|Beneath the surface
with David Law
Maize silage is not just a filler you throw to cows willy-nilly when feed gets low – it is a valuable, quality feed that when fed correctly can make a big difference to your bottom line.
Working on a good yield of 28 tonnes/ha, a 10ha crop of maize produces 280,000kgDM. At a cost of .32c/kg in the stack, you have a feed worth $89,600 sitting at your disposal. A 25ha maize crop has a value of $224,000.
With a crop worth a substantial amount of money on hand, it’s important to feed maize silage strategically so it’s utilised to its full potential.
To get the full benefits of maize silage, it is helpful to first understand what maize is - or rather, what it is made up of nutritionally.
Maize is a high carbohydrate, low protein feed, which works well to put weight on cows or balance out a feed that is too high in protein – such as spring grass, at 25 per cent protein.
However, simply adding maize to your cows’ diet is not enough to increase milk production – it’s a bit more complicated than that.
Cows milk best when fed a diet with an average protein percentage of around 16 per cent; this is enough to help her milk well while maintaining a good body condition score. Too little protein and she’ll put on weight but not milk well; too much protein and she’ll milk for Africa but will drop weight rapidly.
The easiest way to achieve optimum protein levels is to measure everything you feed your cows and adjust accordingly.
For example, if you feed 18kgDM per cow per day – comprising 9kg of maize at eight per cent protein and 9kg of dry grass at 12 per cent protein – you end up with a diet with an average of 10 per cent protein.
To increase protein levels to 16 per cent you need to add feed that contains a higher level of protein, such as DDG with 28 per cent protein or soya meal, which has 48 per cent protein.
It’s also interesting to note that although PK contains 17 per cent protein, it doesn’t lift protein in the milk – so don’t rely on it to balance maize.
I followed this calculation with excellent results when I was dairy farming 450 cows. We excitedly introduced maize on-farm in a season similar to this one – it was dry, and feed was running low.
However, the cows only produced 1kgMS per cow per day with the addition of maize silage. Other farmers I spoke to found it an acceptable level of milk production in a dry spell, but given how much money I’d spent on maize, in my opinion it wasn’t enough.
I hired a nutritionist and asked if there was any way we could get more production out of the cows. We calculated the protein levels in the cows’ diet and the result was 12.5 per cent protein – too low to produce well.
To balance the feed and achieve the ideal protein level, we decreased the amount of maize silage, at 8 per cent protein, increased the amount of spring grass silage, 20 per cent protein; and added soya meal at 48 per cent protein.
Within three days, the cows were producing 1.5kgMS per cow per day – an increase of 50 per cent.
Although farmers gulp at the price of soya meal – we paid $750/tonne then, although it has come down in price a bit now – we only needed 1kg per cow per day to lift protein levels to 16 per cent, making it an economical option.
With this year’s maize harvest over, it’s worth considering your yield. Was your investment wise? If you only yielded 18 tonne/ha, you may have been better off to buy maize in. But if you came away with 30 tonne/ha, you’ll have made a good profit.
By doing a comprehensive soil audit – because it’s such a valuable crop – and determining exactly what fertiliser your soil and maize crop requires, the extra effort could reward you with a bumper yield.
Farmers can no longer afford to take a shotgun approach to growing and feeding maize. If you’re not measuring and analysing your maize, you’re not managing this investment effectively.