Effects of Environmental Enrichment on Welfare, Production, Behavior, and Physiology of Pekin Ducks and the Potential use of Poultry Vocalizations as Welfare Indicators

Animal welfare is an important part of the poultry industry and is increasingly important to consumers. There are many ways to improve welfare, one way being implementing environmental enrichment. Environmental enrichment varies among poultry species, and it is especially distinct for Pekin ducks. Pekin ducks are waterfowl, so many believe that they should be allowed access to open water to increase positive natural behaviors and reduce unwanted behaviors. Beyond physical enrichment, another emerging approach is auditory enrichment, which has been extensively studied in zoos and is now gaining attention in livestock management. Vocalizations are a way to assess welfare and can be used as auditory enrichment. Birds use vocalizations as an effective way to communicate as vocalizations can travel over long distances and can be used in various environmental conditions. Ultimately, the Pekin duck industry could benefit from a variety of environmental enrichment devices and welfare indicators to enhance the welfare of their flocks. Preening cups may be a form of open water that would allow ducks to express preening behaviors. In Chapter 3 we describe an experiment that tested the prediction 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). We took body weights of 30 ducks per pen, and body condition scores on 50 ducks per pen weekly. On days 18 and 43, 5 ducks per pen were euthanized and their spleen, Bursa of Fabricius, liver, and uropygial gland 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 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 lie down compared to controls (25 d: F1,33 = 4.95, P = 0.0330). 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. The results of this initial study led us to investigate a second form of semi-open water source, the Pekino, and also a non-water-based environmental enrichment device, a whiffle style ball with zip-ties attached. This study, described in Chapter 4, assessed the effects of four enrichment treatments: Nipple line (CON), whiffle ball (EED), preening cup (PC), and Pekino (PEK) on duck welfare, behavior and bacterial exposure. 525 grow-out Pekin ducks were housed in 4 pens in 4 rooms with one of the four enrichment types (N=4 pens/treatment). Body weights and body condition scores of 10 ducks per pen and feed conversion ratio (FCR), ammonia level, and litter moisture percentage were recorded weekly. On days 16 and 44, 3 ducks per pen were euthanized and their organs were weighed and whole brains collected. Behavior data were collected using scan sampling with video being recorded for 72 continuous hours for 3 weeks after enrichment placement. Weekly samples were also collected for viable bacterial counts, and 16S rRNA gene sequencing at baseline and 6 hours after baseliner. Body morphometrics, FCR, ammonia levels, litter moisture % and viable bacteria were analyzed by 2-way ANOVA with repeated measures. Body condition scores were analyzed with PROC LOGISTIC (SAS 9.4). The GLIMMIX procedure (SAS 9.4) was used to analyze behavior. Bacterial communities were characterized using 16S rRNA gene sequencing, and functional potential was predicted using PICRUSt2. PEK and PC ducks were largest in weight (p<0.0001) with better nostril scores (p=0.0005) but had dirtier feathers (p<0.0001), worse litter conditions (p<0.0001) and more viable bacteria in their water sources (p<0.0001), the PC and EED ducks had worse feather quality (p=0.0021). Alpha and beta diversity metrics revealed that microbiota composition was significantly (p<0.05) dependent on environmental enrichment type. Likewise, functional pathway analyses revealed distinct (p<0.05) metabolic capacities, including aerobic respiration and amino acid biosynthesis, between microbiotas of each respective environmental enrichment niche. Our study suggests that semi-open water sources and EEDs may lead to an increase in feather pecking and a decrease in feather quality with a low number of ducks per enrichment as well as an increase in bacteria load and litter moisture. A different type of enrichment is auditory enrichment which potentially requires less maintenance and could be more cost-effective than physical enrichment. This study, described in Chapter 5, compared ducks housed in pens with Mozart music (MOZ; N=4, 30 ducks/pen), Pond sounds (POND; N=4, 30 ducks/pen), or a no sound control (CON; N=4, 30 ducks/pen). The POND and MOZ audio started on week 1 (day 7) and was played starting at 0300h (lights on) until 2100h (lights off) one hour on, one hour off, in a cyclic manner and ranged from 65-75dB. A novel object test (NOT) was conducted on each pen every week. Body condition scores were taken on 10 ducks per pen weekly (final N = 80 ducks/treatment/week). Production data were collected weekly. On weeks 2, 4, and 6, 2 ducks per pen were euthanized, and their organs were weighed (final N=16 ducks/treatment/week). Body condition scores were analyzed using the PROC LOGISTIC procedure (SAS v9.4) and Firth’s penalized likelihood method was used to address quasi-complete separation and odds ratios calculated. All other data were analyzed by 2-way