Centennial Review: History and husbandry recommendations for raising Pekin ducks in research or commercial production

Halloysite supplemented in the diet, and sex of Cherry Valley ducks affects growth, carcass composition, meat quality, and jejunum and leg bone strength

BACKGROUND

Natural minerals can be innovative feed additives in the waterfowl nutrition, affecting the production efficiency and the meat quality. The study assessed production results, carcass characteristics, meat quality, and strength of the jejunum and leg bones of male and female Cherry Valley ducks fed with 1% halloysite. The ducks were kept in control groups (males and females) and fed a commercial diet. In the experimental groups (males and females), 1% halloysite was added to the diet throughout the rearing period. 50 ducks in 5 repetitions were in each group. During 42 days of rearing, the ducks' body weight, growth, feed intake, and conversion ratio were controlled and calculated. After rearing, 10 carcasses per group were selected and dissected. The physicochemical characteristics of the leg and pectoral muscles and the strength of the jejunum and leg bones were analyzed.

RESULTS

The application of halloysite reduced the body weight of birds (P = 0.049) and body weight gain (P = 0.048) on day 42 and throughout the rearing period and increased the liver weight of ducks (P = 0.020). Female carcasses were characterized by a higher weight of pectoral muscle (P = 0.005), muscle total (P = 0.015), and abdominal fat (P = 0.007), and males by a higher weight of carcass remains (P = 0.013). In the pectoral muscles of ducks where the mineral was added, significantly lower protein content and higher collagen (P < 0.001), intramuscular fat (P < 0.001), and water (P = 0.014) content were found. The leg muscles of the birds from the control groups were characterized by significantly higher redness (P = 0.003) and yellowness (P = 0.031), and males had a higher content of intramuscular fat compared to females (P < 0.001). Halloysite increased the jejunum tensile strength (P = 0.023).

CONCLUSIONS

Halloysite adversely impacted ducks' body weight and weight gain while altering meat quality by increasing pectoral muscle pH (pectoralis major) and fat content (pectoralis major and pectoralis minor) and changing leg muscles' color. Jejunum tensile strength was higher post-halloysite supplementation. These results suggest halloysite has both positive and negative effects on duck growth, meat properties, and jejunum strength, warranting further research.

Microbiome-metabolomics analysis insight into the effects of dietary chromium picolinate on abdominal fat deposition and lipid metabolism of ducks

This research endeavored to explore the impact of Cr-Pic on the abdominal fat deposition and lipid metabolism of ducks, as well as to uncover the mechanisms at play and identify the optimal dietary supplementation level of Cr-Pic. The results showed that adding 0.6 mg/kg Cr-Pic observably increased the body weight and serum levels of adiponectin and leptin, and decreased serum levels of total cholesterol, triglyceride, and low-density lipoprotein cholesterol in ducks at 14 days (P < 0.05). The addition of 0.6 % Cr-Pic was discovered to regulate lipid metabolism and meat quality through its effects on reducing abdominal fat and drip loss, downregulating the mRNA expression of genes involved in lipid synthesis in the abdominal fat and liver, and upregulating the mRNA expression of genes associated with degradation and transport in these tissues (P < 0.05). Untargeted metabolic profiling indicated that the distinct metabolites between the Cr-Pic and Control groups were predominantly associated with pathways involving amino acids. Microbiome analysis showed that Cr-Pic administration altered the microbial genera related to the adjustment of lipid metabolism in the cecum of ducks, such as increasing the proportion of Bacteroides and Lactobacillus, and decreasing the proportions of Alistipes, Methanobrevibacter, Romboutsia, and Peptostreptococcus (P < 0.05). In summary, Cr-Pic shows promise in reducing the abdominal fat accumulation in ducks by regulating the intestinal microbial composition and the metabolic pathways of amino acids that are linked to lipid metabolism.

Comparison of Nonlinear Models for Describing the Growth Curve of Pekin Ducks

BACKGROUND

Ducks are used to produce a significant amount of meat in some regions of the world. The enhancement of duck production systems necessitates the development of parameterized mathematical models that accurately depict duck growth, encompassing the assessment of various management and nutritional strategies.

OBJECTIVE

This research aimed to elucidate the growth trajectory of Danish and French Pekin ducks by applying nonlinear modelling techniques.

METHODS

A total of 10 nonlinear mathematical functions (Brody, negative exponential, logistic, Gompertz, Von Bertalanffy, Richards, Schumacher, Morgan, Lomolino and Weibull) were employed in this study. The performance of the models was systematically evaluated, and the behaviour of the models was scrutinized throughout the process of fitting nonlinear regression curves. The overall goodness-of-fit for each model to a variety of data profiles was determined through the application of the adjusted coefficient of determination, root mean square error, Akaike's information criterion and Bayesian information criterion.

RESULTS

The adjusted coefficient of determination values associated with each model exhibit generally elevated levels, signifying that the models demonstrate a strong overall compatibility with the data. According to the established goodness-of-fit criteria, the Gompertz model emerged as the most suitable mathematical function for accurately representing the growth trajectory of Danish and French Pekin ducks. In contrast, the Brody model exhibited the least favourable fit to the growth patterns of Danish and French Pekin ducks. Analysing the first derivative of the Gompertz model, the absolute growth rates for Danish and French Pekin ducks as a function of time indicated a progressive increase in these rates with advancing age, peaking at 23 and 24 days of age, respectively, before subsequently declining.

CONCLUSION

An analysis of the various growth models employed in this research revealed that nonlinear functions have the ability to fit Pekin duck body weight records.

Pulsed alternating wavelength system lighting does not negatively impact production or welfare but reduces dopamine activity and may improve bone growth in grow-out Pekin ducks: Effects of PAWS lighting on meat ducks

The production and welfare of Pekin ducks can be affected by the lighting type they are housed under. There is no standard lighting system in industry and little data evaluating effects of different light systems on duck production and welfare. Pulsed Alternating Wavelength System (PAWS) is a novel LED technology that delivers multiple wavelengths of light in pulsating patterns. This study aimed to determine the effects of PAWS on brain serotonin turnover and skeletal quality in ducks. Ducks housed under PAWS were hypothesized to have lower brain serotonin turnover and equal bone quality compared to those housed under control lights (fluorescent with digital ballasts, 4500K, ∼40 lux). Ducks were placed in floor pens under PAWS or control lighting (1200 ducks/pen, n = 4 pens/treatment) at day of hatch until processing at 30 days of age (DOA). Body weights and feed intake were monitored weekly. Brains, femurs, tibiae, and humeri were collected on days 7, 14, 21 and 29 (n = 6 ducks/age/lighting type). Brain serotonin and metabolites were measured. Bone length, width, breaking strength, and ash were determined. Serotonin data were analyzed using 2-way ANOVA for age and lighting treatment with a post-hoc Fisher's LSD test. Bone data were analyzed with independent t-tests between treatments within each age. Ducks housed under PAWS were heavier by 29 DOA than controls (P < 0.001) with no differences in feed conversion. Brain analyses revealed no differences in serotonin turnover between lighting types. Early interstitial growth of PAWS femur and tibia was increased (P < 0.05), and PAWS femurs had increased bone mineral content at 29 DOA (P = 0.001). At 29 DOA, the PAWS humeri were wider than controls (P = 0.025) and had increased geometrical bone mechanical properties (P < 0.003), but no differences in breaking stress were evident. Results suggest that PAWS may have benefits for production traits and skeletal quality, however, a complete understanding of the welfare effects need further study.

