Pollott G E
Imperial College at Wye, Ashford, Kent, UK.
J Dairy Sci. 2000 Nov;83(11):2448-58. doi: 10.3168/jds.S0022-0302(00)75136-8.
Lactation records of milk yield are commonly analyzed with empirical mathematical models. A family of new models is described based on the known biology of the mammary gland during pregnancy and lactation. The new models fit two logistic curves representing secretory cell differentiation and cell death (apoptosis) throughout lactation. A further function describes secretion rate changes. Both additive and multiplicative forms of the new models are described. Additional terms in the model can account for factors that alter the course of milk yield during the lactation, either by new cell differentiation, a change in the rate of milk secretion loss, or both. The new models were compared with three widely used empirical functions and another biologically based function using weekly records of milk yield taken from 40 dairy cows. The new models fitted the data with a lower residual mean square than the other functions. In addition, the parameters of the new models have a biological interpretation and can be used to discuss key characteristics of lactation. The application of the new models to monthly lactation records is possible, although a reduction in the number of parameters is likely to be required. Some parameters in the cell differentiation function of the models will be poorly estimated from monthly records and can be replaced with average or standard values.
泌乳量记录通常采用经验数学模型进行分析。基于孕期和哺乳期乳腺的已知生物学特性，描述了一系列新模型。新模型拟合了两条逻辑曲线，分别代表整个泌乳期分泌细胞的分化和细胞死亡（凋亡）。另一个函数描述了分泌率的变化。文中介绍了新模型的加法形式和乘法形式。模型中的附加项可以解释泌乳期内影响产奶量变化过程的因素，这些因素可能是通过新细胞的分化、乳汁分泌损失率的变化，或者两者兼而有之。使用从40头奶牛采集的每周产奶量记录，将新模型与三个广泛使用的经验函数以及另一个基于生物学的函数进行了比较。新模型拟合数据的残差均方比其他函数更低。此外，新模型的参数具有生物学意义，可用于讨论泌乳的关键特征。新模型也可应用于月度泌乳记录，不过可能需要减少参数数量。模型中细胞分化函数的一些参数从月度记录中估计效果不佳，可以用平均值或标准值代替。
