MILKING PARLOUR INSTALLATIONS
|Construction costs are low per cow place. Operators must bend or crouch to perform most of the routine tasks on each cow. Milking efficiency is hindered by cows crossing the operator's work area. Cows in the exit passage are remote from the operator's control. Individual stalls allow individual attention during milking.|
|Construction costs are high per cow place. Operators can milk standing upright. Cows in the entry/exit passages are remote from the operator's control. Size of parlour and throughput are limited by the distance (2.5m) between udders. Individual stalls allow individual attention during milking. Food troughs can be easily reached and inspected by the operator.|
ORGANISATION OF MACHINE MILKING
Milking machines were developed to meet demands for milking more cows more quickly using fewer people and less effort. Initially, this was achieved by the introduction of bucket units which were carried from cow to cow in traditional cowsheds or milking barns. Pipeline milking achieved considerable improvement in labour efficiency and reduction in manual lifting and carrying, but the major development was the change to parlours where the operators use stationary equipment to milk the cows as they pass through the installation during the course of milking.
At first, static parlour design followed the cowshed stall arrangement with the cows standing side-by-side and a milking unit positioned between each pair of stalls. In these abreast parlours, cows enter across the operator's working area and both are on the same floor level. Later, a step was included to elevate the cows 0.3–0.4 m. Even with this addition milking cannot be carried out in an upright position and it was not until the introduction of the tandem parlour that genuine two-level milking became possible. In these, the cows stand head-to-tail in individual stalls on one or both sides of the operator's pit or work area with a floor level difference of 0.8 m. Each stall is fitted with an entry and exit gate giving access to and from a passage flanking the stalls. A simplified version of the tandem, known as the chute parlour, eliminates the need for separate access passages by having batch entry/exit of cows through the stalls when a division between each stall is opened. The number of cows in each batch equals the number of stalls on each side of the operator's pit. In both the tandem and the chute the distance between udders of adjacent cows is 2.5 m. This disadvantage renders large parlours impracticable, a problem which was solved by the development of the herringbone parlour. By standing a batch of cows in echelon formation at an angle of 30°–35° to the sides of the operator's pit, the distance between udders is reduced to 0.9 m. There are no individual stalls, the cows being restrained on the platform (or standing) by an entry gate, an exit gate and a rump rail parallel to the pit side. Herringbones have become popular in all major milk producing countries, being suitable for herds of 50 to 400 cows. In a recent modification, called the side-by-side, the cows stand at right angles to the pit so that 3 cows can occupy the space required for 2 cows in a herringbone.
|Cheaper, batch milking version of the tandem. Cows enter and leave through the stalls. Operator has control over cow entry/exit.|
|Cows stand in echelon formation at 30°–35° to the operator's pit with no division between cows. Distance between udders is reduced to 0.9 m. Operator has control over cow entry/exit Cows enter and leave in batches. Suitable for herds of 50–400 cows.|
|Three-sided herringbone with, consequently, smaller batches causing less delay from a slow milking cow. Comparative parlour performance capacity will require 20%–25% fewer units and stalls than the conventional herringbone|
Four-sided (polygon) and, more recently, three-sided (trigon) herringbones have been built for larger herds. These multi-sided parlours economise in the number of units and stalls required compared with the conventional two-sided herringbone because fewer units are idle at any one time during milking. (eg. a 16/16 trigon is equivalent to a 20/20 herringbone in terms of parlour performance capacity). Also, the smaller batch size for a given number of units means that a slow milking cow has less effect on batch milking time.
