Welfare challenges in broiler and layer production systems: A review

Introduction

Poultry farming is one of the rapidly growing sectors in Indian agriculture. It plays an important role in the livestock economy and provides an affordable source of animal protein (Ricky, 2024) [57] . India has shown immense growth in poultry production and has excelled in both egg and meat production. India is also one of the leading producers of poultry meat globally. According to BAHS statistics (2025) [3] , India produced 149.11 billion eggs and 10.50 million tonnes of meat during 2024-25, with poultry contributing about 49% to 51% of the total meat production. In recent years, India has witnessed significant advancements in the production of poultry eggs and meat, which is mainly due to the rising demand and the modernisation of production systems. However, the rapid industrialisation of poultry production to meet the increasing consumer demand has raised concerns regarding animal welfare (Sassi et al., 2016) [7] In poultry production, animal welfare refers to ensuring that both broilers and layers are housed in environments that support their physical and emotional health. In contemporary poultry farming, maintaining a balance between humane treatment and production efficiency has become more challenging. Several factors influence the poultry welfare, which include genetics, hatching conditions, housing systems, management practices, transportation, slaughter techniques and the attitudes and care standards of stockpersons (Nicol et al., 2013) [40] . Even though humans and chickens are very different, it is believed that hens can also experience emotions like pain or frustration. Therefore, proper ethical considerations and management strategies are essential to ensure the welfare of poultry farming in large-scale production systems.

Concept of Animal Welfare in Poultry Production

Animal welfare refers to a "state" which includes many complex aspects of the animals, such as biological, psychological and ethical components. Over time, the concept of animal welfare has evolved. It now considers not only the biological functioning, but also the experiences and behaviour of the animals. Therefore, animal welfare assessment should include the animal's physical and emotional well-being as well as how it interacts with its International Journal of Advanced Biochemistry Research 2026; 10(5): 14-21 Surroundings (Carenzi and Verga 2009) [13] . One of the most widely accepted frameworks to assess animal welfare is the concept of the Five Freedoms. These freedoms have strongly influenced international animal welfare standards. They integrate behaviour, health status, and subjective experiences into a single framework (Mellor, 2016) [35] . The Five Freedoms were first proposed in 1965 by the Brambell Committee in the United Kingdom, as a foundation for farm animal welfare regulations (Fernandes et al., 2021) [23] . The five freedoms propose the broad guidelines that should be provided to the animals to prevent suffering and other harms and promote well-being (Clark et al., 2006) [15] . This includes: 1. Freedom from hunger and thirst -Availability of fresh water and a diet to sustain optimal health and vitality 2. Freedom from discomfort -by providing a suitable surrounding that includes a comfortable place for rest and shelter. 3. Freedom from pain, injury, and diseases-by early detection, prompt diagnosis, and treatment of diseases. 4. Freedom from fear and distress -by ensuring circumstances that prevent mental suffering. 5. Freedom to exhibit their normal natural behaviour -by providing the animal sufficient space, appropriate facilities, and the companionship of its own kind.

Thus, following these freedoms help in minimising the stress, health problems, and behavioural issues. This is significant for maintaining the welfare of poultry, including laying hens in traditional production systems.

Welfare-Productivity Relationship

The relationship between production and welfare is more complex. It is commonly assumed that high production will inevitably lead to high welfare. However, this relationship is not always coherent.

In some cases, welfare and production are positively correlated. For example, in certain backyard or village settings, hens may exhibit natural behaviour. However, if they suffer from illness, parasitism, or malnourishment, their general welfare may decline. Addressing these welfare concerns will improve productivity. Similarly, acute or chronic stress will result in decreased productivity. This will lead to a drop in egg production when the hens are transferred from pens to cages. Likewise, long-term stress can weaken the immune system, increase disease incidence and death, and eventually lower productivity.

In some situations, production and welfare are negatively correlated. Intense genetic selection for production traits negatively affects flock health. For example, broiler chickens chosen for extremely rapid growth rates suffer from leg disorders and lameness. Likewise, laying hens selected for high egg production may develop more skeletal problems. Feed restriction in broiler breeder flocks is another example. Although it is used to maintain reproductive performance, it can cause chronic hunger and reduced welfare. These examples demonstrate the complexity of the relationship between productivity and welfare. In some cases, by improving welfare, we can increase productivity.

