by Wiehan Visagie

A young Zambian farmer had recently purchased 15 000 layer hens. New cages were also bought to house the layers in pursuit of the lowest cost in egg production.

A neighbouring farmer suggested that he should feed the hens our Novatek layer feed and he then sat back and waited for the hens to produce quality eggs. After some time, he realised that some of the eggs had raised brown spots and, most importantly, the eggs varied in colour as some were white.

Desperate to solve the problem, he tried a number of strategies. He fed the hens calcium supplements, increased the total feed quantity, tested the water quality and even mixed some stress-packs into the water. But alas, he only got deeper and deeper into trouble with all the changes.

The farmer eventually did a feed trial and used feed from another supplier, but with no improvement. According to him he tried all resources available, but he was stuck and could not work out the problem. Eventually, he became incredibly discouraged.

After the layer farmer contacted Novatek, it was decided to send out a veterinarian. The veterinarian then diagnosed the hens with Infectious Bronchitis (IB). According to him, IB is not easy to detect, but is commonly found in Zambia.

IB is a disease that attacks the reproductive tract of the bird. IB causes the eggshell to become discoloured or pigmented with raised brown spots and variety in colour. Nevertheless, the most practical method to confirm the problem is to break open the eggs and to look at the albumin (egg white) of the egg. This part is produced by the magnum which forms part of the reproductive tract and the albumin should be nice and thick. If it is thin and watery, something is wrong.

From the picture above, you can identify the IB when comparing the brown and white shelled eggs on the farm. Once the eggs have been broken, it is clear that the brown egg contains a thick albumin layer and the white egg has a watery part where the thick albumin should be. An oval shaped egg may also indicate that a watery albumin is present. Older eggs have the same problem, therefore only freshly laid eggs must be checked for the albumin thickness. The virus causes the watery effect and is only present in a certain part of the reproductive tract.

The veterinarian decided to treat the hens with sodium salicylate during the acute phase, and some antibiotics to control secondary infection in the intestinal tract. The best prevention against IB is to use live vaccines of an appropriate serotype. Most of the vaccines and antibiotics are available at Livestock Services in Lusaka.

Many farmers assume that the problem lies with the feed composition or feed intake, but the white eggshells are frequently caused by a virus that is not that easy to detect.

Please feel free to contact Wiehan Visagie at wiehanv@novatek.co.zm or Marné Meyer at nutritionist@novatek.co.zm for all information on feeding and feeds.

Colour variations may indicate the presence of a disease.