| Summary: | 碩士 === 國立中興大學 === 動物科學系所 === 98 === Lipid dysregulation leading to poor reproductive performances in broiler breeder hens has been suggested to etiologically similar to the lipotoxicity theory linking obesity to type-II diabetes in mammals. This theory states that when excessive fatty acids accumulate in non-adipose tissues, inflammatory responses, oxidative damage due to excessive β-oxidation, and bioactive lipid derivatives may cause cell dysfunction or apoptosis. In recent decades, the growth rate of current Taiwan country chickens has been greatly promoted in association with increased adiposity but poor reproductivity as similar as typically exemplified in broiler breeders. This collateral consequence may be attributed to genetic crossbreeding with broilers or is likely due to the intrinsic divergence of growth and reproductive efficacy in avian evolution. In the study, we achieved an obesity model by ad libitum vs. restricted feeding in 3 strains of Taiwan country chicken hens, commercial Red (RF) and black feather (BF) line, and NCHU B-line (BL) and examined the effect of body composition, reproductive functions and physiological responses in reference with broiler breeders. Results showed that body weight, absolute and relative liver and abdominal fat weight, incidence of sudden death were higher in overfed birds than their restricted counterparts. Although restricted feeding failed to improve egg production in country chickens, regression analyses suggested that body weight is negatively correlated with egg production in RF and BF under voluntary feeding but not in B-line. Overfed birds exhibited higher plasma glucose, VLDL lipid, and non-esterified fatty acid (NEFA) levels, and hepatic triacylglycerol (TG) and phospholipids (PL) content. Consistent alterations of metabolic and endocrine signals were also observed as evidenced by promoted circulating bioactive ceramide levels, and inflammatory interleukin-1β (IL-1β) and ceramide contents in the liver and ovary, the final processing destination of egg production, with which a higher incidence of abnormal ovarian morphology noted for hierarchical follicle atresia was observed in birds fed ad libitum. The promoted circulating and tissue ceramide levels in overfed birds were further manifested with upregulation of hepatic and ovarian granulosa cell sphingomyelinase (SMase) and serine palmitoyl transferase (SPT) gene expression. The endocrine and metabolic alterations leading to ovarian dysfunction by overfeeding apparently is more noticeable in a sequence with broiler, RF, BF, and BL line. Taken together, we concluded that current Taiwan country chickens, particularly, RF line have developed obesity and related dysregulations leading to poor reproductive efficacy similar to those in broiler breeders.
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