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Management of Spent Hens
Abstract
When hens kept for commercial egg production reach the end of their economically viable life span, they are usually transported to a processing plant for conversion into meat products. In this article, we review methods used in Canada and the United States for the catching and removing of these "spent" hens from the layer house and the subsequent loading of them onto vehicles for transport, unloading, and slaughter at the processing plant. We outline welfare concerns associated with these procedures with emphasis on bone fractures. We discuss the move toward on-farm euthanasia in North America and the humaneness of the various techniques under investigation. We conclude with recommendations aimed at increasing bone strength and improving the equipment and handling methods used in the movement and slaughter of spent hens.
... In the western world, however, spent hen is generally not processed or accepted for food use, due to a low meat yield and the unacceptable toughness since its meat has a high content of collagen; the presence of brittle, and tiny bone fragments further adds cost and technical difficulty to industrial meat production. Instead, most spent hens are euthanized on the farm or in the processing plants followed by burial, composting, incineration, or rendering into oils and protein meals as animal feeds or pet foods (Cheng et al. 2004;Fritts et al. 2002;Newberry et al. 1999;Pirsich et al. 2017). Disposing spent hens by landfilling and incineration raises animal welfare and environmental concerns. ...
... Disposing spent hens by landfilling and incineration raises animal welfare and environmental concerns. Besides, farmers are liable for paying the cost for their transportation and disposal (Newberry et al. 1999). With these concerns, finding more viable, environmental-friendly approaches for spent hen disposal while yielding residue value to the egg industry are critical. ...
... After laying eggs for nearly one year, a hen's egg production declines to about 65% of its peak productivity, as does the egg quality (Jacob et al. 2014;Seidler 2003). In Canada and America, these hens are considered "spent" and are going to be slaughtered or euthanized on most farms (Newberry et al. 1999); in some countries however, laying hens may instead undergo a feather molt to extend the laying capacity to a second or third cycle, until observing a more significant decline in egg production (Jacob et al. 2014). ...
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
... Information on pathology in DOA layers is scarce. Several studies have reported DOA numbers in layers and identified long travel distance and low external temperatures as two main risk factors [3,[6][7][8][9]. Body weight has also been reported as a risk factor, where flocks with lighter weighing hens had higher DOA [3,10]. ...
... This is similar to the results from a study by Weeks et al. [3] who reported an overall mean of 0.27% DOA from a large sample (n = 13.3 million) of layers from caged, intensive indoor, barn, free-range and organic free-range systems in Great Britain. Several studies have identified long travel distance and low external temperatures as two main risk factors for DOA prevalence in layers [3,[6][7][8][9]. A study from Italy investigating DOA in broilers, turkeys and layers, reported that mortality from farm to slaughter was higher in summer months compared to other seasons for all investigated birds [34]. ...
Background
Meat inspection data is commonly used to monitor health and welfare in commercial broiler production; however, less used in layers. Slaughterhouse records can provide insight into animal and herd health and identify important health and welfare challenges. To gain knowledge of health issues in commercial aviary housed laying hens, the aim of this repeated cross-sectional study was to describe the occurrence and causes of carcass condemnation, including dead-on-arrivals (DOA), in commercial aviary housed layers in Norway, and to explore seasonal patterns and correlation between DOA and number of carcass condemnations.
Results
Data from January 2018 to December 2020 were collected from one poultry abattoir in Norway. In total, 759,584 layers were slaughtered during this period in 101 slaughter batches from 98 flocks and 56 farms. In total, 33,754 (4.4%) layers were condemned, including the DOA. The most common carcass condemnation causes were (percent of all slaughtered layers): abscess/cellulitis (2.03%), peritonitis (0.38%), DOA (0.22%), emaciation (0.22%), discoloration/smell (0.21%), acute skin lesions (0.21%) and ascites (0.17%). Regression analysis showed an estimated higher prevalence of total carcass condemnation during winter compared to the other seasons.
Conclusions
The three most common condemnation causes found in the present study were: abscess/cellulitis, peritonitis, and DOA. We found a large between-batch variation in causes of condemnation and DOA indicating that prevention might be possible. The results can be used to inform and guide further studies on layer health and welfare.
