[Show abstract][Hide abstract] ABSTRACT: The effectiveness of the Hydrodyne process and low voltage carcass electrical stimulation (ES), either alone or in combination, for tenderizing muscle from callipyge and normal lambs was evaluated. One hundred grams of explosive was used for the Hydrodyne treatment. Reductions in shear force with magnitudes of 33 to 67% were observed for the Hydrodyne treatment for the longissimus (LM) muscle from callipyge and normal lambs, respectively. Carcass ES had no effect (P>0.05) on either callipyge or normal lamb shear values. However, ES improved the response (48%) of the Hydrodyne treatment in the LM of callipyge lamb. Shear force for semitendinosus muscles averaged 3.53 kg and showed no response to either tenderizing treatment. Results suggest successful tenderization of lamb LM with the Hydrodyne technology.
[Show abstract][Hide abstract] ABSTRACT: The recently discovered callipyge gene has been associated with muscle hypertrophy in lambs. The objective of this study was to evaluate the effect of normal (n=18) and heterozygous callipyge lambs (n=18) on longissimus (LM) muscle morphological characteristics. Each of the selected lambs was identified as either muscle-hypertrophied (callipyge) or normal, while phenotypically questionable lambs were excluded from this study. The percentage of fast-twitch glycolytic (FG) fibers increased (P<.01), while the percentage of fast-twitch grycotytic/oxidative (FOG) fibers decreased (P<.01) in the callipyge lambs compared to normal lambs. No difference (P>.01) in distribution was observed for slow-twitch oxidative (SO) fibers. Concurrently, the area of FOG and FG fibers increased (86 and 47%, respectively, P<.01) in callipyge lambs. On the contrary, area of SO fibers decreased ( 45%, P<.01) in callipyge lambs compared to normals. These results suggest that the increased lean tissue accretion in callipyge lambs is a result of an increase in size of fast-twitch fibers and an increase in number of FG fibers.