In other cases, high production can negatively affect animal welfare (Surati et al., 2022) [52] .

Welfare Challenges in Modern Broiler Production 3.1 Advances in Broiler Productivity

Due to rising per capita consumption and population growth, there has been a significant increase in the demand for poultry meat over the past few decades (Organisation for Economic Co-operation and Development, 2022) [42] . This increasing demand has led to the development of meat-type birds.

The growth of meat-type birds is mainly due to genetic and genomic selection. As a result, the growth rate, meat yield and feed efficiency all have increased significantly Carney et al., 2022) [14] . Over the years, broiler chickens have been selected extensively for rapid growth, feed efficiency, and meat production. Broilers can reach slaughter weight within a short period of time, with a very low feed conversion rate. Zuidhof et al. (2014) [58] reported that between 1957 and 2005, the growth rates in broilers increased by more than 40%, while the feed conversion ratio decreased by 50%. This implies that it takes only 38 days for broilers to reach a body weight of 2.5 kg.

Almost 85-90% of these improvements are attributed to genetic selection. However, these rapid gains have also led to several welfare concerns. Intense genetic selection is also associated with immune system impairment, metabolic disorders, and leg abnormalities, which in turn negatively affects welfare and health of the birds (EFSA, 2010) [22] . In addition, broilers are generally reared in large groups, often comprising thousands of birds in each group. Slowergrowing strains, used in organic broiler production, may be raised for 49-70 days, whereas conventional broiler chickens are slaughtered at around 30 days of age (Vissers et al., 2019) [53] . This indicates that broilers are slaughtered at a very young age, before reaching full behavioural maturity. Thus, while productivity has increased significantly, it has also led to several welfare challenges that need to be addressed.

Major Welfare Issues in Broilers 3.2.1 Leg disorders and lameness

One of the most important welfare concerns in broilers is leg disorders and lameness. These problems are mainly associated with rapid muscular growth and an underdeveloped skeletal system. Broilers are highly prone to bone, joint, and ligament disorders due to rapid muscle growth. As a result, they are often affected with leg abnormalities and lameness (Whitehead et al., 2003) [56] .

Severe leg issues restrict their movement and can cause pain (Danbury et al., 2000) [17] . Lameness in broilers is commonly assessed using the Bristol Gait Score. It is a 6-point score ranging from 0 to 5. A significant proportion of broilers suffer from lameness, especially at the end of their growing period. Granquist et al. (2019) [26] reported that 19% of birds in a flock had a gait score of three or above. The main cause of lameness is rapid growth due to genetic selection (Kestin et al., 2001) [28] . However, other factors such as infections, age, genetics, housing, environment and diet also contribute to lameness (Bradshaw et al., 2002) [9] . In severe cases, birds may be unable to move between feeders and drinkers. This leads to reduced feed intake and poor body condition (Berg and Butterworth, 2021) [8] .

Lameness not only causes pain but also decreases the ability to exhibit normal behaviours. This, in turn, increases fear due to their inability to escape from perceived threats (Granquist et al., 2019) [26] .

Stocking density

Stocking density is defined as the number of birds per unit of floor space. It shows how closely the animals are crowded together. Stocking density is expressed as the number of birds housed or as the live weight in kg per square meter of floor space at the end of the growing period. Broiler behaviour and welfare are influenced by stocking density in floor systems (Buijs et al., 2011) [12] . High stocking density is considered to be one of the major welfare concerns in poultry production. High stocking density can lead to reduced feed intake, increases in lameness, breast blisters, foot-pad dermatitis, hock burn, infections and elevated corticosterone levels. All of these are regarded as signs of diminished welfare. Also, high housing densities in poultry have been associated with higher mortality. In general, broilers or layers form in hierarchical social groupings. Dominant individuals in a dominance hierarchy have priority access to food, water, and other resources, while the subordinate birds have less access to these resources (Estevez, 2002) [59] .

In intensive systems, broiler chickens are often raised at high stocking densities to improve productivity. However, insufficient space can have detrimental effects on broiler physiology, behaviour, and health. Studies have reported broiler stocking densities ranging from 10 to 50 kg/m 2 floor space (Meluzzi et al., 2003) [36] . When stocking density exceeds 30 kg/m 2, it results in heat stress, which lowers the growth rate and overall performance of birds (McLean et al., 2001) [34] .