... More than 6 billion spent hens were produced worldwide in 2019 (Fan & Wu, 2022). However, the spent hens are less useful for consumption due to disadvantages, such as many bone fragments, low meat yield, and hard texture (Kadıoğlu et al., 2019;Newberry et al., 1999). In Western countries, most spent hens are processed into animal and pet food, used for composting, or even buried and incinerated (Fan & Wu, 2022). ...
Calcium peptide chelates are developed as efficient supplements for preventing calcium deficiency. Spent hen meat (SHM) contains a high percentage of proteins but is generally wasted due to the disadvantages such as hard texture. We chose the underutilized SHM to produce peptides to bind calcium by proteolysis and aimed to investigate chelation between calcium and peptides in hydrolysate for a sustainable purpose. The optimized proteolysis conditions calculated from the result of response surface methodology for two‐step hydrolysis were 0.30% (wenzyme/wmeat) for papain with a hydrolysis time of 3.5 h and 0.18% (wenzyme/wmeat) for flavourzyme with a hydrolysis time of 2.8 h. The enzymatic hydrolysate (EH) showed a binding capacity of 63.8 ± 1.8 mg calcium/g protein. Ethanol separation for EH improved the capacity up to a higher value of 68.6 ± 0.6 mg calcium/g protein with a high association constant of 420 M⁻¹ (25°C) indicating high stability. The separated fraction with a higher amount of Glu, Asp, Lys, and Arg had higher calcium‐binding capacity, which was related to the number of ─COOH and ─NH2 groups in peptide side chains according to the result from amino acid analysis and Fourier transform infrared spectroscopy. Two‐step enzymatic hydrolysis and ethanol separation were an efficient combination to produce peptide mixtures derived from SHM with high calcium‐binding capacity. The high percentage of hydrophilic amino acids in the separated fraction was concluded to increase calcium‐binding capacity. This work provides foundations for increasing spent hen utilization and developing calcium peptide chelates based on underutilized meat.
... In the late stage of egg laying (from week 80 to 100), laying hens will gradually be removed from farms due to the decline in their egg production rate or egg quality; these hens are named "spent hens" and are also classified as old laying hens or aged chickens [4,5]. It is estimated that 4.5 billion spent hens were produced globally in 2018 [6]. ...
The aim of this study is to assess the differences in the meat quality, nutritional composition, carcass traits, and myofiber characteristics between Hy-Line grey chickens (HLG, commercial breed) and Guangyuan grey chickens (GYG, indigenous breed). A total of 20 55-week-old chickens were selected for slaughter. The HLG exhibited a larger carcass weight, breast muscle weight, and abdominal fat weight (p < 0.05). The GYG exhibited a higher crude protein content, lower shear force, and smaller fiber size in the thigh muscles, whereas the HLG presented higher pH values and lower inosine-5′-monophosphate content in the breast muscles (p < 0.05). Darker meat based on higher redness and yellowness values was observed in the GYG instead of the HLG (p < 0.05). The research results also revealed parameter differences between different muscle types. Simultaneously, a correlation analysis showed significant correlations between the meat quality traits and myofiber characteristics (p < 0.05). In conclusion, aged indigenous chickens perform better in terms of tenderness and nutritional value in the thigh muscles, and may exhibit a better flavor in the breast muscles, but have a smaller breast muscle weight. Therefore, the current investigation provides a theoretical basis for the different needs of consumers and the processing of meat from old laying hens.
... Conservation problems associated with the transport of chickens intended for commercial production of eggs, slaughtered after their economically viable lives have been studied. The mortality rate during the transportation of broilers, turkeys, ducks, and geese to slaughter was investigated and the category of poultry most susceptible to stress due to non-optimal transportation conditions was determined [7]. ...