Characteristics of breeding and performance parameters of the different local types of moscovy duck (cairina moschata) reared in south Benin, West Africa

Muscovy duck breeding is a critical component of food security and livelihoods in southern Benin, yet knowledge of breeding practices remains limited. This study characterizes Muscovy duck breeding systems across three agroecological zones using a participatory survey of 420 breeders. The survey revealed a male dominance (77.78%) among breeders, with the Fon ethnic group constituting the majority (85.86%). A consistent male bias was observed across zones in ducks exceeding 6 weeks of age. Free-grazing emerged as the dominant breeding system in Zone 5 (100%), while Zone 6 displayed a more diverse approach (free-grazing: 60%, semi-grazing: 30%, confinement: 10%). Zone 8 primarily utilized semi-grazing (56.25%), followed by free-grazing (31.25%) and confinement (12.5%). Housing also varied across zones, with simple shelters dominating in Zones 5 (100%) and 8 (97.92%), while Zone 6 relied more on duck houses (52.5%). Egg laying performance increased significantly with each breeding cycle, with the third cycle yielding the highest number of eggs (15.37). Hatchability exhibited a different pattern, peaking during the second cycle (95.42%) and showing statistically significant variations across cycles (P < 0.05). Plumage color did not influence reproductive performance. Most surveyed farmers across all three zones relied on traditional natural incubation methods, with 85% allowing ducks to incubate their eggs and only 5% using artificial incubation with locally fabricated incubators. Interestingly, plumage color was associated with duckling survival, with black ducklings exhibiting the lowest mortality risk (P < 0.05). Diseases were reported as the leading cause of mortality.

Differences in central dopamine, but not serotonin, activity and welfare associated with age but not with preening cup use in commercial grow-out Pekin duck barns

Preening cups are a semi-open water source for Pekin duck enrichment. To evaluate the ducks' affective state, we combined measuring welfare by walking a transect in the barn with mass spectrometry and qRT-PCR to measure brain neurotransmitter levels and gene expression for serotonin (5-HT) and dopamine (DA) synthesis and metabolism. 5-HT and DA have been established as indicators of mental state and emotions. We visited 4 standard commercial barns that housed approximately 6000-9000 ducks (one preening cup per 1500 ducks) and collected samples on d21 prior to preening cup placement, d28 one week after preening cup placement, and d35 one day prior to processing. Litter samples (n = 3/barn/day) were collected and transect walks were conducted to evaluate the welfare of the birds. Brain samples (n = 8/day/barn) were collected from two locations: ducks actively using the preening cups (PC) and ducks across the barn not actively using the preening cups (CON). The brains were hemisected and dissected in three brain areas: caudal mesencephalon (CM), rostral mesencephalon (RM), and diencephalon (DI). Litter samples showed no significant differences between collection dates. The transect showed significant differences in feather quality, feather cleanliness, and eye due to age, but not preening cups. The right hemisphere showed no differences in 5-HT turnover. For DA turnover, there are differences in CM (p < 0.05) and DI (p < 0.001) over time, but no differences between PC and CON. The left hemisphere measured TPH1, TPH2, and TH. CM and DI brain areas are not significantly different. Within the RM, there is a significant increase in TPH1 expression for ducks on d35 when compared to ducks on d28 and d21. These results suggest that 5-HT and DA do not differ due to duck location. However, DA activity increases as these ducks age. DA is an important neurotransmitter and activity increases as an animal grows allowing for behavioral development. Our data shows that commercial preening cups do not negatively impact ducks' welfare or affective state.

Transportation increases circulating corticosterone levels and decreases central serotonergic activity in a sex dependent manner in Pekin ducks

Previous studies from our lab suggest that transportation of early adulthood ducks can have long lasting physiological effects. To better understand how transportation affects the ducks' physiology, we evaluated several central and peripheral parameters. Thirty-six, 23-week-old ducks were collected at a commercial breeder facility and randomly assigned to one of three treatment groups (n = 6/sex/treatment): 1) caught and euthanized (control), 2) caught and put in a crated in the pen for 90 min (crate), or 3) caught, crated, and transported in a truck for 90 min (transport) to simulate actual transportation. Blood was collected for serum corticosterone and blood smear analyses. Brains were hemisected and each half was dissected into three brain areas: caudal mesencephalon (CM), rostral mesencephalon (RM), and diencephalon (DI). Mass spectrometry was run on the right half of the brain, and gene expression of TPH1, TPH2, TH, CRH, and NPY were measured on the left half of brain using qRT-PCR. Serum corticosterone levels were increased (p = 0.01) in crated hens and in transported hens and drakes (p = 0.0084) when compared to control. HLR was increased (p = 0.035) in crated hens and transported hens and drakes compared to control. No differences in serotonin turnover were observed in drakes but increased in hens within the CM and RM from control to crate (p = 0.01) and crate to transport (p = 0.016). There were no differences in DA turnover or in gene expression for all brain areas for drakes and CM and RM for hens. Within the DI, hens showed a decrease (p = 0.03) in TPH1 for transport compared to crate. Overall, transportation elicits an acutely stressful event that increases corticosterone and HLR in a sex dependent manner where hens appear to be more reactive to the stressor than drakes. Our data supports that when assessing a stress response, care must be given to the sex of the bird and to the relative timepoint of sampling compared to the perceived onset of the stressor.

