). Ram lambs produced the leanest carcasses (0.11 ± 0.01 in. and 1.5 ± 0.1, respectively). The short-scrotum lambs were intermediate (0.12 ± 0.01 in. and 1.6 ± 0.1, respectively). There was a tendency for sex to influence hot carcass weight (HCW), with short-scrotum lambs tending to have the heaviest HCW.

Sex did not affect dressing percentage (49.2 ± 0.3 percent), body wall thickness (0.60 ± 0.2 in.) REA (3.0 ± 0.1 sq. in.), REA adjusted to 100 lbs. (2.7 ± 0.04 sq.in.), percent kidney and heart fat (KH; 1.9 ± 0.1 percent), leg conformation score (12.2 ± 0.1), or percent boneless closely trimmed retail cuts (BCTRC; 49.9 ± 0.1 percent).

Conclusion
Compared to wether lambs, short-scrotum lambs showed superior growth and produced leaner carcasses. The short-scrotum procedure may offer a viable alternative to traditional castration.

Ultrasound vs. actual carcass measurements
Actual BF measurements were highly correlated with ultrasound BF measurements (r=0.7). REA measurements were also highly correlated (r=0.7) in wether and ram lambs. However, there was not a high correlation in REA measurements in the short scrotum lambs (r=0.4). Correlation coefficients (r values) vary from -1 to 1. The closer r is to -1 or 1, the more closely the variables are related.Closer to 0, the opposite is true.