PEGASE, INRAE, Institut Agro, 35590 Saint-Gilles, France.
Ajinomoto Animal Nutrition Europe, 32 rue Guersant, 75017 Cedex 17 Paris, France.
Animal. 2021 Jan;15(1):100049. doi: 10.1016/j.animal.2020.100049. Epub 2020 Dec 10.
Quantitative estimates of mammary nutrient inputs, outputs and metabolism in sows are scarce, despite being critical elements to identify parameters controlling milk synthesis central for the feeding of lactating sows. The objective of this study was to quantify the mammary gland input and output of nutrients as well as the intramammary partitioning of carbon and nitrogen with the purpose to identify mechanisms controlling mammary nutrient inputs, metabolism and milk production in lactating sows. A data set was assembled by integration of results from four studies. The data set included data on litter performance, mammary arterial-venous concentration differences (AV-difference) of energy metabolites and amino acids, and the contents of lactose, fat and amino acids in milk. Milk yield was estimated based on average litter size and litter gain, and mammary plasma flow (MPF) was estimated using the sum of phenylalanine and tyrosine as internal flow markers. The yield and composition of milk were used to estimate mammary nutrient output in milk, and MPF and AV-difference were used to estimate net mammary input of carbon and nitrogen and output of CO. Carbon and nitrogen used for the synthesis of lactose, fat and protein in milk and CO-yielding processes were represented in a static nutrient partitioning model. The origin of mammary CO output was calculated using theoretical estimates of carbon released in processes supporting mammary synthesis of de novo fat, protein and lactose in milk, mammary tissue protein turnover and transport of glucose and amino acids. Results indicated that total input of carbon from glucose and lactate was partitioned into lactose (36%), fat (31%) and CO-yielding processes (34%). Theoretical CO estimates indicated that de novo fat synthesis, milk protein synthesis and mammary tissue protein turnover were the main processes related to mammary CO production. More than 90% of mammary gland amino acid input was used for milk protein. The quadratic relationship between AV-difference and mammary input of essential amino acids indicated that both changes in AV-difference and MPF contributed to the regulation of mammary input of essential amino acids. The impact of the arterial supply of amino acids on mammary input may be greater for the branched-chain amino acids, arginine and phenylalanine than for other essential amino acids. In conclusion, relationships between input and output parameters indicate that AV-difference and MPF regulate mammary nutrient input to match the supply and demand of nutrients for the mammary gland.
尽管确定控制泌乳母猪产奶的关键参数需要定量估计母猪乳腺的营养输入、输出和代谢，但目前这方面的研究还很少。本研究的目的是定量估计乳腺的营养输入和输出以及碳氮在乳腺内的分配，以期确定控制泌乳母猪乳腺营养输入、代谢和产奶的机制。本研究通过整合四项研究的结果，建立了一个数据集。该数据集包括了关于产仔性能、能量代谢物和氨基酸的乳腺动静脉浓度差（AV 差）以及乳中乳糖、脂肪和氨基酸含量的数据。产奶量是根据平均产仔数和产仔增重来估计的，而乳腺血浆流量（MPF）则是通过苯丙氨酸和酪氨酸的总和作为内流标志物来估计的。利用产奶量和组成来估计乳腺中营养物质的输出，利用 MPF 和 AV 差来估计净乳腺碳和氮的输入以及 CO 的产量。利用静态营养分配模型来表示用于合成乳中乳糖、脂肪和蛋白质以及产生 CO 的碳和氮。通过计算支持乳腺从头合成新脂肪、蛋白质和乳中乳糖、乳腺组织蛋白周转以及葡萄糖和氨基酸转运的过程中释放的碳的理论估算值，来计算乳腺 CO 输出的来源。结果表明，来自葡萄糖和乳酸的总碳输入被分配到乳糖（36%）、脂肪（31%）和 CO 产生过程（34%）中。理论 CO 估算表明，从头合成脂肪、乳蛋白合成和乳腺组织蛋白周转是与乳腺 CO 产生相关的主要过程。乳腺氨基酸输入的 90%以上用于合成乳蛋白。AV 差与必需氨基酸乳腺输入之间的二次关系表明，AV 差和 MPF 的变化都有助于调节必需氨基酸的乳腺输入。动脉供应的氨基酸对乳腺输入的影响可能对支链氨基酸、精氨酸和苯丙氨酸比对其他必需氨基酸更大。总之，输入和输出参数之间的关系表明，AV 差和 MPF 调节乳腺营养物质的输入，以匹配乳腺对营养物质的供需。
