Importance of straw length in dry cow rations
A dry cow diet is often called the Goldilocks diet when it is done right – not too much energy and not too little intakes. It needs to be just right!
One of the main ingredients to achieve the desired effect of the diet is straw. Straw is bulky to keep the rumen full and low in energy to prevent the cows from getting over conditioned. However, straw is dry and bulky meaning high inclusions can reduce your intakes due to slowing rumen passage rates, especially with long particle sizes.
Studies have shown that large particle sizes increase sorting of the diet which can imbalance the nutrient intake of the cows. Dominant cows will get first pick and eat the concentrates and smaller particle size feeds usually resulting in higher energy intakes than desired which in turn can increase BCS during the dry period. As a result, the weak, subordinate cows are left with the sorted feed usually the low energy straw portion of the diet which can cause BCS losses.
A recent trial compared feeding dry cows different straw lengths: 4 inches and 1 inch. It was seen that the cows fed the 1-inch straw diet had increased intakes which were better maintained in the week leading up to calving. We also saw reduced sorting of the diet with the smaller particle sizes. The 4-inch straw diet saw more sorting which slows intake rates, overall reducing the overall intake of the diet. It was seen post-calving the shorter straw diet had improved rumen function as there was a reduced rate of pH drop during early lactation compared to the cows fed the 4-inch straw diet. The post-calving levels of β-hydroxybutyrate were higher in cows fed longer particle sizes in the dry cow diet showing that large particle sizes increases the risk of ketosis post-calving and that they experience a greater negative energy balance.
This shows that pre-calving feeding behaviour influences post-calving success.
For the above reasons we recommend you chop your straw! For more information on feeding your dry cows please contact your Feed Specialist.