Answer by Jim Drackley, Professor, University of Illinois
Q: We have been hearing about use of high-straw rations for dry cows. We have been satisfied with our current dry cow and pre-fresh program. Are there good reasons we should consider changing to a straw diet?
A: My first advice on dry cow and transition programs is always that “if it isn’t broken, please don’t try to fix it”! If you have a system working that leads to minimal incidence of fresh cow problems and cows that start strong, then there is no need to look at drastic alterations.
There are several misconceptions about the high-straw low-energy dry cow programs. First, the approach will not fix problems resulting from overcrowding, poor facilities, or poor management during this critical period. On the other hand, if these facility and management conditions have been optimized, then the choice of dietary program is less critical and a variety of nutritional approaches can work well. If feeding space is not limiting cows, the high-bulk low energy rations often will provide less variation in dry matter intake, will virtually eliminate incidence of displaced abomasum, and can decrease incidence of other fresh cow problems.
The approach must be implemented for the entire dry period, and is not just a close-up or pre-fresh strategy. While larger herds still may wish to keep two dry cow groups, the basic ration can be essentially the same, with adjustment of only additional minerals, vitamins, and rumen-undegradable protein in the close-up group, for example. The rations may work well for single-group dry cow programs where producers are managing for 45-50 day dry periods.
The rations work best where corn silage is the major forage base. The combination of corn silage and chopped straw results in a ration energy density that will allow cows to consume enough energy to meet their pregnancy and maintenance requirements without consuming substantially excessive amounts of energy. Our research has demonstrated that overconsumption of energy during the dry period can predispose cows to health problems around calving if other management is not ideal. The approach is often misconstrued as “straw feeding” when in fact it is important that a balanced ration be fed that contains similar feeds as what the fresh cows will get. Straw serves to dilute the energy density of corn silage, while the presence of corn silage provides some starch and helps keep the rumen adapted to its use after calving. Because of the lower total fermentable energy, the production of microbial protein in the rumen will be insufficient to meet requirements, which necessitates some supplementation of a low-degradability protein source such as blood meal or heat-treated soybean meal.
If straw or other bulky low-energy forages are used, it is absolutely critical that they be processed appropriately so that cows cannot sort them from the TMR. This may mean pre-chopping the straw through a tub-grinder or forage harvester, or using a TMR mixer with knives that can adequately process the straw (2” particles or less) without overprocessing other ingredients. Sorting must be avoided, and access to feed must not be limited for this approach to be effective.