Full season once-a-day (OAD) milking


13 min read

Key considerations Full-season OAD consideration What to expect Transition to full-season OAD Videos

This page outlines the potential benefits of switching to full-season once-a-day (OAD), such as labour flexibility, increasing herd size, reducing energy requirements, and improving grazing management. It also highlights the considerations to keep in mind, including the importance of planning, potential production losses, and the various financial and environmental implications of making the switch. By assessing these factors carefully and understanding the potential changes in profitability and management practices, you can make an informed decision about whether OAD milking is right for your farm.

Successfully switching to full season once-a-day (OAD) milking requires planning and an evaluation of your farm system.

Milking is a time-consuming task; it typically accounts for more than half of the labour hours on New Zealand dairy farms. Halving the number of milkings may increase the attractiveness of the job (more flexible working hours) and increase the pool of labour available by employing part-time workers.

Interested in changing to full-season OAD milking?

Keep an eye on our Events section for the biannual once-a-day milking conference due again in 2023, or have a chat to your local farm performance contact about OAD groups.

Key considerations:

  • OAD can be as profitable as twice-a-day (TAD), with the main factors being minimising any decrease in production and the amount of cost savings achieved by adopting OAD.
  • There are many different motivations for using full-season OAD milking; this influences the productivity/profitability change when moving from TAD milking.
  • Generally, the farmers who see the most benefit from OAD are those whose current resources are putting stress on a TAD system.
  • Before changing your farm system it’s important to assess the potential benefits and determine whether it fits with your future aspirations and goals. So when assessing OAD milking as an option it is recommended that you complete a budget.
  • It is paramount to give attention to detail as you are only observing animals once a day.
  • Production losses will depend on the breeding and TAD production level of the cow:
    • More Friesian & higher TAD production → higher milk production losses (%).
    • Younger Holstein-Friesians (2/3y/o) have higher losses than mature cows.

Regional distribution of OAD herds

Is full-season once-a-day (OAD) right for me?

Farm considerations

Managing capital constraints:

  • Increasing herd size within existing dairy infrastructure (managing long milking times)
  • Integrating new or previously inaccessible land, e.g. poor races, water reticulation etc

Reducing energy requirements and lameness from walking:

  • Where the farm has long walking distances
  • Where paddocks have an uneven contour or there are large differences in elevation between the paddock and the dairy
  • Where walking in the afternoon coincides with times of high temperature/humidity

Minimising cow wastage:

  • Reducing culling due to reproductive performance, lameness
  • Reproductive performance and lameness may be related to walking distances and elevation as described above

Improving grazing management:

  • Irregular paddock sizes make hitting target residuals difficult when constrained by an afternoon milking
  • Cows spend more time on pasture
  • Better matching feed supply/demand on farms with relatively flat pasture growth curves

Labour considerations

Increasing labour flexibility:

  • More productive use of the rest of the day; tasks not interrupted by an afternoon milking

  • Potential for 24hr grazings (i.e., no animal work till next morning)

  • Can handle more cows per full time equivalent (FTE)

  • Accessing new labour pools (e.g., milking can occur at any time during the day)

Improving staff satisfaction:

  • Less hours milking
  • Improved staff retention

Lifestyle benefits:

  • Spending more time with family
  • More time for off-farm activities
  • Reducing physical stress so you can stay on-farm longer

What to expect from full-season once-a-day (OAD)

Data from the Dairy Industry Good Animal Database (DIGAD) and levy milksolids database has been used to compare some of the physical differences between herds milking OAD and paired geographically similar herds milking twice-a-day (TAD), giving you an idea of what you can expect after making the switch.

The results are an association analysis so cause and effect relationships cannot be determined but they do give insight into what OAD farmers have changed along with milking frequency relative to their TAD peers.


Herds milked OAD had more concentrated milk, lower milk volume and higher SCC.

  • Herds milking OAD were producing 11% fewer milksolids before adopting OAD (possibly due to farm limitations or running more extensive farm systems).
  • Herds that adopted OAD experienced on average an 11% decrease in milksolids in their first season OAD but there was variation between herds.
  • Despite production of the OAD herds returning to pre-OAD levels in the 4th season milking OAD, they remained 11% behind their TAD pairs.
  • To retain an equivalent level of profitability, costs must be removed from the farm business when adopting OAD - see the economics section for more details.
  • Somatic cell count (SCC) was higher by about 20,000 cells/ml after adopting OAD.

OAD Production graphs

Once-a-day (black square) performance before (year -4 to -1) and after adopting OAD (year 0 to 4) relative to paired TAD herds (white square).

  • In the current OAD herds, the level of production change after adopting OAD was influenced by the prior level of herd productivity.

OAD Production vs years

Productivity (kg MS/cow) before and after adopting full season once-a-day milking.


