Monday, October 8, 2018

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, 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).

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.

Preliminary data

On June 15, the lambs ranged in weight from 26.4 to 102.4 lbs. and averaged 59.4 ± 13.4 lbs. The median weight was 60.4 lbs. Aged ranged fro...