A chemical analysis of samples of crude glycerol from the production of biodiesel in Australia, and the effects of feeding crude glycerol to growing-finishing pigs on performance, plasma metabolites and meat quality at slaughter

Abstract

The aims of this study were to: (i) determine the chemical composition of 11 samples of crude glycerol collected from seven Australian biodiesel manufacturers; and (ii) examine the effects of increasing levels of crude glycerol fed to growing-finishing pigs on performance, plasma metabolites and meat quality at slaughter. Chemical composition of crude glycerol samples varied considerably; glycerol content ranged between 38 and 96%, with some samples containing up to 29% ash and 14% methanol. One of these samples (76.1% glycerol, 1.83% methanol) was then fed to 64 female pigs (50.9 ± 5.55 kg; mean ± s.d.) allocated to one of five dietary treatments (0, 4, 8, 12 and 16% crude glycerol) until they reached 105 kg liveweight. There were no statistical differences in performance indices with increasing levels of added glycerol, although there was an unexpectedly high variation between treatments. Blood glycerol levels were unaffected by diet in week two of the experiment, but increased linearly (P < 0.001) with increasing levels of dietary glycerol before slaughter. The inclusion of crude glycerol did not influence any meat quality parameters at slaughter (P > 0.05). Diets containing added crude glycerol were less dusty after mixing, but diets that contained 8, 12 and 16% glycerol all formed a firm aggregate within 24 h of mixing that presented some feeding difficulties. This might restrict inclusion of glycerol in mash diets to dietary levels less than 8%. Furthermore, levels of residues such as methanol and ash should be monitored to prevent excessive amounts of these compounds in pig diets.

Growth Performance, Carcass Characteristics, Meat Quality of Growing Pigs Fed Diets Supplemented With Crude Glycerin Derived From Palm Oil

“…The study of Lammers et al (2) evaluated crude glycerin in growing pigs and described animal growth, feed intake, conversion, fat in the 10 th rib, loin area and free fat percentage showing no effects due to treatments, similarly to the results found in the present study. Contrary, in piglets, the inclusion of crude glycerin improved average daily gain in linear form, without affecting consumption and conversion (16) , similar to the results obtained with 8% glycerol in diet (10) and growing pigs (8) .…”

“…Table 1 displays the chemical composition of crude glycerin from PO. The maximum level of inclusion of CG was 10% because it is the level that has not affected the performance of pigs using other sources of crude glycerin (2,6,7,9,10) , although in Australia the use of up to 16% of CG did not affect the performance of animals but there were difficulties in feed management (8) .…”

“…Several studies have revealed that the inclusion of crude glycerin up to 16% in isoenergetic and isoproteic diets for pigs has not affected performance, carcass characteristics and meat quality (2,(6)(7)(8)(9)(10) . However, when corn was replaced by crude glycerin as the source of dietary fatty acids (FA), a reduction in the content of polyunsaturated fatty acids in the loin occurred (2) .…”

Addition of crude glycerin to pig diets: sow and litter performance, and metabolic and feed intake regulating hormones

“…In general, previous studies on glycerin in the diets of growing-finishing pigs found no differences between treatments in insulin , cortisol (Lammers et al, 2008a) or glucose (Hansen et al, 2009). Likewise, Schieck et al (2010a) found that increasing crude glycerin levels in the diet of lactating sows had no effect on plasma glucose.…”

Use of biodiesel co-products (Glycerol) as alternative sources of energy in animal nutrition: a systematic review

“…Products with lower purity, as in the case of crude glycerol, may present contaminants originating from the extraction process, such as methanol, a toxic substance which is considered unsafe at levels above 150 ppm (Dasari 2007). However, pigs fed diets containing glycerol and 2,900 ppm (Hansen et al 2009) and3,200 ppm (Lammers et al 2008) of methanol showed no signs of intoxication. Out of the 17 studies used in this review, seven (41%) used glycerol with purity between 65 and 90%; seven (41%) reported the use of glycerol between 90% and 99.7% purity and three (18%) used products with a purity greater than 99.7%.…”