Metabolic disorders:

The continuous increase in broiler productivity has also resulted in metabolic disorders. Selection programs aim to increase growth rate and improve feed efficiency. However, rapid growth may create an imbalance between energy requirements for production and maintenance (Scheele, 1997) [48] . This imbalance can disrupt normal physiological regulation and lead to metabolic diseases. Rapid growth, effective feed conversion, and an extremely high metabolic rate are the main causes of metabolic disorders. It exerts more pressure on the internal organs.

Ascites and sudden death syndrome are the two most common cardiovascular illnesses observed. The hearts and lungs may not develop fully to support the rapid growth of muscle tissue (EFSA 2010) [22] . Ascites occurs when the cardiopulmonary system is unable to supply adequate oxygen to body tissues, leading to fluid accumulation in the abdomen and lungs. in some cases, right-side ventricular failure may occur. Ascites have been reported worldwide, but it is more common in birds in high altitudes (Knowles et al., 2008) [29] . These disorders not only reduce productivity but also impose serious welfare concerns on the birds.

Heat Stress

One of the major environmental stressors that causes significant economic loss in the poultry industry is heat stress. It causes physiological changes such as oxidative stress, acid-base imbalance, and immunocompetence suppression. These changes, in turn, alter the quality of meat and eggs and increase mortality. It also affects feed efficiency, body weight, feed intake, and egg production (Wasti et al., 2020) [54] .

Fig 3: Effects of heat stress on broiler performance

The ideal ambient temperature for broilers to reach the maximum growth potential during the post-brooding period is between 18 and 24 °C. However, the normal body temperature of broiler chickens is between 40.6 and 41.7 °C (Olanrewaju et al.,2010) [41] . Broiler chickens can suffer from severe heat stress when exposed to temperatures above 30 °C (Saracila et al., 2021) [46] . In general, fast-growing broilers are more susceptible to heat stress, as they produce more metabolic heat when compared to slower-growing broilers (Jong et al., 2012) [19] . Heat-stressed broilers exhibit several behavioural, physiological and immunological responses in an attempt to regulate their body temperature within 40-41 °C (Kumar et al., 2021) [31] . They exhibit behavioural changes like reduced locomotion (Branco et al., 2020) [10] , increased sitting and lying behaviour with wings spread, reduced feed intake and increased water intake (Kumar et al., 2021) [31] due to heat stress. They also tend to remain closer to drinkers and to the air inlets. Broilers become lethargic at some point, which eventually results in death when they fail to cope with the heat stress.

Light system

Light system greatly influences the welfare, behaviour, health and productivity of broilers (Alvino et al., 2009) [2] . It includes factors like light spectrum, intensity, photoperiod, provision of daylight and source of the light. Birds have four types of colour photoreceptors in the eye and are therefore tetrachromatic, whereas humans are trichromatic with three colour photoreceptors (Franco et al., 2022) [60] . Because of this, the light spectrum or colour experienced by birds differs from that of humans (Deep et al., 2012) [20] .

Photoperiod has an influence on broiler growth and welfare. Schwean-Lardner et al. (2012) [49] reported that shorter day lengths increased the feed conversion ratio, whereas body weights were higher under 17 and 20 hours of light. They also observed that reduced day length improved the welfare indicators like ocular weight, gait scores and footpad conditions (Schwean-Lardner et al., 2013) [50] . Providing several hours of darkness during the early life has also been reported to benefit broiler growth and immunity (Magee et al., 2022) [33] . Very low light intensities below 5 lux have a predominant detrimental effect on poultry welfare. It leads to reduced behavioural activity due to impaired scotopic vision. Natural light can increase activity, decrease lying behaviour and improve gait scores (Bailie et al., 2013) [5] . Light spectra such as the ultraviolet light (UV) can improve the expression of natural behaviours (Rana and Campbell, 2021) [61] .

Litter Quality

Broilers generally spend their entire life in contact with the litter; hence, the quality of litter material is of great importance for bird welfare. Litter quality influences the environmental conditions within the poultry house by affecting the dust levels, air humidity and ammonia levels, which, in turn, lead to respiratory problems. Moreover, it also has a direct influence on the skin condition of the birds. Wet litter is a major risk factor for contact dermatitis (SCAHAW, 2000) [47] .

