Lopez Arianna N, Newton Makenzie G, Stenhouse Claire, Connolly Erin, Hissen Karina L, Horner Scott, Wu Guoyao, Foxworth William, Bazer Fuller W
Departments of Animal Science, Texas A&M University, Kleberg Center, College Station, TX, 77843-2471, USA.
Cooperative Extension Service, Prairie View A&M University, Prairie View, Texas, 77446, USA.
J Anim Sci Biotechnol. 2025 Apr 5;16(1):51. doi: 10.1186/s40104-025-01187-9.
Lactational performance depends heavily on age, health, and nutrition. L-Citrulline (Cit) is an effective precursor of L-arginine (Arg), an amino acid that has important roles in synthesis of nitric oxide (NO) and polyamines. Ruminal microbes degrade extracellular Arg; however, extracellular L-citrulline (Cit) is not degraded by ruminal microbes due to lack of uptake and can be fed unencapsulated as a precursor for Arg. As NO is a vasodilator, an increase in blood flow and transport of molecules to mammary tissue may enhance lactational performance and milk composition. Increases in polyamine production may increase milk protein synthesis within mammary tissue, thus increasing milk protein content. This study determined, for the first time, effects of dietary Cit supplementation on milk production and milk composition of Alpine dairy goats.
Does were synchronized to estrus and bred to Alpine bucks. Parturition was induced on d 149 of gestation and does were suckled overnight allowing kid(s) to obtain colostrum before being milked 24 h later (d 1 of lactation). Does were assigned to either control (CON, n = 24) or Cit (CIT, n = 23) diets. The isonitrogenous control diet consisted of 97.63% basal diet and 2.37% supplement (1.37% L-alanine and 1.00% soybean hydrogenated oil). The CIT supplemented diet consisted of 97.63% basal diet and 2.37% supplement (0.5% Cit, 0.5% L-glutamine, 1% soybean hydrogenated oil, 0.37% cornstarch). Diets were group fed ad-libitum by treatment group. Blood samples were collected on d 0 and 30 of lactation, milk volumes measured twice daily, and on d 10, 20, and 40 of lactation, milk samples were collected.
CIT-treated does had greater daily milk production (P < 0.05) and there was an effect of day of lactation on daily milk production (P < 0.0001). Sire had significant effect on daily milk production as well (P < 0.05). Milk compositional analyses revealed Cit supplementation increased solid-non-fat (SNF; P < 0.05) and protein (P < 0.05) content in milk.
Our novel results indicate that dietary supplementation of Cit fed ad-libitum in Alpine does increased daily milk yield, milk SNF content, and protein content. Supplemental Cit may be a proxy for Arg in goats to enhance lactational performance.
泌乳性能在很大程度上取决于年龄、健康状况和营养。L-瓜氨酸（Cit）是L-精氨酸（Arg）的有效前体，L-精氨酸是一种在一氧化氮（NO）和多胺合成中起重要作用的氨基酸。瘤胃微生物会降解细胞外精氨酸；然而，细胞外L-瓜氨酸（Cit）由于缺乏摄取而不会被瘤胃微生物降解，可以直接作为精氨酸的前体投喂。由于NO是一种血管舒张剂，血流量增加以及分子向乳腺组织的转运可能会提高泌乳性能和乳汁成分。多胺产量的增加可能会增加乳腺组织内的乳蛋白合成，从而提高乳蛋白含量。本研究首次确定了日粮添加瓜氨酸对阿尔卑斯奶山羊产奶量和乳汁成分的影响。
母羊同步发情后与阿尔卑斯公羊配种。在妊娠第149天诱导分娩，母羊在夜间哺乳，让羔羊在24小时后（泌乳第1天）挤奶前摄取初乳。母羊被分配到对照（CON，n = 24）或瓜氨酸（CIT，n = 23）日粮组。等氮对照日粮由97.63%的基础日粮和2.37%的补充剂（1.37%的L-丙氨酸和1.00%的大豆氢化油）组成。添加瓜氨酸的日粮由97.63%的基础日粮和2.37%的补充剂（0.5%的瓜氨酸、0.5%的L-谷氨酰胺、1%的大豆氢化油、0.37%的玉米淀粉）组成。日粮按处理组自由采食。在泌乳第0天和第30天采集血样，每天测量两次奶量，并在泌乳第10天、第20天和第40天采集奶样。
接受瓜氨酸处理的母羊日产奶量更高（P < 0.05），泌乳天数对日产奶量有影响（P < 0.0001）。父系对日产奶量也有显著影响（P < 0.05）。乳汁成分分析表明，添加瓜氨酸可提高乳汁中的非脂固形物（SNF；P < 0.05）和蛋白质（P < 0.05）含量。
我们的新结果表明，在阿尔卑斯母羊日粮中自由采食添加瓜氨酸可提高日产奶量、乳汁SNF含量和蛋白质含量。补充瓜氨酸可能是山羊中精氨酸的替代物，以提高泌乳性能。
