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Glycerol tested as a pig feed ingredient

Recent research in Northern Ireland indicates that including glycerol in finishing pig diets increases the number of feeder visits per day.

The trials, which were carried out by Dr Elizabeth Ball, Agri-Food and Biosciences Institute (AFBI), Hillsborough, Northern Ireland, tested the effects of glycerol inclusion in finishing pig diets on performance and meat quality.

Cereal grains
Glycerol is a by-product of biofuel production and it may be used as an energy source in diets for pigs but there is limited research on its optimum level of inclusion or on the effect of performance and meat quality.

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 (Table 1).

Table 1. The effect of glycerol on pig performance and feeding behaviour.

  Level of inclusion
  0% 4% 8% 12%
Feed intake (g/day)    2,527    2,286    2,528    2,395   
Daily gain (g per day) 1,031 927 995     905
Feed Conversion Rate (FCR) 2.45 2.47 2.55  2.66
Number of feeder visits (pigs/day)                           4.9 16.0 14.3 20.9
Drip loss (%) 4.7 3.8 4.9 4.6
Tenderness (kg per cm2 3.6 4.1 3.8 3.7
Feeding behaviour
There was an interesting effect 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.

There was no effect of glycerol inclusion on meat quality as assessed by drip loss or tenderness.

Ball concluded: "Glycerol has the potential to be a new feed ingredient in pig diets and can replace a proportion of cereal in the diet but more research is needed to fully understand how glycerol is utilised by pigs."

Cereal grains
Cereal grains are the main energy source in pig diets but as producers know only too well, prices can fluctuate frequently causing increases in diet cost and lowering profitability.

There is no one feed ingredient which can completely replace cereal as an energy source but it is worthwhile to consider ingredients which could be used as a partial replacement.

The trial was funded by the Department of Agriculture and Rural Development (DARD), John Thompson & Sons and Devenish Nutrition.

Related websites:

• Agri-Food and Biosciences Institute

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