In general, OAD herds had better reproductive results than their paired TAD herds.

  • Calving rate (determined in previous season when herd was TAD) was not different in the first season of OAD.
  • 3 and 6 week calving rates were higher for OAD herds after adopting OAD and relative to their TAD pairs after the first season of milking OAD.
  • The metrics 6-week in-calf rate and not-in-calf rate were difficult to determine from the dataset

Note: with more cows calving earlier there will be an increase in feed demand in early spring if planned start of calving is not changed.

OAD reproduction graphs

Comparison of 3 and 6 week calving rates between OAD (black square) and paired TAD herds (white square).

Herd age structure and culling decisions

Herds milked OAD had a similar age structure, and replacement rate to TAD herds but the removal reasons differed.

  • OAD herds had significantly fewer animals leaving the herds due to being empty (not pregnant).
  • More animals were leaving OAD herds due to low production, and udder/mastitis related causes.

It is important to note that when a farmer removes an animal from the herd only one reason can be selected, so if the animal was both empty and a low producer then it may have been recorded as a low producer. The default reason is “other” and many farmers had not selected the specific removal reason.

Financial and systems

If a production drop is expected when adopting OAD, costs must be removed from the farm business to retain an equivalent level of profitability.

  • The cost reduction required is directly proportional to milk price, using the formula: cost reduction ($/kg MS) = change in production % × milk price.
  • For example, if the longterm milk price is $5/kg MS and a 10% drop in production was experienced when adopting OAD, then $0.50/kg MS of costs must be removed to retain an equivalent level of profit.
  • This means OAD is easier to justify in a low milk price environment, or if the decrease in production minimised.
  • If target cost reduction is not achieved, it doesn’t mean OAD is unprofitable.
  • If target cost reduction can be exceeded, then OAD is likely a more resilient farm system.
  • Costs reductions could come from labour, dairy expenses and electricity, vehicle, R&M, animal health and breeding.

There is limited data available on OAD in DairyBase. Using data from the 2013/14 and 2014/15 seasons the following observations are made:

  • OAD farms had a similar stocking rate to TAD farms
  • OAD farms were more labour efficient
  • OAD farms consequently had less revenue and lower expenses
  • This group of OAD farms did not achieve sufficient cost reduction so had a lower profit/ha.
  • These were relatively high milk price years.
KPI's TAD OAD P value Difference
Stocking rate (cows/ha) 2.8 2.8 0.27 -2%
Kg Milksolids/ha 1159 975 <0.0001 -16%
Kg Milksolids/cow 402 339 <0.0001 -16%
Cows/FTE 139 157 0.00 +12%
Gross Farm Revenue/ha $8,738  $7,490 0.00 -14% 
Operating expenses/ha $6,285 $5,589 0.00  -11% 
Operating profit/ha $2,446 $1,839 0.00  -25% 
Operating return on Dy Assets % 6.0%  5.0% 0.23 -16%

Economic and farm system comparison between OAD and TAD herds from DairyBase in 2013/14 and 2014/15. Differences are statistically significant if the P value is less than 0.05.

Another dataset was published in 2007 that compared the financial performance of 22 farms that have switched from TAD to full season OAD milking. The authors of this paper reported:

  • a 25% reduction in farm working expenses upon switching to OAD
  • a 6% reduction in total milksolids production
  • that farmers switching to OAD milking for lifestyle reasons tended to make lower financial gains than those seeking further farm development

The full paper ‘Can you make money milking OAD’ can be read below.


Modelling was done using Farmax and Overseer to predict the physical and environmental implications of adopting full season OAD milking (nitrogen leaching and greenhouse gas (GHG) emissions). Scenarios were evaluated in four regions; Northland, Waikato, West Coast and Southland.

Three scenarios were compared to a base farm that was typical for the region.

Scenario 1: 10% predicted production loss when switching to OAD (e.g. what could be expected in the first year OAD).

Scenario 2: 10% increased stocking rate to compensate for production drop in Scenario 1.

Scenario 3: Maintaining same production, with a shift in breed (e.g. what could be expected in the 4th season of OAD).

Results varied by region, however the following general observations were made:

  • Scenario 1 had the lowest nitrogen leaching, with decreases of 0-5 kg N/ha/year over the base farm. This scenario also decreased GHG emissions over the base farm.
  • Increasing stocking rate in Scenario 2 had the highest nitrogen leaching, between 0-2 kg N/ha/year higher than the base farm. This scenario increased GHG emissions over the base farm.
  • Scenario 3 produced the same, or a slightly lower (0-2 kg N/ha/year), level of nitrogen leaching compared to the base farm. In this scenario there was less nitrogen leaching on the effluent block due to less being captured, as well as less from other sources (e.g. farm tracks), which was offset by slightly more leaching on the non-effluent block due to cows spending more time on pasture. This scenario produced similar GHG emissions compared to the base farm.

