WestVic Dairy News - April 2010 Edition
Preparing for next lactation – feeding the dry cows
Jo Crosby, Project Manager – Dairy Animal Systems, DPI Warrnambool
The dry period is much more than holiday time for the cows. Good management of the dry cows minimises problems at calving and sets them up for their next lactation.
So how do we make sure the cows are ready for the season ahead?
The early dry period
The cows should be dried off in about condition score five, and the aim is to maintain them in this condition for calving. They will need a diet with the appropriate balance of energy and protein in order to achieve this.
Dry cows will eat about two per cent of their body weight in feed dry matter (DM), and for an average 500kg cow this is about 10kg DM per day.
A 500kg cow requires around 61 megajoules (MJ) of energy to maintain herself, and in the seventh month of pregnancy she needs an additional 9MJ to grow the calf. Her total daily energy requirement is therefore 70MJ. This increases to 78MJ at eight months pregnant and 94MJ at nine months as the calf rapidly develops.
Mature dry cows also need between 10 and 12 per cent crude protein in their diet. First calvers need more protein as they are still growing, and a level of 16 per cent is more appropriate.
The traditional dry cow diet of rough hay may well not be supplying these requirements for energy and protein.
FeedTest results for average pasture hay give us figures of 8.5MJ per kg DM, and eight per cent crude protein. The average 500kg cow at seven months pregnant would need 8.2kg DM of this hay each day to satisfy her 70MJ energy requirement, however she will not meet her protein requirement if fed this hay alone. The problem is even more acute for first calvers with their higher protein needs.
At nine months our 500kg cow would have a daily requirement of 11kg DM of this average quality hay, and her protein requirement would not be met.
FeedTest results for average pasture silage are 9.6MJ per kg DM and 14.7 per cent crude protein. Our 500kg, seven month pregnant cow would need 7.3kg DM of this silage to provide her with 70MJ energy. If she is a mature animal her protein requirement is also well met, but first calvers will still be looking for some extra protein.
It is important that you know both the quantity and quality of the feed the cows are receiving, so that you can be sure you are providing them with a diet that is balanced and adequate. If you do not meet these requirements the cows will lose condition.
Close-up cows
“Close-up” or “transition” cows are those within three weeks of calving. They are “close-up” to calving, or making the “transition” from dry to lactating.
These cows need extra attention and it is during this period that pre-season conditioning really comes to the fore. If she is well prepared she is far more likely to calve without incident, enter the milking team with her full production potential intact and get back in calf early.
During the transition period the aims are to reduce the impact of diseases which often occur around calving and to prepare the rumen for any change in diet likely to occur once the cow enters the herd.
Disease prevention
A cow that goes down with milk fever at calving is like a footballer who pulls a hamstring in the first game of the year. You may get her back on her feet with some TLC, but her contribution to the team effort is reduced for the season.
In Victoria, milk fever alone has been estimated to cost $7 million annually in lost production and in the US it has been estimated that 80 per cent of veterinary costs can be traced back to inappropriate feeding during the dry period.
Much of this cost can be prevented by adequate preparation.
As already indicated, the cows demand for energy increases as pregnancy proceeds, and she must be fed more to meet her needs. If she is underfed, at best she will lose condition and at worst she runs the risk of pregnancy toxaemia.
The most common disease at calving is milk fever, caused by insufficient calcium in the bloodstream of the cow. Calcium is necessary for muscles to function properly, and it has been suggested that low blood calcium at calving may also contribute to the occurrence of displaced abomasums, retained foetal membranes and mastitis.
Calcium is lost from the cow in large quantities in milk so her requirement for calcium increases enormously once she calves.
Calcium is stored in the bones and the key to managing milk fever is to encourage the cow’s system to increase the amount of calcium drawn from this source. Anionic salts are used for this purpose.
Anionic salts may help to slightly acidify the blood of the cow which results in calcium being released from the bones and into the bloodstream. It is necessary to feed the salts for about two weeks prior to calving to achieve this effect.
Unfortunately the effect of anionic salts is much reduced if the cow is being fed a diet which contains a lot of potassium or sodium (known as cations). Pastures, hay and silage from paddocks with high potassium levels are suspect and should be avoided. Also avoid molasses which can have a high potassium level and bicarb which is high in sodium. Fodder can be tested for cation and anion levels and this is recommended if you are feeding anionic salts.
Magnesium is required for calcium absorption so a magnesium supplement (magnesium chloride, magnesium sulphate or magnesium oxide) should be offered to the close-up cows and this should be continued throughout the lactation.
There is debate about whether calcium should be fed during the dry period and traditionally the recommendation has been to avoid calcium supplements at this time. Once they have calved however it is strongly recommended that all cows should receive a calcium supplement (eg limestone) to help them keep up with the huge loss of calcium in milk.
Adapting the rumen
It takes two to three weeks for the rumen to adapt to the introduction of new feeds such as grains or pellets. If the cow is to enter the milking herd eating well and adapted to a new ration some preparation is required and this is referred to as “lead feeding”.
Concentrates must be gradually introduced and pulling the cow straight from the paddock after calving and putting her onto several kilos of grain is inviting acidosis to occur.
While you can introduce the grain component of the milker ration to the dry cows do not feed bicarb in the ration. If a buffer is required before calving use an alternative such as Causmag (magnesium oxide) or the rumen modifier Eskalin. Once the cows have calved bicarb may be introduced.
Lead feed pellets containing anionic salts and relevant minerals are available from most feed manufacturers and these may be a convenient option.
In summary….
To get the cows fit for the season
- Dry them off in the condition in which they are to calve
- Maintain condition by meeting their needs for energy and protein
- Prevent metabolic diseases, especially milk fever
- Gradually adapt the rumen to concentrates.
