O'Meara E S, Del Olmo D M, Aguado J M, Drackley J K, Cardoso F C
Department of Animal Sciences, University of Illinois, Urbana, IL 61801.
Kemin Industries Inc., Des Moines, Iowa, 50309.
J Dairy Sci. 2025 Sep 3. doi: 10.3168/jds.2025-26692.
This experiment was conducted to determine the effects of feeding rumen-protected Met (RPM; KESSENT M, Kemin Industries Inc., Des Moines, IA) and rumen-protected Lys (RPL; LysiGEM, Kemin Industries Inc., Des Moines, IA) prepartum at the same AA-to-ME ratio (3.21 g/Mcal of Lys and 1.21 g/Mcal of Met) with different concentrations of NEL on the performance of dairy cows. Sixty-two multiparous Holstein cows were assigned to 1 of 3 dietary treatments in a randomized, complete block design. Prepartum (-21 d to expected calving), cows were fed a controlled-energy (CE) diet (wheat straw based diet, 1.45 NEL[2.33 ME] Mcal/kg of DM] with RPL and RPM (CEAA; 0.15% RPL and 0.09% RPM of dietary DMI), CE diet without RPL and RPM (control; CENAA), or high-energy (HE) diet (corn silage-based diet, 1.71 NEL[2.70 ME], Mcal/kg of DM] with RPL and RPM (HEAA; RPL 0.22% and RPM 0.12% of dietary DMI). Postpartum, cows received the same lactation TMR (1.73 NEL[2.71 ME] Mcal/kg of DM) without RPL and RPM (CENAA, n = 19) or with RPL and RPM (CEAA, n = 21; and HEAA, n = 21; 0.38% RPL and 0.15% RPM of dietary DMI) until 70 DIM. Cows were milked twice daily, and milk samples were taken once a week from d 2 to 70 DIM. Milk yield and DMI were recorded daily. Blood samples were taken on -7 ± 4.7, 28 ± 1.6, and 70 ± 2.1 DIM. Two treatment contrasts (CENAA vs. CEAA and CEAA vs. HEAA) were compared. Cows in HEAA had higher ECM (50.5 ± 1.77 kg/d) and tended to have greater fat yield (2.04 ± 0.09 kg/d) and BCS loss (-0.71 ± 0.14) during wk 1 to 4 of lactation than cows in CEAA (45.7 kg/d, 1.82 kg/d, and -0.36, respectively). Cows in CEAA tended to have a higher protein proportion in milk (3.43% ± 0.07%) than cows in CENAA (3.26% ± 0.07%) and cows in HEAA (3.24% ± 0.07%) during wk 1 to 4 of lactation. Cows in CEAA had higher milk protein proportion (2.89% ± 0.05%) than cows in CENAA (2.72% ± 0.05%) during wk 5 to 10. Plasma Met concentrations prepartum were greater for cows in CEAA (24.7 ± 1.65 µM) than cows in CENAA (19.8 ± 1.65 µM). Cows in CEAA had higher plasma Lys (81.1 ± 3.35 µM) and Met (39.5 ± 2.04 µM) concentrations postpartum than cows in CENAA (71.5 ± 3.35 µM and 19.5 ± 2.04 µM, respectively). In conclusion, feeding a HE diet may have negatively affected the cows' body composition compared with cows fed a CE diet when both diets were formulated at 3.21 g/Mcal of Lys and 1.21 g/Mcal of Met, whereas, feeding RPL and RPM prepartum improved cows' performance compared with cows that were not fed RPL and RPM.
本试验旨在确定在相同氨基酸与代谢能比例（赖氨酸3.21 g/Mcal、蛋氨酸1.21 g/Mcal）下，给围产期奶牛饲喂不同浓度净能的瘤胃保护蛋氨酸（RPM；KESSENT M，Kemin Industries Inc.，得梅因，爱荷华州）和瘤胃保护赖氨酸（RPL；LysiGEM，Kemin Industries Inc.，得梅因，爱荷华州）对奶牛生产性能的影响。采用随机完全区组设计，将62头经产荷斯坦奶牛分配至3种日粮处理中的1种。围产期（-21天至预产期），奶牛饲喂对照能量（CE）日粮（以小麦秸秆为基础的日粮，1.45净能[2.33代谢能]Mcal/kg干物质），添加RPL和RPM（CEAA；日粮干物质摄入量的0.15% RPL和0.09% RPM）、不添加RPL和RPM的CE日粮（对照；CENAA）或高能（HE）日粮（以玉米青贮为基础的日粮，1.71净能[2.70代谢能]Mcal/kg干物质），添加RPL和RPM（HEAA；日粮干物质摄入量的0.22% RPL和0.12% RPM）。产后，奶牛接受相同的泌乳全混合日粮（1.73净能[2.71代谢能]Mcal/kg干物质），不添加RPL和RPM（CENAA，n = 19）或添加RPL和RPM（CEAA，n = 21；HEAA，n = 21；日粮干物质摄入量的0.38% RPL和0.15% RPM），直至产奶70天。奶牛每天挤奶两次，从第2天至70天每天采集奶样。每天记录产奶量和干物质采食量。在第-7 ± 4.7、28 ± 1.6和70 ± 2.1天采集血样。比较两个处理组（CENAA与CEAA以及CEAA与HEAA）。与CEAA组奶牛（分别为45.7 kg/d、1.82 kg/d和-0.36）相比，HEAA组奶牛在泌乳第1至4周的校正奶量（50.5 ± 1.77 kg/d）更高，且乳脂产量（2.04 ± 0.09 kg/d）和体况评分下降幅度（-0.71 ± 0.14）更大。在泌乳第1至4周，CEAA组奶牛的乳蛋白比例（3.43% ± 0.07%）高于CENAA组奶牛（3.26% ± 0.07%）和HEAA组奶牛（3.24% ± 0.07%）。在泌乳第5至10周，CEAA组奶牛的乳蛋白比例（2.89% ± 0.05%）高于CENAA组奶牛（2.72% ± 0.05%）。围产期CEAA组奶牛的血浆蛋氨酸浓度（24.7 ± 1.65 μM）高于CENAA组奶牛（19.8 ± 1.65 μM）。产后CEAA组奶牛的血浆赖氨酸（81.1 ± 3.35 μM）和蛋氨酸（39.5 ± 2.04 μM）浓度高于CENAA组奶牛（分别为71.5 ± 3.35 μM和19.5 ± 2.04 μM）。总之，当日粮按赖氨酸3.21 g/Mcal和蛋氨酸1.21 g/Mcal配制时，与饲喂CE日粮的奶牛相比，饲喂HE日粮可能对奶牛的体成分产生负面影响，而围产期饲喂RPL和RPM可提高奶牛的生产性能。
