Forage Making – Applying the Theory of Constraints

Forage quality is still a significant bottle neck on most dairy units but with good planning and communication with the forage making team or contractor the situation can be improved. No matter what level of herd milk yield, margins are still directly linked to milk yield from forage.

The theory of constraints applies to forage production and in the quest for local optima, quality is often compromised. Theory of constraint? Local optima? What’s that all about?
Forage harvesterForage production involves a number of processes; cutting, tedding, wind rowing, harvesting, carting, clamping and rolling. Each local operation strives to carry out it’s task at the fastest rate possible. In the mind of the harvester, acres per hour is everything and in most cases with total disregard for the ability of the other processes to maintain the standard of work. As a result, compaction in the clamp is less than optimal and forage quality suffers.

Likewise mowing, the operator sends in mowers with an output that differs greatly to that of the harvester. The result, forage with shorter or longer wilt times than necessary.

In each case the operators are striving for local optima!

One of the fundamentals of good forage production is adequate compaction of the forage in the clamp. Filling the clamp correctly in most cases is the main constraint as a direct result of having insufficient time or resources to complete the task effectively. The pace of the process however is not governed by the time it takes to do a good job but the pace at which forage arrives at the clamp.

Ensiling capacity should be the drum setting the pace of the silage making operation as this is the most significant constraint and the one that has a significant bearing on forage quality and losses. The effective capacity of the constraint is determined by the packing rate. The target packing weight is easily calculated using the rule of 400. Quite simply the rate of ensilage per hour is multiplied by 400. For example, if we are harvesting 150 tonnes an hour we need 60,000Kg of tractor weight per hour consolidating the pit. Changing this rule around the other way we can calculate the capacity of the constraint; weight of packing machinery (in Kg) divided by 400. Using more machinery on the clamp can increase the capacity of the constraint but in many situations this is not achievable due to clamp design or machine type/availability. Increasing the weight of the packing machinery will have the same effect, increase capacity. Matching packing and harvesting pace can be achieved by reducing the harvesting speed; this reduces the machine weight required per hour.

Less trailers bringing the forage into the clamp possibly? However, this would result in the harvester at times becoming idle. In the theory of constraints, idleness is not a dirty word, as in this case it is contributing to efficiency and the quality of the forage produced. Idleness is in fact creating value.

Possibly a better approach would be to match the harvesting speed to the speed of the drum in that way the harvester could run slower more efficiently and potentially incur less wear and tear.

Harvesting forage especially grass silage requires careful planning; failing to plan is planning to fail. The likelihood of making poor forage can be reduced by asking yourself a few simple questions.

  1. How long do I need to adequately pack and consolidate a hectare or acre or a specific number of trailer loads of forage in the clamp. Use the rule of 400 to determine packing capacity/requirements.
  2. What rate of output must the harvester operator achieve in order to match this rate?
  3. How many hectares or acres per day does this equate to?

Armed with these answers you can sit down with your contractor or farm team and plan accordingly. Workers will only work to satisfy the targets or the KPI’s they are evaluated upon. With silage making it is in most cases ha’s or acres per hour. In our revised approach more appropriate KPI’s would be clamp density and forage DM. The former is dictated by speed of harvesting and filling the latter by good forward planning of the areas required to be mown and tedded in front of the harvester.

The winter is an excellent opportunity to assess the density of forage in the clamp. The target is in the region of 250kg DM/M3. Density is important as silage losses in the clamp are inversely related to packing density.

It is important to ensure that the objectives of the forage making campaign are understood by everyone involved, and that they understand what success looks like; not only speed but also clamp density and consistency of quality. Taking charge of the process and overseeing it to ensure success will yield results.

Written by Dr Huw McConochie  – Wynnstay’s Head of Dairy Technical Services
Follow @HuwMcConochie
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