Feeding high levels of vitamin D-3 does not improve tenderness of callipyge lamb loin chops

The objective of this study was to determine whether feeding high doses of vitamin D-3 7 d before slaughter would increase muscle Ca++ levels and resu lt in more tender loin chops. Market lambs (n = 4 callipyge and 4 normal in Exp. 1, and n = 16 calipyge and 16 normal in Exp. 2) were randomly and equ ally assigned to feeding groups based on callipyge genotype and experimenta l diet, (vitamin D3 or control). Serum Ca++, muscle Ca++, Warner-Bratzler s hear force, and troponin-T degradation data were analyzed. In Exp. 1, vitam in D-3 was supplemented at 1 or 2 x 10(6) IU/d. The 2 x 10(6) IU dose resul ted in the greatest serum Ca++ reponse and was chosen for Exp. 2. In Exp. 2 , serum Ca++ concentration was higher (P < 0.05) for normal and callipyge l ambs fed the vitamin D-3 diet than for the control diet fed lambs. Muscle C a++ concentrations, however, were not higher (P = 0.28) for the vitamin D-3 -fed lambs. Warner-Bratzler shear values were higher (P < 0.05) for callipy ge than for normal lambs, but no differences were observed with vitamin D-3 supplementation. These data were supported by results from Western blot an alysis of troponin-T degradation, in which no differences were observed for vitamin D-3 VS control diet lambs at 14 d postmortem. This experiment show ed that feeding 2 x 10(6) IU/d of vitamin D-3 to market lambs, callipyge or normal, raised serum Ca++ concentration, but did not increase muscle Ca+concentration. This lack of response in muscle Ca++ was likely the reason t hat no differences were observed for Warner-Bratzler shear force values or troponin-T degradation data between the vitamin D-3 and control loin chops. A higher dose of vitamin D-3 may be required to improve tenderness.