Adding glycerol to pig rations can impact on feed intake and FCR – but not meat quality
Take Home Message: Glycerol can be included in finishing diets at up to 120g/kg without affecting intake, food conversion or carcass quality although the effects on growth rate are variable and difficult to predict.
Adding glycerol to pig rations significantly affected average daily liveweight gain but the effect was not linear. That was the conclusion of a trial, carried out by scientists in Hillsborough and Belfast, the results of which were presented to delegates at this year’s British Society of Animal Science annual conference.
“Feed intake and FCR were not significantly affected by glycerol inclusion, but there was a tendency for FCR to become less efficient as glycerol inclusion increased,” said Agri-Food and Biosciences Institute’s Elizabeth McCann, who set out to investigate the effect of glycerol inclusion in finishing pig diets on performance and meat quality.
Glycerol, a by-product of biodiesel, may be a useful source of energy in diets for pigs, but there is limited research on the optimum level of inclusion, digestible energy (DE) content or on the effect on performance. Other research has suggested that glycerol reduced pig performance but significantly improved meat quality, as assessed by drip loss.
So Dr McCann and her team formulated four experimental diets, containing 0, 40, 80 or 120g/kg glycerol, 185g/kg crude protein, 9.7g/kg lysine and 14.2MJ/kg DE (fresh basis). Glycerol replaced wheat in the diet formulation.
The performance trial involved 48 pigs housed in groups of six from 14 weeks of age until slaughter at either 152 or 159 days. And feed was supplied ad lib through electronic feeders and individual pig intake, intake per feeder visit, time of visit, duration of visit and number of visits were recorded on a daily basis.
Pigs were slaughtered under commercial conditions, cold weight and back fat at the P2 position recorded and kill-out percentage calculated. A two-inch chop was taken for meat quality analyses (cooking loss, drip loss, sarcomere length and shear force).
“And although there was no significant effect of glycerol inclusion on feed intake or FCR, average daily gain decreased when glycerol was included at 40 or 120g/kg,” said Dr McCann.
“While there was no significant effect of glycerol inclusion on daily feed intake, variability between treatments was high. Glycerol inclusion increased the number of visits to the feeder but decreased the total time spent at the feeder which may be due to reduced palatability.
“There was no significant effect of glycerol inclusion on carcass or meat quality assessments,” she added.
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