Photostimulation decreases fearfulness, but improves growth performance and egg quality of breeder Pekin ducks

Lighting is a critical environmental factor that influences production performance and welfare of poultry, however Pekin ducks can typically be housed under 24 h (24 h) of light. 460 hatchlings were randomly allocated to 4 rooms with two pens in each room. The rooms were allocated to 24 h light or PS. PS was achieved by gradually increasing photoperiod by half an hour per week from days 112 to 238 and held at 18 h light for the rest of life. Prior to the onset of lay, pens were organized with 30 hens and 7 drakes/pen (4 pens/treatment). We measured bodyweight at weeks 0, 1, 2, 5, 10, 19, and 29, feed intake at weeks 1 to 7 and feed conversion ratio (FCR) was calculated for weeks 1, 2, and 5. Eggs laid were recorded daily from weeks 20 to 31. Novel object test (NOT) was done at weeks 1, 5, 10, 19, and 29, transect welfare scoring at week 30, egg quality assessment at weeks 28 and 29, and fertility was determined at weeks 28 and 29. Statistical analyses were done using 2-way ANOVA, T-test, or Friedman Test with a Tukey-Kramer test as post-hoc. A p ≤ 0.05 was considered significant. Drakes bodyweight was higher in the PS compared to 24h treatment at weeks 5 (p < 0.01) and 10 (p < 0.001). No difference was observed in FCR, fertility, or transect data. NOT showed lower fear response (p < 0.05) at weeks 5 and 10 in the PS compared to 24 h treatment. The 24 h treatment increased the percent eggs laid at weeks 23 (p < 0.05), 24 (p < 0.01) and 25 (p < 0.05) compared to the PS. However, there was a higher egg weight (p < 0.001), yolk weight (p < 0.05), Haugh unit (p < 0.05), and shell weight (p = 0.05) in the PS compared to 24 h treatment. Our findings support that PS may help decrease fearfulness, improve growth performance and egg quality of breeder ducks.

Effects of dietary paddy rice on the growth, serum biochemistry, intestinal development, microbiota, and metabolism of young laying ducks in a rice-duck-crayfish farming system

This study investigated the effects of feeding paddy rice on the physiology, metabolism, and gut microbiota of ducks in a rice-duck-crayfish (RDC) system. A total of 540 ducks (20-days-old) were randomly divided into 3 groups with 3 replicates and 60 ducks per replicate. The 40-d experiment involved 3 diet treatments: a complete diet (CD), 50% paddy rice + 50% complete diet (RCD), and 100% paddy rice diet (RD). Results show that feeding paddy rice did not significantly affect duck growth, the final weight in the RD group was reduced by 5%, and the feed-to-gain ratio increased by 7% compared to the CD group. Additionally, compared with the CD group, the keel length, gizzard and proventriculus indices, and serum high-density lipoprotein levels increased (P < 0.05), and duodenal villus height and ileal crypt depth (P < 0.05) reduced in the RD group and ileal villus height decreased in the RCD group (P < 0.05). Compared with the CD group, the cecal abundance of Bacteroidota, Prevotellaceae_Ga6A1_group, and Prevotellaceae_NK3B31_group decreased in the RD group (P < 0.05) while the abundance of Firmicutes, Megamonas and Faecalibacterium increased (P < 0.05). Metabolome analysis revealed that serum citric acid increased (P < 0.05) in the RCD and RD groups, whereas cytidine, cytosine, and 4-aminobutyric acid decreased (P < 0.05) in the RD group. In conclusion, these preliminary results suggest that paddy rice supplementation under an RDC system had no significant effect on duck growth, but it did cause changes in intestinal morphology, microbiota, and serum metabolic profiles. However, it is important to note that the limited overall number of replicates in this study contributed to a certain degree of high variance. While the growth differences among groups were not statistically significant, the full replacement of paddy rice still poses potential performance losses. In practical applications, this finding provides a reference for the RDC system, but further validation through larger-scale trials is required.

A meta-analysis of genetic estimates for economically important traits in ducks

This study aimed to gather published genetic parameter estimates for economically important traits in ducks through a meta-analysis utilizing the random-effects model. The present study used a dataset on genetic parameters of various duck traits, including 275 genetic correlation estimates and 233 heritability estimates from 31 studies published between 1988 and 2024. The heritability estimates for growth traits were generally low to high and varied from 0.154 (for body weight gain) to 0.405 (for body weight at first egg), respectively. Results showed that heritability estimates for egg production and quality traits were generally low to moderate, ranging from 0.119 (for egg shell strength) to 0.340 (for egg weight). The heritability estimates for feeding traits were generally moderate to high and varied from 0.266 (for residual feed intake) to 0.624 (for meal feed intake), respectively. The results indicate that there was a high genetic correlation (0.827, P < 0.05) between feed intake and residual feed intake, but low to moderate genetic correlations (P < 0.05) were found between feed intake and feed conversion ratio (0.318). The results of the current meta-analysis supported the hypothesis that these duck traits exhibit additive genetic variation. Genetic selection schemes for ducks may thus potentially take advantage of the available additive genetic variation in these traits. Furthermore, in cases where accurate estimates for economically significant traits in duck populations across the globe are unavailable, the average genetic parameter estimates presented in this meta-analysis can be used in breeding plans.

CVAE-DF: A hybrid deep learning framework for fertilization status detection of pre-incubation duck eggs based on VIS/NIR spectroscopy

Unfertilized duck eggs not removed prior to incubation will deteriorate quickly, posing a risk of contaminating the normally fertilized duck eggs. Thus, detecting the fertilization status of breeding duck eggs as early as possible is a meaningful and challenging task. Most existing work usually focus on the characteristics of chicken eggs during mid-term hatching. However, little attention has been paid to the detection for duck eggs prior to incubation. In this paper, we present a novel hybrid deep learning detection framework for the fertilization status of pre-incubation duck eggs, termed CVAE-DF, based on visible/near-infrared (VIS/NIR) transmittance spectroscopy. The framework comprises the encoder of a convolutional variational autoencoder (CVAE) and an improved deep forest (DF) model. More specifically, we first collected transmittance spectral data (400-1000 nm) of 255 duck eggs before hatching. The multiplicative scatter correction (MSC) method was then used to eliminate noise and extraneous information of the raw spectral data. Two efficient data augmentation methods were adopted to provide sufficient data. After that, CVAE was applied to extract representative features and reduce the feature dimension for the detection task. Finally, an improved DF model was employed to build the classification model on the enhanced feature set. The CVAE-DF model achieved an overall accuracy of 95.94 % on the test dataset. These experimental results in terms of four metrics demonstrate that our CVAE-DF method outperforms the traditional methods by a significant margin. Furthermore, the results also indicate that CVAE holds great promise as a novel feature extraction method for the VIS/NIR spectral analysis of other agricultural products. It is extremely beneficial to practical engineering.

