Endocrine factors in genetic improvement of milk production.
The endocrine role in lactation is undisputed, but attempts to correlate milk production with various endocrine products have had limited success. Recent work has suggested that placental hormones, in particular placental lactogen, may be an important regulator of lactation capacity. In addition to concentrations of hormones in blood, it is important to consider receptors in target tissue for the hormones. The concentration of receptors in a tissue may vary with genotype of the individual or under the influence of hormonal state. Other aspects of the target tissue's system for response also must be considered.