Thursday, October 10, 2019

Lamb Served in Dining Halls

For the second year in a row, the lamb from our comparison study of ram, wether, and short-scrotum lambs was served in the dining halls at the University of Maryland College Park. On October 2nd, a Harvest Festival was held to promote local food, including the lamb. Sliced leg of lamb and lamb burgers were served to students, faculty, and visitors.

Results: Growth and Carcass Data

This was the second year of a 2-year study comparing the growth and carcass characteristics of (intact) ram, wether, and short-scrotum lambs from a commercial sheep dairy in Maryland.

After weaning, lambs were grazed and fed for 107-d at the University of Maryland's Western Maryland Research & Education Center in Keedysville. At the end of the study, they were harvested to collect carcass data.  Data was collected on 21 rams, 25 wethers, and 18 short-scrotum lambs. 

Ram lambs had the heaviest final weights and highest ADG. The wether lambs had the lightest final weights and lowest ADG.  Short scrotum lambs were not statistically different from ram lambs. Ram lambs had the heaviest hot and cold carcass weights. Wethers had the lightest. Short scrotum lambs were intermediate.

A 4% pencil shrink was applied to the lambs to calculate dressing percentage. Dressing percentage was determined by dividing hot carcass weight (HCW) by "shrunk" live weight. Wether lambs had the highest dressing percentage. Ram and short scrotum lambs were not statistically different.

Rib eyes (REA) from the ram carcasses were largest. Wethers had the smallest rib eyes. Short scrotum lambs were intermediate. However, when adjusted to a common weight (of 100 lbs), there were no statistical differences in rib eye area among treatment groups.

Wethers produced the fattest carcasses, as evidenced by greater back fat (BF) and yield grade (YG). Short scrotum lambs had more back fat and higher yield grades than ram lambs, but the differences were not statistically significant. At the same time, none of the lambs carried excess back fat or internal fat.

Sex did not affect body wall thickness (BWT), percent kidney and heart fat (KH), or leg conformation score (LC). Ram carcasses yielded a higher percentage of boneless closely trimmed retail cuts (BCTRC) than wether lambs. Short scrotum lambs were intermediate. BCTRC is calculated using the following formula: 49.936 - (0.0848 x HCW) - (4.376 x BF) - (3.530 x BW) + (2.456 x REA).

Due to inadequate backfat, seven ram carcasses failed to quality for the USDA Choice grade, as there is a minimum requirement of 0.08 inches. Two short scrotum carcasses failed to grade. All of the wether carcasses graded Choice or above.  Despite the leanness of the carcasses, there was evidence of quality in all the carcasses: maturity, flank streaking, and conformation.

For the second year in a row, ram and short scrotum lambs demonstrated superior growth and carcass composition compared to wether lambs.

Final Data

The lambs were weighed for a final time on September 25. This was 91 days after they were split into their two treatment groups. For this fi...