Baled Silage for Dry Cows

Author: 
Dr. D. Davies (Silage Solutions)

The eight weeks between drying cows off and the subsequent calving are a key point in dairy cow management.  If the management of the dry cow is wrong then this can, at best, significantly reduce the next lactation milk yield and, at worst, incur greater veterinary bills for problems such as milk fever and retained placentas alongside increased time to get the cow back in calf.

According to Dr Dave Davies, independent scientist for the Silage Advisory Centre (SilAC), by feeding dry cows correctly these problems can be avoided and milk yields in the subsequent lactation, and consequently profitability, can be enhanced.

The eight weeks between drying cows off and the subsequent calving are a key point in dairy cow management.  If the management of the dry cow is wrong then this can, at best, significantly reduce the next lactation milk yield and, at worst, incur greater veterinary bills for problems such as milk fever and retained placentas alongside increased time to get the cow back in calf.

According to Dr Dave Davies, independent scientist for the Silage Advisory Centre (SilAC), by feeding dry cows correctly these problems can be avoided and milk yields in the subsequent lactation, and consequently profitability, can be enhanced.

“The basal diet of many Dry Cows is forage of one sort or another” he says.  “One key fact to be remembered at all times is that both over- and under- feeding of the dry cow can cause problems in the subsequent lactation. “

 UK farms have different approaches to Dry Cow feeding, some practices being considerably better than others (Table 1).  However, all examples rely on their current silage making practices to be sufficient to fulfil the requirements of the Dry Cow.  With the size of UK dairy herds increasing, total dry matter silage requirements for the dry cow are now very significant.  Is now the time to be considering specialist Dry Cow silage?

 

Table 1 - Current Approaches to Dry Cow feeding on UK farms

Diet

Advantages

Dis-Advantages

Other Considerations

Same silage as milking cows + Straw

Simple silage system.
  • Silage quality maybe too good.
  • Dry Cows maybe distant from milking herd.

 

Silage from the top of the clamp

Removes poorer quality silage from the milking cows
  • Probably high in ME, higher risk of moulds and mycotoxins.
  • Likely poorer palatability due to higher levels of acetic and butyric acids.

Moulds and mycotoxins reduce intake and can cause health problems such as abortion.

Late Autumn Cut Silage

Removes poorer quality silage from the milking cows.
  • Generally wetter with a poorer fermentation so can potentially reduce intake.
  • Risk of high levels of Potassium.

High levels of Potassium increase the risk of grass staggers and milk fever.

Grazing + free access to straw

Simple system that utilizes fields away from the main holding.
  • If not managed closely can lead to over fat or thin cows.

 

Source: Silage Solutions

 

The ideal silage for dry cows

The silage for dry cows needs to be palatable, free from moulds and mycotoxins (silage from the top of the clamp is more prone to these problems) and ideally have a relatively high DM content (ideally between 35 and 50 %). 

The silage needs a relatively long chop length and needs to be stemmy in nature to improve scratch factor and thus promote rumen function and cudding so that the rumen is ready to digest the high levels of intake required by early lactation cows.

  • Energy

Meeting the energy requirements of the dry cow with grass silage is easy as a ration energy density of 9 – 10 MJ of ME/kg DM is all that is needed - so a mature grass with flower heads fully emerged at cutting will suffice. 

  • Protein

The protein requirements of the dry cow is between 13 – 14% total dietary crude protein,  diets with less than 12% crude protein have been shown to reduce early lactation milk yields and intake and also the quality of colostrum. 

“This may look difficult to achieve alongside the suggested stage of growth at cutting for the energy requirements to be met,” says Dave.  “However, in one of the last dairy cow feeding studies conducted at the Grassland Research Institute site at Hurley in the early 1990’s (funded by the MMB) a grass silage with an ME of 10.4 MJ/kg DM and crude protein content of 135 g/kg DM was produced by ensuring correct nitrogen  fertilization”.

  • Minerals

Whilst there are a number of essential minerals (Calcium, Phosphorus, Potassium, Sodium and Magnesium) that need to be balanced for in the dry cow ration, possibly the most important from a grass silage perspective is Potassium.  Over supply of Potassium can result in the reduced absorption of Magnesium leading to hypomagnesaemia or grass staggers.  In addition high levels of Potassium can also cause milk fevers.

“Late cut autumn grass silage has the increased risk of high levels of Potassium and so should really be avoided as a feed for dry cows”, he adds.  “Further reduction of potassium levels in silage can be managed through the use of artificial fertilizers rather than slurries on grass for dry cows, by using this approach exact plant requirements can be met through correct fertilizer applications without the over-supply of Potassium.”

 

Baling or clamping?

Given all of the above it is difficult to achieve the ideal dry cow silage in the same pit as the milking cow silage.  In addition given the stemmy nature, long chop length and DM content of the silage, adequate compaction in a silage clamp is going to prove impossible. 

Alongside this the need to avoid mould and mycotoxins which are commonly associated with poorly compacted mature, long chop silage, then the ideal ensiling technique is the bale.

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