Methods to address poultry robustness and welfare issues through breeding and associated ethical considerations

Overview of Avian Sex Reversal

Sex determination and differentiation are processes by which a bipotential gonad adopts either a testicular or ovarian cell fate, and secondary sexual characteristics adopt either male or female developmental patterns. In birds, although genetic factors control the sex determination program, sex differentiation is sensitive to hormones, which can induce sex reversal when disturbed. Although these sex-reversed birds can form phenotypes opposite to their genotypes, none can experience complete sex reversal or produce offspring under natural conditions. Promising evidence indicates that the incomplete sex reversal is associated with cell autonomous sex identity (CASI) of avian cells, which is controlled by genetic factors. However, studies cannot clearly describe the regulatory mechanism of avian CASI and sex development at present, and these factors require further exploration. In spite of this, the abundant findings of avian sex research have provided theoretical bases for the progress of gender control technologies, which are being improved through interdisciplinary co-operation and will ultimately be employed in poultry production. In this review, we provide an overview of avian sex determination and differentiation and comprehensively summarize the research progress on sex reversal in birds, especially chickens. Importantly, we describe key issues faced by applying gender control systems in poultry production and chronologically summarize the development of avian sex control methods. In conclusion, this review provides unique perspectives for avian sex studies and helps scientists develop more advanced systems for sex regulation in birds.

Adaptability Challenges for Organic Broiler Chickens: A Commentary

Simple Summary

Organic poultry shows an increasing productive trend, rising from 3% in 2017 to 8% in 2019. Regulation EU 848/2018 puts great emphasis on the ability of broilers to adapt to outdoor systems as being essential for organic production. Organic poultry operators meet with regulatory constraints, consumer concerns, and challenges in terms of nutrition, welfare, health, and sustainability. The present commentary considers recent studies on and innovations in these topics that can affect organic production in addition to recent studies on animal adaptability to this production system. It reflects on the concept of broiler adaptability to organic systems not only as a classic genotype–environment interaction but as a necessary prerequisite for facing these relevant challenges.

Abstract

As organic and conventional poultry production increased in the last decade, so did consumers’ concerns, sustainability requirements, and animal welfare as well as health issues. According to Reg. EU 848/2008 on organic production, poultry must be adapted to organic outdoor systems and cope with all the regulatory constraints in terms of nutrition, health, and welfare. Adaptability must take into account the above challenges, constraints, and concerns. Chicken adaptability should not only mean being able to use pasture and outdoor areas, but also mean being able to overcome, or be resilient to, the challenges of organic farming without compromising welfare, performance, and product quality. This commentary identifies solutions to the new challenges that organic poultry chains must face in future productive scenarios, detects consumer viewpoints to provide a perspective on organic poultry production, and summarizes as well as defines chicken adaptability to organic production, assessing the main factors of chicken adaptability.

Bird Welfare in Zoos and Aquariums: General Insights across Industries

Animal welfare is a priority across accredited zoological institutions; however, historically, research has been prioritized for mammals. Bird-focused studies accounted for less than 10% of welfare research in zoos and aquariums over the last ten years. Due to the lack of scientific publications on bird welfare, zoo scientists and animal practitioners can look to other industries such as agriculture, laboratories, and companion animal research for insight. This qualitative review highlights findings across industries to inform animal care staff and scientists on the welfare needs of birds within zoos and aquariums. Specifically, the review includes an overview of research on different topics and a summary of key findings across nine resources that affect bird welfare. We also highlight areas where additional research is necessary. Future welfare research in zoos and aquariums should prioritize studies that consider a diversity of bird species across topics and work to identify animal-based measures with empirical evidence. Moving forward, research from other industries can help develop innovative research on bird welfare within zoos and aquariums.

Effects of Stocking Density in Group Cages on Egg Production, Profitability, and Aggressive Pecking of Hens

There is an increasing concern about welfare issues related to battery cages, which are commonly used in Vietnam, and requires a modified cage that improves hen welfare while retaining its economic and management advantages. We combined adjacent conventional cages to form group cages to examine the effects of stocking density on egg production, economic returns, and aggressive pecking of hens. The control group included triplicate conventional cages with four birds/single cage (12 hens per three cages) or 450 cm² area per hen. Three group cage treatments were set up with 10, 12, and 14 birds per group cage or 540, 450, and 386 cm² of floor area per hen, respectively. Compared to 14 birds per cage, hens housed at 10 birds per group cage had a higher hen-day production, consumed less feed, and thus had a better feed conversion ratio/dozen eggs. Reducing the stocking density to 10 birds per group cage resulted in additional production cost, but it was compensated for by a high egg income, and significantly decreased aggressive pecks. Group cages benefit hen performance, profitability, and welfare when decreasing the stocking density to 10 birds per cage with 540 cm²/hen.