New evidence for gut-muscle axis: Lactic acid bacteria-induced gut microbiota regulates duck meat flavor

The interaction between gut microbiota and muscles through the gut-muscle axis has received increasing attention. This study attempted to address existing research gaps by investigating the effects of gut microbiota on meat flavor. Specifically, lactic acid bacteria were administered to ducks, and the results of e-nose and e-tongue showed significantly enhanced meat flavor in the treatment group. Further analyses using GC-MS revealed an increase in 6 characteristic volatile flavor compounds, including pentanal, hexanal, heptanal, 1-octen-3-ol, 2,3-octanedione, and 2-pentylfuran. Linoleic acid was identified as the key fatty acid that influences meat flavor. Metagenomic and transcriptomic results further confirmed that cecal microbiota affects the duck meat flavor by regulating the metabolic pathways of fatty acids and amino acids, especially ACACB was related to fatty acid biosynthesis and ACAT2, ALDH1A1 with fatty acid degradation. This study sheds light on a novel approach to improving the flavor of animal-derived food.

Ferroptosis: First evidence in premature duck ovary induced by polyvinyl chloride microplastics

Ferroptosis is frequently observed in fibrosis and diseases related to iron metabolism disorders in various mammalian organs. However, research regarding the damage mechanism of ferroptosis in the female reproductive system of avian species remains unclear. In this study, Muscovy female ducks were divided into three groups which were given purified water, 1 mg/L polyvinyl chloride microplastics (PVC-MPs) and 10 mg/L PVC-MPs for two months respectively, to investigate the ferroptosis induced by PVC-MPs caused ovarian tissue fibrosis that lead to premature ovarian failure. The results showed that the high accumulation of PVC-MPs in ovarian tissue affected the morphology and functional activity of ovarian granulosa cells (GCs) and subsequently caused the follicular development disorders and down-regulated the immunosignaling of ovarian steroidogenesis proteins 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD), CYP11A1 cytochrome (P450-11A1) and CYP17A1 cytochrome (P450-17A1) suggested impaired ovarian function. In addition, PVC-MPs significantly up-regulated positive expression of collagen fibers, significantly increased lipid peroxidation and malondialdehyde (MDA) level, along with encouraged overload of iron contents in the ovarian tissue were the characteristics of ferroptosis. Further, immunohistochemistry results confirmed that immunosignaling of ferroptosis related proteins Acyl-CoA synthetase (ACSL4), Cyclooxygenase 2 (COX2) and ferritin heavy chain 1 (FTH1) were significantly increased, but solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase (GPX4) were decreased by PVC-MPs in the ovarian tissue. In conclusion, our study demonstrates that PVC-MPs induced ferroptosis in the ovarian GCs, leading to follicle development disorders and ovarian tissue fibrosis, and ultimately contributing to various female reproductive disorders through regulating the proteins expression of ferroptosis.

Classification of Behaviour in Conventional and Slow-Growing Strains of Broiler Chickens Using Tri-Axial Accelerometers

Behavioural states such as walking, sitting and standing are important in indicating welfare, including lameness in broiler chickens. However, manual behavioural observations of individuals are often limited by time constraints and small sample sizes. Three-dimensional accelerometers have the potential to collect information on animal behaviour. We applied a random forest algorithm to process accelerometer data from broiler chickens. Data from three broiler strains at a range of ages (from 25 to 49 days old) were used to train and test the algorithm, and unlike other studies, the algorithm was further tested on an unseen broiler strain. When tested on unseen birds from the three training broiler strains, the random forest model classified behaviours with very good accuracy (92%) and specificity (94%) and good sensitivity (88%) and precision (88%). With the new, unseen strain, the model classified behaviours with very good accuracy (94%), sensitivity (91%), specificity (96%) and precision (91%). We therefore successfully used a random forest model to automatically detect three broiler behaviours across four different strains and different ages using accelerometers. These findings demonstrated that accelerometers can be used to automatically record behaviours to supplement biomechanical and behavioural research and support in the reduction principle of the 3Rs.

Vocalizations of the Pekin duck (Anas platyrhynchos domesticus): how stimuli, sex, and social groups affect their vocal repertoire

Pekin ducks are exposed to stressors such as heat stress, enteric pathogens, mycotoxins, and other environmental stressors. We know from wild bird literature that birds communicate through vocalizations. We hypothesized that Pekin ducks would have a diverse repertoire that is affected by the sex, social group, and specific stimuli. We utilized adult Pekin ducks to develop a vocal repertoire. We placed 1 to 4 ducks of varying sexes into a sound chamber with various stimuli used to encourage new vocalizations. Birds were recorded for 20 min with several variations of number and sexes of ducks. Once the ducks were recorded each vocalization that was clipped was named based on a predetermined naming system. We characterized the vocal system of the ducks under each stimulus and social treatment in 4 ways: overall call rates, call diversity, call repertoire, and call spectral properties. In all cases, normality of residuals and homogeneity of variances for GLM and ANOVA models were confirmed using Proc Univariate (SAS v9.4) where a p ≤ 0.05 was considered significant. We found that Pekin ducks produce up to 16 different vocalizations. The treatments had a significant effect on the overall rate of calls given by the ducks (ANOVA: F6,31 = 8.55, p < 0.0001). Ducks produced the most calls by far when someone was sitting in the chamber with them (30.04 ± 4.45 calls/min). For call diversity, we found that there was a significant main effect of hen number (F218 = 12.21, p = 0.0004) but no main effect of drake number (F3,18 = 3.04, p = 0.0555). Cluster analyses indicated that certain types of calls were given under specific conditions. There were generally 6 major clusters of vocal repertoires (R-square = 0.899, Cubic Clustering Criterion = 9.30). Our results suggest that Pekin ducks are affected by the types of stimuli and social environment in how much they vocalize and in the properties of the calls they use. In addition, males and females differ somewhat in the repertoire of the calls they use, and in the spectral properties of their calls.

