The question is often asked as to how many cows are needed to justify a rotary milking parlour. That may be a simple question, but the answer is often more complex.

As a basic rule of thumb, there probably needs to be 300 cows on the farm before a rotary is considered. This is because a 30-unit herringbone can be operated by one person milking 10 rows of cows, which is definitely at the upper end of what is a reasonable ask of anyone.

If there are more cows to be milked, it involves either a larger herringbone involving two operators or more rows per operator.

There are substantial differences in terms of capital costs between herringbones and rotary parlours. Because there are huge differences in spec between parlours, it’s hard to compare like with like but in the main you are talking about anywhere between €500,000 and €1m of a spend for a 50-bail rotary parlour on a greenfield site.

This figure excludes VAT but includes all other costs associated with construction such as steel, plant, concrete, builder, wiring, plumbing, electricity connection, etc.

Contrast that to a herringbone parlour which is much cheaper to construct and fit out. They’re a much smaller-scale, have less moving parts and are easier to construct. Having said that, costs vary massively depending on specification.

So, a 30-unit herringbone can cost anywhere from €250,000 to €500,000, depending on the specification.

I have been in yards where the capital budget has been blown on herringbones and where other farmers would have a rotary built for the same money, so it’s all about spec and how well the project is managed.


The answer gets even more complex when you consider other factors such as the proportion of the land leased, the term of the lease, labour availability, stocking rate and how much debt is already on the farm. At larger-scale, there is a definite trade-off between higher capital costs and lower labour requirements.

For example, take a 400-cow farm that is being converted to dairy and presume there are no existing milking facilities on the farm. Presume also that a 40-unit herringbone parlour is going to cost €350,000 to construct, while a 50-bail rotary is going to cost €700,000 to construct. In both cases, there are three full-time employees on the farm.

The difference in capital cost is €350,000, which equates to just over €31,000 per year in annual repayments if the amount is borrowed over 15 years.

Let’s presume that all other costs are the same (in reality, rotary parlours use more electricity, more detergents and more water).

Essentially, the rotary parlour is a one-person parlour for most of the year whereas the herringbone parlour is a two-person parlour for all the year. With three labour units on the herringbone farm and even accounting for holidays, there should be sufficient manpower to milk the cows during the week but the problem is at weekends.

Smaller herringbone parlours are another option on large farms.

A relief milker will be needed every weekend if the full-time employees are to have every second weekend off. At, say, €60 per milking and presuming there are cows milked for 46 weeks a year the total cost of weekend relief milkers will be €11,000 per year. This is still €20,000 per year short of the higher capital costs of the rotary.

However, it is not comparing like with like because overall hours worked per full-time employee are likely to be much lower on the rotary farm.

For example, if one person can milk in the rotary then it should be possible to have two out of three weekends off on the rotary farm. This means each employee on the herringbone farm would be expected to work up to 23 weekends per year whereas the employees on the rotary farm would be expected to milk on 15 weekends per year. That’s a difference of eight weekends more per employee per year, which equates to a total of 48 days more in the year.

While it could be argued that the employees on the herringbone farm should get paid more, what probably happens in reality is that employees on both farms get paid the same but those on the rotary farms have more time off and a better work-life balance.

The question is whether that is worth, the extra €20,000 in debt servicing costs each year?

It is also important to note that the benefits of the rotary are only accrued where there is one person milking. On many rotary parlours, there ends up being two people involved in milking which undermines any labour efficiency.

There is a third approach and that is to build smaller and cheaper herringbone parlours on large farms where a rotary parlour cannot be justified, such as on leased farms. For example, some large farms have recently been developed with a 26 or 30-unit herringbone even though they are milking 400 cows.

While milking times are longer compared to larger parlours, they are one-person parlours which enable employees to do just one milking per day. With relief milkers employed at weekends, it is still possible to have a good work-life balance and to only work one weekend in three for the main season.

On top of this, the capital spend has been more than halved when compared to building a rotary so the return on capital is far greater.

Stocking rate

Stocking rate is another key consideration when deciding on what size of milking parlour should be built. This is particularly important in light of proposed changes to the nitrates derogation.

Whether we agree with it or not, there is a strong likelihood that some farms will have to reduce cow numbers over the coming years. Sometimes, a reduction in stocking rate can be for the right reasons.

Take a 100ha farm milking 360 cows, which is a stocking rate of 3.6 cows/ha on the milking platform. While this stocking rate may have been justified in the past with higher chemical nitrogen use and more benign weather patterns, with less nitrogen being used and more disruptive weather patterns running high stocking rates is leading to higher costs and more workload.

Stocking the farm at three cows/ha may increase profitability and greatly reduce workload. It may also mean that a smaller milking parlour is required, potentially saving a lot of money in capital expenditure.

Look for an appropriate stocking rate before deciding on what size parlour to build.

Milking efficiency

Research carried out by Teagasc has shown that rotary milking parlours are significantly more efficient than herringbone parlours.

The research looked at a number of key performance indicators and found that cows milked per operator was almost 90% higher in a rotary parlour. The results were captured by placing cameras for two one-week periods at milking facilities on commercial dairy farms. Seventeen of the farms had herringbone parlours, while 10 had rotary parlours.

The results showed that, on average, herringbone parlours milked 94 cows per hour while rotaries milked 170 cows per hour. The researchers concluded that the difference in milking efficiency between farms with the same type of parlour warrants further research to see what is driving that efficiency.

In brief

  • There is a substantial difference in capital costs between rotary and herringbone parlours.
  • On larger farms, the advantage of a rotary is improved work-life balance provided one person does the milking for most of the season.
  • Some farmers are building smaller herringbone parlours on larger farms, where a rotary cannot be justified.
  • There is a big variation in milking efficiency between farms with the same parlour type.