Determining the variation in premaxillary and dentary bone morphology that may underlie beak shape between two pure layer lines

Beak treatment is an effective method of reducing the damage inflicted by severe feather pecking (SFP) but there is significant pressure to eliminate these treatments and rely solely on alternative strategies. Substantial variation in beak shape exists within non-beak treated layer flocks and beak shape appears to be heritable. There is the potential to use this pre-existing variation and genetically select for hens whose beak shapes are less apt to cause damage during SFP. To do this, we must first understand the range of phenotypes that exist for both the external beak shape and the bones that provide its structure. The objective of this study was to determine the variation in premaxillary (within the top beak) and dentary (within the bottom beak) bone morphology that exists in 2 non-beak treated pure White Leghorn layer lines using geometric morphometrics to analyze radiographs. Lateral head radiographs were taken of 825 hens and the premaxillary and dentary bones were landmarked. Landmark coordinates were standardized by Procrustes superimposition and the covariation was analyzed by principal components analysis and multivariate regression using Geomorph (an R package). Three principal components (PCs) explained 85% of total premaxillary bone shape variation and showed that the shape ranged from long and narrow with pointed bone tips to short and wide with more curved tips. Two PCs explained 81% of total dentary bone shape variation. PC1 described the dentary bone length and width and PC2 explained the angle between the bone tip and its articular process. For both bones, shape was significantly associated with bone size and differed significantly between the two lines. Bone size accounted for 42% of the total shape variation for both bones. Together, the results showed a range of phenotypic variation in premaxillary and dentary bone shape, which in turn may influence beak shape. These bone phenotypes will guide further quantitative genetic and behavioral analyses that will help identify which beaks shapes cause the least damage when birds engage in SFP.

The Effect of the Type of Non-Caged Housing System, Genotype and Age on the Behaviour of Laying Hens

This study investigated the welfare of laying hens in different non-caged housing systems, namely a deep-litter barn system (BS), a free-range system (FRS) and an organic system (OS). The study was conducted on 270 hens of a native breed Green-legged Partridge (Z-11) and 270 Hy-Line Brown hybrids. Visual scans were performed to record behaviour of hens. Hens were housed in groups of 30 and observed over the course of one day at 20, 36 and 56 weeks of age. Dustbathing, scratching, wing stretching, wing flapping and preening were recorded as comfort behaviours. Pecking, fighting, threatening and chasing were recorded as agonistic behaviours. The percentage of run use was higher in native hens than in commercial hens (p < 0.05). The proportion of hens exhibiting comfort behaviours housed in the FRS and OS was similar but over twice as high as in the BS (p < 0.05). In the FRS and OS, the percentage of hens displaying comfort behaviours increased with age (p < 0.05). In all the production systems, the percentage of birds displaying comfort behaviours was higher in native breed hens than in commercial breeds (p < 0.05). In the BS, the higher proportion of hens displaying an agonistic behaviour was seen more in commercial breed than in the native breed hens (p < 0.05). The percentage of birds displaying an agonistic behaviour declined with hen age, both in commercial and native breed hens.

Research of selected physical indicators of table eggs in the small-scale breedings from the aspect of health safety

The purpose of this study was to investigate selected indicators of the table eggs in small-scale breedings, focusing mainly on the eggshell and its contamination and damage. Our object of study was eggs, shell, damage, and contamination of table eggs. Four small-scale breedings were randomly selected in Slovakia. These breeds were alternatively with an outdoor free-range. Laying hens Dominant was bred under conditions small-scale breeds No.1, No. 2 and No. 3 in the 1st laying cycle, and No. 4 in the 2nd laying cycle. Egg weight was balanced in three small-scale breedings. Egg weight was significantly higher in the fourth small-scale breeding, statistically significant (p <0.05) compared to egg weight in the studied 3 small-scale breedings. Shell weight and shell thickness in the equatorial plane of the egg were balanced in three small-scale breedings and in the fourth small-scale breedings were significantly higher, statistically significant (p <0.05). The higher egg weight per breeding is related to the higher laying hens age that was in the 2nd laying cycle compared to laying hens 3 small-scale breedings in the 1st laying cycle. Higher eggshell weight in three farms may be related to improved conditions in breeding hygiene, as confirmed by the results of investigations into contamination and damage to table eggs. These differences may also be related to nutrition.