The results of this study on the loss of live poultry at various stages of delivery from the farm to the processing plant by road are given. A factor analysis of the reasons for the loss of livestock delivered from the farm to the processing plant was carried out. The dependencies of livestock losses on loading delays and the duration of the movement of the loaded poultry farm to the processing plant were established. Methodological recommendations for rationing the number of injuries observed during delivery were developed. The study of losses of live birds during delivery to the processing plant from the density of stocking in shipping boxes was carried out; the economic and mathematical model for optimizing the landing of live birds in shipping boxes was proposed. The calculation of the economic impact of the implementation of the results of the study is given.
... Therefore, the Canadian Code of Practice (NFACC, 2001) and the Canadian Food Inspection Agency (CFIA, 2020) have not outlined separate requirements (particularly for feed and water withdrawal) between the 2 species, EOCH and broilers, despite significant metabolic differences. Age, metabolic exhaustion, body condition, feather cover (FC), and limited customized slaughter plant equipment resulting in longer transport durations are just a few of the unique challenges associated with the transportation of EOCH (Gregory and Wilkins, 1989;Knowles and Broom, 1990;Knowles, 1994;Gregory and Devine, 1999;Newberry et al., 1999;Richards et al., 2012;Weeks et al., 2012). ...
Transportation is a stressful procedure that can alter end-of-cycle hen (EOCH) behaviour and physiology. This study (5 × 3 × 2 factorial arrangement) aimed to assess the effects of temperature (T)/relative humidity (RH) (-10°C uncontrolled RH (-10), +21°C 30%RH (21/30), +21°C 80%RH (21/80), +30°C 30%RH (30/30), +30°C 80%RH (30/80)), duration (4, 8, 12 h), and feather cover (well (WF) and poorly-feathered (PF)) on white-feathered EOCH (65-70 wk) behaviour and physiology. EOCH (n=630) from 3 commercial farms were housed for adaptation (3-5 d), fasted (6 h), crated (53 kg/m²), and placed in a climate-controlled chamber. Data collected included chamber and crate conditions, feather condition score, mortality, core body temperature (CBT), behaviour, and delta (∆) blood physiology. Analyses were conducted via ANOVA in a randomized complete block design (farm of origin) with significance declared at P≤0.05. PF EOCH had higher mortality than WF hens during cold exposure (-10). EOCH ∆CBT demonstrated a greater (positive) change at 12 h for all T/RH compared to 4 h at 21/30, 21/80, and -10 (negative). Cold exposure (-10) resulted in a higher percentage of time spent shivering and motionless, while heat exposure resulted in a higher percentage of time spent panting for WF EOCH exposed to 30/30 and WF and PF hens exposed to 30/80. Hen ∆glucose had a greater (negative) change at 4 and 12 h for -10 compared to 4 h at 21/30, and all durations for 21/80, 30/30, and 30/80. PF hens exposed to -10 had a greater (positive) change in ∆sodium, ∆hemoglobin, and ∆hematocrit compared to WF birds (negative). The development of metabolic alkalosis was supported by the increase in ∆blood pH over time and the increase in ∆partial pressure of carbon dioxide, ∆bicarbonate, and ∆base excess extracellular fluid during cold exposure (-10). These results indicated that EOCH exposed to heat endured thermal stress while PF hens exposed to cold were unable to cope with cold stress.
This study aimed to evaluate the modulatory effects of four chicken muscle-derived peptides [VRP, LKY, VRY, and VVHPKESF (V-F)] on angiotensin II (Ang II)-induced inflammation in rat vascular smooth muscle A7r5 cells. Only V-F could significantly attenuate Ang II-stimulated inflammation via the inhibition of NF-κB and p38 MAPK signaling, being dependent on the Mas receptor (MasR) not on the Ang II type 1 or type 2 receptor (AT1R or AT2R). V-F accelerated Ang II degradation by enhancing cellular ACE2 activity, which was due to ACE2 upregulation other than a direct ACE2 activation. These findings demonstrated that V-F ameliorated Ang II-induced inflammation in A7r5 cells via the ACE2/Ang (1-7)/MasR axis. Three peptide metabolites of V-F─VHPKESF, PKESF, and SF─were identified but were not considered major contributors to V-F's bioactivity. The regulation of peptide V-F on vascular inflammation supported its functional food or nutraceutical application in the prevention and treatment of hypertension and cardiovascular diseases.