Originally, rotary parlours were built for very large herds but more recently smaller ones have been designed to provide an alternative to the herringbone. As in the case of static parlours, the cows stand either side-by-side, ie, rotary abreast; head-to-tail ie, rotary tandem or in echelon formation, ie, rotary herringbone. During milking, cows walk onto a rotating platform singly with the operator standing at the point of entry to prepare the udders for milking and attach the teatcup clusters. The cows leave the platform when rotation brings them opposite the exit passage, the clusters having been removed automatically when milk flow ceased. High capital and maintenance costs, mechanical faults and the introduction of automation into static parlours have all contributed to a declining interest in rotaries. The most successful version is undoubtedly the rotary abreast which has no moving parts on the platform, the cows face inwards towards the centre and the operator is positioned at the circumference of the platform to control cow entry.
|Modification of the herringbone. Cows stand at right angles to the operator's pit, so that 3 cows occupy the length required for 2 in the herringbone. Cows must be milked through the back legs.|
|Least expensive rotary per cow place in terms of cost and space requirement. Cows face inwards separated by static tubular metal divisions. No moving parts on the platform. Operator standing at the platform perimeter can assist cow entry but cannot see the cows during rotation.|
|Most expensive per cow place in terms of cost and space requirement. Cows stand nose-to-tail in stalls circling the operators work area. Operator cannot assist cow entry but can see all cows easily during rotation.|
|Cows stand in echelon formation facing outwards around a central work area. Designs vary from simple yoke ties only on the platform to rotationally operated moving divisions which position the cows and allow entry and exit.|
TYPES OF PARLOUR
|ONE MILKING UNIT PER TWO STALLS (½) Each milking unit is shared between two stalls. Comparatively short unit idle time of 0.2 mins. Slow milking cows can delay throughput.|
|ONE MILKING UNIT PER STALL (1/1) Each stall has a milking unit. More costly installation than ½. Throughout milking, about 50% of units will, on average, be idle with an average unit idle time of 1.2 mins. “Doubling-up” the number of units is equivalent to adding one more unit (eg. 5/10 to 10/106/12) in terms of available milking time per cow. Work routine time and feeding time per cow will be unaffected (in batch milking). Operators can select sequence of cluster attachment. More regular interval between udder preparation and cluster attachment.|
Even though there are several parlour designs and configurations there are only two basic types; those having one milking unit to each pair of stalls (eg. 5 units, 10 stalls), or one unit to each stall (eg. 10 units, 10 stalls). With the exception of rotaries, trigons and polygons, milking parlours can be of either type. In recent years, many 1 unit per 2 stall parlours have been “doubled-up” to the 1 unit per 1 stall version and it is important that the effect of this change is understood, particularly in relation to comparative parlour performance capacity. The operator's work routine time (ie. the time available to carry out the routine jobs on each cow) is unaffected. This is because, in the doubled-up version about 50% of the units will, on average, be idle at any one time, and the content of the work routine will be unchanged (see multiple activity charts). Also unaffected is the available eating time for cows in parlours where batch milking is practised, (eg. the herringbone). Although the average interval between cluster attachment and removal (ie. the available milking time per cow) becomes greater in the doubled up version for a given performance level, this advantage can be exploited only if the operator had previously been waiting for cows to milk out. In terms of performance capacity (ie. available milking time per cow) doubling up a 5/10 herringbone to a 10/10 for example, is equivalent to adding one more unit to the 5/10 to make a 6/12 (see page ).
Other advantages of one unit per stall installations are that delays caused by slow milking cows can be minimised because the operator can select the sequence of cluster attachment to cater for known differences in the milking out times of cows; the interval between cow preparation and cluster attachment is likely to be more constant and, milk flow can be gravity assisted to pipelines below udder level.
The expense of doubling-up will achieve only a marginally improved throughput created by an increase in the available milking time per cow, improved flexibility in the use of the milking units and a work routine unimpeded by equipment hanging from the centre of the operator's work area.