Large-Scale Phenotyping of Livestock Welfare in Commercial Production Systems: A New Frontier in Animal Breeding

Genomic breeding programs have been paramount in improving the rates of genetic progress of productive efficiency traits in livestock. Such improvement has been accompanied by the intensification of production systems, use of a wider range of precision technologies in routine management practices, and high-throughput phenotyping. Simultaneously, a greater public awareness of animal welfare has influenced livestock producers to place more emphasis on welfare relative to production traits. Therefore, management practices and breeding technologies in livestock have been developed in recent years to enhance animal welfare. In particular, genomic selection can be used to improve livestock social behavior, resilience to disease and other stress factors, and ease habituation to production system changes. The main requirements for including novel behavioral and welfare traits in genomic breeding schemes are: (1) to identify traits that represent the biological mechanisms of the industry breeding goals; (2) the availability of individual phenotypic records measured on a large number of animals (ideally with genomic information); (3) the derived traits are heritable, biologically meaningful, repeatable, and (ideally) not highly correlated with other traits already included in the selection indexes; and (4) genomic information is available for a large number of individuals (or genetically close individuals) with phenotypic records. In this review, we (1) describe a potential route for development of novel welfare indicator traits (using ideal phenotypes) for both genetic and genomic selection schemes; (2) summarize key indicator variables of livestock behavior and welfare, including a detailed assessment of thermal stress in livestock; (3) describe the primary statistical and bioinformatic methods available for large-scale data analyses of animal welfare; and (4) identify major advancements, challenges, and opportunities to generate high-throughput and large-scale datasets to enable genetic and genomic selection for improved welfare in livestock. A wide variety of novel welfare indicator traits can be derived from information captured by modern technology such as sensors, automatic feeding systems, milking robots, activity monitors, video cameras, and indirect biomarkers at the cellular and physiological levels. The development of novel traits coupled with genomic selection schemes for improved welfare in livestock can be feasible and optimized based on recently developed (or developing) technologies. Efficient implementation of genetic and genomic selection for improved animal welfare also requires the integration of a multitude of scientific fields such as cell and molecular biology, neuroscience, immunology, stress physiology, computer science, engineering, quantitative genomics, and bioinformatics.

Mobile Poultry Processing Unit as a Resource for Small Poultry Farms: Planning and Economic Efficiency, Animal Welfare, Meat Quality and Sanitary Implications

Simple Summary

Poultry meat production is now based on fast-growing strains, with consequences for animal health and welfare. There is also an increasing demand for products from extensive rearing systems; there are, however, several criticisms including the difficulty of slaughtering chickens from a logistic, legislative and economic point of view. A possible solution could be represented by the use a Mobile Poultry Processing Unit (MPPU), which directly reaches the poultry farms. The aim of this review is to analyse the requisites and economic efficiency of a MPPU prototype in Italy; further, the related animal welfare aspects and the qualitative and sanitary implications are discussed.

Abstract

Nowadays there is an increasing demand for poultry products from alternative rearing systems. These systems, commonly named pastured poultry production (PPP), are more expensive than intensive rearing system but sustain biodiversity, local economies and farm multi-functionality besides providing meat to which consumers attribute high ethical value and quality. PPP generally uses large outdoor runs, small number of animals and requires chickens adapted to natural environment. One of the most relevant obstacles to further development of PPP systems is related to the slaughtering of animals economically and at the same time complying with the sanitary regulations to maintain food safety standards. A possible solution could be represented by a Mobile Poultry Processing Unit (MPPU), which directly reaches the poultry farms. MPPU can consider a good compromise for the niche production providing an opportunity to small farmers to exploit the full potential of their production system. The aim of this review is to analyse the essential requisites and MPPU economic viability in an Italian system. Qualitative, societal aspects are discussed together with bird welfare and hygiene implications. The case study indicates the viability of MPPUs but notes that up scaling to medium sized operations would not be permissible under current EU regulations.