Making a successful transition to full-season once-a-day (OAD)

Careful planning and preparation during the final season on twice-a-day (TAD) are important to making a successful transition and minimise adverse effects in year one of OAD.

Drying off at the end of the final season

  • Take this opportunity to eliminate/control/cull any mastitis problems, and cows with weak udders, before OAD begins.
  • If there is evidence of a mastitis problem in the herd (e.g. herd SCC above 250,000), serious thought should be given to the use of dry cow therapy and teat-seal on all cows. The use of teat-seal in the heifers, about 4 to 5 weeks before calving for their first time, should also be assessed.
  • At the very least, stick to the guidelines given by SmartSAMM, with respect to treatment and culling.
  • Including a high percentage of replacements into the herd will enable more voluntary culling; 2-year-olds generally have lower SCC than older cows, and higher BWs. But 2-year-olds produce about 25% less per cow than mature cows, and their milksolids yield is decreased by OAD to a greater extent than the yield of older cows.

Source: Lower North Island OAD discussion group

Cow selection

  • Current herds that have adopted OAD have more Jerseys and crossbreeds and fewer Holstein-Friesians (DIGAD* data). They also use more Jersey and crossbred semen.While cause and effect cannot be determined, the analysis of DIGAD data may indicate farmers believe Jerseys are more suited to OAD and have increased the proportion of Jerseys and crossbreeds in their herds, or alternatively it may mean that Jersey farmers have been the early adopters of OAD. DIGAD Dairy Industry Good Animal Database
  • Good udder conformation is especially important under full season OAD
  • Cull/sell cows that have a record of clinical mastitis and/or high SCC before OAD begins.

Breed proportion graphs OAD

Comparison of breed between OAD herds (black square) before (year -4 to -1) and after adopting OAD (year 0 to 4) and paired TAD herds (white square).

Stocking rate and pasture management

Decreased milk production per cow during the first season of OAD reduces the feed requirement of the cow. To ensure maximum pasture utilisation stocking rate may be increased but this should be done with caution.

Stocking rate

In the first year or two on OAD, an increase in cows/ha (by 5 to 10%) is often recommended to compensate for culling unsuitable animals, the expected decreases in pasture eaten per cow and milk produced per cow.

If you were overstocked on TAD, i.e. minimal/no spring surplus and consistent low grazing residuals, no increase in stocking rate may be required.

After the first season or two on OAD and unsuitable cows have been culled and per cow production begins to increase it may be no longer necessary to carry additional cows.

You will quickly know if you have got your stocking rate wrong:

  • Too low – large spring surplus that needs controlling
  • Too high – no spring surplus and low grazing residuals

Another consequence of stocking rate being too high is the likely decrease in pasture intake and yield per cow. In this case, milksolids yield per cow would be depressed by OAD and by underfeeding.

So, any increase in stocking rate should be calculated carefully, to ensure that there will be enough cows on-farm to enable early culling and to fully utilise the pasture without over-stocking the farm.

Pasture surplus

If you initially opt not to increase stocking rate and find you have excess feed you will need to decide what to do with it:

  • Feed remaining cows better – a good option if you were overstocked anyway/per cow production was below district average.
  • Increase cow numbers.
  • Become more self-contained – i.e. wintering more cows on or retaining young stock.
  • Sell surplus feed – either as standing grass/crop or baleage/hay/silage.

Grazing management

Cows milked OAD can be successfully managed with either 12 or 24 hour grazing. The key determinant of which you choose will be paddock size and personal preferences.

On farms with a large range in paddock sizes OAD increases the flexibility of when cows can be moved during the day, potentially making it easier to achieve target grazing residuals. Alternatively, some farmers don’t want the hassle of moving cows in the afternoon so choose 24 hour grazing.

Quality and quantity of feed on offer is of greater importance.

  • Cows milked OAD are more sensitive to feed deficits and declining pasture quality and respond by reducing production.
  • When additional feed is available, or pasture quality improves, OAD cows are less likely to increase production. Instead they use the additional feed for body condition score gain.

Pasture management for cows milked OAD is critical to the success of the system. Any mistakes with feeding will quickly be seen in the vat and are often difficult to correct.

Winter grazing

Cows milked OAD generally dry off in better condition than TAD cows. If you are purchasing winter grazing do so on a kg DM/head/day basis not per cow/week. This way you can specify the level of feeding required and will not be paying for feed you don’t need.

Milking machine and milk cooling

On OAD, udders are likely to be at maximum capacity. Therefore, during milking, the rate of milk flow through the milking machine will be faster than on TAD. These conditions may necessitate some changes in the machine.

