Quality of Fresh Lamb from Pasture-Raised Purebred and Crossbred Hair Sheep Lambs Gradually Removed from Soy Hull Supplementation before Harvest

Soy hull-supplementation (SH) in grazing lambs increased growth rate and altered carcass traits. Yet SH removal effect before harvest on the quality of fresh lamb has not been studied. This grazing trial with lambs grazing cool season pastures evaluated the effect of SH removal before harvest on the quality characteristics of fresh lamb. Thirty-six, 6-mo old purebred hair (Barbados Blackbelly or BB, BW = 20.0 ± 1.9 kg; St. Croix or SC, BW = 20.4 ± 3.1 kg) and crossbred wool (Dorset, D) × hair (BB; BW = 24.8 ± 3.1 kg or SC; BW = 24.5 ± 4.0 kg) sheep lambs rotationally grazed predominantly stockpiled tall fescue (13.3 to 19.4% CP) and ryegrass (16.5% CP) pastures. Lambs were allocated to four supplementation treatments (no supplementation; and supplementation until 42, 21 and 0 d before harvest) and SH was provided at 2% BW daily at individual feeding stations. After 63 d of grazing, lambs were harvested using standard procedures. After 24 h cooler storage (2°C), each carcass was fabricated to obtain 2.5-cm thick loin chops (Longissimus muscle or LM) for meat quality analyses. Data were analyzed as a completely randomized design with a 2 x 4 factorial treatment arrangement (breed type and supplement duration). The CIE L* (lightness), a* (redness), and b* (yellowness) values of lamb chops were significantly influenced by supplement duration. Chops from lambs removed from SH 42 d before harvest had lower (P < 0.001) CIE a* values than those from lambs removed from supplementation 21 or 0 d before harvest. The amount of protein in LM was higher (P < 0.05) in crossbred than purebred lambs. LM from non-supplemented lambs (22.0 and 2.49 %, respectively) had lower (P < 0.05) protein and fat contents than that from supplemented lambs. Furthermore, LM from lambs removed from SH 0 d before harvest had the highest (P < 0.05) fat content (4.23%). The percent metmyoglobin and thiobarbituric acid reactive substances (TBARS) of LM from lambs were significantly affected (P < 0.05) by breed type and supplement duration. Chops from lambs removed from SH 0 d before harvest had higher (P < 0.01) shear force values (3.74 vs 2.91 kg) than those from lambs removed from SH 42 d before harvest. Discontinuing supplementation before lamb harvest changed the meat quality of fresh lamb, but changes in meat quality were not consistently related to the time lambs were removed from supplementation.