Rapid whole blood assay using flow cytometry for measuring phagocytic activity of chicken leukocytes

Phagocytic activity of leukocytes in whole blood was assessed as a potential immune competence trait in chickens. A flow cytometry based whole blood phagocytosis (WBP) assay was set up and evaluated using blood from chickens homozygous for four different MHC haplotypes, B12, B15, B19 and B21. Fluorescent latex beads and two serotypes of fluorescently labelled heat-killed bacteria (Salmonella Infantis and Salmonella. Typhimurium) were evaluated as phagocytic targets. In addition, the opsonophagocytic potential (OPp) of individual sera from the birds was included in a phagocytosis assay using the HD11 chicken macrophage cell line. Results showed that both serotypes of bacteria but not the latex beads were effectively phagocytosed by leukocytes in the whole blood cultures. Differences were observed in the phagocytic capacity of monocytes and thrombocyte/lymphocytes, respectively between the different MHC lines. No significant differences on the OPp of serum was identified between MHC lines. In addition, for both phagocytic activity of leukocytes and OPp of serum large variations between individuals were observed within MHC haplotypes. No significant relationships were observed between the phagocytic activity of leukocytes and serum OPp or Salmonella-specific IgY levels. In conclusion, our results suggest that the WBP assay, using a no-lyse no-wash single staining method, is a rapid and convenient method to assess phagocytic functions of different leukocyte populations.

In vitro phagocytosis of opsonized latex beads by HD11 cells as a method to assess the general opsonization potential of chicken serum

Opsonins, an important arm of the innate immune system, are various soluble proteins, which play a critical role in destruction of invading pathogens directly or via engulfment of pathogens through the intermediate of phagocytosis. The diversity of opsonin profiles is under genetic influence and may be associated with variation in disease resistance. The aim of this study was to set up an assay to determine serum opsonophagocytic potential (OPp) for chicken sera by flow cytometry and to evaluate the assay using samples from different chicken lines. Two chicken lines selected for high and low concentrations of mannose-binding lectin, a known opsonin, in serum were used to establish the method. Furthermore, the presumed "robust" Hellevad chickens and two other commercial chicken lines (Hisex and Bovans) were tested to evaluate OPp as a parameter reflecting general immune competence. The results showed that Hellevad and Bovans chickens had higher OPp than Hisex chickens. There were no correlations between concentrations of total IgY or mannose-binding lectin and OPp. However, a strong positive correlation was observed between vaccine-induced infectious bronchitis virus titres and OPp. Moreover, inverse relationships were observed between concentrations of total serum IgM as well as natural antibody levels, and OPp. In conclusion, in vitro opsonophagocytosis assessment and determination of OPp may be of relevance when addressing general innate immunocompetence. RESEARCH HIGHLIGHTS A flow cytometry method was developed to assess poultry serum opsonophagocytosis potential. This method is based on serum-opsonin-coated polystyrene beads and HD11 cell phagocytosis. Serum samples from different commercial chicken lines were compared. Opsonophagocytic potential may be included in assay panels for general immune competence of poultry.

Novel Graphical Analyses of Runs of Homozygosity among Species and Livestock Breeds

Runs of homozygosity (ROH), uninterrupted stretches of homozygous genotypes resulting from parents transmitting identical haplotypes to their offspring, have emerged as informative genome-wide estimates of autozygosity (inbreeding). We used genomic profiles based on 698 K single nucleotide polymorphisms (SNPs) from nine breeds of domestic cattle (Bos taurus) and the European bison (Bison bonasus) to investigate how ROH distributions can be compared within and among species. We focused on two length classes: 0.5-15 Mb to investigate ancient events and >15 Mb to address recent events (approximately three generations). For each length class, we chose a few chromosomes with a high number of ROH, calculated the percentage of times a SNP appeared in a ROH, and plotted the results. We selected areas with distinct patterns including regions where (1) all groups revealed an increase or decrease of ROH, (2) bison differed from cattle, (3) one cattle breed or groups of breeds differed (e.g., dairy versus meat cattle). Examination of these regions in the cattle genome showed genes potentially important for natural and human-induced selection, concerning, for example, meat and milk quality, metabolism, growth, and immune function. The comparative methodology presented here permits visual identification of regions of interest for selection, breeding programs, and conservation.

