Age-related changes of yolk precursor formation in the liver of laying hens

Abstract

A rapid decline in egg production of laying hens begins after 480 d of age. Such a rapid decrease results predominantly from the ovarian aging, accompanied by endocrine changes, decreased yolk synthesis and accumulation, and the reduction in follicles selected into the preovulatory hierarchy. In this study, hens at 90, 150, 280, and 580 d old (D90, D150, D280, and D580, respectively) were compared for yolk precursor formation in the liver to elucidate effects of aging on laying performance. The results showed that liver lipid synthesis increased remarkably in hens from D90 to D150, but decreased sharply at D580 as indicated by the changes in triglyceride (TG) levels. This result was consistent with the age-related changes of the laying performance. The levels of liver antioxidants and total antioxidant capacity decreased significantly in D580 hens and the methane dicarboxylic aldehyde in D580 hens was much higher than that at other stages. The serum 17β-estradiol level increased from D90 to D280, but decreased at D580 (P<0.05). The expression of estrogen receptor α and β mRNAs in the liver displayed similar changes to the serum 17β-estradiol in D580 hens. Expressions of the genes related to yolk precursor formation and enzymes responsible for fat acid synthesis were all decreased in D580 hens. These results indicated that decreased yolk precursor formation in the liver of the aged hens resulted from concomitant decreases of serum 17β-estradiol level, transcription levels of estrogen receptors and critical genes involved in yolk precursor synthesis, and liver antioxidant status.

The Golden Egg: Nutritional Value, Bioactivities, and Emerging Benefits for Human Health

“…However, when considering the chemical composition of eggs, the results are quite controversial, although some have shown some difference in fatty-acid composition (docosahexaenoic acid and arachidonic acid) of egg depending on hen’s age [158]. Overall, these alterations in egg quality with age are, however, consistent with physiological changes and maybe some primary metabolic dysfunctions occurring in commercial hens at the end of the laying cycle [159].…”

Transcriptome profiling analysis of underlying regulation of growing follicle development in the chicken

“…In poultry breeds, high-efficiency follicular development implies huge economic output for the egg industry. Birds have a unique follicular development process with large amount of yolk in the oocyte cytoplasm ( Johnson, 2015 , Liu et al., 2018 ). During follicular development, a series of key events such as gene transcription and protein expression occur in series and are governed by specific gene expression, which is an intrinsic factor regulating follicular recruitment, selection, and apoptosis of follicular cells ( Beg et al., 2002 ).…”

Alpha‐lipoic acid improves the reproduction performance of breeder hens during the late egg‐laying period

“…In this study, 600 mg/kg ALA-treated group decreased the level of MDA and improved the activity of TAOC and SOD in ovary. Previous studies have noted that ALA can enhance the antioxidants enzymes like superoxide dismutase, by reducing the substrate and free radicals to promote the lipid stability in birds (Kofuji, Nakamura, Nakamura, Isobe, Murata, & Kawashima, 2008;Li et al, 2019 (Liu, Lin, Mi, Li, et al, 2018;Liu, Lin, Mi, Zeng, et al, 2018). ALA has been reported to increase the reproductive hormones in ovarian oxidative damage rats (Nair et al, 2020).…”

“…These yolk precursors play a vital role in hatching eggs (Crossin et al, 2012). Our study suggested that ESR1, ESR2, ApoB and VTGⅡ mRNA expression levels were upregulated in the livers of birds exposed to 600 mg/kg ALA. For oviparous animals, the synthesis of VTG and ApoB in the liver is related to E2 (Liu, Lin, Mi, Li, et al, 2018;Liu, Lin, Mi, Zeng, et al, 2018;Verderame & Limatola, 2010;Yilmaz et al, 2015). E2 activates VTG gene expression through specific ERs genome (Liu, Lin, Mi, Li, et al, 2018;Liu, Lin, Mi, Zeng, et al, 2018);…”

“…In poultry, many factors are in connection with fertility. Senescent ovary is responsible for decreased fertility (Liu, Lin, Mi, Li, & Zhang, 2018; Liu, Lin, Mi, Zeng, & Zhang, 2018; Saleh, Ahmed, Ahmed, & Ebeid, 2019). Oxidative stress caused by reactive oxygen species is reported to be involved in ovarian ageing (Devine, Perreault, Perreault, & Luderer, 2012; Luderer, 2014).…”