Litter materials such as wood shaving has better litter quality because of their high water-holding capacity when compared to the litter materials with lower water-holding capacity, such as straw (SCAHAW, 2000) [47] . Litter management plays a major role in maintaining the health, welfare, productivity and sustainability of the farm (Jong et al., 2012) [19] . High litter moisture caused by faecal matter, water leakage, and humidity can increase ammonia production and bacterial growth. These conditions may lead to hock burns, footpad dermatitis and breast blisters (Jong et al., 2012) [19] .

The performance of litter depends on several factors, which include particle size, litter depth, texture and source of the material (Diarra et al., 2021) [21] . Although reuse of litter is common in commercial production, repeated use may increase the chance of footpad dermatitis and other health problems (Paz et al., 2013) [43] .

Air Quality

Another key factor that affects the broiler welfare is air quality. Ammonia is considered one of the major pollutants in poultry houses (Kristensen and Wathes, 2000) [30] . It is produced when the microorganisms convert the protein in the poultry excreta into ammonia with the help of water and moisture in the litter. High levels of ammonia may lead to respiratory diseases and keratoconjunctivitis.

Dust in broiler houses is made up of small pieces of feathers, skin scales, litter and dried manure. These particles can be classified as inspirable and respirable depending on the particle size. Poor air quality can affect both the health of poultry and the workers in poultry houses.

Birds have a unique respiratory system with air sacs that help ensure the continuous flow of air through the lungs. Consequently, they are particularly sensitive to airborne pollutants. In broiler houses, birds are commonly exposed to ammonia, carbon dioxide, and dust (Adler et al., 2021) [1] . Higher concentrations of ammonia above 30 ppm in the air can irritate mucous membranes and conjunctiva, and increase the incidence of coccidia, clostridia and other infections. Recommended levels of ammonia should remain below 20 ppm (Miles et al., 2004) [37] . Proper ventilation, good litter management, leak-free drinking systems and appropriate litter materials are important measures for maintaining good air quality in broiler houses.

Welfare Challenges in Laying Hen Productivity 4.1 Advances in Laying Hen Productivity

Over the past few decades, the laying hen productivity has improved due to genetic selection, improved feeding strategies, and better management practices and the use of advanced technologies, which has resulted in increased egg production (Arulnathan et al., 2024) [4] . These improvements have increased egg production and efficiency. Similar to broilers, genetic and genomic selection have contributed to major improvements in laying hens. These benefits include a flatter egg size curve, increased flock longevity without moulting, decreased incidence of metabolic disorders and higher peak production (Preisinger, 2018) [62] . Nowadays, laying hens are maintained up to 100 weeks of age in many countries. Each hen can produce more than 500 eggs during the production cycle (Bain et al., 2016; Preisinger, 2018) [6,62] . Modern laying hens maintain more than 90% production between 50-60 weeks of age. Peak production may reach nearly one egg per day. Induced moulting has been used to extend laying cycles. However, this practice remains controversial. (Preisinger, 2018) [62] . although it improves production and egg quality, it raises welfare concerns such as starvation, weakened immunity, and increased mortality (NFACC, 2017) [39] .

Major Welfare Issues in Laying Hens

Killing of male chicks

In commercial layer productivity, only female chicks are required. Chicks are sexed at hatch, and male chicks are culled. Nearly 50% of the chicks are eliminated as they have no economic value (Buhl, 2013) [11] . This raises serious ethical and welfare concerns. Different methods are used in different regions. The aim is to ensure rapid and humane killing (EFSA, 2005) [64] .

Common methods include carbon dioxide gas chambers, cervical dislocation, and high-speed maceration. However, these methods may cause distress before death. In order to address this issue, alternative approaches are being explored. These include in ovo sex determination, use of dual-purpose breeds, and rearing of layer cockerels (Haas et al., 2021) [18] .

Feather pecking and beak trimming:

Feather pecking is a major welfare issue in laying hens and occurs in both cage and non-cage systems. It may be gentle or severe. Severe feather pecking can lead to feather loss, skin damage, wounds, and even cannibalism.

Beak trimming is commonly used to reduce feather pecking and aggressive behaviour. However, this procedure can cause acute and chronic pain due to tissue and nerve damage. It may also impair normal behaviour by reducing the bird's ability to explore and peck (Pickett, 2008) [63] . Due to these concerns, beak trimming has been banned in some countries. The age at which trimming is performed influences pain and recovery. Early trimming causes less damage, whereas trimming at older ages may result in chronic pain due to neuroma formation (Hughes and Gentle, 1995) [27] . [44] . This behaviour may result in severe injury or death. Vent pecking can be controlled through proper management. This includes reducing light intensity in nesting areas, providing appropriate perching arrangements, and avoiding the early onset of laying. Birds are attracted to red colour; therefore, injured or prolapsed birds are more prone to pecking (Sirovnik et al., 2018) [51] .

