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Effect of Caponization and Testosterone Implantation on Hepatic Lipids and Lipogenic Enzymes in Male Chickens

K. L. Chen^*, W. T. Chi^*, C. Chu, R. S. Chen and P. W. S. Chiou^,1

^* Department of Animal Science, Department of Applied Microbiology, and Department of Molecular and Biological Chemistry, National Chiayi University, Chiayi, Taiwan, China; and Cheng-Jen College of Nursing, Health Sciences and Management, Chiayi, Taiwan, China

¹ Corresponding author: wschiou{at}dragon.nchu.edu.tw

This study was conducted to determine the role and effects of testosterone in lipogenesis by measuring and analyzing the lipid composition and lipogenic enzyme activity of livers from capons treated with various doses of exogenous testosterone implant. Healthy and uniform male Single Comb White Leghorn chickens were caponized at 12 wk of age. Sixteen-week-old capons were randomly selected for a 10-wk experiment. Fifteen intact males and 15 capons were used for trial 1. In trial 2, 10 sham-operated males and 40 capons were used. The capons were randomly divided into 4 independent treatments with sialistic implants of cholesterol (1.62 mm i.d., 3.6 mm o.d., 9.24 ± 0.36 mg; CHOL), low testosterone (1 mm i.d., 3 mm o.d., 5.88 ± 0.23 mg), medium testosterone (1.62 mm i.d., 3.16 mm o.d., 9.81 ± 0.17 mg), or high testosterone (2 mm i.d., 4 mm o.d., 16.7 ± 0.24 mg). In trial 1, the results showed that caponization increased total hepatic lipid and triacylglycerol contents and decreased the nonesterified fatty acid content (P < 0.05) compared with the intact male. Meanwhile, caponization increased nicotinamide adenine dinucleotide phosphate -malic dehydrogenase (MDH) activity and MDH mRNA content (P = 0.09) simultaneously. In trial 2, comparing treatments with the various implantation doses of testosterone, the liver triacylglycerol content of capons the medium-dose implantation was decreased as compared with those receiving CHOL (P < 0.05). The total lipid and phospholipid contents of liver were decreased in capons receiving the high-dose implantation (P < 0.05), whereas the relative weight and nonesterified fatty acid content were increased (P < 0.05) and reached the same level as those in the sham treatment (P > 0.05). With an increased implantation dose, MDH activity of capons receiving the medium dose or higher was not different from those receiving the CHOL and sham treatments (P > 0.05). The increase in MDH activity at the transcriptional and translational levels suggests that caponization may positively regulate hepatic lipogenesis. In contract, implantation of testosterone up to the threshold concentration depressed hepatic lipogensis and lipid accumulation.

Key Words: cockerel • caponization • testosterone implantation • hepatic lipid composition • hepatic lipogenic enzyme