To starch or not to starch?
Dairy cows do not have a starch requirement and they can have high milk production with low starch diets. At the 2016 Cornell Nutrition Advanced Course, Dr. Buzz Burhans presented some data showing that two of his consulting customers, one in Idaho and another one in New York, had very different levels of dietary starch yet produced similar level of milk and components (85 lb/d, 3.76% fat, and 3.25% true protein).
Dr. Burhans, owner of Dairy-Tech Group, is one of the most intelligent and experienced dairy nutritionists in my view. He emphasized that (as shown in Table 1) although starch levels were very different (16.2 vs. 25.6%), the total carbohydrate fermentability of the two diets was quite similar (37.5 vs. 37.0%), and that helps to partially explain why these two diets were able to support similar levels of milk production.
Due to the feed availability in different regions, dairy herds in the Western US are typically fed higher amounts of sugar and soluble fiber and lower starch compared with the diets in Midwest or Eastern US. In many scenarios, replacing starch with some good quality of sugar and soluble fiber can be a cost-effective way to improve cow health and ruminal fiber digestion while maintaining milk production. The take home message is that when evaluating ration, we should emphasize the characteristics of total carbohydrates, and not only the individual types of carbohydrates (i.e. starch).
Table 1: Diets of two large dairy herds producing similar level of milk and components (85 lb/d, 3.76% fat, and 3.25% true protein). The rations were presented by Dr. Buzz Burhans at the 2016 Cornell Nutrition Advanced Course.
