1. THE USE POSSIBILITIES OF GLYCEROL AT ANIMAL NUTRITION
Mürsel ÖZDOĞAN1 Erkan TOPAL2
1 :Adnan Menderes University, Agriculture Faculty, South Campus, Aydın/TURKEY
2: Agriculture and Rural Ministry, Province Control Laboratory Isparta/TURKEY
Introduction
Glycerol is a product which occurs during biodiesel production and which has wide usage area. Evaluating glycerol as a by-product; is a positive factor in the economical aspect of the biodiesel production. Glycerol produced during biodiesel production, has got water absorbent and characteristic. At the same time, it has high energy value, and it has been seen at the researches that it could be beneficial if it is used as feed material for farm animals. Glycerol is used a nutrient in many medicines and bacteria fermentation for antibiotic production. While the use of glycerol as an alternative energy source in pig, poultry and ruminant feeding is possible, moreover, there have been studies being made for glycerol to be used both as an energy source and to increase the pellet quality of the feed.
Table 1. The chemical properties of pure glycerol
Properties of the glycerol
Glycerol (C3H5(OH)3), is a product known as glycerin-glycerine in the market and produced in the biodiesel production. Oil mainly gets into an interaction with alcohol (methanol) and with the catalyst (sodium or potassium hydroxide), it forms methyl esters and glycerin. Glycerol is an alcohol with three values. It is a thin, viscose, yellow-brown, sweet liquid. It can get mixed with water and ethyl alcohol at any rate. It doesn’t dissolve in ether, chloroform and benzoyl. For each 9 kg of biodiesel production; approximately 1 kg of glycerol is produced as a by-product.
Physical form
Liquid
Mol. weight
92.09 g/mol
Boiling point
290 °C
Melting point
18 °C
Relative density
1.26 at 20 °C
1. Ruminants
2. Pigs
Glycerol was used especially in the pre-birth and post-birth periods during which energy need is high in the ruminants. In addition, there have been studies made for glycerol to be used in calves and fattening bulls.
While it was been reported that the milk protein and its amount shown increase and the body condition score was been improved when “Total Mixed Ration“containing glycerol is given to the cattle in lactation, in another study it was been shown that glycerol didn’t effect the fat and protein level, but also liquid glycerol has a tendency to drop the level of protein and lactose.
When the application with the glucagon injection and ration containing glycerol in the cure of the cows for post-birth was applied, the plasma glucose and insulin was increasing, plasma keton compounds (NEFA and BHBA) values were been decreased. When glucagon and glycerol were applied together, it had been shown that syndrome development based on metabolism in milk cows decreases with it.
It was been shown that crude glycerol increased up to 16 % in the finisher diet of the fattening bulls, especially the glycerol addition up to 8 % level dry matter in ration has increased the live body weight and feed conversion ratio.
There are studies about the use of glycerol as an energy source in pig feeds. Glycerol and barley were compared in the aspect of being energy sources and the ration containing 10 % glycerol advised for pigs were found out to have a higher daily body weight gain, and also demonstrated that there is no negatif effect on pig fattening performance, carcass composition, meat quality or lesion scores.
Digestible energy (DE) of crude glycerol in the growing pigs was shown to be nearly kcal/kg and the metabolizable energy (ME) to be nearly kcal/kg and that it is a good source of energy.
Crude glycerol (0, 3, 6, 9, 12 and 15 %) increased the pellet durability index, production rate and the production efficiency in corn-soybean based pellet feeds. Moreover, it was said that only the pellet durability of the mixed feeds containing crude glycerol was better compared to the fat addition in feeds or fat-crude glycerol combination. The average daily gain of the pigs feeding crude glycerol was increased.
3. Poultry
Conclusion
Glycerol, which is found to be rich in the aspect of energy due to the results of the previous studies, is found to be useful in animal feeding, and it has been shown that there won’t be any negative effects.
However, the glycerol using over 10 % level can causes problems in feed flow and in feed preparation. Further studies are required to determine the optimal storage conditions of feeds containing glycerol at different levels, and the effect of glycerol on carcass quality and blood parameters of fattening bulls and broiler. Studies should make to standardize the chemical composition of glycerol.
One of the targets by creating use of glycerol in animal nutrition will be accomplished to prevent possible environmental pollution.
It was found that body weight and live weight gain were higher in the 5 % pure glycerol addition to the broiler rations, while it was seen that feed conversion ratio and carcass yield were shown improvement. It was observed that there was an increase in the liver weight at the 10 % pure glycerol consumption and on the other hand, there was a decrease in the gizzard weight. Glycerol addition at different levels was made to the poultry feeds. However, it was seen that glycerol adding up more than 10 % causes problems in the feed flow and feed preparation process. Apparent metabolizable energy (AME) of glycerol for the broilers was determined to have values changing between kcal/kg. These results were shown that the AME of glycerol is used by the broilers efficiently.
Glycerol was added 0, 2.5, 5 and 10 % levels of broilers feeds; the addition of 2.5 and 5 % glycerol were found to be used efficiently in broilers and the breast meat amount of the broilers were found to be higher than the ones that didn’t consume glycerol. While the AMEn value of crude glycerol in hens; it was reported to be nearly 3805 kcal/kg in the usages till the levels 5, 10 and 15 %, the use of crude glycerol in high-production laying hens had no effect on feed consumption, egg weight and mass.
When 5 % and 10 % pure (methanol taken) and crude (methanol not taken) glycerol occurred no difference in egg quality parameters known as shape index, breakage resistance, yellow index, white index and haugh unit. The egg shell thickness was found to be significantly low both in 10 % pure and crude glycerol. Moreover, while the 10 % pure glycerol was decreasing egg efficiency, 5% pure and crude glycerol has increased egg efficiency at the rates of 1.69 and 0.82 % respectively.