Organic broilers need more methionine

In organic diets, an increase of the amount of organic
produced raw materials seems to result in a higher crude fibre and a lower
methionine concentration. Until now, the effects of these nutritional changes on
performance and slaughter quality of organic broilers are unclear. Possible
interaction effects with different strains of slow growing broilers are also
unknown. Wageningen University researchers therefore set up an experiment to be
able to develop 100% organic diets that not negatively affect performance and
welfare of broilers.

Decreased growth and feed intake
From the
study with 1680 slow growing broilers (1 – 70 days of age) it can be concluded
that an increase of the dietary crude fibre content will decrease growth rate
and feed intake of the birds. The effect of crude fibre content on feed
conversion ratio, however, depends on the age of the bird. Over the first 50
days, an increase of the crude fibre content results in a reduced feed
conversion ratio, whereas this increase will improve feed conversion ratio over
the last 20 days of the growth period. Over the whole growth period, crude fibre
content of the diet do no affect feed conversion ratio. A reduction of the
dietary methionine concentration results in a lower final weight of the
broilers.

Methionine levels
Slaughter results are not affected
by dietary crude fibre and methionine concentrations, but they are affected by
strain. Nearly all slaughter quality parameters were reduced in Master Gris
compared to JA957 broilers. Therefore, Master Gris birds seem less appropriate
for organic broiler husbandry. Finally, it was concluded that dietary crude
fibre and methionine concentrations should be kept on the standard levels to
maintain performance of broilers that are fed 100% organic
diets.

Related website:
Animal Sciences Group WUR

Related link:
The full report (in Dutch)