Dairy cows need a non lactating 'dry-period' of approximately 60 days to maximise milk production in the following lactation. A dry period less than 40-50 days is believed to result in less than maximal milk yield.
When feeding you dry cows the main aims are to:
- Maintain Body Condition Score (BCS);
- Increase BCS if required;
- Prepare transition cows for calving and early lactation;
- Reduce the risk of metabolic diseases (e.g. Milk Fever).
Dry Cow Requirements
During the dry period the energy needs of the cow differ to those in lactation. The cow no longer needs energy to produce milk, however she still needs energy for maintenance, pregnancy, walking and to maintain condition. In the eighth month of pregnancy a 500 kilogram dry cow will need approximately 80 megajoules (MJ) of metabolisable energy (ME) per day and this increases to around 95 MJ of ME per day in the ninth month.
Mature dry cows need twelve per cent crude protein in their diet. First-time calvers need more protein as they are still growing. A level of 16 per cent crude protein is therefore more appropriate.
All cows require their diet to contain around 35 per cent neutral detergent fibre (NDF), irrespective of the cow's stage of lactation. Too little NDF in the diet can lead to rumen health problems and too much can decrease feed intake by slowing the passage of feed through the digestive system.
Feeding the Dry Cow
Dry cows will eat about two per cent of their body weight in dry matter (DM) each day. A 500 kilogram cow will therefore eat approximately ten kilograms a day. However, when feeding your cows, remember that the lower the quality of the feed the more the cow will need to eat to meet her energy requirement. The common practise of feeding dry cows the lowest quality feed may mean their requirements for energy and protein are not being met.
Supplying dry cows with inferior quality feed may physically fill them up, but nutritionally they will be starving.
Scenario: A farmer feeds straight cereal hay to his dry cows. We know from feed test values that cereal hay can range in energy from 4.3 to 12.9 MJ ME/kilogram DM.
If the farmer feeds hay that is only 6 MJ ME, a 500 kilogram dry cow would need to eat around 13.5 kilograms of the cereal hay to meet her energy requirements (80 MJ divided by 6).
The cow would be physically incapable of eating this much in one day, especially with fibrous, stalky hay which we would expect from a feed test of only 6 MJ! In addition, the protein levels in the hay would not meet the cow's requirements.
On the other hand, if the farmer feeds hay that is 10.5 MJ ME the cow would only require about 7.5 kilograms to meet her daily needs.
Protein also needs to be considered. Cereal hay averages about 9.2 per cent crude protein which is insufficient for dry cows. In this case, you would need to consider another feed source to increase the protein percentage of the diet - such as good quality clover hay/silage, canola hay/silage or high protein pellets or grain mix.
Feed wastage also needs to be taken into account. There may be far less feed actually going down the cow's throat than you think. For example, hay or silage fed out on the ground may have wastage of around 20 per cent or even more if conditions are wet. You need to allow for this when working out what the dry cows are getting and when doing feed budgets for the winter months.
Body Condition Score (BCS)
Ideally cows should be dried off in the same condition that you want them to be in when they calve. Therefore, when drying your cows off aim for a BCS of between 4.5 and 5.5 as cows within this BCS range at calving are more likely to cycle, be submitted for insemination and conceive at the next mating.
If it necessary to improve the body condition of cows after they are dried off, feeds high in energy can be used, e.g. cereal grain or high quality hay. However, it is much less efficient to put weight on the cows when they are dry. While it takes 44 MJ of metabolisable energy to put on one kilogram of body weight when the cow is lactating, it takes 55MJ to put on one kilogram when the cow is dry. The difference in energy required to put on one full condition score in the dry period versus while the cow is milking is equivalent to an extra 40 kilograms DM of barley or 57 kilograms DM of pasture hay.
Avoiding Milk Fever
Milk fever is caused by a sudden and severe decrease in blood calcium levels at the onset of lactation, due to the demand for calcium for milk production. High producers are more susceptible because the fall in their blood calcium level is greater.
Two of the mechanisms cows have to prevent this are:
- Increasing the absorption of calcium from the intestine;
- Mobilising calcium reserves held in the bones.
To reduce the occurrence of milk fever, the key is to stimulate these mechanisms prior to calving so the cow is ready to meet the demand for more calcium after calving using strategies such as:
Feeding diets low in calcium during the dry period
Calcium-high feeds (e.g. green feed) should be restricted and plenty of calcium-low feeds (e.g. hay) fed for at least 2-3 weeks before calving. On the point of calving and afterwards, feed sources that contain normal levels of calcium should be available to the cow. Calcium feed supplements may be helpful at this point, but should not be given earlier.
Altering the Difference between Cations and Anions in the Diet (DCAD)
DCAD refers to the difference between the cations (positive ions, e.g. sodium and potassium) and anions (negative ions, e.g. chloride and sulphate) in the diet. Every feed source contains positive and negative ions and ideally the anions should outweigh the cations. Feeding the cows a diet high in anions produces a condition called metabolic acidosis. This can cause cows to remove calcium from their bones faster and is beneficial as it prepares the cow for the increase in calcium demand at calving. Therefore the cow's diet must have more negative ions than positive ions, which can be done using feeds that have low levels of potassium and sodium and so shouldn't be included in the dry cow diet. Cereal grain concentrates, maize silage, cereal hays and straws should be used as the first option as generally they have lower levels of potassium and sodium.
- Cows need to be dried off for at least 40-50 days to achieve maximal milk yield.
- Dry cows require about two per cent of their body weight in dry matter, The diet must also contain twelve per cent crude protein and 35 per cent NDF.
- A 500 kilogram dry cow will need 80 MJ ME/day in the eighth month and 95 MJ ME/day in the ninth month of her pregnancy.
- Adding condition to cows after they are dried off can be done but is inefficient when compared with adding condition to a lactating cow.
- A diet low in calcium during the transition period will reduce the risk of milk fever.
If you would like more information on feeding your cows through the dry period you can seek advice from a Dairy Extension Officer, your milk factory field representative or a nutrition advisor.