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MMN November 2023 – Investigating the Causes of Poor Milk Production

10 November 2023

It can often be the case that cows are not milking according to expectation. While reviewing the current ration is a good starting point along with up-to-date forage analysis, there could be other reasons why milk output is below expectation. Some potential areas to investigate are discussed below:


Feeding management

Firstly, how much are the cows eating? Work out the dry matter intake of the herd – is it as expected given the stage of lactation? Very wet and very dry forages can impact on intake. Wet silages tend to be more acidic, with higher levels of volatile fatty acids and are not as palatable. Combined with a high starchy diet, there is risk of acidosis which could also be affecting intake. On the other hand, dry silages can also restrict intakes and this is where the addition of water can help. Target a dry matter of the TMR of around 40%. It goes without saying that regular forage analysis is essential, especially if forages have changed in terms of cut, dry matter or even appearance.

Remember to check the number of portions being fed for the number of cows and if it is more than 5% out, then get the ration reformulated. For example, if silage is drier than the analysis suggests, cows will not be able to eat as much and the number of portions fed might have been reduced to avoid too much waste, rather than reducing the amount of silage fed. In this case, concentrates will also be underfed.



Mycotoxins can be present in feed even in the absence of obvious signs of mould/spoilage. There are a number of symptoms of mycotoxin poisoning in dairy cattle ranging from abortion, scouring, reduced feed intake and milk yield, raised somatic cell counts and swollen hocks, plus many others. Either test the TMR for the presence of mycotoxins or try a binder for 3 weeks to see whether symptoms subside. This will help determine whether mycotoxins are an issue in the feed. For more information on mycotoxins see:


Body condition score

Is body condition score acceptable? Cows that have lost a lot of condition in early lactation will not milk to their potential and will also be more at risk of poorer fertility which will have a knock-on effect on milk production further down the line. Thin cows may be due to them being in poor condition during the dry period, or transition disease lowering feed intake and cows losing condition quickly in early lactation. These cows will not milk or peak as well.


Days in milk

The target for an all-year-round calving herd is an average of 180 days in milk. Milk yield declines at a rate of around 10% per month. A herd normally averaging 30 litres/day could be “losing” 3 litres of milk if the herd is 210 days in milk.


Peak milk yield and persistency

Investigate peak yields by lactation. Poorly performing heifers could be due to problems during the rearing period and inadequate size at calving. If stocking density is high, with lying space and feed space restricted, heifers will tend to suffer the most.

If cows are failing to reach expected peak yield, assess transition period nutrition and incidence of transition diseases. Complications at calving will impact peak milk yield and how quickly cows get back in calf. Nutrition especially in the last 3 weeks before calving is critical for transition success.

Is the decline in milk production post peak greater than normal? Look for excessive body condition loss indicative of underfeeding energy (this may show up as low milk protein %).


Stocking density

Have cow numbers increased lately? If so, is there a minimum 0.7m of feed space per cow and 5-10% free cubicle space? Overcrowding in fresh/early lactation cows can reduce peak milk yields and the more feed space the better for this group of cows. Also, if feed space is restricted the yields will be down across the board.


Herd heath    

It goes without saying that herd health will also have an impact. Has the incidence of lameness increased recently? Also, a common cause of declining milk production is subclinical or clinical mastitis, and this can also shorten lactations. Monitor the incidence of transition diseases and intervene when incidence is above your target level. A guide to transition disease targets is given below.


Many factors can impact on poor milking performance and the above list is not exhaustive, with heat stress being a key one in the warmer summer months, even in Scotland. If you would like some advice on herd nutrition this winter, please contact the Farm Advisory Service on 0300 323 0161 or email


Lorna MacPherson,; 07760 990901

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