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991.
Vitamin D3 supplementation of cull cows: effects on longissimus and semitendinosus muscle tenderness
Previous studies have shown that supplementation of vitamin D3 to cow diets for 4 to 10 d before slaughter lowers Warner-Bratzler shear force (WBSF) values and increases sensory tenderness scores in beef cuts. The present study was conducted to evaluate the effects of vitamin D3 supplementation on muscle calcium concentration, WBSF values, and sensory tenderness ratings of LM and semitendinosus (ST) muscles from cull, predominately Angus, cows (eight cows per treatment). Treatments included 0 (control), 5 million IU, or 7.5 million IU of vitamin D3 supplemented daily for 7 d preslaughter. Twenty-four hours after slaughter, 2.54-cm-thick LM and ST muscle steaks were cut; aged for either 0, 7, 14, or 21 d (ST steaks aged for 7 d only); and frozen at -20 degrees C for WBFS and sensory analysis. Mean values for LM calcium concentration tended to increase (P = 0.14) with vitamin D3 supplementation (154, 176, and 183 microig/g, fresh basis, for 0, 5, and 7.5 million IU/d, respectively). After 7 d of aging, LM steaks from cows fed 7.5 million IU had lower (P < 0.05) WBSF values than 7-d steaks from controls and cows fed 5.0 million IU/d aged 7 d; however, vitamin D3 supplementation had no (P > 0.05) effect on WBSF values of ST steaks aged 7 d. Vitamin D3 supplementation did not (P > 0.05) affect sensory tenderness ratings for either LM or ST steaks at any aging period. Aging, however, had a linear (P < 0.001) effect on tenderness, with an increase in tenderness as aging time increased from 0 to 21 d. Thus, results from the present study indicate that vitamin D3 supplementation, at these levels and duration before slaughter, provided little benefit to muscle tenderness of beef from cull cows. 相似文献
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Lei X 《Science (New York, N.Y.)》2002,296(5572):1379
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人工同龄纯林树冠面积比例系数计算及林分标准密度(立木株数)确定的研究 总被引:4,自引:0,他引:4
人工同龄纯林树冠面积比例系数计算及林分标准密度(立木株数)确定的研究熊奎山(甘肃省林业勘察设计研究院兰州730020)关键词人工同龄纯林,树冠面积比例系数,林分标准密度确定Reineke(1983)指出:具有完满立木度的同龄纯林,具有相同的单位面积株... 相似文献
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兔颈动脉窦和颈动脉体的神经支配 总被引:1,自引:1,他引:0
用HRP法对兔颈动脉窦和颈动脉体的神经支配进行了分析,表明,支配颈动脉窦和颈动脉体的标记细胞均出现于舌咽神经远节和颈上节。颈动脉体感觉传入中枢突终未见于延髓闩部邻近极后区的腹外侧,颈上节的标记细胞分布于尾侧半部。提示颈动脉窦和颈动脉体对心血在管活动的调节存在着经舌咽神经将感觉传入中枢的通路和经颈上节进行交感神经活动支配的传出通路。为研究心和管生理提供了形态学资料。 相似文献
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AIM: To evaluate the alterations in calcium metabolism of the vascular smooth muscle in the late phase of septic shock and test the hypothesis that nitric oxide might be involved in sepsis-induced vascular hyporeactivity. METHODS: Male Sprague-Dawley rats were subjected to sepsis by cecal ligation and puncture (CLP). 18 hours post CLP, rat aortic rings were employed for measurement of contractile responses by using organ bath technique. RESULTS: In endothelium-denuded aortic rings from CLP rats, concentration-contraction curves to phenylephrine (PE) and KCl were significantly decreased when compared to that from sham control rats. The transient contraction induced by PE in calcium-free Krebs solution and the concentration-dependent contraction to CaCl2 in KCl-depolarized medium were also markedly reduced. The hyporeactivity was partially reversed by treatment with aminoguanidine, a selective inducible nitric oxide synthase inhibitor. CONCLUSION: An impairment in calcium handling in vascular smooth muscle is involved in the vascular hyporeactivity during the late phase of septic shock, in which an excessive nitric oxide production might be the major mechanism. 相似文献