Weighing Birds and Monitoring Growth in Ghana

How many birds you need to weigh

How many birds do you need to weigh to know what the whole flock weighs? Fewer than most farmers think, if you choose them properly, and more than most farmers actually weigh. The rule we give is simple: take the greater of 20 birds or about one in ten of the flock. For a small house that means 20 birds, which is about half of a flock of 40. For a larger house it means more.

The sample only works if the birds are chosen at random. Walk the house, pick up birds from different corners and different parts of the feeder line, and take the first bird you catch in each spot. Do not go to the flock and pick the largest bird, because it is the one you are proud of, and do not take the one that looks poorly, because it is the one you are worried about. Both choices tell you about one bird, not the flock.

Scales, buckets and the way to hold a bird still

Choose the scale to match the bird. A digital kitchen scale that reads to a gram is right for day-old chicks and young birds. Once the birds pass about a kilogram, a scale that reads to 10 grams is more useful, and a hanging spring scale is good for birds past two kilograms, provided you check it against a known weight first. A spring scale that has been dropped or left in the rain will drift.

Use a bucket or a bag on the hook, and zero the scale with the empty bucket on it before the first bird goes in. The bird's weight is the reading with the bird in the bucket, minus the empty bucket. Write the weight down straight away, with the bird's number if you are marking them, so a mistake can be spotted before the sample is finished.

Hold the bird gently, with one hand under the body and the other round the wings, and keep her calm. A bird that has been chased round the house for ten minutes will be panting, and her crop may be full of feed or water that changes the reading. Weigh in the morning before the feed goes out, when the crops are at their emptiest, and do the whole sample in the same way each week.

Day-old weights, and what the box can tell you

Weigh a sample of day-old chicks on the day they arrive, before they go under the brooder. A meat-type day-old chick usually weighs somewhere in the low forties of grams, and a dual-purpose chick tends to be a little lighter. A sample that averages well below the range you expect, or that has a lot of very small birds in it, is worth a note in your record and a message to us with the hatch date and the box you received.

Chicks travel in ventilated boxes of 50, and they leave the hatchery the day they hatch. A long trip in a hot vehicle can drop their weight a little, and a chick that arrives tired will often eat less in the first 24 hours. Do not judge the hatch from one box. Weigh a sample from two or three boxes if you have them, and compare the averages before you decide anything.

Averages, spread and what uniformity means on the farm

The average tells you where the flock is on the whole. The spread tells you whether the flock is growing as one group or as two or three separate groups. A flock with a good average and a wide spread will sell well on the day, but it will have a tail of small birds that cost feed and time to finish.

Take a worked example. A sample of 20 birds at week four gives weights that add up to 18.18 kilograms, so the average is 0.91 kilograms. Ten per cent either side of that average gives a band from 0.82 to 1.00 kilograms. In this sample 12 birds fall within the band, which is 60 per cent. The rest are either lighter than 0.82 or heavier than 1.00, and the lightest bird in the sample weighs only 0.66 kilograms, while the heaviest is 1.10.

A flock where 80 per cent or more of the birds sit within ten per cent of the average is a uniform flock, and it is the one you want. A flock at 60 per cent is telling you that something is holding back a part of the house. That part is usually the birds at the far end from the feeder, the birds on the wet side, or the birds that were weaker at placement.

Reading the chart week by week, and the gap that matters

The target chart is what makes the weights useful. Use the chart from your supplier or the breed guide for the bird you are raising, and write its figures next to each week's sample. A single week that falls below the chart is not a crisis. Two weeks in a row, with the gap growing, is a trend, and a trend is the thing to act on. Our broiler weight chart sets out the weekly figures we use as a starting point for meat birds.

The table below uses example figures to show the pattern. The target numbers are not a standard for any breed, and your own chart will differ. What matters is the way the gap moves from week to week.

In the example, the gap went from a small loss in week three to a larger one in week four, and the flock was still behind in week five. That is the moment to stop reviewing the chart and start looking at the birds, the feed bin and the water tank. The weigh day fits best inside the rest of the week, and our daily routine guide shows where it sits alongside the feeding and the count.

