In last week’s blog, I discussed feed loss from the field to the bunk. This week, we will look at feed loss in the bunk and during feeding. I have identified 5 ways you could be losing feed at the bunk, but I am sure you can think of a few more, and I would love to hear back from you on other sources of loss you are monitoring and how we can work to address them. 


  1. Fermentation – Poor fermentation in the bunk can result in pretty large spoilage losses during storage. Poor fermentation is caused by inadequate packing, high or low moisture at harvest, and particle size. The moisture at harvest and the particle size will both influence the ability to pack the feed to eliminate oxygen from the pile and create a good fermentation environment. Feed that is too dry will not pack well, while feed that is too wet will pack well, and there will be losses from leaching of liquid during fermentation. Shorter particles will pack better than longer particles, but shorter particles are not always best for the cow, so it is important to balance the length of chop for packing and animal nutrition.
  2. Covering – When covering a bunk, how you cover it and what you use to cover it are both important. Losses of silage will be greatest when silage is not covered. Cornell Cooperative Extension reports 30 to 40 % DM loss when bunks or piles are not covered . There are a few cover options available including polyethylene plastic alone or an oxygen barrier in combination with a polyethylene plastic. Whether you choose tires or gravel filled bags, the most important part of the weight is to have to distributed to hold the plastic tight to the silage. A few things to think about if you choose whole tires are mosquitos and mice. If you live in an area where West Nile Virus occurs, having more area for breeding mosquitos can be a risk for people and animals, while mice can chew holes in your cover.
  3. Feed Out Rate and Open Bunk Face – How fast you remove feed from the storage and how much is exposed will influence losses at the bunk. If you have too large of a bunk face open and are not feeding off of it fast enough or feeding from the whole face, feed will spoil due to prolonged oxygen exposure. Work with your nutritionist to determine your daily feed out rate and how much bunk face to work with.
  4. Re-stored Feed – Do you leave piles of feed removed from the bunk to use the next day? While there are times of the year when there will be little or no loss from this practice, as temperatures and humidity rise, the amount of spoilage in these “hold over” piles increases waste and reduces the feeding value. In general, you should avoid this practice whenever you can.
  5. Spills – Most of the time spills are hard to avoid, but one way to prevent them is to make sure you have a smooth, level driving surface. Having a good driving surface will decrease feeding time, spills, and likely prevent contamination with spilled feed or mud and dirt.

Remember: every pound of feed lost is one less pound of feed that won’t be converted to milk or meat

Calculating Bunk Losses

In the previous post I explained calculating bunk volume. For example calculations for losses at the bunk would look like on a 1,000 cow farm feeding 50 lb of as fed corn silage per cow per day:

Initial inventory = 10,000 tons

Current Inventory = 8,000 tons

Daily Feed Out = 25 tons

Number of Days Fed = 70

Inventory Change = 10,000 t – 8,000 t = 2,000 t

Feed Fed to Cows = 25 t/d x 70 days = 1,750 t

Feed Loss = 2,000 t – 1,750 t = 250 t

% Feed Loss = (250 t / 2,000 t) x 100 = 12.5%

More frequent monitoring of feed loss will let you pinpoint the loss gap in the operation. Daily monitoring will give the best management information, but will be hard to manage.  Weekly or every other week will be a good place to start. The data will be most useful when you begin to accumulate it over time and find where and why you are having losses.

Cost Calculations

The next step in evaluating loss is the cost. This can be looked at as the dollars lost or the lost opportunity to feed cows. To calculate dollars lost, multiply the amount of lost forage by the current value of the silage in your area. Crop insurance providers or feed dealers should be able to help you come up with that number. The lost opportunity to feed cows is found by dividing the lost pounds of feed by the pounds of feed per cow per day. Knowing this information can tell you 1) will changes in bunk cover pay for themselves, 2) is there new feeding management equipment you should purchase, and/or 3) if we were to lose less during storage and feed out, could we add cows or reduce input costs?