Conventional use and sustainable valorization of spent egg-laying hens as functional foods and biomaterials: A review

Abstract

Spent hen are egg-laying hens reaching the end of their laying cycles; billions of spent hens are produced globally each year. Differences in people’s attitudes towards spent hen as foods lead to their different fates among countries. While spent hens are consumed as raw or processed meat products in Asian countries such as China, India, Korea, and Thailand, they are treated as a byproduct or waste, not a food product, in the western society; they are instead disposed by burial, incineration, composting (as fertilizers), or rendering into animal feed and pet food, which either create little market value or cause animal welfare and environmental concerns. Despite being a waste, spent hen is a rich source of animal proteins and lipids, which are suitable starting materials for developing valorized products. This review discussed the conventional uses of spent hens, including food, animal feed, pet food, and compost, and the emerging uses, including biomaterials and functional food ingredients. These recent advances enable more sustainable utilization of spent hen, contributing to alternative solutions to its disposal while yielding residual value to the egg industry. Future research will continue to focus on the conversion of spent hen biomass into value-added products. Graphical abstract

The Impact of Varying the Amount of Octacosanol Added to Laying Hens’ Productive Performance and Various Oxidative Tests with and Without Vitamin E

“…Through the results of table (1), we note the existence of significant increase (P ≤ 0.05) in egg production in treatments with octacosanol alone or with vitamin E compared to the control treatment. With a significant increase (P ≤ 0.05) in the efficiency of food conversion in these treatments compared to the first treatment.…”

“…Global egg production reached 86 million metric tons by the start of the first two decades of the present century, an increase of nearly 26% over what was produced in the first decade, with rising egg consumption demand [1]. Its production mostly depends on flocks of chickens that lay table eggs, with an average annual production rate of about 300 eggs [2].…”

Chicken Muscle‐Derived ACE2‐Upregulating Peptide VVHPKESF Reduces Blood Pressure Associated with the ACE2/Ang (1‐7)/MasR Axis in Spontaneously Hypertensive Rats

“…Chicken muscle proteome is a great source of bioactive peptides. [ 22 ] Our previous work reported a chicken (laying hen) muscle hydrolysate, prepared using food‐grade thermoase PC10F, reduced BP significantly in SHRs. [ 23,24 ] Subsequently, three ACE‐inhibitory peptides (Val‐Arg‐Pro [VRP], Leu‐Lys‐Tyr [LKY], and Val‐Arg‐Tyr [VRY]) and one ACE2‐upregulating peptide (Val‐Val‐His‐Pro‐Lys‐Glu‐Ser‐Phe [VVHPKESF (V‐F)]) were isolated.…”

Chicken Muscle-Derived ACE2 Upregulating Peptide VVHPKESF Inhibits Angiotensin II-Stimulated Inflammation in Vascular Smooth Muscle Cells via the ACE2/Ang (1–7)/MasR Axis

“…Spent laying hens are egg-laying chickens reaching the conclusion of their egg-laying cycles. Being the major byproduct in the egg industry, spent hens are often disposed by landfilling, incineration, or rendering into oil and protein meal as pet food or animal feed. − Over a decade, our lab has developed various valorized applications for spent hens, with one of the major focuses on bioactive peptide-based functional food ingredients. − In our recent work, a spent hen muscle protein hydrolysate has been prepared using thermoase PC10F, possessing great antihypertensive effect in spontaneously hypertensive rats. , Four RAS-regulating peptides have been identified from the hydrolysate, including Val-Arg-Pro (VRP), Leu-Lys-Tyr (LKY), Val-Arg-Tyr (VRY), and Val-Val-His-Pro-Glu-Lys-Ser-Phe (VVHPKESF; V–F); VRP, LKY, and VRY are ACE-inhibitory peptides possessing IC 50 values of 0.64–5.77 μg/mL, while V–F is an ACE2-upregulating peptide, which upregulates ACE2 expression by 0.84-fold in rat vascular smooth muscle A7r5 cells (VSMCs A7r5) . Amelioration of vascular inflammation and oxidative stress is beneficial to the treatment of hypertension. , These peptides demonstrated antioxidant effects in vascular cells, however, the effects of these peptides on modulating vascular inflammation remain unknown.…”