The ruminal starch degradability of corn silage depends on the growing and harvesting conditions. When this is low, an enzyme can be added to the feed to boost degradability and hence animal production, fertility and herd profitability.
For all dairy farmers, achieving herd efficiency and increasing milk yield are top priorities. For this reason, dairy producers invest in corn silage and corn grain that will deliver the most in terms of energy concentration as well as cost savings. In this process, special attention is paid to the starch content of corn (a potent source of energy for milk production) and its rumen degradability, as well as fibre content and digestibility. Corn silage and high moisture corn are typically high in starch availability and therefore result in the production of good quality milk.
However, 2016 was particularly challenging for dairy farmers due to the unusually rapid corn drying during the summer months, which lead to very mature grain with increased vitreousness and, as a result, decreased ruminal starch degradability. This was particularly evident in some parts of Europe, where corn dried at a rate of 1.5% per day, three times the normal rate. As ruminal corn starch digestibility is strongly influenced by corn maturity, farmers have found corn silage to be higher in by-pass starch, which means less starch is being digested in dairy cow rumen. This negative impact on feed utilisation and waste of energy supply is associated with reduced cow performance i.e. lower milk production, decreased milk quality and poorer fertility as well as significant incurring costs.
Assessing starch digestibility
Low starch digestibility can be assessed by farmers in a number of ways. For instance, normal amounts of starch in faeces are typically lower than 3%. However, decreased degradability in the rumen shifts starch digestion towards the intestines. As cows have a limited capacity to digest starch entering the duodenum, farmers may see higher amounts of corn grain and starch excreted in the faeces. This not only implies less available digestible starch to the cow but it also indicates decreased rumen function resulting in reduced fibre digestion. In this case, dairy farmers can take a number of steps to promote better herd efficiency and milk productivity from the corn grain they produce. These include keeping corn silage for longer so as to increase starch digestibility, reducing the amount of corn silage in the ration, using a different grain processing method and/or increasing the amount of rumen fermentable starch. However, these solutions have limitations in application. This is because old corn, or corn kept for an extended period of time, will also result in poor cow performance, and farmers may have limited space for prolonged corn storage. For this reason, a new approach involving the addition of the feed enzyme amylase has been recently developed to help maximise corn starch utilisation and fibre digestion in cows.