Now that the New Year has dawned and, in most dairy herds, the spring calving season is on the horizon, so it’s a good time to think about the management of cows during ‘the transition period’. The transition cow period is from three weeks pre-calving to three weeks post-calving.

Cows are under a lot of pressure during this time; their metabolic needs increase dramatically, and how they cope with this high-energy transition period will impact how well they perform during the rest of the lactation. Farmers have to manage this time very carefully to avoid diseases such as milk fever, grass tetany, ketosis, displaced abomasum and cows retaining placentas (cleanings).

Key Points:

Monitoring the body condition score (BCS) of cows.

Dairy cows that are too fat (BCS > 4) in the late dry period eat less immediately pre-calving, compared to cows with a lower BCS, and this makes them more prone to the diseases mentioned above. At the other end of the spectrum, very thin cows will have reduced milk production and will be harder to get back in calf. The optimum body condition score at calving is 3.25. You have to monitor this during the dry period, in particular watch out for late calvers as these cows are most likely to get over-conditioned. Restrict their feed intake if necessary. Blood samples from a number of at-risk cows can be used to test for ketones; this will indicate whether your cows are getting enough energy. Discuss with your vet if these tests could be useful on your farm.

Prevent milk fever in all its forms

Subclinical hypocalcaemia (cows will not go down but have low blood calcium) and clinical hypocalcaemia (milk fever) are associated with an increased risk of retained placentas, ketosis, displaced abomasum, prolonged calving and calves slow to suckle. If you see an increased incidence of these conditions on your farm it suggests there may be a calcium problem in the transition cows. Calcium levels can be checked by getting your vet to take blood samples from cows calved within the previous 24 hours. BCS plays a major role in the monitoring and prevention of milk fever, as cows that are over-conditioned at calving have a higher risk of developing the condition.

An adequate level of magnesium in the dry cow diet is very important. Discuss with your vet if you are giving enough magnesium; you must consider how much magnesium is in your silage and in the dry cow minerals you are using. Most dairy cows will need to be getting 40g of magnesium per day for the three weeks prior to calving.

Cal mag

Remember if you are feeding calcined magnesite (‘cal mag’) this has only 60% magnesium. The potassium (K) concentration in silage fed to cows before calving has a significant effect on the incidence of milk fever. It is very useful to get your silage tested for minerals. If you spread a lot of slurry on your silage ground you could have high potassium in your silage. Cutting stage and season also have an effect on silage potassium content, with higher leaf content and earlier cutting tending to increase K levels. Silage with K levels >2.5% may be unsuitable to feed cows in the last two to three weeks of pregnancy. Your agricultural advisor will advise on optimising silage K content.

If you have experienced an increased incidence of any of the production diseases mentioned above in the past or if you wish to monitor your cows during the transition period, consult your veterinary practitioner now; he/she will be best placed to advise you on what actions to take in the remainder of the current dry period to prevent problems later in the spring and can advise you on whether you need to submit samples for testing to the laboratory.

***Denise Murphy is a veterinary research officer in Athlone Regional Veterinary Laboratory (RVL). The RVLs carry out animal health surveillance within the Dept of Agriculture in association with veterinary practices.