Knowing how much a cow eats is useful for two things: checking whether the paddock is enough for the group and buying just the right amount of hay or concentrate, without running short in the dry season or spending too much.
The percentage-of-weight rule
Cows eat according to what they weigh. The sum is done in dry matter, that is, the feed without the water it carries:
- Beef or growing cow: 2.5 % of her weight per day.
- Milking cow: 3.5 % of her weight per day.
- Dry cow: 2 % of her weight per day.
Intake table by weight
Dry matter at 2.5 % of weight, and the same feed as fresh grass at 20 % dry matter (each kilo of dry matter is 5 kg of fresh grass).
| Cow weight | Dry matter per day | Fresh grass per day (20 % DM) |
|---|---|---|
| 300 kg | 7.5 kg | 37.5 kg |
| 400 kg | 10 kg | 50 kg |
| 450 kg | 11.25 kg | 56.25 kg |
| 500 kg | 12.5 kg | 62.5 kg |
| 600 kg | 15 kg | 75 kg |
| 500 kg in milk (3.5 %) | 17.5 kg | 87.5 kg |
These are averages. A high-yielding cow, a very thin cow or very young, tender grass will change the sum.
How to convert dry matter to fresh grass
Divide the dry matter by the forage’s dry matter percentage. With grass at 20 %, 11.25 kg of dry matter is 11.25 / 0.20 = 56.25 kg of fresh grass. Tender rainy-season grass has less dry matter (more water), so you need to feed more kilos; hay carries almost all dry matter, so you feed much less weight.
The feed calculator does this sum for the whole group and for as many days as you need.
Water
Water is what a cow consumes most of. As a general guide, a beef cow drinks 40 to 60 litres a day, and a milking cow or a cow in hot weather drinks a good deal more. Exactly how much depends on the climate, how much milk she gives and how dry the feed is. What does not change: clean, fresh water that is always available. A cow that drinks little eats less and gives less milk.
What makes her eat less
- Old or very fibrous grass. It digests slowly and the cow fills up before eating what she needs.
- Strong heat. Cows eat less in the sunniest hours.
- Too little water or dirty water.
- Illness or lameness. A drop in intake is often the first warning sign.
Keep track in the app
In the Ganaderos app you record each animal’s weight and see its daily gain, so you know whether the ration is working. You also log what you spend on hay and concentrate in the farm’s accounts.