Nearly all maize grown in the UK is the flint type because its tolerant of our cool climate and able to emerge strongly in cold soil conditions. But this comes at a price. A high proportion of the starch in flint-type maize varieties is hard and vitreous, meaning its breakdown in the rumen is slow and incomplete. As a result, more starch passes through the gut unused, ending up in manure.
In contrast, maize with a dent grain texture contains more soft, floury starch in kernels less tightly packed and with a greater surface area. This makes it easier and quicker to break down and digest in the rumen.
The impact of these differences has been shown clearly by comparing the faecal starch content of lactating cows fed flint-type and dent-type maize silage. Faecal starch was measured after feeding maize ensiled for two months and for six months. The amount of faecal starch from cows fed the flint-type ‘two-month’ silage was double that of the dent-type silage of the same age.
This was not unexpected. It is well known starch becomes more degradable the longer it’s in the clamp. The difference in the amount of starch seen in the cows’ manure was therefore expected to be lost over time. But this wasn’t the case. Although the faecal starch content from cows fed the flint-type silage did drop by roughly 50%, it was still double the amount seen after feeding dent-style silage.
The importance of this becomes clear when calculating the cost. Based on previous research showing a 1% reduction in faecal starch resulted in extra milk production of 0.35 litres/cow, the following calculation shows the financial benefit of minimising starch loss.
Based on feeding a tonne of maize silage/day:
The calculation shows the financial benefit of using dent-type maize silage compared to flint-type could be £93/acre after two months in the clamp. After six months, the benefit is less, but still £46.50/acre, based on a 1% difference in faecal starch loss.
Dent is the grain texture of choice in the major maize-growing regions of the world, but these areas offer warmer, more suitable, conditions than the UK. This is why recent plant breeding efforts have focused on producing a cold-tolerant, early-flowering dent hybrid. Pioneer’s P7034 is the first of these, showing encouraging results in both on-farm growing trials and for farmers who have integrated it into their forage management. It is one of the M3 class of high rumen-degradable starch hybrids.
Mike King has a 570-cow all-year-round calving high-yielding herd near Bristol. He feeds a 60% maize/40% grass silage and saw quick results when changing to dent hybrid maize: “We noticed the difference within 48 hours of starting to feed the P7034 and soon had to take 1.5 kg caustic wheat out of the ration to allow for the additional available starch coming from the maize. We also saw a small increase in milk yield and, by analysing the manure, found there was less starch coming out of the back end.”
It makes sense to harvest dent-type hybrids last so they’re fed out of the clamp first, giving the most digestible silage and allowing any flint-type maize silage time to ferment. By capturing this additional nutritional value, other ration components can be reduced. Lower feed costs and increased milk production and/or quality make these new dent-type hybrids a compelling addition to the maize varieties available.