These aspects are not considered in the formulation of a ration. However, minerals and vitamins can be included in the concentrates (2-3% when NaCl is provided ad lib), the amounts and composition depending on the calculated needs / deficiencies. When high amounts of concentrates are fed one may consider to add some extra concentrates to cater for the nutrient value “occupied” by the minerals in the concentrates.
Example
10 kg of concentrates carries 300 gram of minerals. Nutrients are probably calculated for. One may add 0.25 kg of concentrates to balance the “calculation-gap” in FUM and DCP.
.Selectivity (Refusal) and Waste
In order to allow for selective intake from roughage, the quantity of roughage offered should be more than calculations made. Depending on quality, the “refusal” (the quantity not eaten on a voluntary basis) may be as high as 35 % of the amount fed to the animal. Chopping roughage below 10 cm will reduce selectivity. The overall digestibility of roughage will be reduced, demanding more quality and quantity of concentrates to balance the requirements.
Within a zero-grazing system an allowance of 10-35% of extra roughage has to be considered to allow the selective intake by the animal (percentages may vary per type of roughage). Waste is the quantity of roughage spilled on the ground/floor and trampled and thus not fit any more for animal consumption (really a waste).
Losses by waste can be reduced by: proper feed-trough / feed-rack design, sufficient space per animal at the manger, chopping roughage to 20-25 cm (does not affect selectivity) and dehorning (in yards, animals become less “bossy”). Allowances for refusal and waste can be determined by observation (and weighing, consider extra weight from moisture/dirt).
Note: It should be realized that the overall DMI and total nutrient requirements of an (individual) animal are not affected by the above mentioned aspects. Advise is to offer more roughage than the calculated requirements.