By Lorna MacPherson, dairy consultant, SAC Consulting

Stress during the dry period can impact on milk production and fertility after calving.

The dry cow will experience stress in a number of ways from changes in diet as she moves from the lactating ration to a dry cow ration and then again to the milking ration once she calves down.

Other stressors include the threat from pathogens, with a high proportion (up to 75%) of disease often occurring within the first month of lactation.

The effects of social stress caused by pen moves and grouping unfamiliar animals cannot be underestimated and the more moves an animal experiences, the more detrimental it is to calving performance and subsequent lactation.

Research from the University of British Colombia shows that when unfamiliar cows were introduced into a group, aggressive interactions at the feed fence doubled, reducing dry matter intake by 10% in the first 48 hours.

It can take around three to four days for the social hierarchy to be re-established and it tends to be the more subordinate animals that are affected the most (ie. heifers and small cows). When heifers are affected by group disturbances in the last week of pregnancy they have been shown to produce 1000kg less milk during lactation.

The immune system is downregulated around calving time to as low as 40% and stress can impact on the immune system further.

An Italian study found that cows exhibiting a high stress response (more inflammation in the first month after calving) produced almost six litres less milk per day and had poorer fertility with higher services per conception (2.7 versus 1.7), compared to cows with a lower stress response (Bertoni et al, 2008).

It is very difficult for dry cow groups to achieve social stability as animals are regularly entering and leaving the group, with the pecking order having to be re-established each time. Move animals in pairs or small groups and aim to move once a week. This is especially important for heifers and they should ideally be moved into the far off group six weeks before calving.

Timing of pen moves is important to minimise disruption to feeding behaviour and dry matter intake. Avoid moving cows close to feeding time and moving them later in the day can minimise the reduction in intake as a high proportion of consumption takes place two hours after feeding out.

Also, if animals are introduced to a group later in the day when activity is low, there is less competition at that time for feed, lying and water trough space for those being introduced. For animals in the last week of pregnancy, frequent additions to the pen can increase the risk of milk fever, retained foetal membranes and metritis, impacting upon fertility.

Dry cow pens with inadequate feed or lying space will experience greater problems with transition. A good rule of thumb is to provide 1m2 per 1000 litres of milk production. This rule should help ensure sufficient space at the feed fence, plenty of lying space for less dominant animals and space to find a quiet area to calf in, if separate calving pens are not available.

Aim for a minimum trough space of 75cm but up to 1m is even better to help maximise intakes and obtain good rumen fill scores, especially for less dominant cows or heifers. A dominant cow can easily guard three times her own width of feed fence space. If using yokes, there should be no more than 80% occupancy (i.e. have 8 cows for every 10 yokes).

It is recommended to move the cow to a calving pen at the point of calving and minimise the time spent here. The longer the cow is in the calving pen, the greater the risk of transition disease.

Research from the University of Wisconsin has shown that cows that were moved into the calving pen three or more days before calving, were double the risk of having ketosis, a displaced abomasum and being culled within 60 days of calving, compared to those that spend two days or less in the calving pen.

Some group changes are unavoidable, but there is a lot which can be done to minimise stress around this time, allowing a smoother transition into the milking herd.


Bertoni, G., Trevisi, E., Han, X. and Bionaz, M. 2018. Effects of Inflammatory Conditions on Liver Activity in Periparturient Period and Consequences for Performance in Dairy Cows. Journal of Dairy Science, 91: 3300-310.