When a new 1 stall per 1 unit installation is proposed in preference to a 1 unit per 2 stall alternative, these same marginal advantages are relevant together with a small saving in building space which occurs. For example a 10/10 herringbone requires approximately 1 m less length of building than the 6/12 equivalent.
|PARLOUR MILKING PERFORMANCE||WORK ROUTINE TIME||SIZE OF HERRINGBONE (units/stalls)|
|(cows/hour)||(mins/cows)||AVERAGE||AVAILABLE MILKING TIME (mins/cow|
MULTIPLE ACTIVITY CHART 4/8
MULTIPLE ACTIVITY CHART 8/8
Milking installations, like most other agricultural machinery, should be purchased on the basis of cost and required performance or throughput. During each milking the work done by the operator remains virtually the same, whereas the amount of milk produced per hour will fluctuate throughout the year. Therefore, the throughput of a milking installation is best measured in terms of cows milked per hour and performance as cows milked per manhour. For example, if two operators milking together achieve a throughput of 120 cows per hour that is a performance of 60 cows per manhour. The required rate of throughput is determined initially by three management decisions:
In herds large enough to warrant division of labour, the trend is towards one operator milking with increasing mechanization and automation. It has been shown that long milking shifts do not affect performance adversely, but in most herds where milking and the work between milkings is done by the same people, duration of milking is usually limited to 1–2 hours. The three factors that determine the throughput or performance (P) of a milking installation are:
1. The average milking-out time of the cows (MOT).
The milking-out time plus the time that units are not attached to cows (ie. unit idle time) is called the unit time (UT) and this prescribes the maximum number of cows that can be milked in one hour using one unit
Although milking times of individual cows vary considerably and will be affected by vacuum level and pulsation characteristics the most important factor influencing the average milking-out time of the cows in a herd is the average herd milk yield; the higher the average yield the longer the average MOT. The relationship between these factors is expressed as:
t = 0.21y + 2.75
where t = herd milking time (mins/cow)
and y = average herd milk yield (litres/cow)
Thus, if the average yield of milk at a milking is 11 litres the average milking-out time will be 0.21 × 11 + 2.75 or about 5 minutes per cow.
2. The number of milking units (N) per operator.
Providing each milking unit is used to maximum efficiency the total number of cows milked per hour (P) will be the number of units (N) times the number that can be milked with one unit in an hour. Therefore for an installation:
There is a limit to the number of units that can be used effectively by one operator and if this is exceeded there will be an increase in the unit idle time or the units will be idle or left on the cows or hanging up after milk flow has ceased. This will increase the unit time (UT) and consequently lower performance (P).
3. The operator's work routine time (WRT).
This is the average time spent on the various tasks associated with milking each cow (ie. attaching and removing clusters, udder preparation, etc.). If the operator spends 2 minutes working on the routine tasks on each cow, the number of cows that can be milked in an hour cannot exceed 60å2 = 30 cows/hour. However, if the work routine time can be reduced to 1 minute the performance can be increased to 60 cows/hour providing the operator has a sufficient number of units. In most large parlours it is the work routine time that limits the performance.
Planning the correct operation of any milking installation is mainly a matter of adopting the correct work routine for the number of units to give the required performance. The relationships are shown in the Table for a herd which has an average unit time (ie. milking-out time plus machine idle time) of 6 minutes and calculated from P = N × 60 and
|Number of unites (N)||Unit Time (UT)|
|Work Routine Time (WRT)|
Thus in this herd an operator will milk 20 cows/h with 2 units providing the work routine does not exceed 3 minutes on each cow. However if 4 or 8 units are used then performances of 40 or 80 cows/h can be obtained if the work routines are reduced to 1.5 or 0.75 min respectively. It is important to appreciate that if 8 units are used and the work routine time remains at 3 minutes the performance cannot exceed 20 cows/h.
In cowshed milking, although the cows are stationary, operator time is spent walking from cow to cow, carrying udder preparation and milking equipment and transporting milk to the dairy. A substantial proportion of this time (25%) can be saved by placing milk cans, preparation equipment and spare milking machine buckets on a trolley which is moved as milking proceeds along the shed. If a pipeline is installed, milk can be transported direct from cow to dairy by vacuum, thereby allowing time to use additional milking units. Standard work routine times for the three alternatives are:
|Bucket milking machine :||2.0 mins/cow|
|Bucket milking machine with trolley :||1.5 "|
|Pipeline milking machine :||1.0 "|
In parlour milking, work routine times are minimised by reducing operator movement and either mechanising or fully automating jobs like cluster removal and teat disinfection. The effect is to halve a standard 1.2 minute WRT and thus raise potential throughput or performance above 85 cows per hour as shown in the Table.
