When cows leave long forage particles while selecting other portions of a TMR, the diet consumed differs from the ration delivered. Start by measuring that difference and tracing where it develops.
A review of feed sorting identifies ration characteristics and feeding management as interacting influences.1 There is no single chop length, moisture percentage or mixer setting that eliminates sorting for every ration.
Compare feed at loading, discharge and later in the bunk. Record ingredient dry matter, particle distribution, mixer operation, feed access and refusals before changing one factor at a time.
Useful records include batch weights, loading order, mixer fill, mixing time and speed, delivery time, temperature and the amount left before the next feeding. Keep comparisons within the same animal group and feeding routine where possible.
Controlling Particle Length: Measure the Delivered Ration
Long, unpalatable or poorly incorporated forage can be rejected, but reducing all material to a short uniform length can also compromise the ration's physical structure. The objective is the particle distribution required by the formulated diet.
Sample Before Making a Cutting Change
Use a consistent method such as the Penn State Particle Separator procedure2. Identify the separator version, sample amount and method used so results remain comparable.
| Sample Location | What It Helps Distinguish |
|---|---|
| Individual forage ingredients | Incoming variation in particle distribution and dry matter |
| Beginning, middle and end of discharge | Variation arising during loading, mixing or unloading |
| Freshly delivered TMR along the bunk | Differences between positions before animals sort it |
| Feed remaining later and before clean-out | Changes after access and selective consumption |
Record the fraction retained on each screen and the pan, along with offered and refused quantities. Ask the nutritionist to interpret results against the actual diet. A mouth-width rule or a universal 2–5 cm cut does not replace those measurements, and chopping does not remove lignin chemically.
Where pre-processing is needed, test the proposed forage and machine together. Check that the result improves incorporation without excessive fines or unacceptable changes to effective fibre.
Resolving TMR Mixer Faults and Wear
If material differs along the discharge, inspect the whole process. Incorrect weighing, loading order, fill level and unloading can produce variation as well as worn knives, augers or scrapers.
A Practical Mixer Check
- Verify scale operation and compare actual batch weights with the ration sheet.
- Check the loading sequence and fill range for the machine and ingredients.
- Isolate the machine safely before inspecting knives, augers, scrapers and clearances. Use the model's service limits and replacement procedure.
- Run at the specified operating speed and test mixing time with representative batches.
- Sample discharge from several points and compare the results before concluding that one worn component caused the problem.
For a replacement TMR mixer, specify the smallest and largest batches, ingredient forms, desired mixing result, power source and delivery route. Wall thickness alone does not establish mixing performance or freedom from sorting.
Moisture and Liquid Ingredients: Test the Response
Measure dry matter in the actual ingredients and ration. A hand-squeeze observation can flag a change but cannot replace a suitable measurement when formulating or comparing diets.
A controlled study of water addition to an already moist TMR found that making it wetter did not reduce sorting.3 Results from a particular ration cannot establish one seasonal moisture target for all diets.
Plan a Controlled Trial
| Item | Record Before and After the Change |
|---|---|
| Ration | Ingredient dry matter, forage proportion and the formulated adjustment |
| Liquid addition | Product, quantity, distribution and its contribution to the diet |
| Physical result | Particle fractions at discharge and later in the bunk |
| Feed condition | Temperature change, spoilage observations and time exposed |
| Animal response | Intake, refusals, milk records and relevant health observations |
Molasses, wet co-products and water affect the diet as well as its texture. Use the nutritionist's formulation and monitor the response. Do not prescribe a blanket 3–5% addition or assume that a sticky ration prevents every animal from selecting particles.
Bunk Management: Keep Feed Accessible
Check when feed moves out of reach, where competition occurs and whether some animals lose access after milking or group movements. Distinguish pushing existing feed within reach from supplying fresh feed.
A 2017 study comparing three and five daily push-ups found no effect on sorting under its conditions.4 It therefore does not support a universal push-up-every-20–30-minutes rule or a guaranteed sorting reduction.
Check the Actual Access Pattern
- Observe feed reach after delivery, after milking and before the next feeding.
- Record displacement, empty sections, crowding and the time feed becomes unavailable.
- Inspect cattle headlocks for fit, usable positions and unobstructed feeding reach.
- Keep the bunk clean and remove spoiled material according to the feeding plan.
- Review resting access and conditions at cow free stalls and cow mattresses as part of the complete daily routine.
Select the delivery and push-up schedule from these observations. Salt blocks or a separate fruit snack should not be introduced as a generic sorting treatment; any supplement changes the nutritional and hygiene plan.
Health and Intake Checks Alongside the Feed Review
Changes in intake, manure consistency, milk components or behaviour can prompt investigation, but none alone diagnoses sorting or ruminal acidosis. Share the batch, sampling and animal records with the nutritionist and veterinarian.
Inspect frozen, spoiled or unusually warm feed and follow the feed-management plan for rejection or handling. Do not stage material in a warm area indefinitely or add a separate bicarbonate dose before each meal as a universal precaution.
Where a NexAgri-Sense monitoring system is proposed, confirm the selected model's measurements and alerts. Match them to animal ID and direct observations. Do not assume every ear tag measures rumination minutes or identifies a particular digestive disease.
Conclusion and an Actionable Check Sequence
Measure incoming material and delivered feed first. Then check weighing, loading, mixing and unloading, followed by bunk access and changes in refusals. Trial one planned adjustment at a time and retain comparable records so its effect can be assessed before the next change.
Miller-Cushon, E. K., and DeVries, T. J. (2017). Feed sorting in dairy cattle: Causes, consequences, and management. Journal of Dairy Science, 100(5), 4172–4183. doi:10.3168/jds.2016-11983. ↩
Penn State Extension (n.d.). Penn State Particle Separator. Particle-size assessment and feed-sorting procedures. ↩
Miller-Cushon, E. K., and DeVries, T. J. (2009). Effect of dietary dry matter concentration on the sorting behavior of lactating dairy cows fed a total mixed ration. Journal of Dairy Science, 92, 3292–3298. doi:10.3168/jds.2008-1772. ↩
Miller-Cushon, E. K., and DeVries, T. J. (2017). Short communication: Associations between feed push-up frequency, feeding and lying behavior, and milk yield and composition of dairy cows. Journal of Dairy Science, 100(3), 2213–2218. doi:10.3168/jds.2016-12004. ↩
