Dairy advice: Taking stock of your winter feed

January is an important time to assess remaining winter feed stocks, and particularly following the year we had, which proved to be very challenging for grass growth and subsequently, on many farms, there may not be enough silage to reach turn out date.

For many farmers, the good back end to the year proved to be a saviour, in that farmers were able to keep cows out at grass right into December, which relieved the stress on feed stocks somewhat.

However, the remaining few weeks of silage feeding will be the telling factor on how much that back end really saved farmers as many farmers still may run tight as we edge closer to spring.

Elizabeth Calvin, College of Agriculture, Food and Rural Enterprise (CAFRE) dairy adviser offers timely advice in that: “It is important to re-assess your fodder budget and if necessary, take steps sooner rather than later to stretch silage stocks or reduce demand.”

Every farm situation is different, as for many herds will have another few months of full-time silage feeding left and for many, cows will be out at grass in the next couple of weeks.

Fodder budget

The first step is to calculate the volume of fodder in stock is to firstly, measure the silage in the pits and count the number of bales in stock and then use the dry matter percentage (DM%) to identify the density of forage conversion factor.

The forage volume to weight conversion factors are as follows:

For a pit silage calculation – multiply the length by width by average height (in metres) of silage in the pit to give a volume (m³).

Then use the appropriate conversion figure, based on the dry matter of the silage, and multiply volume by the conversion figure which will give a weight of silage in tonnes.

For baled silage calculation – multiply the number of bales by an average weight of a silage bale to give a total weight in kgs. Then multiply the total weight by the appropriate conversion figure to give a total weight of silage in tonnes.

Take an example of a silo clamp – length 18m x width 10m x average height 4m = 720m³ at 25% DM (720m³ x 0.68) = 489.6t of fresh weight of silage.

A bale stack of 120 bales at 0.8t/bale will leave 96t of fresh weight the current total silage stock on farm in the clamp and including the bales= 586t

The next step is to calculate total demand of the herd and assess that against total silage in stock to identify if there will be a shortfall.

The generic intake figures for dairy cows, dry cows and young stock, assuming the silage DM is 25%.

Calvin stressed: “It is important to account for every animal on farm that is eating silage, and also to use actual intake figures plus an allowance for waste/safety margin.” 

Conserved forage demand example calculation is as follows:

In this example the silage in stock of 586t is not sufficient to meet herd demand of 696.5t (excluding a safety margin of 10%). Therefore, there is a minimum deficit of 110t.

However, for many herds, the turn-out date to grass will be in the next month or so with buffer feeding of silage required, meaning they might only require a months supply of silage with a 10% safety margin.

The conserved forage demand calculation is something that can be done with your dairy adviser or nutritionist to ensure that it is tailored to the silage you have on-farm and the diet formulation you are using.

At this stage of the winter, we have the benefit of hindsight and can cross check this calculation with what has been used in previous months to ensure it is accurate. This is especially important if you are working on tight margins.

Winter feed deficit

So, where a deficit is identified, Calvin has suggested that there are several options to stretch forage and ensure there is enough available feed to get through the winter season.

She continued: “Firstly, it is important to consider culling unproductive stock, for example, infertile, lame, high somatic cell count, and older poorer performing cows. 

“This will reduce demand on silage and provide an additional source of income and help cash flow. Make these decisions as soon as possible to make a bigger impact on lowering demand for silage.”

Secondly, reduce silage DM in the diet and increase concentrates as current milk to concentrate ratio price is favourable to feed extra concentrates and reduce forage levels accordingly.

Increasing the level of concentrates in the diet can also increase the cow’s energy intake which may improve milk performance, milk quality, cow condition and fertility. 

Calvin said that dairy farmers need to: “Remember cows are ruminants, they need a minimum of 40% forage, on a DM basis, in the diet.

“A typical cow diet is 40% forage, 60% concentrate on a DM basis and if forage content is reduced to below 40% of the diet, there is a risk of digestive upsets.” 

In addition, if silage is wet and acidic then consider feeding a fibre-based concentrate rather than starch based to reduce risk of rumen upset. 

Thirdly, stretch silage by considering using soya hulls or sugar beet pulp.  E.g., 1kg soya hulls will replace 4 kg silage on a fresh weight basis (assuming silage is 25% dry matter.

The next thing to consider is feeding dry cows a 50:50 straw/silage diet on a dry matter basis, which is good for rumen function and health.

However, cows will require a higher level of concentrate feeding as straw has limited nutritional value so additional concentrates are required to achieve high energy intake to support the cow’s maintenance and the developing unborn calf.

Farmers could consider feeding all young stock on a straw and concentrate diet.  For example, a maiden heifer, assuming in good condition, could be fed 4 kg of straw and 4 kg of concentrate (on a DM basis).

Due to the low energy content of straw compared to silage (four vs 10 MJ/kg DM respectively) a higher level of concentrate feeding is required. 

Finally, if there is the option to purchase additional silage if available and prioritise the best silage on-farm to fresh calved cows and high yielding cows. Use any lower quality forage for young stock.

Calvin advises that animal needs must be met, and any diet changes should be made gradually.