Skeletal Health

Skeletal problems are one of the major welfare concerns in laying hens, especially in cage systems. Limited movement and high egg production contribute to bone weakness and fractures (EFSA, 2005) [64] .

Osteoporosis is a major issue characterised by loss of bone mass, leading to fragile bones that are prone to fractures, particularly in the keel, legs, and wings (Fleming et al., 2005) [24] . Bone loss begins around sexual maturity and continues throughout the laying period. Nutritional deficiencies in calcium, phosphorus, and vitamin D can further worsen this condition (Webster, 2004) [55] . Keel bone fractures are common and may occur due to collisions, poor landings, or handling during depopulation. These fractures cause chronic pain and discomfort. The prevalence of keel fractures is generally higher in cage systems compared to non-cage systems (Nicol et al., 2006) [65] . Cage layer fatigue is associated with severe bone weakness and continuous calcium depletion due to high egg production. It leads to paralysis and skeletal deformities. In some cases, recovery is possible if birds are provided with adequate nutrition and allowed movement (Kumar and Sahu, 2017) [32] .

Moulting

Moulting is a natural process in which birds shed old feathers and grow new ones, accompanied by reduced egg production (Mishra et al., 2022) [38] . In commercial systems, moulting is often induced to extend the laying cycle. In commercial systems, moulting is often induced to extend the laying cycle. This is done by restricting feed, altering light exposure, or both. This results in weight loss, regression of the reproductive system, and temporary cessation of egg production. After moulting, egg production resumes, improving overall productivity. However, induced moulting raises welfare concerns. Feed restriction causes stress, weight loss, increased aggression, and feather damage. It may also weaken immunity and increase disease susceptibility (Sandhu et al., 2007) [45] . Fasting-based moulting practices have been strongly criticised by animal welfare organisations.

Various moulting methods are used, including short-term and prolonged feed withdrawal. However, such practices may increase the risk of infections such as Salmonella enteritidis and compromise food safety (Gast et al., 2003) [25] .

Conclusion

High productivity and rapid growth are the major factors contributing to welfare issues in both broilers and laying hens. Intensive poultry production systems often lead to overcrowding, restricted behaviour, and increased health problems such as lameness, metabolic disorders, and respiratory issues. Several factors, including stocking density, litter quality, air quality, lighting, feeding, management practices, and genetic selection, influence poultry welfare. The concept of animal welfare extends beyond the Five Freedoms and includes biological, social, economic, and ethical dimensions. Improving poultry welfare requires a comprehensive approach. Providing adequate space, proper nutrition, and opportunities for natural behaviours such as perching, dust bathing, and foraging is essential. Reducing stress, improving management practices, and ensuring proper veterinary care are also important. Thus, prioritising animal welfare can lead to healthier birds, improved productivity and more sustainable and ethical poultry production systems.