Insect live larvae as a new nutritional model in duck: effects on gut health

BACKGROUND

This study aimed to evaluate the effects of Hermetia illucens (Black soldier fly-BSF) and Tenebrio molitor (Yellow mealworm-YMW) live larvae as a new nutritional model on duck's gut health, considering gut histomorphometry, mucin composition, cytokines transcription levels, and microbiota. A total of 126, 3-days-old, females Muscovy ducks were randomly allotted to three dietary treatments (6 replicates/treatment, 7 birds/pen): (i) C: basal diet; (ii) BSF: C + BSF live larvae; (iii) YMW: C + YMW live larvae. BSF and YMW live larvae were administered on top of the basal diet, based on the 5% of the expected daily feed intake. The live weight, average daily gain, average daily feed intake and feed conversion ratio were evaluated for the whole experimental period. On day 52, 12 ducks/treatment (2 birds/replicate) were slaughtered and samples of duodenum, jejunum, ileum, spleen, liver, thymus and bursa of Fabricius were collected for histomorphometry. Mucin composition was evaluated in the small intestine through histochemical staining while jejunal MUC-2 and cytokines transcription levels were evaluated by rt-qPCR. Cecal microbiota was also analyzed by means of 16 S rRNA gene sequencing.

RESULTS

Birds' growth performance and histomorphometry were not influenced by diet, with a proximo-distal decreasing gradient from duodenum to ileum (p < 0.001), respecting the physiological gut development. Mucin staining intensity and MUC-2 gene expression did not vary among dietary treatments, even though mucin intensity increased from duodenum to ileum, according to normal gut mucus physiology (p < 0.001). Regarding local immune response, IL-6 was higher in YMW group when compared to the other groups (p = 0.009). Insect live larvae did not affect cecal microbiota diversity, but BSF and YMW groups showed a higher presence of Helicobacter, Elusimicrobium, and Succinatimonas and a lower abundance of Coriobacteriaceae and Phascolarctobacterium compared to C birds (p < 0.05).

CONCLUSIONS

The use of BSF and YMW live larvae as new nutritional model did not impair gut development and mucin composition of Muscovy ducks, but slightly improved the intestinal immune status and the microbiota composition by enhancing regulatory cytokine IL-6 and by increasing minor Operational Taxonomic Units (OTUs) involved in short-chain fatty acids production.

Nutritional Considerations for Juvenile Exotic Companion Animals

Pediatric exotic companion animal nutrition is a broad topic, spanning small mammals, reptiles, and birds. Little research has been performed focusing on the juvenile life stages of these species because they are largely acquired by clients at the young adult stage. The information that does exist has been compiled by wildlife rehabilitators, commercial breeders, and/or exotic captive breeding programs, such as those that exist in zoologic facilities. In this article, we discuss natural history, feeding strategies, energy requirements, digestive physiology and diet digestibility, and key nutrients of concern as factors for determining an appropriate diet for pediatric exotic species.

Preening cups in duck housing are associated with an increase in central dopamine activity that suggests a negative affective state

Preening cups are a form of environmental enrichment that provides Pekin ducks a semi-open water source to express their natural behaviors. We recently observed that preening cups may increase feather pecking behaviors in ducks. Thus, we set out to determine if this form of enrichment can impact the affective state of Pekin ducks. To accomplish this goal, we evaluated the effect of preening cups on serotonin (5-HT) and dopamine (DA) turnover via mass spectrometry and their respective synthetic enzyme gene expression via qRT-PCR. Our study investigated the link between aggressive pecking with levels and activity of brain 5-HT and DA. Brain 5-HT and DA levels and activity have been established for decades to be associated with affective states. Grow-out Pekin ducks (n = 260) were housed at Purdue and raised per industry standards. On day 18, brains were collected from ducks in pens before preening cups were placed (PRE, n = 6) and, again on day 43, in pens with (PC, n = 6) and without (CON, n = 6) preening cups. Brains were dissected into right and left halves, then further microdissected into 4 brain areas: caudal mesencephalon (CM), rostral mesencephalon (RM), diencephalon (DI), and forebrain (FB). The right hemisphere was used for mass spectrometry to determine the neurotransmitter concentration (ng/mg of tissue) and those concentrations were applied to neurotransmitter turnover equations. There were no differences across treatments for 5-HT turnover in any brain area. There were differences in DA turnover across age (P = 0.0067) in the CM and across treatments (P = 0.003) in the RM. The left hemisphere of the brain was used to perform qRT-PCR on the genes of 5-HT and DA production enzymes. Within the CM, day 43 duck brains had increased (P = 0.022) tryptophan hydroxylase and tyrosine hydroxylase relative mRNA levels. All other brain areas showed no differences. Our data suggest that ducks housed with preening cups and that showed increased feather pecking are associated with increased brain DA activity. The increased DA in the brain may lead to a predisposition for increased aggression in the form of feather pecking.

Preening cups increase apparent wet preening behaviors, but have no impact on other behaviors, body condition, growth, or body morphometrics of grow-out Pekin ducks

Preening cups may be a form of open water that would allow ducks to express preening behaviors. We set out to test the hypothesis that preening cups would not have detrimental effects on ducks or their environment. Control pens (N = 6, 65 ducks/pen) had nipple lines while experimental pens (N = 6, 65 ducks/pen) had the same nipple line plus one preening cup (PC). Body weights of 30 ducks per pen, and body condition scores on 50 ducks per pen were recorded weekly. On d 18 and 43, 5 ducks per pen were euthanized and their spleens, Bursas, liver, and uropygial glands were weighed. Behavior data were collected using scan sampling with video being recorded for 72 continuous hours at 4 different ages: 25 d, 30 d, 36 d, and 40 d. Body morphometrics were analyzed by 2-way ANOVA with repeated measures. Body condition scoring was analyzed by Pearson's chi-square. The GLIMMIX procedure (SAS 9.4) was used for behavioral analyses to examine treatment differences in the proportion of ducks performing dry preening, wet preening, eating, drinking, standing, and laying down. Feather pecking, feather picking, preening conspecifics (also known as allopreening), dunking head, and drinking from preening cup were analyzed using PROC LOGISTIC with the Firth bias correction for quasi-complete separation and odds ratios were calculated. More PC ducks housed with PC performed wet preening compared to control ducks (25 d: F1,26 = 6.90, P = 0.0143; 30, 36, and 40 d; F1,78 = 24.53, P < 0.0001). Ducks in the PC group were also more likely to lay down compared to controls (25 d: F1,33 = 4.95, P = 0.0330). No differences were observed for any other behavior, body condition score, body weight or morphometrics at any age. Although ducks in the preening cup group showed an increase in wet preening, our data suggest that open water is not necessary to maintain feather condition or uropygial gland size.

