Free Cow Feed Cost calculator with clear step-by-step results.
Cattle rations are costed on a dry matter basis because forage moisture varies enormously. Splitting intake between forage and concentrate at their respective prices gives cost per head per day - the single most useful figure for comparing rations - and scaling by herd size and days gives the feed bill.
Cost per head per day
Cost = (forage kg DM x forage price + concentrate kg x concentrate price) / 1000
Period cost
Period = cost per head per day x head count x days
Roughly 3-3.5% of body weight: about 20-24 kg DM for a lactating dairy cow, 10-12 kg for a dry cow and 8-10 kg for a growing heifer.
Home-grown forage still consumes land, fertiliser, machinery and storage. Costing it at market value is what makes ration comparisons and stocking decisions meaningful.