The physiology of the sow mammary gland is qualitatively well described and understood. However, the quantitative effect of various biological mechanisms contributing to the synthesis of colostrum and milk is lacking and more complicated to obtain. The objective of this study was to integrate physiological and empirical knowledge of the production of colostrum and milk in a dynamic model of a single sow mammary gland to understand and quantify parameters controlling mammary gland output. In 1983, Heather Neal and John Thornley published a model of the mammary gland in cattle, which was used as a starting point for the development of this model. The original cattle model was reparameterized, modified, and extended to describe the production of milk by the sow mammary gland during lactation and the prepartum production of colostrum as the combined output of immunoglobulins (Ig) and milk. Initially, the model was reparameterized to simulate milk synthesis potential of a single gland by considering biological characteristics and empirical estimations of sows and piglets. Secondly, the model was modified to simulate more accurately the responses to changes in milk removal rates. This was done by linking the ejectable milk storage capacity to the number of secretory cells rather than being constant throughout lactation. Finally, the model was extended to include the prepartum synthesis of milk and the kinetics of Ig into and out of the mammary gland. A progressive capacity of secretory cells to synthesize milk was used to differentiate the time between the onset of milk synthesis and Ig transfer. Changes in maximum milk removal rate, duration of milk ejection, and nursing interval exerted a great impact on the modeled milk output. Changes by ±60% in one of these parameters were capable of increasing milk output by 28% to 39% during the first 4 wk in lactation compared with the reference parameterization. This suggests that the ability of the piglet to remove milk from the gland exerts a key control on milk synthesis during lactation. Modeling colostrum as the combined output of Ig and milk allowed to represent the rapid decline in Ig concentration observed during the first hours after farrowing. In conclusion, biological and empirical knowledge was integrated into a model of the sow mammary gland and constitutes a simple approach to explore in which conditions and to what extent individual parameters influence Ig kinetics and milk production.

中文翻译：

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描述泌乳母猪初乳免疫球蛋白转移和产奶的动态乳腺模型


母猪乳腺的生理学已经得到了很好的描述和理解。然而，缺乏对初乳和乳汁合成的各种生物机制的定量效应，并且获得起来更加复杂。本研究的目的是将初乳和牛奶生产的生理学和经验知识整合到单头母猪乳腺的动态模型中，以了解和量化控制乳腺产量的参数。 1983 年，希瑟·尼尔 (Heather Neal) 和约翰·桑利 (John Thornley) 发表了牛乳腺模型，该模型被用作开发该模型的起点。对原始牛模型进行了重新参数化、修改和扩展，以描述母猪乳腺在哺乳期间产生的牛奶以及作为免疫球蛋白 (Ig) 和牛奶的联合产出的产前初乳的产生。最初，通过考虑母猪和仔猪的生物学特征和经验估计，对模型进行了重新参数化，以模拟单个腺体的乳汁合成潜力。其次，对模型进行了修改，以更准确地模拟对泌乳率变化的响应。这是通过将可排出的乳汁储存容量与分泌细胞的数量联系起来而不是在整个哺乳期间保持恒定来实现的。最后，该模型扩展到包括产前乳汁合成以及 Ig 进出乳腺的动力学。分泌细胞合成乳汁的渐进能力被用来区分乳汁合成开始和 Ig 转移之间的时间。最大排奶率、排奶持续时间和哺乳间隔的变化对模型产奶量有很大影响。 与参考参数相比，其中一个参数变化 ±60% 能够在哺乳期的前 4 周内将产奶量增加 28% 至 39%。这表明仔猪从腺体中排出乳汁的能力对哺乳期间的乳汁合成发挥着关键控制作用。将初乳建模为 Ig 和乳汁的总输出量，可以代表分娩后最初几个小时内观察到的 Ig 浓度的快速下降。总之，生物学和经验知识被整合到母猪乳腺模型中，并构成了一种简单的方法来探索哪些条件以及个体参数影响 Ig 动力学和产奶量的程度。