中文摘要：

研究日粮添加过瘤胃胆碱（RPC）对喀斯特山区奶牛泌乳性能及其延续效应的影响。以10头喀斯特山区泌乳盛期奶牛为试验动物．进行自身对照试验设计。试验按照对照期、正试期（试验I期、试验Ⅱ期）、延续效应期（试验Ⅲ期）连续进行，每期12d。其中，正试期RPC每头奶牛的添加水平为40g／d；试验Ⅲ期停喂RPC以观察其是否可对奶产量产生延续效应。结果表明，对照期、试验I期、试验Ⅱ期、试验Ⅲ期奶牛干物质采食量差异不显著（P〉0．05）。试验I期奶产量显著高于其他3期（25．5：27．7：26．5：24．8kg／d，P〈0．05）；正试期（试验I期、试验Ⅱ期）奶产量显著高于对照期、延续效应期（25．5：27．2：24．8kg／d，P〈0．05）；当停喂RPC后，延续效应期奶产量即下降至对照期水平（25．5：24．8kg／d，P〉0．05）。奶成分不受日粮添加RPC的影响（P〉0．05），乳脂、乳固型物含量数值上较对照期有所增加。由此可见．日粮添加RPC有利于提高喀斯特山区奶牛泌乳性能，但未对奶产量表现出延续效应，生产实践中需持续添加。

英文摘要：

The study was conducted to investigate the lactation performance and its carry-over response of dairy cows fed rumen-protected choline （RPC）.Ten peak-lactation dairy cows,from Karst area,were used as experimental animals and were allocated to self-pair control experimental design.Four continuous and individual 12-day duration were set to be control phase,trial phase （trial phase I and trial phase II ）,and carry-over phase （trial phase III ）,respectively.The RPC （40 g/d） was not provided in trial III phase for the determination of carry-over effect of RPC on milk yield.The results were as follows：there was no difference in dry matter intake for the continuous 4-trial durations （P 〉 0.05）.Feeding of RPC in trial phase I resulted in higher milk yield than other 3 trial durations （25.5：27.7：26.5：24.8 kg/d,P 〈 0.05）.The pooled trial phase I and trial phase II had also more milk production compared with control phase and the carry-over phase （25.5：27.2：24.8 kg/d,P 〈 0.05）.Milk yield was decreased to be similar to control level in the carry-over phase,without the provision of RPC （25.5：24.8 kg/d,P 〉 0.05）.Milk compositions were unaffected by the addition of RPC （P 〉 0.05）,with minor increase of milk fat and solid content value. In conclusion,there was a positive effect of RPC supplementation on lactation performance.However, RPC did not carry over to increase milk yield, and therefore,it needed to be added continuously in the practice.