Compliments of Nutrition Department

The macro in situ technique is a new method Mycogen Seeds is using to estimate corn silage starch degradation in the rumen. Samples of silage are placed as is – without drying or grinding – into polyester bags and incubated in the rumen of cannulated dairy cows for a period of time (16 or 24 hrs). A cannulated cow has an opening on her side used to reach inside her rumen and introduce samples. Mycogen has been working on this new technique in cooperation with some universities. Researchers feel that the standard method of drying and finely grinding silage samples before analysis for ruminal starch degradation eliminates differences among hybrids due to kernel texture, moisture, starch type or other factors. When the sample is finely ground, any type of starch could potentially be degraded by the rumen microbes because of the reduction in particle size of the grain and removal of barriers to digestion, such as a harder seed coat or a harder endosperm.

Two hybrids (a TMF Silage-Specific and a dual purpose) were harvested at three stages of grain maturity – early dent, half milkline and black layer – and stored in minisilos. There was a very significant reduction of 39% on ruminal starch degradation when corn silage was harvested at black layer compared to early dent or half milkline. Silage moisture at black layer was only 49.9% compared to 69.1% at early dent and 63.4% at half milkline. Whole plant harvest moisture of 65% is recommended for optimal silage quality. It is important from a ration balancing point of view to consider starch availability in the rumen. Routine lab results do not include starch degradation, so the energy value of mature silage will look similar on paper to silage harvested at appropriate moisture, even though digestibility of the starch in the cow would be different. You can contact our nutrition department at http://www.mycogen.com or 1-800-MYCOGEN (1-800-692-6436) if you have any questions.

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