Metabolomic characterization of Liancheng white and Cherry Valley duck breast meat and their relation to meat quality

Liancheng white duck is a typical local duck breed in Fujian Province famous for its meat traits. To better understand how meat quality varies with breed, the chemical composition of breast meats of Liancheng white ducks (LD) and Cherry Valley ducks (CD) were examined using ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS).The correlation between meat quality and the differential metabolites was further analyzed. The results showed that the effects of breed on duck breast meat were significant for pH, color, cooking loss, and shear force. Liancheng white duck breast meat exhibited a higher shear force and pH, and lower cooking loss and lightness (L*24), redness (a*24), and yellowness (b*24) than CD. Metabolomic analysis revealed significant differences between the meat extracts from the 2 duck breeds. A total of 49 and 57 significantly different metabolites were identified in positive and negative ion modes, respectively. These differentially accumulated metabolites (DAMs) could be divided into 28 classes, of which the 4 main categories were carbohydrates, amino acids, fatty acids, and eicosanoids. Liancheng white duck might have better nutritional and medicinal value considering the higher content of (4Z,7Z,10Z,13Z,16Z,19Z)-4,7,10,13,16,19-docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), eicosapentaenoic acid (EPA), and prostaglandinF3α (PGF3α), having anti-inflammatory orantioxidant effects. Carbohydrate concentration negatively correlated with pH24. The 4 metabolites positively correlated with the shear force. These results provide an overall perspective for bridging the gap between variation of duck meat quality and metabolites with respect to breed.

Experimental pathogenesis of aquatic bird bornavirus 1 in Pekin ducks

Aquatic bird bornavirus 1 (ABBV-1) is a neurotropic virus that causes persistent infection in the nervous system of wild waterfowl. This study evaluated whether Pekin ducks, the most common waterfowl raised worldwide, are susceptible to ABBV-1 infection and associated disease. Groups of Pekin ducks were inoculated with ABBV-1 through the intracranial (IC; n, 32), intramuscular (IM; n, 30), and choanal (CH; n, 30) routes. Controls (CO; n, 29) received carrier only. At 1, 12, and 21 weeks postinfection (wpi), 7-14 birds were euthanized to assess virus distribution and lesions. Infection rates in the IC and IM groups were over 70%, while only 4 ducks in the CH group became infected. Neurological signs were observed in 8 ducks only, while over 25% of IC and IM birds had encephalitis and/or myelitis. Seroconversion was highest in the IC and IM groups, and mucosal ABBV-1 RNA shedding was most frequent in the IC group (53%). None of the fertile eggs laid during the experiment tested positive for ABBV-1 RNA. This study shows that Pekin ducks are permissive to ABBV-1 infection and partly susceptible to associated disease. While mucosal shedding may be an important route of transmission, congenital infection appears unlikely.

Chronic Heat Stress Part 2: Increased Stress and Fear Responses in F1 Pekin Ducks Raised from Parents That Experienced Heat Stress

The effects of HS on the welfare of poultry have been reported to have a transgenerational effect on phenotype plasticity. The goal of our experiment was to determine whether parental exposure to HS would impair the performance, HPA axis response, or behavior of their offspring. We treated adult drakes and hens (n = 80 ducks/treatment) at peak lay with HS or the control temperature for 3 weeks and incubated eggs collected from the last 3 days of the experiment. We utilized 76 ducklings/parental treatment group: control (CON-F1) and HS (HS-F1). Weekly data for body weights, body condition scores (BCSs), and novel object test (NOT) were collected. At 3 weeks of age, the ducks (n = 6/treatment) were subjected to adrenocorticotropic hormone (ACTH/cosyntropin, 0.0625 mg/kg) challenge or vehicle as the control. Blood samples were collected at 0, 1, 2, 3, and 4 h relative to treatment for serum glucocorticoid and heterophil-to-lymphocyte ratio (HLR) analyses. All injected birds were euthanized with pentobarbital on the second day relative to ACTH administration, and the spleen and bursa were removed and weighed immediately. Duck level analyses were completed using one- or two-way ANOVA as appropriate. BCSs were analyzed using a chi-squared test. The HS-F1 ducks had a lower hatch weight (p < 0.05) compared with the CON-F1 ducks but no significant difference in growth rates during the 5-week period. NOT (n = 4) analyses showed that the HS-F1 ducks had a greater fear response (p < 0.001) compared with the CON-F1 ducks. Similarly, an ACTH stimulation test showed that the HS-F1 ducks had significantly (p < 0.05) heightened corticosterone and HLR responses compared with the CON-F1 ducks. The HS-F1 ducks showed altered baseline and ACTH-stimulated levels of cortisol compared with the controls. Our data suggest that parental exposure to HS impacts the HPA response and fearfulness of the F1 generation in Pekin ducks.

Strategies to improve genomic predictions for 35 duck carcass traits in an F2 population

BACKGROUND

Carcass traits are crucial for broiler ducks, but carcass traits can only be measured postmortem. Genomic selection (GS) is an effective approach in animal breeding to improve selection and reduce costs. However, the performance of genomic prediction in duck carcass traits remains largely unknown.

RESULTS

In this study, we estimated the genetic parameters, performed GS using different models and marker densities, and compared the estimation performance between GS and conventional BLUP on 35 carcass traits in an F₂ population of ducks. Most of the cut weight traits and intestine length traits were estimated to be high and moderate heritabilities, respectively, while the heritabilities of percentage slaughter traits were dynamic. The reliability of genome prediction using GBLUP increased by an average of 0.06 compared to the conventional BLUP method. The Permutation studies revealed that 50K markers had achieved ideal prediction reliability, while 3K markers still achieved 90.7% predictive capability would further reduce the cost for duck carcass traits. The genomic relationship matrix normalized by our true variance method instead of the widely used [Formula: see text] could achieve an increase in prediction reliability in most traits. We detected most of the bayesian models had a better performance, especially for BayesN. Compared to GBLUP, BayesN can further improve the predictive reliability with an average of 0.06 for duck carcass traits.

CONCLUSION

This study demonstrates genomic selection for duck carcass traits is promising. The genomic prediction can be further improved by modifying the genomic relationship matrix using our proposed true variance method and several Bayesian models. Permutation study provides a theoretical basis for the fact that low-density arrays can be used to reduce genotype costs in duck genome selection.