Opinion of Belgian Egg Farmers on Hen Welfare and Its Relationship with Housing Type

Simple Summary

Until 2012, laying hens in the EU were often housed in conventional cages that offered limited space and few opportunities to perform highly motivated behaviors. Conventional cages are now banned in the EU in order to improve animal welfare. In this study, egg farmers were surveyed (winter 2013–2014) to assess whether they perceived any changes in animal welfare since changing housing systems, what role hen welfare played in choosing a new housing system, and which aspects of hen welfare they find most important. The data show that the answers differ depending on which housing system the farmers currently use and whether they had used conventional cages in the past.

Abstract

As of 2012, the EU has banned the use of conventional cages (CC) for laying hens, causing a shift in housing systems. This study’s aim was to gain insight into farmers’ opinions on hen health and welfare in their current housing systems. A survey was sent to 218 Belgian egg farmers, of which 127 (58.3%) responded, with 84 still active as egg farmer. Hen welfare tended to be less important in choosing the housing system for farmers with cage than with non-cage systems. Respondents currently using cage systems were more satisfied with hen health than respondents with non-cage systems. Reported mortality increased with farm size and was higher in furnished cages than in floor housing. Feather pecking, cannibalism, smothering and mortality were perceived to be higher in current housing systems than in CC, but only by respondents who shifted to non-cage systems from previously having had CC. Health- and production-related parameters were scored to be more important for hen welfare as compared to behavior-related parameters. Those without CC in the past rated factors relating to natural behavior to be more important for welfare than those with CC. This difference in opinion based on farmer backgrounds should be taken into account in future research.

Review of rearing-related factors affecting the welfare of laying hens

Laying hens may face a number of welfare problems including: acute and chronic pain caused by beak trimming; exaggerated fearfulness that may cause stress and suffocation; difficulties in locating resources, resulting potentially in emaciation and dehydration; frustration and boredom, caused by an environment that is barren; feather pecking; cannibalism; foot lesions; and bone fractures. In Europe, a greater proportion of laying hens are housed in non-cage systems compared to the rest of the world. The extent of the different welfare problems may therefore vary between countries as the type of housing system influences the risk of suffering. More generally, many of these welfare problems are influenced by the rearing environment of the pullets. This article therefore focuses on welfare problems in laying hens that can be traced back to rearing. Factors that have been studied in relation to their effects on bird welfare include beak trimming, housing type, furnishing, enrichment, feeding, stocking density, flock size, sound and light levels, concentration of gasses, age at transfer from rearing to production facilities, similarity between rearing and production facilities, competence of staff, and interactions between bird strain and environment. The present review aims to summarize rearing-related risk factors of poor welfare in adult laying hens housed according to European Union legislation. It aims to identify gaps in current knowledge, and suggests strategies for improving bird welfare by improving rearing conditions. Two main conclusions of this work are that attempts should be made to use appropriate genetic material and that beak trimming should be limited where possible. In addition to this, the rearing system should provide constant access to appropriate substrates, perches, and mashed feed, and should be as similar as possible to the housing system used for the adult birds. Finally, young birds (pullets) should be moved to the production facilities before 16 weeks of age. The measures outlined in this review may be useful for improving the welfare of pullets and adult laying hens.

The prospects of selection for social genetic effects to improve welfare and productivity in livestock

Social interactions between individuals living in a group can have both positive and negative effects on welfare, productivity, and health of these individuals. Negative effects of social interactions in livestock are easier to observe than positive effects. For example, laying hens may develop feather pecking, which can cause mortality due to cannibalism, and pigs may develop tail biting or excessive aggression. Several studies have shown that social interactions affect the genetic variation in a trait. Genetic improvement of socially-affected traits, however, has proven to be difficult until relatively recently. The use of classical selection methods, like individual selection, may result in selection responses opposite to expected, because these methods neglect the effect of an individual on its group mates (social genetic effects). It has become clear that improvement of socially-affected traits requires selection methods that take into account not only the direct effect of an individual on its own phenotype but also the social genetic effects, also known as indirect genetic effects, of an individual on the phenotypes of its group mates. Here, we review the theoretical and empirical work on social genetic effects, with a focus on livestock. First, we present the theory of social genetic effects. Subsequently, we evaluate the evidence for social genetic effects in livestock and other species, by reviewing estimates of genetic parameters for direct and social genetic effects. Then we describe the results of different selection experiments. Finally, we discuss issues concerning the implementation of social genetic effects in livestock breeding programs. This review demonstrates that selection for socially-affected traits, using methods that target both the direct and social genetic effects, is a promising, but sometimes difficult to use in practice, tool to simultaneously improve production and welfare in livestock.