Avian orthopedic injuries are common and may result from trauma, nutritional imbalances, or congenital malformations. While orthopedic injuries may be obvious, complete, and well‐timed examination of the avian patient is critical. The goals of surgery should be to minimize hemorrhage, trauma, and anesthetic time, preserve soft tissues, reduce pain, and restore intended function. A successful outcome requires an understanding of orthopedic surgical principles, the avian musculoskeletal system, and the physiologic characteristics that make birds unique.
The present review examines the impact of management and husbandry decisions on the welfare of laying hens in Australia. The literature on many of these aspects is lacking for the Australian egg industry, and, indeed, for the egg industry in general. Management decisions that can affect hen welfare relate to the initial farm design, husbandry routines, and staff selection and training. As modern laying houses represent a considerable financial investment, the decisions made during the design phase are likely to affect both the hens and stockpeople for substantial periods. Hens in cage systems may benefit from fewer tiers and greater space allowances. In non-cage systems, the brown genotypes used in the Australian egg industry may benefit from lower structures that accommodate their heavier and less agile bodies. Keel fractures can be reduced by improving the skeletal health and spatial cognition of laying hens during the rearing period, in addition to minimising the distances they need to jump when navigating aviary structures. The addition of a wintergarden to fixed free-range systems appears to be beneficial. Housing hens in mobile units on free-range farms may challenge their welfare, particularly in relation to heat stress. There is also room for improvement in biosecurity practices and health monitoring of hens, as these appear to be lacking at some farms. The current strains of hen used in free-range systems may not be best suited to these conditions, on the basis of their body condition and flock uniformity. Feed quality may also need to be monitored for quality assurance and optimal hen nutrition. Hen welfare during depopulation can be improved through staff training and by reducing staff fatigue. Euthanising spent hens on farm offers welfare benefits over transporting spent hens to an abattoir. Both hen welfare and working conditions for stock people should be considered when designing laying houses to provide suitable conditions for both hens and stockpeople. This will help improve the job satisfaction of stockpeople, which may translate into better care for the hens and may aid in retaining quality staff. Stockpeople must be recognised as vital contributors to hen welfare in the egg industry, and it is important for the egg industry to continue to attract, train and retain skilled stockpeople to ensure that they enjoy their job and are motivated to apply best-practice care for their flocks. Promoting the animal-care aspect of stockmanship in combination with a supportive managerial environment with optimal working conditions may increase the attractiveness of the egg industry as a place to work.
The expansion in supplies of spent heavy fowl and the increasing use of broiler meat in further processed food products have reduced the market for spent laying hens to the point that these birds frequently have no value. If spent hens cannot be sold through traditional channels, egg producers must seek alternative ways to dispose of old flocks. A fowl removal program must first address the problems of where and how the spent hens should be killed. Without a centralized site for slaughter, the most suitable place to kill spent hens is on the farm itself. The work reported herein has been dedicated to the development of a cost-effective and humane method for on-farm killing of spent hens. A mobile MAK (modified atmosphere killing) unit was built consisting of a 21 ft.3 closed cart with spring-loaded doors through which hens can be placed inside. A carbon dioxide (CO2 cylinder is mounted on the unit so CO2 can be dispensed into the interior as needed to stun and kill hens. The prototype MAK unit has proven to be effective in on-farm trials, with about 30,000 hens having been killed in it thus far. The efficiency of the unit should make it possible to recover the cost of the CO2 used to kill the hens.
Three field experiments were conducted to determine the influence of midnight feeding of commercial egg layers on eggshell quality. Experiment 1 consisted of four houses containing 90,000 hens each, which received feed at midnight. Four other houses served as controls. Specific gravity increased on the eggs collected at 09:00 hr from hens fed at midnight. Shell weight also increased in three of the four comparisons as did specific gravity of eggs collected at 15:00 hr. Shell weight decreased in three of the four comparisons when the hens were given the midnight feeding and eggs were collected at 15:00 hr. In Experiment 2, eggshell quality was measured before initiating the midnight feeding program in two cool-cell-pad houses (containing 71,000 hens each). There was an improvement in shell weight, percent shell, and shell weight per unit surface area (SWUSA) in the cool end of both houses. However, shell weight was not affected in the warm end of the houses. In Experiment 3, comparisons were made in two pairs of houses. Eggshell quality was measured on day 1 and after four days of midnight feeding. Shell weight was increased with both comparisons. However, percent shell and SWUSA were not affected.