Welfare of ducks, geese and quail on farm

This Scientific Opinion concerns the welfare of Domestic ducks (Anas platyrhynchos domesticus), Muscovy ducks (Cairina moschata domesticus) and their hybrids (Mule ducks), Domestic geese (Anser anser f. domesticus) and Japanese quail (Coturnix japonica) in relation to the rearing of breeders, birds for meat, Muscovy and Mule ducks and Domestic geese for foie gras and layer Japanese quail for egg production. The most common husbandry systems (HSs) in the European Union are described for each animal species and category. The following welfare consequences are described and assessed for each species: restriction of movement, injuries (bone lesions including fractures and dislocations, soft tissue lesions and integument damage and locomotory disorders including lameness), group stress, inability to perform comfort behaviour, inability to perform exploratory or foraging behaviour and inability to express maternal behaviour (related to prelaying and nesting behaviours). Animal-based measures relevant for the assessment of these welfare consequences were identified and described. The relevant hazards leading to the welfare consequences in the different HSs were identified. Specific factors such as space allowance (including minimum enclosure area and height) per bird, group size, floor quality, characteristics of nesting facilities and enrichment provided (including access to water to fulfil biological needs) were assessed in relation to the welfare consequences and, recommendations on how to prevent the welfare consequences were provided in a quantitative or qualitative way.

Catecholamine concentrations in duck eggs are impacted by hen exposure to heat stress

Rapid "fight-or-flight" responses to stress are largely orchestrated by the catecholamines. Moreover, catecholamines and catecholamine precursors are widely recognized to act as interkingdom signaling molecules among host and microbiota, as well as to serve as chemotactic signals for bacterial foodborne pathogens. While albumen and yolk concentrations of glucocorticoids have received extensive attention as non-invasive indicators of hen response to stress, little is known regarding the impact of the hen's stress response on in ovo catecholamine and catecholamine precursor concentrations. The aim of the present study was to determine norepinephrine and L-dopa concentrations in albumen and yolk of eggs laid by hens maintained under normal or heat stress conditions. Norepinephrine and L-dopa concentrations were also measured in oviductal tissue. Breeder ducks (∼35 weeks/age) were kept under normal (22°C) conditions or subjected to cyclical heat stress (35°C day/29.5°C night) for 3 weeks. Eggs (n = 12 per timepoint/group) were collected on a weekly basis. Hens were sacrificed at baseline or after 3 weeks of heat stress for oviductal tissue collection. Albumen, yolk, and oviduct concentrations of norepinephrine and L-dopa were determined using ultra high-performance liquid chromatography with electrochemical detection. Norepinephrine and L-dopa were detected in oviductal tissue as well as egg albumen and yolk. Norepinephrine concentrations were elevated (p < 0.05) in the yolk of eggs laid by the heat stress group compared to those of the control group. Norepinephrine concentrations in albumen were elevated (p < 0.05) in the heat stress group compared to control group at week 2. L-dopa concentrations were not significantly affected (p > 0.05) by heat stress in albumen, yolk, or oviductal tissue. Together, the present study provides the first evidence of the stress neurohormone, norepinephrine, in duck eggs and identifies that hen exposure to heat stress can affect in ovo norepinephrine concentrations. These data highlight the potential utility of in ovo catecholamine concentrations as non-invasive measures of the hen's response to stress, as well as warrants future research into whether hen deposition of stress-related neurochemicals into the egg could serve as a chemotactic signal in the vertical transmission of foodborne pathogens.

Effects of Swimming Pool Conditions and Floor Types on White Roman Geese's Physical Condition Scores and Behaviors in an Indoor Rearing System

Biosecurity problems, including the continual risk of avian influenza spread by wild birds, have severely affected traditional free-range waterfowl production systems. Regulations and techniques for indoor goose production require more considerations for animal welfare. This study investigated the effects of swimming pool conditions and different floor types on the physical condition scores and behaviors of indoor-reared White Roman geese. A total of 48 male and 48 female White Roman geese reared from the age of 15 to 84 days were randomly allocated to pens with or without a swimming pool and with either mud or perforated plastic floors. Providing a swimming pool improved geese's eye and feather cleanliness and breast blister scores at the age of 84 days. Compared with geese reared on a mud floor, those reared on a perforated plastic floor had better feather cleanliness and higher breast blister scores at the age of 56 and 84 days. Providing a swimming pool to indoor-reared geese may reduce the proportion of abnormal behaviors, such as injurious feather pecking, by increasing water-related behaviors. This study suggests a more appropriate environment design for better balancing commercial goose production with animal welfare in an indoor rearing system.

Chronic heat stress part 1: Decrease in egg quality, increase in cortisol levels in egg albumen, and reduction in fertility of breeder pekin ducks

Global warming poses detrimental effects on poultry production leading to substantial economic losses. The goal of our experiment was to test the hypothesis that heat stress (HS) would alter welfare and egg quality (EQ) of breeder ducks. Furthermore, we wanted to test if HS would increase cortisol levels in egg albumen. Adult Pekin ducks were randomly assigned to two different rooms at 85% lay with 60 hens and 20 drakes per room. Baseline data including body weight, body condition scores (BCS), and egg production/quality were collected the week preceding heat treatment. Ducks were subjected to cyclic HS of 35°C for 10h/day and 29.5°C for the remaining 14h/day for 3 weeks while the control room was maintained at 22°C. Eggs were collected daily and analyzed weekly for quality assessment, and for albumen glucocorticoid (GCs) levels using mass spectrometry. One week before the exposure to HS, 10 hens and 5 drakes were euthanized and the same number again after 3 weeks and birds necropsied. Data analyses were done by 1- or 2-way ANOVA as appropriate with a Tukey-Kramer post hoc test. BCS were analyzed using a chi-squared test. A p ≤ 0.05 was considered significant. Circulating levels of corticosterone were significantly (p < 0.01) elevated at week 1 only in the HS hens. The circulating levels of cortisol increased significantly at week 1 and 2 (p < 0.05), and week 3 (p < 0.01) in the hens and at weeks 2 and 3 only (p < 0.05) in the drakes. Feather quality scores (p < 0.01), feather cleanliness scores (p < 0.001) and footpad quality scores (p < 0.05) increased significantly in the HS group. HS elicited a significant (p < 0.001) decrease in egg production at weeks 1 and 3. Hens in the HS group showed significantly decreased BW (p < 0.001) and number of follicles (p < 0.05). Shell weight decreased significantly at week 1 only (p < 0.05) compared to controls. Yolk weight decreased significantly at week 3 (p < 0.01) compared to controls. HS elicited a significant increase in albumen cortisol levels at week 1 (p < 0.05) and week 3 (p < 0.05). Thus, cortisol may provide critical information to further understand and to improve welfare.

