Quarter-controlled milking in dairy cows

Abstract

The design of a milking stall with special functions for monitoring and control is described. The milk removal process per quarter is described. The milking stall was equipped with four milk containers, whose advancing weight was recorded permanently. The data were online converted into milk flow rate profiles for each quarter. Quarter milk flow profiles were analysed and translated into variables such as milk yield and milking duration for the whole milking or for the increase, steady state, declining and overmilking phases. These variables were used to test the effect of technical milking machine settings (pulsation or milking vacuum, pulsation rate or ratio and detachment level) on quarter milking performance. Also the effects of the factors of quarter position and milking time were examined. An experiment with three milking vacuum levels, carried out in a milking parlour with these quarter milking facilities is described. Significant effects of vacuum level, quarter position and time of milking on milk yield and milking duration in the defined milk removal phases were shown. Moreover, the effects differed significantly among cows and quarters.

The study reveals marked differences in milk flow profiles per quarter. For optimal milking the milking process control should anticipate these differences and use the information for more efficient milking and safeguarding teat and udder health.

Introduction

Genetic progress, improved management and feeding, and higher milking frequencies are causing a strong increase in the daily milk yields per cow. As a consequence, the duration of milk removal increased drastically (Ipema and Benders, 1992). More mechanical stress is exerted on the cows’ teats and udder, which is reflected by harmful effects on teat sphincters (Ipema and Benders, 1992). Severe abnormalities in sphincters are often associated with mastitis (Neijenhuis et al., 2004). In current milking practice, often only half of the machine-on time is needed for removing more than three quarters of the available milk (Hogewerf and Ipema, 2000). The large inefficient parts in the milk removal process might also lead to a higher somatic cell count (SCC) in the milk (Naumann et al., 1998) and occasionally result in mastitis. High SCC in milk is undesirable for further processing into consumer products. Moreover, mastitis is a painful disease for the cow. Together with the growing public concern about items as food safety, animal welfare and animal health, these aspects require the milking process to be adapted to a more animal friendly approach.

It is important to realize that the quarters of the udder are four separate compartments. Milk in a quarter can be divided in two categories: the alveolar milk stored in the alveoli and small ducts, and the cisternal milk, stored in the larger ducts of the udder and in the teat cistern. Mechanical stimulation of udder and teats causes the release of the hormone oxytocin in the blood. This release results in the milk letdown reflex, whereby milk from the alveoli is pressed into the ducts and cisterns of the udder.

The action of the milking unit removes the milk from the teat. Milking units consist of a pulsator, milking claw with teat cups, milk container, tubes and pipelines. A teat cup consists of a shell and a liner. The pulsator provides a regular opening and closing of the liner. During a pulsation cycle of about 1 s the liner is open for 50–70% and closed for 30–50% of the time. When the liner is open milk flows from the teat (suction phase). During the time the liner is closed milk removal is stopped.

For efficient milk removal, information about the amount of available milk in the teat cistern is needed. Four main phases in the availability of milk during milking can be distinguished. In the first phase, milk ejection from the alveoli has not started yet. Milk removed from the udder is cisternal milk that has leaked from the alveoli during the interval since last milking. The duration of this first phase is normally less than 90 s. In the second phase, the flow rate of milk removed from the udder and teat cistern is at least equal to the flow rate of ejected milk from the alveoli. In the third phase, the flow rate of milk ejected from the alveoli is smaller than the flow rate of the removed milk. In the fourth phase, the flow of milk from the alveoli has stopped and the available amount in the udder and teat cistern approaches the zero level.

The objectives of this paper were to present: (1) a technique for measuring milk flow per quarter; (2) a description of the general pattern of the milk flow and differences between quarters and (3) the effect of milking machine technical settings.