By Francis Ndungu

A Laikipia farmer, who was selling his pigs to traders at estimated weights of just 30kg-50kg, discovered his animals were really averaging 40kg-100kg when he moved to string measuring, almost doubling his selling prices.

“Intially, we used estimation when selling our pigs. The buyer selected which pig he wanted and started to bargain, claiming the pig’s weight was low. He would even fake lifting the pig, saying  ‘This one is barely 30 kilos,’ even where it was much heavier,” said Edward Kariuki of Marmanet Farm in Laikipia County.

Pig breeds such as Landrace and Duroc Jersey can reach weights of over 180kg when fed properly for 4-5 months, seeing some traders selling on pigs for as much as ten times the price they paid to farmers. 

“In one case, I sold a pig to a trader who ran a butchery. I sold it to him for Sh50 per kilo, and then found it being sold in the butchery for Sh900 per kg,” said Edward. “He told me it wasn’t even a weight of 30kg and I had no way to prove it was more than that. But I did the math and even without the extra kilos he got for free, he paid me Sh1,500 for the pig, but sold just 30kg of it  for over Sh25,000, after telling me it had too much fat and too many intestines.”

“That pig was huge, but I couldn’t prove it,” he said. But then a friend who visited from Kajiado showed him how to calculate a pig’s weight with the string method – using a piece of string and a tape measure to calculate the pig’s weight from its heart girth and body length.

“I measured one pig and got 50 inches for the girth, 72 inches for the length. I followed the formula — girth times girth times length divided by 400 — and realised that pig weighed over 180kg,” said Edward.

As well as more accurate weight calculations, he is now more savvy about the price per kilo, normally getting around Sh500 per kg, and is using weight calculations to produce more.

“Before, I guessed everything — including the dosage for deworming or vaccines. Now, I measure the weight regularly. Sick pigs lose weight, slow-growing pigs are easy to spot and cull. I even plan my next batch based on when the current pigs hit target weights.”

As well as transforming his own pig operation, he has become a champion of strong measurement in his village.

“Weighing scales can break or be tampered with. Some buyers even carry their own, set to under-read. But with my string and tape, I don’t need to argue with anyone. I show them the numbers. If they don’t like it, they can leave.”

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How to measure a pig using the string method

Use:

• A piece of string long enough to go around the pig’s body
  
• A tape measure
  
• A calculator of your phone
  

Step 1: Measure the heart girth

• Wrap the string around the pig’s body just behind the front legs, around the chest.
  
• Mark where the ends of the string meet.
  
• Lay the string flat on the tape measure to find the pig’s girth in inches.
  

Step 2: Measure the body length

• Place one end of the string at the base of the pig’s ears on the top of the head.
  
• Stretch it along the pig’s spine to the base of the tail (not the tip).
  
• Again, use the tape measure to get the length in inches.
  

Step 3: Do the Math

The eight  in pounds is the:

Heart Girth × Heart Girth × Length

÷ 400

To convert the pounds into kilograms, calculate the pounds × 0.45.

An example from a real pig:

• Heart Girth = 50 inches
  
• Length = 72 inches

(50 × 50 × 72) ÷ 400 = 450 pounds

450 × 0.45 = 202.5 kg

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