Poultry nutrition

Nutrition is the most important environmental factor affecting development, health status, growth performance and profitability of poultry production. Feeds for poultry constitute up to 70–75% of total production costs. Poultry nutrition differs considerably from that of other livestock, which is determined by the specific anatomy of the gastrointestinal tract. Protein, energy, fat, fiber, minerals, vitamins, and water are of basic importance for poultry nutrition and their content in feeds must cover the requirement that differ depending on the bird’s age and species. In general, feed protein must be of good value including the content of essential amino acids. Among them lysine, methionine, cysteine, threonine and tryptophan are the limiting ones. The main ingredient of poultry feeds are cereal grains, i.e. wheat and maize, which predominantly constitute an energy source because their protein content is insufficient for birds. Because of that cereals cannot be the only feed for poultry and must be combined with protein sources such as soybean or rapeseed meal, legume seeds or protein concentrates. Despite birds’ requirement for nutrients and chemical composition of feeds are well known, nutrition must face many problems. One of the most important issues is to find alternatives to antibiotic growth promoters.

The Impacts of Female Access during Rearing on the Reproductive Behavior and Physiology of Pekin Drakes, and Flock Fertility

Simple Summary

Male and female ducklings are typically reared in same-sex groups. With the goal of improving the males’ reproductive performance, and overall flock fertility, some flock owners place several female ducklings into the otherwise all-male pens during rearing. However, the relationships between rearing, drake reproductive success, and flock fertility have not been confirmed. To fill these knowledge gaps, we compared the frequencies of correctly oriented mounts and circulating testosterone levels of drakes reared with and without physical access to females, and the impacts of these rearing treatments on flock fertility. Rearing treatment did not impact any of the measured variables; however, all were affected by age. Individual variation in behavior and testosterone measures were noted in both treatment groups. We conclude that rearing male ducklings with auditory and visual, but without physical access to female ducklings is sufficient for promoting reproductive behavior and physiology, and securing high fertility within this Pekin duck breed.

Abstract

Commercially housed Pekin ducks (Anas platyrhynchos) are typically reared in same sex groups to facilitate separate diet provisioning. Several female ducklings are sometimes mixed into the otherwise all-male pens. This practice is thought to increase flock reproductive success. To evaluate this hypothesis, we reared ducklings in alternating same-sex groups (150 hens or 30 drakes/pen; 8 groups/sex) and evaluated the impacts of rearing on drake mounting behavior, testosterone levels, and flock fertility. At 12 days, three females were placed into four of the male duckling pens. At 20–22 weeks of age, adjacent male and female pens were moved into pens within a breeder barn, and combined to form mixed-sex pens. The number of correctly aligned mounts performed by 10 focal drakes per pen was evaluated over 3 days (12 h/day) at 26, 32, and 45 weeks of age. Circulating testosterone concentrations were analyzed from blood plasma samples collected from the focal drakes at 15 (baseline), 22, 28, 34 and 45 weeks of age. Pen-level fertility was determined at 33–34 and 45–46 weeks of age. Mount and testosterone data were analyzed using a Generalized Linear Mixed Model and a Linear Mixed Model in R 4.0.5, with duck in pen as a random effect. A Linear Mixed Model was used to analyze fertility data, with pen as a random effect. None of the measured variables were impacted by rearing treatment, but all varied with flock age. Physical access to female ducklings during rearing did not enhance flock reproductive success.

Investigation of volatile flavor compounds and characterization of aroma-active compounds of water-boiled salted duck using GC-MS-O, GC-IMS, and E-nose

To clarify the characteristic aroma substances of water-boiled salted duck (WSD), headspace-gas chromatography-mass spectrometry-olfactometry (HS-GC-MS-O), gas chromatography-ion mobility spectrometry (GC-IMS) combined with an electronic nose (E-nose) were used to analyze the volatile flavor profile of three types of WSD (containing four samples). Thirty-one and fifty volatile flavor components were identified by GC-MS and GC-IMS, including aldehydes, alcohols, esters, ketones, hydrocarbons, and others. The characteristic aroma compounds of WSD, including pentanal, hexanal, heptanal, octanal, nonanal, (E)-2-octenal, benzaldehyde, (E)-2-nonenal, decanal, 1-octen-3-ol, 1-octanol, 1-pentanol, ethyl acetate, d-limonene, and 2-pentylfuran, were confirmed by GC-O, odor activity values (OAVs), and aroma-recombination and omission experiments. The aroma description of these aroma-active compounds can be divided into 6 categories, namely, "fruity", "mushroom", "fat", "sweet", "faint scent" and "potato, scorch" aromas. The difference between samples was mainly caused by the differential volatile compounds, followed by the identification method.

Setting research driven duck-welfare standards: a systematic review of Pekin duck welfare research

Globally, the production of Pekin ducks for meat and eggs is considerable, with an estimated >200 million ducks slaughtered yearly for their meat in the United States and the European Union alone. However, despite the size of the Pekin duck industries, there is a lack of research-based guidance regarding the welfare of the ducks. The purpose of this systematic review is to examine and summarize available scientific literature related to the welfare of Pekin ducks raised on commercial farms for meat and eggs. Specifically, we aimed to identify topics where sufficient literature exists to support best-practice duck welfare recommendations, as well as further research needs. The literature search targeted original research papers and review articles published in English. Six pre-establish inclusion/exclusion criteria were applied, yielding 63 publications. We summarized their content based their main topic of focus. For all original studies, we additionally recorded the country where the study was executed, scale of the project (commercial or experimental barns), general information about the housing system and management (waterers, flooring, ventilation, group size, and space allowance), and the types of outcome variables collected. We begin with an overview of key publication trends. We then synthesize and discuss welfare outcomes related to key housing/management decisions: bathing water, flooring and litter, stocking density and space availability, ventilation/air quality, lighting, outdoor access, and for egg laying birds the availability of nest boxes. Throughout, we outline specific research gaps, as well as overarching research needs.

Water for Domestic Ducks: The Benefits and Challenges in Commercial Production

Although we have been farming ducks for at least 4,000 years, with some accounts suggesting domestication having begun more than 38,000 years ago, there are still many unknowns for optimizing domestic duck welfare in a commercial setting. Ducks being waterfowl, are semi-aquatic and have unique behavioral needs when compared to other commonly farmed poultry species. Providing ducks with open water which allows for full body immersion so that they may perform their full repertoire of water-related behaviors is important for their health and welfare. However, in a commercial setting this remains challenging due to biosecurity, contamination, health, and management concerns. An important question is therefore how best to provide ducks with a commercially feasible and safe water source in which they can derive maximum welfare and health benefits with no adverse consequences to health or global water resources. This review considers the amount of water provision necessary to satisfy duck's water-related needs to enhance yet not compromise their welfare in a commercial setting based on current knowledge, as well as identifies the outstanding questions for future research to address.