  • Cup slip can be a problem on OAD. Seek advice from experienced OAD farmers or from milking specialists, about the type of teat-cup liner, long milk tube, and milking cluster that have been found to work effectively with cows milked OAD. Predominantly it is the liner that may need to be changed.
  • Ensure that the machine’s vacuum level is stable, and at the correct level, during the whole milking. The machine must be able to hold vacuum with a higher milk flow. This is potentially an issue with a long 50 mm milk line.
  • The milk pump and receiver must have sufficient capacity to cope with the faster rates of milk flow expected on OAD. Cows milked OAD have a rapid letdown and flooding of the milk line has been a common problem in older sheds.
  • The plate cooler and refrigeration unit must have sufficient capacity. Refrigeration is particularly a problem on daily collection where all the milk enters the vat only once. If a silo is 60% full at 18°C it will take 3 hours to get to less than 7°C. A cooling tower or chilled water may be required to ensure compliance at pick up.

Cows milked OAD take longer to milk – approximately two minutes. If milking is already taking 3+ hours you may need to reconsider staff tasks to ensure milkers don’t become fatigued during the milking process i.e. staff swapping roles half way through milking. In herringbone dairies slow milkers may need to be managed separately to prevent every row being delayed.

Mastitis and treatments

Cows milked OAD or TAD are at a similar level of risk of developing new infections. Milking OAD does not by itself increase the risk of mastitis.

After cups-off, it is not possible to inspect the teats/udders closely for the next 24 hours, a much longer time period than on TAD. This longer inter-milking interval may enable mastitis infections to become more firmly established before the next milking.

Somatic cell count

Cows milked OAD have a somatic cell count (SCC) that can be twice as high as cows milked TAD.

This difference starts to show up once cows have moved beyond peak lactation (weeks 6-8 after calving) and remains until the end of lactation. There is likely to be greater increases in SCC during the second half of lactation, which may require high SCC cows to be dried off early.

Dairy farms have shown that it is possible to supply high quality, low somatic cell count milk in spite of OAD milking. The best way of achieving this is to keep SCC low in first half of lactation, meaning days in milk can also be maximised.

Preventing mastitis on OAD

  • During milking ensure that teat cups are aligned correctly on the teats, and that they remain firmly in place without slipping.
  • Before cup removal ensure that all udders/quarters have been milked-out evenly.
  • After cup removal look for, detect and attend to, any abnormal quarters (e.g. full/hard/hot), even if cups are removed by automatic devices.
  • Implement teat spraying during lactation and improve the degree of teat coverage with teat sanitiser.
  • The herd should be stripped more regularly.
  • The use of dry cow antibiotic therapy at the end of lactation will reduce the existing infection levels and lower the risk of calving with mastitis in the following season.

Detecting and treating mastitis on OAD

Detection by regular herd testing and use of SCC information is an important tool for keeping your SCC levels within appropriate levels.

Cows with high SCC should be checked for mastitis by stripping out the foremilk and examining for visual signs, or by using the Rapid Mastitis Test (RMT) or by testing foremilk conductivity.

Advice on sub-clinical treatment options should be sought from your local veterinarian.

Treat clinical mastitis as you would a cow being milked TAD. Antibiotic treatments with 12 hr treatment intervals should be avoided. Consult your veterinarian for drugs more suited to OAD, including 48 hour treatments.

Withholding times

If a product is not registered for OAD milking, use the number of milkings recommended for TAD. For example, if 48 hours and four milkings recommended on TAD, then use four milkings, or 96 hours, on OAD; that is, the withholding time on OAD will be twice as long as for TAD. Consult your veterinarian for drugs with shorter withholding periods.

Seasonal herd management

Milking OAD can bring some additional herd management considerations.


Cows can be milked OAD from the day they calve. Fonterra’s rules state that colostrum from each cow should be withheld from the vat for at least 8 milkings, equivalent to four days for herds milked TAD.

While the newly-calved cow is still in the colostrum herd, check all quarters/cows with the Rapid Mastitis Test (RMT). Do not put a cow’s milk into vat unless RMT indicates a low SCC.

It is advisable to inspect newly-calved colostrum-cows twice a day, to minimise losses e.g. from milk fever. If dusting pastures in wet weather e.g. with magnesium chloride, do it twice a day.


With cows only visiting the dairy once daily there is less chance to observe heats during mating. Most OAD farmers use tail paint to assist with detection of cows on heat. Some use scratch pads as an additional device.

Some OAD farmers observe cows and their tail paint for signs of heat only at the one milking per day, while some also observe the cows while they are undisturbed in the paddock.

Videos: Why milk once-a-day? - A farmers perspective

Why milk once-a-day? - Georgie and Adam McCall

Video 14:08 min

Why milk once-a-day? - Leo Vollebregt

Video 10:02 min

Last updated: Sep 2023
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