• Steve McGill

Reduce Post peak decline - Get more days in milk

Peak milk production normally occurs 6 weeks after the cow has calved and cows should not drop more than 6-7% month on month. However, it is possible to rein this in to 4-5% month on month. On non-irrigated properties, pasture quality and quantity has become increasingly difficult to maintain. For those with the benefit of irrigation, quality of pasture is generally good, but the quantity of pasture available can be limited due to irrigation systems struggling to meet evapotranspiration rates on hot days. The challenge is how to provide adequate levels of high-quality forage to keep your cows milking well.

What is the cost of post-peak decline?

Herd Test Average 2020/21

% Rate of Post Peak Decline

Lost Production (kg MS/cow/month

































$/COW LOST @$7.54kg Milksolids Pay out


$ Lost per average farm (351 cows)


Source: Adapted from NZ Dairy Statistics 2020/21 season

In the 2020/21 season post-peak decline cost the average Waikato dairy farmer $209.08/cow or $73.388.05 in lost milk production from post-peak decline. This season due to hotter days, less rain fall, lower pasture growth rates and higher milk solids pay-out the cost of this will potentially range much higher. These figures are extracted from average herd test data. The rate of your post-peak decline could be better or worse than this based on factors such as stocking rate, supplements and pasture growth rates. We are more than happy to help work out the cost of post peak decline for your individual farms.

What are the factors that increase post-peak decline and what can we do about this?

Too much Neutral Detergent Fibre (NDF)

The higher the NDF of the feed the more space it takes up in the rumen and the longer it takes to break-down. Simply put animals feel full earlier. The optimum average NDF level in the diet for a lactating dairy cow is 32%/kg DM. We can see that if we have summer pasture with an NDF of 45%/kg DM and pasture silage with an NDF of 55%/kg DM that we are going to struggle to reduce the average NDF in the diet to maximise dry matter intake.

We may also have the situation that cows are full but rapidly losing body condition due to insufficient energy in the diet. Cows in this situation may rapidly lose weight and poor body condition will limit days in milk.

To maximise dry matter intake then we need to use lower NDF concentrates to help us achieve that.

Lack of nutrient density in the diet:

Many people talk about Metabolizable energy which is not detailed enough to meet the individual nutrient requirements of the cow. It is necessary to provide the right balance of nutrients.

Summer pasture is often low in rumen degradable protein and amino acids such as Lysine and Methionine. Supplementation of cows with protein meals that are high in lysine and methionine are necessary to ensure that energy available to cows is being partitioned into milk production and not excessive body condition. Forage based supplements such as silage (pasture or maize), hay, chicory and brassica crops are often fed during the summer months to fill gaps in pasture availability. Often, they are not enough to meet the nutrient requirements of the cows for lactation.

It is also necessary to evaluate the macro and micro mineral levels provided by the diet. Forage based supplements such as silage (pasture and maize), hay and brassica crops can be low in essential macro-minerals such as Calcium (Ca), Phosphorous (P), Magnesium (Mg) & Sodium. These macro minerals are essential for maintenance, milk production and animal health, therefore supplementary sources should be made available daily.

Heat Stress:

Heat stress is not only a major animal welfare concern but also a reason cows can lose substantial amounts of milk volume over the summer months. Cows not only take on heat from the environment but also from heat generated by the rumen (The rumen contributes over 50% of the cows’ metabolic heat). The temperature the cows feels is a combination of ambient temperature, radiant heat, and humidity. High humidity and lack of breeze can make cows feel even hotter. As temperatures increase above 20 degrees Celsius and 70% humidity cows will start to experience varying degrees of heat stress. As the cow becomes more heat stressed. The increased breathing rate and increased pulse rate push maintenance energy requirements up by 20-30%. As daytime temperatures push over 25 degrees Celsius then cows will drop dry matter intake by 10-20%. Cows suffering from heat stress often lose milk volume substantially if heat stress is not managed effectively.

Providing plenty of access to water and shade are the absolute bare minimum things to provide the cows

Key nutrition approaches to help reduce both post peak decline and heat stress.

1. Maintain maximum levels of dry matter intake.

This can be challenging when we have limited pasture availability and it has high Neutral Detergent Fibre (NDF)

2. Offer a total ration with NDF values within the range of 32-35%.

The fermentation of fibrous products always generates more heat. Silage or lucerne hay produces much less heat than Cereal Straws such as Barley or Wheat. Low NDF concentrates help reduce the heat load on cows

3. Provide a stable rumen pH

The ration needs to have adequate physically effective rumen NDF to maintain rumen motility, as this allows Volatile fatty acids (VFA’s) to be transported to the rumen wall for absorption. Diets high in silages also increase the acid load in the rumen. Rumen Buffers such as Acid Buf should be the product of choice as peer reviewed research has shown that they have consistently stabilized rumen pH for longer during times of acid challenge

4. Increase supplementation of feeds that generate glucose for the cow.

Under heat stress cows favour glucose as the premium source of energy. We want to provide a balanced supply of fermentable carbohydrates while maintaining a stable rumen pH. A combination of cereal grains such as wheat, barley and maize provide a good mix of fast and slow fermenting starches to increase glucose production at the liver.

Increasing UDP or bypass protein supply in the ration will provide a secondary source of glucose substrates that the cow can utilise. Soybean and Canola meal both provide elevated levels of quality UDP.

5. Natural Betaine

Natural Betaine is an additive that has proved immense value in the fight against heat stress. Betaine acts as a methyl donor which spares energy otherwise used by sodium and potassium cellular ‘pumps’ for the role of maintaining hydration. The energy that is spared by this is then available for glucose production meaning we have reduced the maintenance requirement of our heat stressed cow. Betaine is also an osmolyte which means it also helps to maintain hydration and prevent ‘leaky gut’ in cows. As a result, cows will feel cooler with more energy available for milk production. Peer reviewed studies have shown natural betaine to be the most effective form of betaine at helping reduce the effects of heat stress.

Using Waikato herd test cows averaged 0.17kg less milksolids per day over the month of February. This equates to $1.51/cow/day lost revenue (@ $8.90 milk solids payout). The cost of treating cows with natural betaine is $0.14-$0.15/cow/day over the heat stress period Treating cows for heat stress is highly profitable!

For more information on how to reduce post peak decline and heat stress within your farm then please contact us!

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