Because of the possible short-term stress or injury in birds that may result from the effects of vibration during transport in road vehicles, studies have been initiated to characterize the various vibration frequencies in different axes found within bird containers on typical poultry transporters. Bird response is now being explored experimentally within the boundary conditions of vibration frequency and magnitude that have been established.
1. The effects of age at sexual maturity, age at culling, and stunning frequency and current on the incidence of broken bones were examined in end‐of‐lay hens. In addition comparisons were made between 4 different egg‐laying breeds, and between battery, perchery and free range husbandry systems.2. High frequency stunning (1500 Hz) caused a reduction in the incidence of broken bones compared with 50 Hz.3. Battery birds had a higher incidence of recently broken bones in comparison with perchery and free range birds. However, there were more old breaks in the perchery and free range systems than in the battery system.4. Breed of bird, age at sexual maturity and age at culling had no effect on the incidence of broken bones.
Animals are exposed to various vibration and movement stimuli during transport. The vibrations are a potential source of stress in birds because the resonances they set up in the internal organs are likely to be major aversive stimuli. This paper considers the possible effects of vibration on broilers in transport by reference to the known effects of vibration on other species. The fundamental frequency of poultry transporters is between 1 and 2 Hz, with a secondary peak of 10 Hz and a chassis vibration in the lateral axis of 12–18 Hz. Suggested resonance frequencies for the viscera of broiler chickens exposed to vertical vibration are around 10 Hz, and so coincide with the secondary peak. Skeletal muscle responds to movement and vibration in order to maintain postural stability and reduce the effects of resonance. Standing birds maintain stability by wing extension and by flapping or squatting. Involuntary muscle and cardiac muscle are also affected by vibration with blood circulation, heart beat and possibly gut control changing as a result. Vibration-induced vasodilatation may occur, as may blood pooling in the organs, pulmonary damage and impaired thermoregulation. Biochemical changes resulting from vibration could have adverse effects on meat quality in birds unable to recover before slaughter.
The behavioral responses of laying hens to a 4-day fast were investigated. Three hundred and sixty Hyline W77 (W77) and 360 Hyline Brown (Brown) 19-week-old pullets were housed as pairs in cages in separate rooms for each stock. At 63 weeks of age, feed was withdrawn for 96 h from half of the W77 hens. Brown hens were fasted in like manner one week later. For both stocks, time-lapse videorecordings of 8 cages were made each day of the fast (total = 64 hens per stock). In weeks 1, 3, 5 and 9 after the fast, an additional 32 hens of each stock were videorecorded. Fasting appeared to raise the arousal of W77 hens, judging from their increased head flicking and standing behavior. Fasted Brown hens increased head flicking to a lesser extent than W77s and did not alter standing behavior. They performed more preening, however, which could indicate a mild level of frustration. Both stocks increased cage pecking and feather pecking during the fast. No significant change in aggressive pecking was observed. After the fast, W77 hens reduced head flicking, preening and standing, relative to non-fasted hens. Brown hens which had been fasted showed no significant behavioral differences from their respective controls. Although post-fast cage pecking and feather pecking did not differ significantly between treatments, these activities generally were lower for fasted hens. Overall, the W77 stock appeared to be more affected by the fast. The apparent post-fast calming effect, particularly evident for W77 hens, may reflect a renewed behavioral adaptation to the cage environment.
Hens were presented with drinking water ranging in temperature from 20 to 45°C, and their behaviour was investigated before and after partial beak amputation. Amputation resulted in significant behavioural changes with reductions in environmental pecking, beak wiping and head shaking. Pecking at water presented at 45°C, and drinking at all temperatures, were also reduced after amputation. These behavioural changes are interpreted as instances of guarding behaviour and hyperalgesia which persisted for 6 weeks, at least 3 weeks after the beak had healed. They provide evidence for possible chronic pain in birds following partial beak amputation.
