Elizabeth Calvin, College of Agriculture, Food and Rural Enterprise (CAFRE) Dairying Adviser
January is an important time to assess remaining winter fodder stocks. The past year of 2024 was challenging for grass growth and subsequently, on many farms, there may not be enough silage to reach turn out date.
Elizabeth Calvin, College of Agriculture, Food and Rural Enterprise (CAFRE) Dairying 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.”
Fodder Budget
The first step is to calculate the volume of fodder in stock. 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 (from Table 1). 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, from Table 1 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 (from Table 1) 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@ 25%DM (720m3 x 0.68) = 489.6 tonnes fresh weight of silage.
And a bale stack of 120 bales @ 0.8T/bale) = 96 tonnes fresh weight.
Therefore, the current total silage stock on farm in the clamp and including the bales= 586 tonnes.
Table 1: Forage Volume to Weight Conversion Factors
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. Table 2 shows the generic intake figures for dairy cows, dry cows and youngstock, assuming the silage DM is 25%.
Elizabeth stresses: “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.”
Table 2: Conserved Forage Demand Example Calculation
In this example the silage in stock of 586 tonnes is not sufficient to meet herd demand of 696.5 tonnes (excluding safety margin). Therefore, there is a minimum deficit of 110 tonnes.
The conserved forage demand calculation is something that can be done with your CAFRE 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.
Dealing with a Deficit
So, where a deficit is identified Elizabeth has suggested that there are several options to stretch forage and ensure there is enough available feed to get through the winter season.
She continues that: “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 cashflow. Make these decisions as soon as possible to make a bigger impact on lowering demand for silage.”
Secondly, reduce silage dry matter in the diet and increase concentrates. 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.
But Elizabeth says that dairy farmers need to:
“Remember cows are ruminants, they need a minimum of 40% forage, on a dry matter basis, in the diet. A typical cow diet is 40% forage: 60% concentrate on a dry matter basis. 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. For example, 1 kg soya hulls will replace 4 kg silage on a fresh weight basis (assuming silage is 25% dry matter).
Fourthly, consider feeding dry cows a 50:50 straw/silage diet on a dry matter basis. This is good for rumen function and health; however, cows will require a higher level of concentrate feeding. 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.
Fifthly, consider feeding all youngstock on a straw and concentrate diet. For example, a maiden heifer, assuming in good condition, could be fed 4 kg straw and 4 kg concentrate (on a DM basis). Due to the low energy content of straw compared to silage (4 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 youngstock.
Elizabeth advises that animal needs must be met, and any diet changes should be made gradually. For any option considered, it is important that the diet is re-formulated to reflect the different level of nutrition available to the cow or heifer. It may also be necessary to look at cash flow to support the purchase of extra inputs.
Consult your CAFRE dairy adviser or nutritionist as soon as possible so action can be taken to deal with a deficit. The options available are best put in place sooner rather than later.