How Much Silage Does One Cow Need? A Simple Calculation for Kenyan Dairy Farmers

3 min read

Every January, milk drops on many Kenyan dairy farms. Pasture dries up, hay prices climb, and the silage that was made in the long rains runs out weeks too early. In most cases the silage was not bad. There simply was not enough of it, because nobody did the maths before planting.

I make pit silage on my farm in Bomet every year. Here is the simple calculation I use, which you can do on your phone in a minute.

Step 1: How much does one cow eat per day?

A common planning figure for a mature dairy cow on a silage-based ration is about 20 kg of maize silage per day, fed alongside hay or grass, dairy meal and minerals. High-yielding cows may take more and heifers less, so adjust for your own herd.

Step 2: How long is your dry season?

Count the days you actually need to feed silage. In much of the Rift Valley that is roughly 90 to 120 days. Use 120 if you want a safety margin.

Step 3: Multiply

• 20 kg × 120 days = 2,400 kg (2.4 tonnes) per cow
• For 5 cows: 5 × 2.4 = 12 tonnes
• Add about 10% for losses at the top, sides and face of the pit: about 13.3 tonnes to make

Step 4: How many acres of maize?

A well-managed acre of maize cut at the right stage can give somewhere around 15 to 20 tonnes of fresh silage material, depending on variety, rainfall and fertiliser. At 18 tonnes per acre, 13.3 tonnes needs about 0.75 acre. If your yields are usually lower, plant more.

Step 5: How big should the pit be?

Well-compacted maize silage weighs roughly 600 to 700 kg per cubic metre. So 13.3 tonnes needs about 20 cubic metres of pit, for example 5 m long × 2 m wide × 2 m deep. Poor compaction means a lighter, bigger and more mouldy silage, so compact every layer.

Know your cost per kilo

Add up seed, fertiliser, land preparation, chopping, transport, polythene and labour, then divide by the kilos of silage you made. On my farm this works out at a few shillings per kilo, which is why silage beats buying hay in the dry season. Knowing the figure lets you compare honestly.

Three mistakes that waste silage

1. Air left inside. Fill in thin layers and compact every one, especially the edges.
2. A torn or loose cover. Weigh the polythene down fully and patch holes quickly.
3. The face left open too long. Open from one end and take a full slice daily.

Questions about your own pit? Leave them in the comments and I will answer.

Want every farm tool in one go? The Farm Records Mega Bundle has the silage guide and calculator, dairy and poultry trackers, and goat, chicken and beekeeping record books for KES 1,499 (worth KES 2,647).