Does milk production differ for cows milked Once- or Twice-A-Day?
Updated: Apr 21
Traditionally, dairy farming in NZ has included twice-a-day (TAD) milking, however, milking once-a-day (OAD) for the entire season has become more and more common.
Current estimates of full season OAD is between 4-9% of NZ herds (Edwards 2019).
Previous research has been completed using controlled research studies (i.e. half the herd milked OAD and the other TAD). These studies suggested that cows milked OAD produced between 20-32% less milk than those milked TAD.
This study used data from commercial herds (rather than research herds) to compare full season OAD milking to full season TAD.
The second part of this series on milking frequency can be found here --> Do herds milked once daily have better 6-week in-calf rates than twice daily herds?
Holstein-Friesian-Jersey crossbreed (FxJ) and Jersey (J) cows appeared to be less affected by OAD milking than Holstein-Friesian (F) cows
Persistency (or flatter lactation curves) were superior for cows in OAD herds compared with TAD herds
In commercial herds, the difference in milk production between OAD and TAD milked cows was smaller than those reported in previous experiments.
On average, cows milked OAD all season produced 21% less milk, 17% less fat and 17% less protein than cows milked TAD.
The figure below shows the difference in milk yield between cows milked in the 2 systems.
But what about breed?
As has been previously published, Holstein-Friesian-Jersey crossbreed (FxJ) and Jersey (J) cows appeared to be less affected than Holstein-Friesian (F) cows by OAD milking.
For FxJ cows, those milked OAD produced 19% less milk than those milked TAD. The difference for J cows was even less at 17% less milk. These are graphically displayed in Figure 2 below.
The difference between OAD and TAD milked F cows was 25% for milk (Figure 2 below), 19% for fat and 20% for protein.
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How does their milk production persist over the lactation?
Milk production curves (as below in Figure 3) showed that there was a rapid increase in milk production up to 30-50 days after calving followed by a gradual decline until the end of lactation.
There is some discussion that cows milked OAD all season dry themselves off early as their milk production persistency is less than that of TAD milked cows.
In this study, lactation persistency was defined as how much milk was produced between days 121 and 180 in relation to how much was produced between days 1 to 60 as a percentage.
For example, if a cow produced 500 L between days 121 and 180 and 1,000 L between days 1 and 60, she would have a lactation persistency of 500 ÷ 1,000 = 50%.
If another cow produced 800 L between days 121 and 180 and 1,000 L between days 1 and 60, she would have a lactation persistency of 800 ÷ 1,000 = 80%. This second cow was able to maintain her milk production better than the first cow, hence her lactation persistency was higher.
Contrary to popular belief, cows milked OAD all season in this study had greater persistency than cows milked TAD all season (Figure 4).
Did breeds differ in persistency?
F cows milked OAD had on average 4.7% greater persistency than F cows milked TAD (Figure 5).
The same held true for FxJ cows, with those milked OAD having greater persistency than FxJ cows milked TAD.
Interestingly, J cows had similar persistency for milk and protein production in both OAD and TAD herds. This is evident in the graph below with J cows milked OAD having a persistency of 78.3% and J cows milked TAD having a persistency of 77.4%.
These results presented show that the cows milked OAD actually had more persistent (or flatter lactations) than the cows milked TAD; opposite to what was originally hypothesised.
Potentially there may be an important genetic component that make some cows more adaptable to OAD milking and hence have less of a decrease in milk yield than other cows. It appears that this may also be related to breeds in that Jerseys appear to tolerate OAD milking compared with Friesians.
What data were used?
This study included data from 11,848 F, 11,677 J and 27,720 F × J spring-calving cows located in OAD herds (278 herds) or TAD herds (248 herds) over multiple lactations.
OAD herds were selected where 100% of the cows were milked OAD for the whole lactation.
TAD herds were selected using GPS coordinates in a 30 km range from the OAD herds.
Data were provided by LIC and spanned the 2008 to 2012 milking seasons. The authors did not have access to the data regarding how long herds/cows had been milked OAD or TAD for, or the feed inputs for each farm (i.e. pasture only or large amounts of imported feed).
Previous research (not commercial herds) has placed the difference in milk production to be more than 20% between cows milked OAD and those milked TAD.
This study has shown that out in industry, the difference (on average) between herds that milk cows OAD vs TAD appears to be not as large. As it was not known how long herds had been milking OAD, it is not known how much selection had occurred (i.e. culling of cows that were not suited to OAD milking).
Additionally, this study did not report herd size. In another study (that we have summarised here!), OAD herds tended to have fewer cows than TAD herds did. This may be a factor that would help explain some of the differences between the 2 milking frequency systems.
This study also looked into the effects of lactation number for OAD or TAD milked cows. Please let us know if you would like to see a summary on this and we will whip one up for ya!
Lembeye F, Lopez-Villalobos N, Burke JL, Davis SR. 2016. Milk production of Holstein-Friesian, Jersey and crossbred cows milked once-a-day or twice-a-day in New Zealand. New Zealand Journal of Agricultural Research. 59(1):50-64.