In a selection experiment, halothane gene-free Swedish Yorkshire pigs were performance tested for improved lean tissue growth rate (LTGR) on a high protein [HP, 18.5% crude protein (CP)] or a low protein (LP, 13.1% CP) diet. LTGR was determined based on ultrasonic measurements and repeated weighings. In total, 2885 pigs were tested in generation zero and four selected generations. Genetic parameters were estimated with REML using a multiple trait animal model. Heritabilities for growth rate and lean percentage were 0.37 and 0.49 in the LP-line and 0.31 and 0.46 in the HP-line. The genetic correlation between growth rate and lean percentage was favourable (0.25) in the HP-line but unfavourable (-0.67) in the LP-line. As a result, lean percentage in the LP-line decreased during the course of selection. Growth rate increased in both lines, since it was highly correlated (0.96) with LTGR.
An experiment was carried out to study the dynamics of various body-Ca pools in the hen during a single ovulatory cycle. One hundred 32-wk-old Single Comb White Leghorn hens were used. For experimental purposes the ovulatory cycle was divided into four periods: 1–6, 6–12, 12–18 and 18–24 h post-oviposition.At 0, 6, 12 and 18 h post-oviposition 25 hens each were intubated proventricularly with 15 μCi of ⁴⁵Ca as CaCl2 solution. Approximately 1 mL of blood was collected from the leaf brachial vein, and the bird was subsequently placed in an individual cage. Red blood cells, labelled with ¹⁵Cr, were re-injected into the same bird from which it was collected. At 0.5, 1, 2, 4 and 6 h post-intubation with ⁴⁵Ca, blood samples were taken from the right brachial vein of five hens and the birds were immediately killed, carcasses were dissected, the left femur and tibia-fibula were excised, and an egg, if present, was removed. Whole blood was assayed for ⁵¹Cr activity, and plasma, bones and shells were assayed for ⁴⁵Ca activity and Ca concentration.Another five hens were injected in the right brachial vein with 15 μCi of ⁴⁵Ca immediately following oviposition. Subsequently, the left brachial vein was catheterized and blood was sampled at 0.5, 1, 2, 4, 6, 12, 18 and 24 h post-injection.There were no significant (P > 0.05) differences in blood volume or plasma-Ca concentration for the four periods assayed. Following intubation, plasma-⁴⁵Ca activity decreased quadratically (P < 0.05) with time for all four periods assayed. Regression analysis showed that the biological half-life of plasma ⁴⁵Ca was 3.30, 2.13, 1.80 and 1.77 h for periods 1, 2, 3 and 4 respectively. When birds were injected intravenously with ⁴⁵Ca the half-life of plasma ⁴⁵Ca was 0.116 h.There were no significant (P > 0.05) changes over time in ash or Ca content of bone ends (BE) or medullary bone (MB). Only MB accumulated ⁴⁵Ca during the first 6 h of the cycle. There was no difference (P > 0.05) in ⁴⁵Ca activity of either BE or MB over time in period 2. Only BE experienced a significant (P < 0.05) loss in ⁴⁵Ca during period 4.There were no differences (P > 0.05) in total shell ash. shell Ca or ⁴⁵Ca with time in period 1. Shell ash increased (P < 0.05) by 188, 348 and 237 mg h⁻¹ and shell Ca increased by 69, 128 and 82 mg h⁻¹ in periods 2, 3 and 4, respectively. Accumulation of shell ⁴⁵Ca confirmed that the transfer of Ca was greatest during period 4 of the ovulatory cycle. Using ⁴⁵Ca dynamics, we estimated that over the entire ovulatory period 1716 mg of Ca was absorbed from the digestive tract and 1704 mg was secreted as shell. Key words: Calcium-45 activity, calcium-45 half-life; plasma ⁴⁵Ca, bone ⁴⁵Ca, shell ⁴⁵Ca, shell secretion, Ca absorption