By Emmy Koeleman

Glycerol (sometimes also called glycerin) was recently tested as a pig feed ingredient by a research team in Northern Ireland. They concluded that incorporating glycerol in finishing pig diets increases the number of feeder visits per day. The trials looked at the effects of glycerol inclusion in finishing pig diets on performance and meat quality.


More feeder visits
Four diets were produced to contain 0, 4, 8 or 12% glycerol and offered to 48 pigs in pens of six. The pigs were housed in the specialised research facility at AFBI Hillsborough which enabled individual feed intake and behaviour to be measured.


There was no difference in feed intake but average daily gain decreased at 4 and 12% glycerol inclusion and feed conversion rate (FCR) tended to be less efficient as glycerol level increased. An interesting effect was seen on feeding behaviour with glycerol inclusion significantly increasing the number of feeder visits per day which may be due to reduced palatability of glycerol diets.


US research
A research team in the US also looked at the effect of crude glycerol on nursery pig growth performance. Pigs fed increasing crude glycerol had increased Average Daily Gain (ADG). ADG tended to increase with increasing soy oil in the diet or a soy oil/crude glycerol blend. Adding crude glycerol to the diet did not affect G:F compared with the control. Gain:feed tended to increase with increasingsoy oil or the soy oil/crude glycerol blend. The researchers concluded that the addition of 3 or 6% crude glycerol, soy oil, or a blend of soy oil and glycerol in diets for 11- to 27-kg pigs tended to increase ADG.


Upper limit
Researchers at Iowa State University and the US Department of Agriculture's Agricultural Research Services (ARS) carried out a study in which they fed 5 and 10% glycerin to pigs from weaning to market weight. Results showed equal growth performance between the glycerin-supplemented diet and a more conventional corn-soymeal diet.


One problem identified in the swine metabolism trial is that the diet containing 20% glycerol would not have flowed well in a dry self-feeder so Mark Honeyman, animal science professor and coordinator of Iowa State's Research Farms said the 10% inclusion level may be the upper limit.