References

1. Adler C, Schmithausen AJ, Trimborn M, Heitmann S, Spindler B, Tiemann I, Kemper N, Büscher W. Effects of a partially perforated flooring system on ammonia emissions in broiler housing: Conflict of objectives between animal welfare and environment. Animals. 2021. https://DOI.org/10.3390/ani11030707
2. Alvino GM, Archer GS, Mench JA. Behavioural time budgets of broiler chickens reared in varying light intensities. Appl Anim Behav Sci. 2009;118(1-2):5461. https://DOI.org/10.1016/j.applanim.2009.02.003
3. Department of Animal Husbandry and Dairying, Ministry of Fisheries, Animal Husbandry and Dairying, Government of India. Basic Animal Husbandry Statistics (BAHS). 2025.
4. Arulnathan V, Turner I, Bamber N, Ferdous J, Grassauer F, Doyon M, Pelletier N. A systematic review of potential productivity, egg quality, and animal welfare implications of extended lay cycles in commercial laying hens in Canada. Poult Sci. 2024;103(4). https://DOI.org/10.1016/j.psj.2024.103475
5. Bailie CL, Ball ME, O'Connell NE. Influence of the provision of natural light and straw bales on activity levels and leg health in commercial broiler chickens. Anim. 2013;7:618-626. https://DOI.org/10.1017/S1751731112002108
6. Bain MM, Nys Y, Dunn IC. Increasing persistency in lay and stabilising egg quality in longer laying cycles: What are the challenges? Br Poult Sci. 2016;57(3):330338. https://DOI.org/10.1080/00071668.2016.1161727
7. Ben Sassi N, Averós X, Estevez I. Technology and poultry welfare. Animals. 2016;6(10):62. https://DOI.org/10.3390/ani6100062
8. Berg C, Butterworth A. Health and disease impacts on broiler welfare. In: Butterworth A, Berg C, de Jong I, Mench J, Raj M, Manteca X, editors. Broiler Chickens Welfare in Practice. Essex: 5m Books Ltd; 2021. p. 6586.
9. Bradshaw RH, Kirkden RD, Broom DM. A review of the aetiology and pathology of leg weakness in broilers in relation to their welfare. Avian Poult Biol Rev. 2002;13(2):45-103. https://DOI.org/10.3184/147020602783698421
10. Branco T, Moura DJ, Naas IA, Oliveira SRM. Detection of broiler heat stress using the generalised sequential pattern algorithm. Biosyst Eng. 2020;199:121-126. https://DOI.org/10.1016/j.biosystemseng.2019.10.012
11. Buhl AC. Legal aspects of the prohibition on chick shredding in the German state of North RhineWestphalia. Glob J Anim Law. 2013;2:1-8.
12. Buijs S, Keeling LJ, Vangestel C, Baert J, Tuyttens FAM. Neighbourhood analysis as an indicator of spatial requirements of broiler chickens. Appl Anim Behav Sci. 2011;129:111-120.
13. Carenzi C, Verga M. Animal welfare: Review of the scientific concept and definition. Ital J Anim Sci. 2009;8(1):21-30. https://DOI.org/10.4081/ijas.2009.s1.21
14. Carney VL, Anthony NB, Robinson FE, Reimer BL, Korver DR, Zuidhof MJ, Afrouziyeh M. Evolution of maternal feed restriction practices over 60 years of selection for broiler productivity. Poult Sci. 2022;101:101957.
15. Clark JAM, Potter M, Harding E. The welfare implications of animal breeding and breeding technologies in commercial agriculture. Livest Sci. 2006;103:270-281.
16. Cunningham DL. Beak trimming effects on performance, behaviour and welfare of chickens: A review. J Appl Poult Res. 1992;1:129-134.
17. Danbury TC, Weeks CA, Chambers JP, WatermanPearson AR, Kestin SC. Self-selection of the analgesic drug carprofen by lame broiler chickens. Vet Rec. 2000;146:307-311.
18. de Haas EN, Oliemans E, van Gerwen MAAM. The need for an alternative to culling day-old male layer chicks: A survey on awareness, alternatives, and willingness to pay. Front Vet Sci. 2021;8:662197. https://DOI.org/10.3389/fvets.2021.662197
19. de Jong IC, Berg C, Butterworth A, Estevez I. Scientific report updating the EFSA opinions on the welfare of broilers and broiler breeders. EFSA Support Publ. 2012;EN-295:1-116.
20. Deep A, Schwean-Lardner K, Crowe TG, Fancher BI, Classen HL. Effect of light intensity on broiler behaviour and diurnal rhythms. Appl Anim Behav Sci. 2012;136(1):50-56. https://doi.org/10.1016/j.applanim.2011.11.002