What a slow week usually points to

When the average falls behind, the first place we look is the feed, because it is the thing that changes most often on a farm. A new bag from a different batch, a bin that has taken in damp, or a ration that has been stretched because money was short will all slow the birds down within a few days. Smell the feed, check for clumps and mould, and compare the bag you are using with the last one.

Water is the second. A blocked nipple line or a dirty bell drinker can cut the water a bird drinks by enough to hold back growth, and the birds will not tell you. Check that every drinker is running, and that the tank has not been empty at any point in the week. Heat is the third. A house that reaches the upper thirties by mid-afternoon will slow the birds whatever the feed.

Disease comes last on the list in our experience, but it is the one with the biggest consequences. Coccidiosis and other gut problems slow growth quietly, and a flock with a dip after a vaccination day or a move may be recovering from a reaction rather than sick. Our guide to birds that are not gaining weight walks through the signs, and our coccidiosis notes cover the gut side. Whatever you find, follow your vet's advice on any treatment. Do not start a course of medicine because the weights are down. Keep the vaccination dates in view with our poultry vaccination schedule, because a missed date is one of the first things to check.

Putting the weights next to the feed record

A weight on its own tells you where the flock is. Put it next to the feed used and you can tell whether the feed is working. The simplest figure is the feed conversion ratio, which is the feed eaten divided by the weight gained over the same period. Our feed conversion guide explains the sums in full, so the example here is short.

Say a house of 300 birds ate 500 kilograms of feed in one week, and the flock gained 300 kilograms over the same week. The ratio is 500 divided by 300, which is 1.67. If the same house gains only 240 kilograms on 500 kilograms of feed, the ratio jumps to about 2.08, and you are paying for feed that the birds are not turning into weight. That is a cost you can see in the bag count, and it is the reason the weights and the feed record belong on the same sheet.

The record also shows the cost of a slow week in money. At the feed price you pay, a week with a poor ratio will often cost more than a week of extra vaccinations, so the weighing day is not an extra job. It is the cheapest insurance on the farm.

Weighing pullets and layers, which is a different job

Laying hens are not weighed to the same schedule as meat birds. The growth you care about is the pullet growth to point of lay, and then the body weight that holds through the lay. Weigh a sample of pullets at about six weeks, at around twelve weeks, and again before lay, and compare the figures with the pullet chart from your supplier. Our layer chicks page lists the breeds and the box sizes we hatch for layer systems.

Do not weigh the adult hens every week. Once the flock is laying, the weights change slowly, and each weighing is stress on birds that are already working hard. Once a month is usually enough for a sample of hens, and it is more useful to watch the egg count and the feed than to weigh the flock every few days. A hen that drops in weight while the lay holds up is a hen to look at, and a hen that drops in both needs a vet on the day.

The same sample method applies. Take 20 birds at random, use the same scale and the same time of day, and write the average and the band on the record sheet.

Running a weigh day from the scale to the record sheet

1. Check the scale against a known weight, and zero it with the empty bucket on it.
2. Pick the sample at random from different parts of the house, and write the number of birds you plan to weigh.
3. Weigh in the morning, before the feed goes out, and do the whole sample in the same order each week.
4. Write each weight down as you go, with the bird's number if you are marking them.
5. Work out the average, the band and the share of birds inside it before you leave the house.
6. Compare the average with the chart target for that week, and note the gap in the record.
7. Check the feed bin and the drinkers while the birds are still in the house.
8. Return the birds to the house gently, and wash your hands before you go to the next house.

The weighing habits that give false comfort

• Weighing only the biggest birds on the day the buyer is coming, which makes the flock look better than it is.
• A spring scale that has been dropped and never checked, so every weight is a few hundred grams out.
• Weighing at a different time each week, so the crop fullness changes the figures more than the birds do.
• Recording the average but not the spread, so a flock split into two groups looks fine.
• Waiting until the end of the cycle to weigh, when the slow weeks can no longer be fixed.
• Changing the feed and the water on the same day as the weigh, so nobody knows which change made the difference.

Planning the next cycle? Start with the broiler day-old chicks page and the current price list, then send us the bird count and the date you want them on WhatsApp at +233 24 915 1503. We can talk through the weigh plan for the cycle while we agree the order.

Questions farmers ask