As maize harvest approaches, Louise Hartley talks to Silage Solutions’ Dave Davies for advice on cutting and clamping this year’s crop.
WITH the maize harvest rapidly approaching, it is important you assess both your maize crops in the field before harvesting and silage already conserved.
That is according to independent consultant Dave Davies, of Silage Solutions, who says with huge pressure on milk prices, the industry needs to ensure they maximise the potential of what they have already heavily invested in.
“Many of our continental colleagues do this as a routine, but generally here in the UK we do not focus on our ensiled forages as much as we should.”
In many areas maize has ‘caught up’ after a very challenging start, however there are two things which are worth bearing in mind this year, says Dr Davies.
Firstly, total maize forage yield may be lower than anticipated and secondly, while cobs were filling out nicely, they were challenged due to the weather at pollination and as a result may be exposed due to poor sheath coverage.
By assessing everything before harvest you can make key decisions and potentially alter the winter ration now, says Dr Davies.
“If you wait until it is in the pit you cannot change what forage you have, putting you at the mercy of the feed representative,” he adds.
Dr Davies says maize around the country, in general, is not standing so tall, implying reduced yields.
“This leaves you with two options, either cut lower and leave less stubble in the field, or maintain your normal harvest height and take a cut in yield.
“To make your decision, I recommend you first assess what silage you have in store for quality and quantity.”
Cutting maize lower has two effects on maize silage nutritive value, he says. “The lower the maize is cut, the higher the acid detergent fibre (ADF) and lignin content for every kilogram of silage in your clamp – these are the parts with poorer digestibility.
“Secondly, the starch content per kilogram of silage will be lower because it has been diluted by the higher ADF.”
In terms of stubble height, Dr Davies says various figures exist in scientific publications. One study showed changing from 10cm to 30cm (4in-11.8in) stubble height increased the digestibility of the neutral detergent fibre (NDF) by 2.4 per cent, which is equivalent to 0.6kg of 4 per cent fat corrected milk.
Other figures quote an increase of about 0.18 MJ ME per kg DM for a 100mm (4in) increase in stubble height.
“So, if you are short of winter forage, consider a lower cutting height, but be aware of the downside.
“If you have more than enough lower than ideal digestibility grass silage, then maintain a higher cutting height to increase the energy density of your maize silage.
“If you have really good grass silage, you have a dilemma. The lower cutting height will give you more fibre which could help maintain rumen health, but it will reduce the energy density of your maize, so you should seek some nutritional advice.”
Exposed cobs have a much higher risk of fungal contamination, resulting in two potential problems, says Dr Davies.
“Firstly moulds and yeasts [the fungi] cause aerobic spoilage/heating during feed-out of silage. They increase the risks, and I emphasise the word risk, of field borne mycotoxins.
“If you have a lot of cobs which are exposed from the sheath then make doubly sure you compact the silage in the clamp in small – no more than 150mm (6in) layers and consolidate well. Aim for 250kg DM/sq.m – for a 33 per cent DM silage this is 750kg DM/sq.m.
“Also consider a silage additive which will reduce the risks of aerobic spoilage, generally this will involve a chemical salt or combination of inoculant plus chemical salt.
“Unfortunately, if field-borne mycotoxins are present they will survive the ensiling process and this is something to bear in mind at feed-out. If milk yields are not where you would expect given the cow’s ration, mycotoxins could be one of the many reasons why.
“Recent studies in Ireland have shown maize silage is a bigger risk factor than grass silage,” says Dr Davies.