21. Diarra S, Lameta S, Amosa F, Anand S. Alternative bedding materials for poultry: Availability, efficacy, and major constraints. Front Vet Sci. 2021;8:669504. https://DOI.org/10.3389/fvets.2021.669504
22. EFSA Panel on Animal Health and Welfare (AHAW). Scientific opinion on the influence of genetic parameters on the welfare and the resistance to stress of commercial broilers. EFSA J. 2010;8:1666. https://DOI.org/10.2903/j.efsa.2010.1666
23. Fernandes JN, Hemsworth PH, Coleman GJ, Tilbrook AJ. Costs and benefits of improving farm animal welfare. Agriculture. 2021;11(2):104. https://DOI.org/10.3390/agriculture11020104
24. Fleming RH, McCormack HA, McTeir L, Whitehead CC. Nutritional and genetic interactions in avian osteoporosis. In: Proceedings of the 15th European Symposium on Poultry Nutrition; 2005 Sep 25-29;
25. Gast RK, Ricke SC. Symposium: Current and future prospects for induced molting in laying hens Introduction. Poult Sci. 2003;82:964.
26. Granquist EG, Vasdal G, de Jong IC, Moe RO. Lameness and its relationship with health and production measures in broiler chickens. Anim. 2019;13(10):2365-2372. https://DOI.org/10.1017/S1751731119000466
27. Hughes BO, Gentle MJ. Beak trimming of poultry: Its implications for welfare. World's Poult Sci J. 1995;51:51-61.
28. Kestin SC, Gordon S, Su G, Sørensen P. Relationships in broiler chickens between lameness, liveweight, growth rate and age. Vet Rec. 2001;148(7):195-197. https://DOI.org/10.1136/vr.148.7.195
29. Knowles TG, Kestin SC, Haslam SM, Brown SN, Butterworth A, Pope SJ, Pfeiffer D, Nicol CJ. Leg disorders in broiler chickens: Prevalence, risk factors and prevention. PLoS One. 2008;3:e1545.
30. Kristensen HH, Wathes CM. Ammonia and poultry welfare: A review. World's Poult Sci J. 2000;56:235245.
31. Kumar M, Ratwan P, Dahiya SP, Nehra AK. Climate change and heat stress: Impact on production, reproduction and growth performance of poultry and its mitigation using genetic strategies. J Therm Biol. 2021;97:102867. https://DOI.org/10.1016/j.jtherbio.2021.102867
32. Kumar S, Sahu AR. Welfare issues associated with caged layer birds. In: Bhanja SK, et al., editors. Stress and Welfare: Concepts and Strategies for Addressing Current Challenges in Poultry Production. ICAR Sponsored Summer School; 2017 Sep 6-26; ICARCARI, Izatnagar.
33. Magee CL, Olanrewaju HA, Campbell J, Purswell JL. Effect of photoperiod on live performance in broiler chicks from placement to 14 days of age. J Appl Poult Res. 2022;31(4):100295. https://DOI.org/10.1016/J.JAPR.2022.100295
34. McLean JA, Savory CJ, Sparks NHC. Welfare of male and female broiler chickens in relation to stocking density. In: Proceedings of the 6th European Symposium on Poultry Welfare; 2001; Zollikofen, Switzerland. p. 234-242.
35. Mellor DJ. Updating animal welfare thinking: Moving beyond the "Five Freedoms" towards "A Life Worth Living". Animals. 2016;6(3):21.
36. Meluzzi A, Sirri F, Petracci M, Bianchi C. Improving the rearing condition of broiler chickens: Effects on performance and carcass and meat quality. In: Proceedings of the 16th European Symposium on Quality of Poultry Meat; 2003; Ploufragan, France. p. 414-420.
37. Miles DM, Branton SL, Lott BD. Atmospheric ammonia is detrimental to the performance of modern commercial broilers. Poult Sci. 2004;83:1650-1654. https://DOI.org/10.1093/ps/83.10.1650
38. Mishra R, Mishra B, Kim YS, Jha R. Practices and issues of moulting programs for laying hens: A review. Br Poult Sci. 2022;63(5):720-729. https://DOI.org/10.1080/00071668.2022.205933
39. NFACC. National Farm Animal Care Council poultry layers code of practice. Egg Farmers of Canada; 2017.
40. Nicol CJ, Davies A. Poultry welfare in developing countries. Poult Dev Rev. 2013.
41. Olanrewaju HA, Purswell JL, Collier SD, Branton SL. Effect of ambient temperature and light intensity on physiological reactions of heavy broiler chickens. Poult Sci. 2010;89(12):2668-2677. https://DOI.org/10.3382/ps.2010-00806
42. Organisation for Economic Co-operation and Development (OECD). OECD-FAO Agricultural Outlook 2022-2031. 2022.
