11 June 2020
Whilst many farmers will welcome hot and dry weather when making their silage, it does bring different challenges. In drought conditions, we must focus on ensuring that we have high quality silage, accepting that crop yield is likely to be affected.
Before the decision is taken to mow, it is very important to keep a close eye on the stage of maturity. Any crop under stress, including heat and drought, very quickly transitions from vegetative to reproductive growth stage, particularly in hot weather. The vegetative stage is where the crop is lush and green leafed and provides a high digestibility, energy content and often protein when made into silage. The reproductive stage is where the crop is stemmy with seed heads which is of low digestibility, energy and protein. Whilst the latter is ideal for dry cows, the former is required for productive animals, be they dairy, beef or sheep. In addition, as the crop converts from vegetative stage to reproductive stage, two other things happen. The recovery time for the regrowth becomes longer, thus affecting overall annual yield of forage per acre, and as the crop begins to senesce it becomes more prone to infection by undesirable microorganisms, especially yeasts and moulds, making it more likely to produce mouldy and aerobically unstable silage by feed-out time.
Once the decision to mow has been made, don’t forget the rules of silage making; spread the crop and wilt rapidly. The big advantage of hot weather is that the wilt time can be reduced. This means that less nutrients and silage mass is lost in the field and the silage nutritive value can be higher. But don’t take your eye off the ball, in hot weather and especially if the yield is lower due to drought, the wilt time may only be 2-6 hours.
Therefore, ensure that you:
- Keep an eye on how quickly the crop is drying.
- Line up the contractor before you mow to ensure it is ready to go when you give the order.
Just because the weather is good, don’t increase your target percentage of dry matter (%DM). Too dry is not ideal for preservation. The ideal %DM for a clamp is 30-32% and 35-45% DM for bales. Whatever you do ensure good consolidation, whether it’s a bale or clamp, because trapping air is a far greater risk in drier than wetter silages.
Producing a silage of too high a %DM does challenge the good lactic acid bacteria to conduct a good fermentation. It also means there is less acid in the bale upon opening reducing the bale’s keeping quality at feed-out. In addition, in hot weather, a high %DM bale is more prone to getting hot in the initial stages of fermentation due to the sun’s heat energy as there is less water within the silage than a lower %DM bale. We can compare this to boiling a kettle; less water means the kettle boils quicker. The same is true in silage; the water protects the bale to some extent from overheating.
Silage inoculants
The ideal temperature for silage inoculants is around 30oC. When inoculants get above 38oC, many start to die, even the strains that can grow at these elevated temperatures don’t grow well above 42oC. However, the undesirable Enterobacteria are very happy at 39oC and the Clostridia even at 45oC so the warmer temperatures can favour the undesirable fermentation. This is another reason for not going above the target %DM content. If you have bought a silage inoculant, don’t leave it in your vehicle on a warm day. If the temperature reaches 60oC in the car for 30 minutes, you will have killed 50% of the bacteria in your additive; not much longer and they are all dead. The same goes for the applicator on the baler or forage harvester; make sure it’s far enough from heat sources. If it’s in direct sunlight think about protecting it.
The continued dry spell is challenging cereal crops even at this early stage in the season. With many livestock farms not geared up for irrigation, the likelihood is that these crops will not reach their intended yield or quality targets. My advice in this time of uncertain yields of grass silage and challenged cereal crops would be to assess the cereal regularly. If there are signs of the crop dying, then harvest immediately, with minimum wilt and ensile like you would with grass. By harvesting at the first signs of the crop dying you will have high quality with respect to crude protein and digestibility (and thus ME). Yield may be poor, but the early harvest will give you better quality. Waiting to see if the rain comes and watching the crop die in the field will not only reduce quality but also yield and will increase the risks of mycotoxins. In addition, cutting early will give the crop the chance of regrowth and a second harvest if rain appears. Or you can get on and irrigate, even if this is using a slurry tanker. Adaptation to the conditions is the key.
Good luck!
Dave Davies, Silage Solutions Ltd