Production and Safety Assessment of a DHA-rich Fungal Meal and Its Effects on Lipid Metabolism and Lipogenic Genes Expression in Chickens
Date Issued
2007
Date
2007
Author(s)
Chin, Hung-Jung
DOI
en-US
Abstract
Schizochytrium limacinum SR21 (SR21) is a marine fungus which can accumulates a high content (32.7% of total fatty acid) of docosahexaenoic acid (DHA) and is a potential candidate for use as a DHA-rich ingredient in poultry diets. In this study, effects of dietary SR21 supplementation on DHA accumulation in the egg or tissues and on mRNA expression of lipogenic genes in livers of laying hens or broilers were examined. The safety of SR21 was also tested to ensure it can been safely utilized as a dietary supplement for laying hens
Experiment I : the optimal cultural condition for the DHA production of SR21 was a medium containing 5.0% glucose, 2.0% sea salt, 1.0% yeast extract. The highest DHA productivity of SR21 was 874 mg/L. Using freeze dried SR21 fungal meal (FM) for 3 wk feeding study in laying hen showed that dietary supplementation of 1 and 3% FM did not have an effect on egg production, egg weight and egg yolk weight. The DHA concentration in yolk was increased from 0.36% to 1.17% (1% FM) and 1.81% (3% FM) of total fatty acids. Dietary DHA enrichment had no effect on the mRNA expression of lipogenic genes in the liver of laying hens.
Experiment II : the 3 wk feeding trial for broiler showed that dietary supplementation of 3% FM can increase the daily weight gain and feed efficiency. Compared with the control, the 3% FM treatment decreased the content of plasma triacylglyceride (from 126.03 mg/dL to 118.88 mg/dL) while the 1% FM decreased the content of hepatic total lipids (from 114 mg/g to 92 mg/g) suggested the DHA-enriched FM can influence the lipids metabolism in broilers. The 3% FM treatment increased the DHA content of breast muscle from 2.48 to 7.50% of total fatty acids. The mRNA expression of hepatic sterol regulatory element binding protein 1, acetyl coenzyme A carboxylase, fatty acid synthase, and malic enzyme genes were significantly decreased by the supplementation of either 3% FM or 1% DHA oil (P<0.05), suggesting that dietary DHA can inhibit the expression of lipogenic genes.
Experiment III : the isoenergetic and isonitrogenic experimental diets were used to study whether dietary SR21 supplementation has the growth-promoting effect in broi8lers. Results showed that feeding broilers with 1 or 3% FM for 3 wk had no significant effect on the growth performances. The broilers were fed the control diet (0% FM) for an 2 extra wk. The data showed tissues except plasma of 1 and 3% FM treatments still contained much higher DHA levels than the control, suggesting a carryover effect of the DHA on the breast muscle and liver tissues. The inhibitory effect of dietary DHA on the mRNA expression of hepatic lipogenic genes was abolished when broilers fed the control diet for 2 wk.
Experiment IV : laying hens were fed with 0, 3, 6, and 12% FM diets for 6 wk to evaluate the safety of the FM. The egg production and hatchability of layers were not significant different among treatments. Serum biochemistry markers included glutamate pyruvate transaminase, glutamate oxaloacetate transaminase, gamma-glutamyl transpeptidase , and creatinine concentrations were not significant different among treatments. Histopathologic evaluation of the tissue biopsies showed the 6-wk dietary 12% SR21 fungal meal treatment did not elevate percentages of samples represented as lesions. These results suggested the dietary SR21 bioproduct was not harmful to the reproduction, liver and kidney functions of laying hens during the 6 wk feeding age.
In conclusion, dietary DHA-enriched FM obtained from S. limacinum SR-21 can be digested, absorbed and incorporated into egg or muscle. Such a DHA enrichment is beneficial for the production of the functional DHA-enriched chicken meat or eggs. Dietary DHA can inhibit the lipogenic genes expression in the liver of broilers. The SR21 FM can be used safely as a feed supplement for laying hens at a low level at least 6 weeks.
Subjects
Schizochytrium limacinum SR21
二十二碳六烯酸
脂質生成相關基因
來航產蛋雞
白色肉雞
Docosahexaenoic acid
Lipogenic genes
Laying Leghorn hen
White broiler chicken
SDGs
Type
thesis