Peak Milk Yield and Breeding. Managing The Dairy Herd

The next three to six weeks will focus on peak milk yield and breeding as the main objectives in managing the dairy herd.


Managing the dairy herd requires information and records. In regards to breeding, heat detection is critical. It is important to get cows that had metabolic issues at calving such as retained placenta and metritis back cycling. Keeping stress to a minimum is also crucial. Stress increases the demand for energy, which can be equal to 1-2 Kg of glucose or the energy required for 14 litres of milk. In regards to grazing management, second round grazing covers are starting at around 1,000 kg due to weather buffering and increased supplementation may be required. Remember these lower covers will have a higher Crude Protein (22-27%), which is way in excess of current requirements impacting on available energy and BCS (body condition score). If looking at using sexed semen, cows that have had metabolic issues including mastitis are not suitable.


Due to the weather over the last month, there is a purple tinge showing on the tips of the leaves. This is indicative of low phosphorous in the plant due to soil moisture deficit. Continuous low phosphorous intake can lead to ‘PICA’ and animals can be observed eating stones. Back in the drought of 2018 along with phosphorous, calcium and magnesium were also low. These are critical macro minerals in the cow’s diet for milk yield, rumen buffering, muscle contraction and fertility. The calcium inclusion in the concentrate should be 1.3% to 1.5%/kg fresh weight. If buffer feeding, top dress the buffer with 100 grams/cow/day of a post calving mineral.

Peak Milk Yield

Peak milk yield should occur at 55-65 days in milk so if the mean calving date is 15/02 to 20/02 then peak will be in 3 weeks time, but for the mid-March and April calvers this will be mid to late May. There is one opportunity to peak and then its managing persistency. This starts with managing the cow from calving and again information is critical.

  • The first milk recording should be taken 60 days after the first cow calved or 30 days after the mean calving date.
  • Go through the recording sheet and establish the number of cows over the average and their yield. Normally 48-50% of cows will be over the average by roughly 3 litres.
  • Of those over performing cows, 18% can be producing a further 2 litres higher in milk production.

It is important to know this and manage the dry mater intake required for your herd, working on average milk yield can result in the peak milk yield not being achieved and conception rates to first service not meeting the target.

Other information available on a collection basis are milk composition and milk lactose.

Milk fat % to milk protein % ratio after calving should be less than 1.4:1 and by 30 days in milk should be less than 1.3:1. The milk lactose by 30 days in milk should be in the range of 4.85%-4.95% and maintained to 100 days in milk.

Milk lactose is the perfect barometer for the energy status of the cow. A drop of 0.05% in milk lactose is very large as it is an osmolyte and a driver of milk volume. A drop in milk lactose will result in lower milk yields and protein. This can be seen from the milk composition in Table 1 (Farming Press: March 6th to April 10th), where there is a potential issue with negative energy balance. These are averages so there is a high percentage of cows over these ratio’s that are definitely in negative energy balance for longer than they should be. In this situation the cow will mobilise body fat to supply energy to meet requirements, so for the milk yield being produced these cows can produce more. As the rumen is restricted in size until 60-70 days in milk supplementation is critical.

In table 2 taking the average milk composition for a Coop for 2020 of milk fat% 4.22 and milk protein% 3.61 one can see achieving an extra 1 to 1.5 litres at peak has a potential to deliver 17.58Kg to 26.37Kg milk solids per cow worth €77.36 to €116.04 per cow. Supplementing an extra 2Kg/cow/day of concentrate for 35 days from 25 days calved to peak would cost €23.10. The return being considerable. The response to concentrate supplementation is optimum over the first 120 days in milk and in particular over the first 80 days.

Factors affecting milk lactose:

  1. Grazing swards too high in protein percentage as the cow will require to use energy to get rid of this, this requirement can be of the order of 1-2kg of ration supplemented.
  2. The high protein can also result in the sugar percent in the grazing sward being down in single figures rather than being up in the high teens. This will result in reduced microbial synthesis resulting in low milk protein.
  3. Mastitis
  4. Stress
  5. Sward fertilisation. It is important to have a green leaf and potash plays a crucial role. Swards can have pale green leaves and yellowing at the tips and edges this can be due to high sodium readings very noticeable on the coast. These swards will not photosynthesise to their optimum reducing the sugar reading. Sodium does not sweeten grass sulphur does.
  6. Drop in digestibility of the sward.
Milk Composition
Farming Press Table 1
Date March Ratio March Ratio March Ratio March Ratio April Ratio April Ratio
6th.   13th.   20th.   27th.   3rd.   10th.  
BF%     4.96 1.44:1 5.56 1.57:1 4.73 1.37:1 5.02 1.43:1 4.83 1.33:1 4.68 1.36:1
MP%     3.45   3.55   3.46   3.51   3.64   3.43  
BF%     5.32 1.39:1 5.11 1.45:1 5.04 1.47:1 4.43 1.32:1 4.97 1.44:1 4.41 1.19:1
MP%     3.83   3.52   3.43   3.35   3.44   3.72  
BF%     4.80 1.30:1 4.94 1.46:1 5.23 1.48:1 5.23 1.48:1 4.92 1.42:1 4.37 1.23:1
MP%     3.68   3.38   3.54   3.54   3.47   3.56  


Peak Potential-Table 2 Times
Litre (+) Kg Peak Kg BF% MP% Kg MS €/Kg
Peak 1 1.03 218 224.54 4.22% 3.61% 17.58 4.40 77.36
1.5 1.55 218 336.81 4.22% 3.61% 26.37 4.40 116.04
Supplementation Total
Kg (+) Days Kg c/Kg
2 35 70 33.00 23.1


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