Bateman H G, Williams C C, Gantt D T, Chung Y H, Beem A E, Stanley C C, Goodier G E, Hoyt P G, Ward J D, Bunting L D
Department of Dairy Science, LSU Agricultural Center, Louisiana State University and A & M College, Baton Rouge 70803, USA.
J Dairy Sci. 2004 Aug;87(8):2571-7. doi: 10.3168/jds.S0022-0302(04)73382-2.
Four nonlactating, mature, Holstein cows were fitted with ruminal cannula and used in a 4 x 4 Latin square-designed experiment to evaluate the impact of supplemental Zn and monensin on ruminal degradation of Lys and liquid 2-hydroxy-4-methylthiobutanoic acid (HMB). Cows were fed 4.54 kg (as fed) of alfalfa hay top-dressed with 4.54 kg (as fed) concentrate once daily. Concentrates were formulated to provide 0 or 500 mg/kg of Zn as ZnSO4 and 0 or 40 mg/kg of monensin in the total diet. Zinc supplementation provided approximately 22-fold greater dietary Zn than estimated by NRC requirements. On d 14 of each period, cows were dosed via the rumen cannula with 50 g of HMB and 100 g of Lys-HCl, and the concentrations of Lys and HMB were monitored every 0.5 h for 8 h. Supplemental Zn tended to decrease the proportion of acetate in ruminal fluid postfeeding and increased the proportion of propionate in ruminal fluid postfeeding. Supplemental Zn increased mean fluid passage rate from the rumen. Monensin decreased the proportion of acetate and increased the mean proportion of propionate in ruminal fluid, resulting in a decrease in the ratio of acetate to propionate. Monensin also increased the mean fluid passage rate from the rumen. Neither Zn nor monensin affected the apparent rate of ruminal disappearance of HMB or Lys. However, Zn and monensin interacted to alter the ruminal degradability of free Lys but not HMB. These data indicate that Zn and monensin may interact to alter ruminal degradability of free amino acids.
选用4头非泌乳的成年荷斯坦奶牛，安装瘤胃瘘管，用于一项4×4拉丁方设计试验，以评估补充锌（Zn）和莫能菌素对瘤胃中赖氨酸（Lys）和液体2-羟基-4-甲基硫代丁酸（HMB）降解的影响。奶牛每天饲喂一次4.54千克（按饲喂时计）苜蓿干草，并在其上补加4.54千克（按饲喂时计）精料。精料配方设计为在全日粮中提供0或500毫克/千克硫酸锌形式的锌以及0或40毫克/千克的莫能菌素。补充锌所提供的日粮锌比美国国家研究委员会（NRC）建议量高约22倍。在每个试验期的第14天，通过瘤胃瘘管给奶牛灌服50克HMB和100克盐酸赖氨酸（Lys-HCl），并在8小时内每隔0.5小时监测赖氨酸和HMB的浓度。补充锌倾向于降低采食后瘤胃液中乙酸盐的比例，并增加采食后瘤胃液中丙酸盐的比例。补充锌提高了瘤胃的平均液体通过率。莫能菌素降低了瘤胃液中乙酸盐的比例，增加了丙酸盐的平均比例，导致乙酸盐与丙酸盐的比例降低。莫能菌素还提高了瘤胃的平均液体通过率。锌和莫能菌素均未影响HMB或赖氨酸在瘤胃中的表观消失率。然而，锌和莫能菌素相互作用改变了游离赖氨酸的瘤胃降解率，但对HMB没有影响。这些数据表明，锌和莫能菌素可能相互作用改变游离氨基酸的瘤胃降解率。
