You also get manure from your calves .
Fertilizers are expensive.
In one year, your 18 tons of compost manure from 2 cows has the same nutrients as 200 kg of urea and 100 kg of triple superphosphate. It improves hygiene and health. If you use only straw for compost, it is too loose and airy. If you use only manure for compost, it is too wet and heavy. 21 Cow manure and straw make a good compost manure and also kitchen waste.