Let´s get more concrete now and calculate the feed costs for a model farm, taking into account different basic ration qualities.
Example calculation: 50-head dairy herd
The following calculation compares three different qualities of grass silage and their impact on the quantity of concentrate needed in a feed ration for dairy cows.
For the purposes of the calculation we will assume we are feeding a 50-head Holstein herd with a 305-day-milk-performance of 9,000 kg EMCMilk, corrected to an identical energy content in order to be able to compare milk with different fat and protein contents.. In order to compensate for variations in milk performance per lactation period, and to simplify the example, the different feed rations are all calculated for an average performance of 29.5 kg per day.
All calculations are made using the feed ration calculator for dairy cows from the “Bildungs- und Wissenszentrum Aulendorf” in Baden-Württemberg, Germany.
Different grass silages in the ruminants´ ration
The grass silages used in this example differ in energy, crude protein and crude fiber content. They illustrate realistic examples that can be observed in practice on a daily basis.
Composition of the three grass silages:
In order to compare the grass silage qualities, the different rations are each calculated using the same feed components. The roughage portion, consisting of grass silage, maize silage, hay and straw as well as the quantity of feed additives (such as feed lime, animal feed salt and mineral feed) remained constant.
The only variables are the concentrates: barley, rapeseed extraction meal and dairy concentrate. In this way the lower energy and nutrient contents of the lower quality grass silage are compensated for.
Composition of the different feed rations and assumed costs and prices for feed components:
The effect on cost is huge
The results of this example calculation (shown in the table below) clearly demonstrates the impact of the grass silage quality on the total feed cost and therefore on the operation´s profitability. Due to the decreasing energy and nutrient content of the grass silages in the second and third feed ration, replacement costs of 2,555 € and 4,015 € respectively, have to be considered for a herd of 50 cows. For larger operations, for example 200 lactating cows, with the same milk performance, this value would increase to 16,060 € per year – money which could be otherwise used to invest in the farm.
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