Measuring the success of a maize crop

Maize is one of the most valuable forms of home-grown forage when grown, managed, harvested and fed correctly. It is only at this time of year, just before harvest, that we can accurately assess how successful the crop has been and identify whether issues exist which can be corrected to get even better results in future. Also at this time of year we get the first indication of the likely feed quality. Consequently, many will be looking at what makes a profitable maize crop and whether 2017 has been a successful season.

What makes a good maize crop?

A high dry matter yield is important and big, green, bulky crops with low starch yield and late maturity are not ideal. There are a few very early maturing varieties which are also high yielding and these are becoming more and more widely grown as livestock producers recognise the benefits.

However, for improved animal performance, the nutritional characteristics of a maize crop should receive close scrutiny since it is this that will make a real difference to increasing outputs and on-farm margins. Maize which is grown for yield alone may compromise the quality of the crop and impact on animal performance when fed.

Starting with DM%; The target is to chop the crop as close to 32% DM as possible, since at this point harvest, ensiling and feed-out losses are potentially at their the lowest. Too wet and there is the possibility of losses through effluent, fermentation losses are greater and less starch has been laid down in the cob. Too dry and losses increase due to undigested grains and aerobic spoilage at the shoulders and face of the clamp. Also, the dry matter of the silage has a significant effect on potential intake and below the target of 32% DM the animal will eat less.

There are two ways to measure starch in the crop. Starch % influences the energy density of the silage, however starch yield (tonnes/ha) should not be overlooked. A variety with a high starch % may have a low starch yield (and vice versa). A high starch % and high starch yield would be ideal.

ME is a measure of the energy value in mega-joules (MJ) of each 1kg of dry matter of silage produced and is extremely important when analysing your samples. A silage with a high ME will be more digestible and so pass through the rumen quicker meaning intakes and animal production levels are higher.

Cell wall digestibility is also another important factor, particularly for those with high levels of maize in the ration. This characteristic is genetically controlled and can be improved by plant breeding. Maize varieties with a higher CWD are more digestible and will be broken down in the rumen quickly to increase DMI. According to Oba and Allen (1999) 1% increase in CWD increases dry matter intake by 0.17kg per day, increasing milk yield by 0.25kg per day.

When considering variety performance, the ME yield/ha shown on the BSPB/NIAB descriptive list is a function of DM yield, starch yield and CWD. An early maturing variety with high DM% and high ME yield/ha should give extremely good results and produce a profitable crop for the livestock producer.

Dr Simon Pope’s target maize results at harvest:

DM% Starch % ME Yield MJ/ha
32% 32%+ >190,000

Silage Analysis

Once the crop is in the pit the information gained from analysis of the silage at regular intervals can help you and your Wynnstay specialist get the right nutrient balance to increase milk yield for diary producers or live weight gain for beef units. The nutritional value of the silage often changes over time and something to watch out for is the increase in starch degradability which could heighten the risk of acidosis.

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