ANOVA with repeated measures using PROC MIXED (SAS v9.4) and Tukey’s test for post-hoc analyses. A p≤0.05 was considered significant. The study was repeated, resulting in experiment 1 and experiment 2. For experiment 1, no significant differences were observed among groups for weekly body weights, dissection measures, or FCR. Ducks in the POND group were more passive towards the novel object than ducks in the CON group (p=0.0085). For experiment 2, ducks in the MOZ group weighed less than ducks in the POND (p=0.0010) and CON groups (p=0.0109). POND ducks approached the novel object more than MOZ ducks (p=0.0277) and CON ducks (p=0.0238). CON ducks were more fearful of the novel object than POND (p<0.0001) and MOZ ducks (p<0.0001). MOZ ducks had worse feather cleanliness scores, worse foot pad scores, and worse feather quality scores than POND and CON ducks. These two experiments resulted in different levels of effects, so future research is needed to fully understand how different auditory enrichment affects the behavior, production, and welfare of Pekin ducks under more specific flock conditions. The next step of this dissertation was to develop a complete vocalization repertoire of Pekin ducks. We know from wild bird literature that birds communicate through vocalizations. In this study, described in Chapter 6, 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 1-4 ducks of varying sex ratios into a sound chamber with various stimuli used to encourage new vocalizations. Birds were recorded for 20 minutes with several variations of number and sexes of ducks. Once the ducks were recorded each vocalization was clipped and was named based on a pre-determined naming system. We characterized the vocal system of the ducks under each stimulus and social treatment in four 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. The next step of the Pekin duck vocal repertoire study was to determine how different vocalizations affected conspecific physiology. We exposed Pekin ducks to playbacks of 5 different vocalizations plus a no noise and white noise stimulus as our controls (N=15 ducks/sex/treatment). The “AM long” call is a common vocalization made by both sexes. “Honk” is also produced by both sexes and is thought to be an alarm or distress call. “Pips” and “harmonics” are common vocalizations made only by hens. The “egg laying squiggle” is also only made by hens. Trials consisted of an initial recording in a quiet condition with 5 consecutive measurements of heart rate, blood pressure and respiratory rate. A specific vocalization was then played on repeat while 8 more measurements of blood pressure, heart rate and respiratory rate were taken. Finally, 5 measurements of heart rate and blood pressure were taken post playback along with a final recording of respiratory rate. Data from all blood pressure measurements (systolic, diastolic and mean arterial pressure [MAP]), heart rate (HR) and respiratory rate (RR) were subject to a principal component analysis (Proc Princomp in SAS 9.4). The significant principal components (Prin 1 loaded strongly on blood pressure and Prin 2 loaded strongly on HR and RR) were then analyzed by ANOVA with repeated measures (Proc Mixed, SAS 9.4, subject=duck ID). Our results showed there was a significant main effect of playback type on the blood pressure of ducks during the playbacks (p=0.0276). Ducks experienced an increase in blood pressure when played back the honk vocalization, as well as the white noise control. Additionally, there was a significant interaction between sex and treatment on the after-stimulus blood pressure (p= 0.0008): after the harmonic vocalization was played, the drakes still experienced an increase in blood pressure, but the hens experienced a decrease. The drakes, but not the hens, experienced a decrease in blood pressure after the AM long vocalization was played. Our data show that there are sex differences when it comes to vocalization playbacks in Pekin ducks, but overall, the honk vocalization and white noise control significantly increased ducks’ blood pressure. This study represents a critical steppingstone toward understanding how Pekin duck vocalizations affect conspecific physiology. In conclusion, environmental enrichment is an important part of Pekin duck welfare and production. Though more research is needed to determine the appropriate number of ducks to semi-open water sources. More research is also needed to assess the effects of auditory enrichment during different seasons. The vocalizations of Pekin ducks should also be investigated to see how other calls of their repertoire affect conspecific physiology. We observed that the honk call increased the blood pressure of the ducks, suggesting it is a stress call, so an automated detection system could be used to detect the honk call and alert the producer when their flock produces the call. This system would alert the producer and in turn, the producer is proactive in reducing the flocks’ stress before they drop in production and welfare. Other Pekin duck calls could be used as auditory enrichment or as calming sounds. We found that the egg laying call reduced the hens’ blood pressure so this call could be used during routine management practices or entice the hens to lay their eggs in their nest boxes.