Standard Work Routine Times Element
|Let in cow||0.2||Let in cow||0.1|
|Wash & dry udder||0.2||Wash & dry udder||0.2|
|Attach cluster||0.2||Attach cluster||0.2|
|Remove cluster||0.1||Automatic cluster removal||.|
|Disinfect teats||0.1||Automatic teatdisinfection||.|
|Let out cow||0.2||Let out cow||0.1|
|PLAN PARLOUR SELECTION||EXAMPLES|
|in a methodical way||Herd X||Herd Y|
|A.||Estimate the maximum number of cows that will be in milk||75||225|
|B.||Decide on the maximum duration of milking (hours)||1½||1½|
|C.||Calculate the required throughput A-B (cows/hour)||50||150|
|D.||Decide on the number of operators to be used||1||2|
|E.||Calculate the required performance C-D (cows/manhour)||50||75|
|F.||Estimate the maximum peak milk yield at a milking (kg or litres/cow)||20||14|
|G.||Determine (from E and F) the required parlour type and size (units and stalls) per operator||14/14|
|H.||Determine the available work routine time 60-E (mins/cow) and decide on the content of the work routine (from standard times) and the degree of automation required||1.2||0.8|
In milk producing countries where labour is either a scarce or costly resource the management of milking installations is an important aspect of farm management. Very large herds employ specialist milkers whose work is solely milking the cows and certain associated jobs such as record keeping and cleaning the milking premises and equipment. All other cow management tasks such as feeding, re-littering and manure removal are done by other people. In numerous smaller herds the milkers carry out many of these other tasks in the interval between morning and evening milking but even here labour economy in milking is important if all the many jobs in cow-management are to be completed each day. When plans are being prepared for a new milking system, management's first task is to decide on the duration of milking, and this determines the required rate of milking. For example, if a herd of 120 cows is to be milked in 2 hours, they must be milked at the rate of 60 cows/hour. This can be achieved only by installing the correct number of milking units (per operator) for the mean peak yield level and then planning the work to be done on each cow during milking to obtain the necessary work routine time. The following example of two herds, each with an average 300 day lactation and milk yield of 6000 litres per cow illustrates the point.
HERD A: All the year round calving policy; 12 hourly milking intervals. 20 litres/cow/day or 10 litres/cow/milking (mean peak yield)
HERD B: All cows calve within 3 months; 16 hour and 8 hour milking
30 litres/cow/day for first 100 days or 20 litres/cow at morning milking (mean peak yield)
For Herd B it is necessary to plan for the longer milking-out time per cow requirement which means more milking units than for Herd A to achieve the same performance.
(+0.2 mins machine idle time)
then Herd A requires 5 units (eg. 5/10) and Herd B requires 8 units (eg. 8/16).
Similar calculations have been tabulated to show the correct size of milking installation for a range of three milking performance. The Table shows the relationship between performance (P) work routine time (WRT) and static herringbone milking parlour capacity in terms of mean milk yield (kg/cow) up to which maximum performance is possible
|P cows per hour||WRT mins per cow||STATIC HERRINGBONES (units/stalls)|
|Mean milk yield (kg/cow) up to which maximum performance is possible *|
(* above these yields the milking-out times are too long for theperformance to be achieved.)
Two further examples will indicate how to use the Table. If a herd has an average peak yield of 16 litres/cow at a milking and a performance of 75 cows/hour is required the parlour should be either 14 units/14 stalls or 8 units/16 stalls. If 50 cows/hour is all that is required then a 10 unit/10 stall or 6 unit/12 stall parlour is sufficient. Obviously neither performances will be achieved unless the work routine times are 0.8 mins in the first example and 1.2 minutes in the second example. There are other general principles which can also be illustrated by the Table. To maintain performance when mean herd milk yields increase, or to increase performance at a constant herd milk yield, it is necessary to increase the number of units used. In order to increase performance, it is essential to reduce the work routine time per cow proportionally.