43. Paz ICLA, Garcia RG, Bernardi R, Seno LO, Nääs IA, Caldara FR. Locomotor problems in broilers reared on new and re-used litter. Ital J Anim Sci. 2013;12(2):e45. https://DOI.org/10.4081/ijas.2013.e45
44. Rodenburg TB, Koene P. Feather pecking and feather loss. In: Perry GC, editor. Welfare of the Laying Hen. Wallingford, UK: CABI Publishing; 2004.
45. Sandhu MA, Rahman ZU, Rahman SU, Hassan IJ. Dynamics of innate immune response in Gallus domesticus using two methods of induced molting. Vet Immunol Immunopathol. 2007;120:106-114.
46. Saracila M, Panaite TD, Papuc CP, Criste RD. Heat stress in broiler chickens and the effect of dietary polyphenols, with special reference to willow (Salix spp.) bark supplements: A review. Antioxidants. 2021;10(5):686. https://DOI.org/10.3390/antiox10050686
47. SCAHAW. The welfare of chickens kept for meat production (broilers). Report of the Scientific Committee on Animal Health and Animal Welfare. European Commission, Brussels; 2000.
48. Scheele CW. Pathological changes in metabolism of poultry related to increasing production levels. Vet Q. 1997;19:127-130.
49. Schwean-Lardner K, Fancher BI, Classen HL. Impact of daylength on the productivity of two commercial broiler strains. Br Poult Sci. 2012;53(1):7-18. https://DOI.org/10.1080/00071668.2012.659652
50. Schwean-Lardner K, Fancher BI, Gomis S, van Kessel A, Dalal S, Classen HL. Effect of day length on cause of mortality, leg health, and ocular health in broilers. Poult Sci. 2013;92(1):1-11. https://DOI.org/10.3382/ps.2011-01967
51. Sirovnik J, et al. Feeding from perches in an aviary system reduces aggression and mortality in laying hens. Appl Anim Behav Sci. 2018.
52. Surati U, Paul D, Diwakar V, Das S, Koul Y. Welfare concerns of poultry farming. Poult Planner. 2022.
53. Vissers LSM, de Jong IC, van Horne PLM, Saatkamp HW. Global prospects of the cost-efficiency of broiler welfare in middle-segment production systems. Animals. 2019;9:473. https://DOI.org/10.3390/ani9070473
54. Wasti S, Sah N, Mishra B. Impact of heat stress on poultry health and performances, and potential mitigation strategies. Animals. 2020;10:1266. https://DOI.org/10.3390/ani10081266
55. Webster AB. Welfare implications of avian osteoporosis. Poult Sci. 2004;83:184-192.
56. Whitehead CC, Fleming RH, Julian RJ, Sorenson P. Skeletal problems associated with selection for increased production. In: Muir WM, Aggrey SE, editors. Poultry Genetics, Breeding and Biotechnology. Wallingford, UK: CABI Publishing; 2003. p. 29-52.
57. Ricky S. Identifying Key Drivers of Insurtech Adoption Intentions in Indonesia: An Extended UTAUT Approach. Journal of Logistics, Informatics and Service Science. 2024.
58. Zuidhof MJ, Schneider BL, Carney VL, Korver DR, Robinson FE. Growth, efficiency, and yield of commercial broilers from 1957, 1978, and 2005. Poultry science. 2014 Dec 1;93(12):2970-82.
59. Estevez I, Newberry RC, Keeling LJ. Dynamics of aggression in the domestic fowl. Applied Animal Behaviour Science. 2002 Apr 2;76(4):307-25.
60. Franco D, Calabrese G, Guglielmino SP, Conoci S. Metal-based nanoparticles: antibacterial mechanisms and biomedical application. Microorganisms. 2022 Sep 3;10(9):1778.
61. Rana MS, Campbell DL. Application of ultraviolet light for poultry production: a review of impacts on behavior, physiology, and production. Frontiers in Animal Science. 2021 Sep 8;2:699262.
62. Preisinger R. Innovative layer genetics to handle global challenges in egg production. British Poultry Science. 2018 Jan 2;59(1):1-6.
63. Pickett CA, Jackson JL, Hemann BA, Atwood JE. Carotid bruits as a prognostic indicator of cardiovascular death and myocardial infarction: a metaanalysis. The Lancet. 2008 May 10;371(9624):1587-94.
64. European Food Safety Authority (EFSA). Opinion of the Scientific Committee on a request from EFSA related to a harmonised approach for risk assessment of substances which are both genotoxic and carcinogenic. EFSA Journal. 2005 Oct;3(10):282.
65. Nicol C, Avela J, Komi PV. The stretch-shortening cycle: a model to study naturally occurring neuromuscular fatigue. Sports medicine. 2006 Nov;36(11):977-99.