Substituting ground woody plants for cottonseed hulls in lamb feedlot diets: carcass characteristics, adipose tissue fatty acid composition, and sensory panel traits

Abstract

Effects of using ground woody plants in Rambouillet wether lamb (n = 48) feedlot diets on carcass characteristics, adipose tissue fatty acid composition, and sensory panel traits were evaluated. In a randomized design study with two feeding periods (period 1 = fed a 70% concentrate diet from days 0 to 27; period 2 = fed an 86% concentrate diet from days 28 to 57), lambs were individually fed six diets that differed only by roughage source (n = 8 animals/treatment; initial BW = 32.9 ± 3.2 kg): cottonseed hulls (CSH; control) or ground wood consisting of either redberry (RED), blueberry (BLUE), one-seed (ONE), or eastern red cedar (ERC) Juniperus spp., or Prosopis glandulosa (MESQ). After 57 d, the lambs were humanely harvested and after chilling (2 ± 1 oC) 24 h, carcasses were evaluated for carcass traits. At 48 h postmortem, the longissimus thoracis (LT) was removed from the left side of the carcass, and after freezing for no more than 3 mo, were thawed for 24 h, cooked, and evaluated by a trained sensory panel. Additionally, volatile aroma chemicals on the LT were determined by gas chromatograph/mass spectrometer/olfactory (GC/MS/OF, respectively) analyses. Lamb HCW was greater (P = 0.01) for lambs fed CSH compared with all other diets, but lambs had similar (P > 0.08) LM area, back fat thickness, leg circumference, and body wall. Neither adipose tissue fatty acid composition (P > 0.08) nor trained sensory panel evaluation (P > 0.18) was affected by finishing diet roughage source. Of the 81 volatile aroma compounds found in the grilled lamb chops, only seven were affected (P < 0.05) by dietary roughage source and included 1-pentanol (a sweet, pleasant aroma), heptenal (a fishy aroma), pentanal (fermented, bready aroma description), 1-(1H-pyrol-2yl)-ethanone (caramel-like), 2-heptanone (cheesy, banana, fruity aromatic), 6,7-dodecanedione (unknown aroma), and butanoic acid (a sweaty, rancid aroma). The addition of any of four species of juniper or mesquite may be substituted for CSH without negatively affecting carcass fat and muscling, fatty acid, or sensory traits.