Efficient milking units
The fastest milking is obtained with a 16mm bore long milk tube, simultaneous pulsation and Moorepark-type wide-bore tapered liners. Most old milking machines have milk tubes with a 13.5-14mm bore. There is no advantage in increasing the claw volume above 150ml, particularly with simultaneous pulsation. For new machines and conversions, 16mm bore long milk tubes are a firm recommendation.
Excessive sagging of milk tubes below the standing cow can reduce the vacuum at the teat end. Liner life is about 2,000-2,500 cow milkings. Milk yield losses of about 5pc occur if liners are not changed.
While selection of a milking system that has established milking performance data is of paramount importance, maintenance of milking systems is given a low priority with many farmers and the under-milking due to worn liners can contribute to increases in cell count. The changing of liners on time gives probably one of the highest returns in investment to a dairy farmer.
The optimum cow throughput achieved in a swing-over parlour, by one operator, is 120 cows per hour, when minimal cow preparation practices (pre-milking) are employed. Additionally, the maximum cow throughput achieved in a swing-over parlour, by one operator, is 86 cows per hour, when full cow preparation practices are employed.
For commercial herds of more than 150 cows carrying out pre-milking, or herds greater than 120 cows carrying out full preparation, a second labour unit and additional milking units would be required in a swing-over parlour, if milking (cluster on/off) was to be conducted in less than 1.25 hours. (This limit is considered the maximum time for milking operators to spend in the pit.)
The proportion of farmers in this category will be increasing in future and they will be producing a significant amount of the national milk quota.
Large herd sizes can be milked in swing-over type parlours by increasing the number of units but an additional labour unit will be required. This adds considerably to cost.
The contribution of new technology will have a limited effect in improving labour productivity in this type of unit. The use of a rotary parlour offers great potential to substantially improve labour productivity for the larger herd size category.
Working problems associated with old rotary milking systems are now eliminated -- centre bearings, washing system and overall design for example. A 50-stall rotary can deliver a cow throughput of 200 cows per hour, by one operator, when minimal cow preparation (pre-milking) is employed. The output is reduced to 150 cows per hour, by one operator, when complete cow preparation practices (washing, pre-milking and drying) are employed. The investment in a rotary is high but the output is impressive.
Selection of steelwork and bailing options
This is a complex area and can be controversial. The placing of milking units at 760mm centres is popular in milking parlours of up to 16 units. Above this, units are spaced at 650-710mm centres, depending on the manufacturer.
The choice of straight or herringbone (zig-zag) rump rail depends on the bailing or breast rail in front. Cluster removers require swing-over arms. Some of the rump/stall combinations are listed below for herringbone and side-by-side parlours:
- Straight double rump and straight double adjustable breast rail.
This is a simple option. The main disadvantage is that cows are not positioned for the proper function of cluster removers and concentrate feeders.
- Straight double rump rail with angled concrete or steel mangers. Cluster removers and a feeding system are easy to fit. Units are generally spaced at 760mm centres. This design is popular up to 14 units and can fit in existing parlours.
- Straight double rump with straight manual bailing. Units are usually at 650mm centres. Cows take time to be trained to use this bailing efficiently. Cluster removers are easily installed.
- Straight double rump rail with sequential bailing in front and cows exiting at front. Units are usually spaced at 685-710mm. It offers good cow control and perfect positioning for cluster removal, particularly in large one-man parlours. Fast exit when bailing is lifted vertically, allowing cows an unrestricted exit.
- Zig-zag rump rail with double breast rail at front. A straight trough can be placed in front, supported on the breast rail. Pig feeders are often installed in these parlours. Usually units are at 760mm centres. Cow control is not as good as sequential bailing but the cost is less.
- Straight double rump rail with sequential bailing in front and cows exiting at side. Units are usually spaced at 685-710mm. Good cow control and perfect positioning for cluster removal particularly in large one-man parlours. Fast exit when bailing is lifted and cows exit into side passage. Automatic feeders can be installed.
The rotary option is for the large herds above 300 cows. The rotary abreast with the operator(s) outside the platform is the most popular type.
There is price variation, due to the type of stallwork, panelling in front of cows and large variations in the design and specification of the platform and hydraulic drives.
Cluster removers are usually standard but the absence of reliable pre- and post-disinfection systems can result in additional operators. It is efficient in terms of units per operator, but the large investment compared to conventional side-by-side and herringbone parlours can be an issue.
One major advantage of rotaries is that future automation is easier and the investment is rarely regretted. Also, the number of units on a rotary cannot be changed.
A complete financial and technical appraisal is required before a decision is made on investment in milking technology. While emphasis on maximising the number of milking units is correct, it is important to have a milking system where basic automation, such as cluster removers or bailing, can be installed at a future date. In some low-cost milking installations there is limited scope for basic automation to be installed.
Dr Eddie O'Callaghan is a dairy specialist working with Milk Quality Solutions. He can be contacted on 087 257 9831