All good nutritionists know that every single farm has a minimum of three rations. The first is the ration that the nutritionist formulates, the second is the one that is loaded, mixed and fed out and the third is the one the cows sort out and consume. The difference between the first and final ration can be enormous & the principal affects grass-based herds as much as TMR fed ones. Afterall there is the grass that is measured (either by eye, sward stick or plate meter), the grass that is allocated to the cows (by field or fence) and the grass (and concentrate) that the cows consume and digest.
There is research that shows that a single ration performs very differently depending on how it is presented. If you take this ration principal to the extreme then it becomes very easy to see how ration presentation affects performance. As an example, consider a dairy diet which is 50:50 Grass and Maize Silage along with 4kg per head of rolled cereals and 4kg per head of blend.
If this diet is fed unmixed with cereals and blend top-dressed onto the silage then the cows will consume large quantities of rapidly fermentable carbohydrates which will drop ruminal pH below 5.5 for a considerable length of time, therefore clinical acidosis. This prolonged period of acidosis will reduce intake, digestion and therefore performance.
Taking the same quantities of feed and mixing into a consistent ration will spread out the rapidly fermentable element throughout several meals in the day, meaning a much lower impact on rumen pH and therefore greater performance from the same feed.
Whilst these examples are at opposite ends of the scale, they highlight the importance of maximising a ration and its presentation. In terms of how this can be achieved, there are different rules for different types of mixers. Generally, a horizontal or paddle mixer has a higher chance of undermixing a ration whereas a vertical or tub feeder is more prone to over-processing a mix. In Horizontal/paddle feeders a lot of work has been done on the optimal way to load the feeder to get the most from the mix. Typically, Straw and Liquids are loaded first, followed by root crops and moist feeds, then dry straights and blends before finally adding forage. Vertical/tub feeders require a different approach. Due to having greater capacity (like for like in terms of M3) than a paddle feeder, it is important to get a good volume of feed in a tub early on. With the chopping and mixing being more aggressive feeds such as Hay or high dry matter grass silage bales are well suited to this task. From here root crops, moist feeds, and dry concentrates can be added before forages. Liquids should be added towards the end of the mix to get the greatest possible dispersion.
Signs of incorrect processing are easy to spot with the right attention to detail. An easily identifiable example of undermixing is when a large amount (relative to the amount loaded) of concentrate comes out of the wagon when starting or finishing unloading (depending on when it was added to the mix). This increases acidosis risk as the biggest or fastest animals to the feed fence will be able to gorge on concentrate, dropping rumen pH rapidly. An overprocessed mix will have big lumps of feed when unloaded. When broken up they will contain a lot of concentrates where it has essentially been folded into a ball. This will cause big problems in the rumen as once the coating of silage is digested then rumen is hit by a big slug of concentrate which will rapidly drop pH, leading to acidosis.
Ration Sorting will have a similar effect to incorrect processing as large amounts of concentrate can be consumed rapidly if sorting is simple. The trend of soaking concentrate overnight and compact feeding was developed in part to address sorting in the ration. Whilst this is a perfectly viable feeding strategy a lot of sorting issues can be addressed with a close focus on the ration presentation and physical supply of the mix.