Adequate udder stimulation of dairy cows before milking is critical for the harvest of high-quality milk. It is essential for the milk-ejection reflex to obtain the alveolar milk, which represents approximately 80% of the udder’s milk volume. Currently applied pre-milking stimulation regimens fail to accommodate the physiological requirements of dairy cows. This hampers our ability to elicit their maximum milk-ejection capacity resulting in delayed milk ejection. Delayed milk ejection leads to reduced milk yield, longer milking duration, impaired udder health, and diminished animal well-being. Conservative estimates suggest that delayed milk ejection results in an income loss of approximately $250,000/year on a 1,000-cow dairy. Traditionally, pre-milking stimulation has been achieved through stripping the cow’s teats by hand. With the advancement of milking technology, alternative forms of pre-milking stimulation through automated systems have been developed. However, the potential of these automated pre-milking stimulation (APS) systems for providing supplemental stimulation to cows to meet their physiological needs has not been investigated. We lack methods to efficiently stimulate cows and elicit their maximum milk ejection capacity. Our global hypothesis is that the physiological requirements for pre-milking stimulation of cows can be achieved through a combination of manual and automated stimulation and that this is superior to manual stimulation alone. Our objective is to study the effect of supplemental premilking stimulation through APS on milking performance, udder health, and animal well-being in dairy cows. In the requested 1-year funding period, the global hypothesis and the broad objective will be addressed by the following 3 aims:

(1) To study the effect of supplemental pre-milking stimulation on milk yield and milking duration.
(2) To assess the effect of supplemental pre-milking stimulation on somatic cell count and clinical mastitis incidence.
(3) To determine the effect of supplemental pre-miking stimulation on fecal glucocorticoid metabolites, postmilking teat tissue condition, and hind-leg activity during milking.

In a randomized field study, cows (n = 290) will be allocated to either treatment or control group. Treatment will consist of supplemental pre-milking stimulation, which will be applied in addition to the manual stimulation through the APS system. Cows in the control group will only receive manual pre-milking stimulation. Data on milk yield, milking duration, somatic cell count, clinical mastitis incidence, fecal glucocorticoid metabolites, postmilking teat tissue condition, and hind-leg activity during milking will be obtained. We will use multivariable generalized linear regression models to determine the effect of supplemental stimulation on the selected outcome variables.