Department of Animal Science, Purdue University, West Lafayette, IN 47907, USA.
J Anim Sci. 2013 Jul;91(7):3332-40. doi: 10.2527/jas.2012-5962.
Two hundred and ten Angus × Simmental steers (initial BW 314 ± 11 kg) were separated into heavy and light BW blocks and allotted evenly by BW to 6 treatments (3 heavy and 2 light pens per treatment) to determine the effect of supplemental vitamin D3: 0 IU (no D), 250,000 IU for 165 d (long-term D), or 5 × 10(6) IU for 10 d (short-term D) on plasma and muscle calcium concentrations and gene expression in steers fed either 0 (NZ) or 8.38 mg/kg (ZH) zilpaterol hydrochloride (ZH) daily for 21 d. Placebo or ZH was added to the diet 24 d, and short-term D was added 13 d before slaughter. Treatments were removed from all diets 3 d before slaughter. Plasma total calcium (Ca(2+)) was determined at study initiation, start of ZH and short-term D feedings, and at vitamin D3 and ZH withdrawal. Both plasma total and ionic Ca(2+) were determined when animals were sent to harvest. Longissimus muscle total and ionic Ca(2+) were determined in meat aged 7 and 4 d postmortem, respectively. When ZH was fed, long-term D decreased plasma total Ca(2+) at slaughter (P < 0.04). Short-term D increased (P < 0.01) plasma total and ionic Ca(2+) at slaughter regardless of ZH inclusion in the diet. Long- and short-term D, with or without ZH, did not affect (P > 0.28) LM total Ca(2+); however, both long- and short-term D increased LM ionic Ca(2+) when ZH was not fed (P < 0.01). Long-term D reduced LM ionic Ca(2+) when ZH was fed (P < 0.02). Neither long- nor short-term D affected PPARα or δ gene expression (P = 0.19) whether or not ZH was fed. Expression of MYH1 and 2A (P < 0.05) but not 2X (P = 0.21) was decreased in steers fed ZH. Long-term D had no effect on MYH2A expression (P = 0.21). Short-term D increased MYH2A expression when ZH was not fed (P < 0.03). Calpain mRNA tended to be lower in steers fed ZH (P = 0.09), but was not affected by long- or short-term D regardless of whether or not ZH was fed (P = 0.39). Expression of calpastatin did not differ with vitamin D supplementation (P = 0.35). In conclusion, ZH decreased oxidative myosin expression, and when combined with long-term D, ZH decreased LM ionic Ca(2+). Moreover, vitamin D3 supplementation did not increase calpain mRNA. These results help explain why vitamin D3 does not improve tenderness in steers fed ZH.
两百一十头安格斯×西门塔尔阉牛（初始 BW 314 ± 11 千克）被分为重 BW 块和轻 BW 块，并根据 BW 均匀分配到 6 个处理组（每个处理组有 3 个重 BW 栏和 2 个轻 BW 栏），以确定补充维生素 D3：0 IU（无 D）、250,000 IU 持续 165 天（长期 D）或 5×10(6) IU 持续 10 天（短期 D）对饲喂 0（NZ）或 8.38 毫克/千克（ZH）齐帕特罗盐酸盐（ZH）的牛血浆和肌肉钙浓度和基因表达的影响，每日饲喂 21 天。在添加齐帕特罗盐酸盐（ZH）的饮食中添加安慰剂或 ZH 24 天，在屠宰前 13 天添加短期 D。在屠宰前 3 天从所有饮食中去除处理。在研究开始时、开始添加 ZH 和短期 D 饲养以及维生素 D3 和 ZH 停药时测定血浆总钙（Ca(2+))。当动物被送到收获时，测定血浆总离子钙（Ca(2+))和离子钙（Ca(2+))。宰后分别在肉成熟 7 天和 4 天时测定背最长肌总钙（Ca(2+))和离子钙（Ca(2+))。饲喂齐帕特罗盐酸盐（ZH）时，长期 D 降低了屠宰时的血浆总 Ca(2+)(P < 0.04)。短期 D 增加了（P < 0.01）无论饮食中是否含有 ZH，屠宰时的血浆总钙（Ca(2+))和离子钙（Ca(2+))。长期和短期 D，无论是否含有 ZH，都不会影响（P > 0.28）LM 总钙（Ca(2+))；然而，当不饲喂 ZH 时，两者都增加了 LM 离子钙（Ca(2+))（P < 0.01）。当饲喂 ZH 时，长期 D 降低了 LM 离子钙（Ca(2+))（P < 0.02）。无论是否饲喂 ZH，长期和短期 D 都不会影响 PPARα或δ基因表达（P = 0.19）。饲喂 ZH 时，MYH1 和 2A（P < 0.05）但不是 2X（P = 0.21）的表达减少。长期 D 对 MYH2A 表达没有影响（P = 0.21）。当不饲喂 ZH 时，短期 D 增加了 MYH2A 表达（P < 0.03）。钙蛋白酶 mRNA 在饲喂 ZH 的牛中趋于较低（P = 0.09），但无论是否饲喂 ZH，长期或短期 D 都不会影响钙蛋白酶 mRNA（P = 0.39）。钙蛋白酶抑制剂的表达不因维生素 D 补充而不同（P = 0.35）。总之，ZH 降低了氧化肌球蛋白的表达，当与长期 D 结合时，ZH 降低了 LM 离子钙（Ca(2+))。此外，维生素 D3 补充剂不会增加钙蛋白酶 mRNA。这些结果有助于解释为什么维生素 D3 不能提高饲喂 ZH 的牛的嫩度。
