The use of glycerol in diets for broilers (PhD)


Cereals & Oilseeds
Project code:
01 September 2007 - 30 November 2010
AHDB Horticulture
AHDB sector cost:
£30,000 from HGCA
Project leader:
Linda McLea (previously Griffiths), Queens University, Belfast Agri-Food and Biosciences Institute (AFBI)



About this project


For every litre of biodiesel produced, thirty percent of crude glycerol is also produced as a by-product. Thompson and He (2006) analysed the nutrient content of crude glycerol and reported that the main component was carbohydrate. Previous research is lacking into the optimum inclusion level of glycerol in broiler diets, the energy potential of glycerol, nutrient digestibility within broilers and the subsequent effect on broiler meat quality. As a result, this project aimed to investigate these parameters.

During this study it was reported that glycerol inclusion had positive effects on feed efficiency. The AME content of glycerol was determined as 16.8MJ/kg and the optimum inclusion level of glycerol was 6.7% when incorporated into broiler diets. Glycerol had significant positive effects on total starch and amino acid digestibility, specifically threonine digestibility, which was significantly increased with glycerol inclusion. In regards to meat quality, glycerol inclusion had no effect of the moisture content and tenderness of broiler breast meat.

Glycerol was also integrated into broiler diets as a partial/complete replacement for the soya oil content. It was reported that birds offered the diets containing a partial replacement of soya oil with glycerol showed increased feed efficiency compared to birds offered only glycerol. It was also observed that glycerol may provide some of the same beneficial attributes of soya oil.

Glycerol contains methanol, which is toxic and so it is important to find a rapid means to measure the methanol. Therefore, crude glycerol samples containing known quantities of methanol were scanned using NIR (near infra-red) and Raman spectroscopy. It was found that both methods have the potential to measure the methanol content in crude glycerol, and Raman spectroscopy gave rise to more accurate predictive findings than NIRS.

In conclusion, glycerol had positive effects on performance, nutrient digestibility and the AME (apparent metabolisable energy) content of diets, with no subsequent decline in meat quality. Depending on the market price of wheat and glycerol, glycerol could be successfully incorporated into broiler diets as a partial replacement of wheat.