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.

Effects of different dietary vitamin D combinations during the grower phase and the feed restriction phase on growth performance and sternal morphology, mineralization, and related genes expression of bone metabolism in Pekin ducks

Our study aimed to investigate the effects of different dietary vitamin D (VD) combinations during the grower (1-32 d of age) and feed restriction (33-52 d of age) phases on growth performance. We also evaluated sternal morphology, mineralization, and related genes expression of bone metabolism as well as absorption of calcium and phosphorous in duodenal mucosa and kidney in Pekin ducks. During the grower phase, we used 2 VD regimes (Group A: 3,160 IU/kg VD3; Group B: 400 IU/kg VD3 + 69 μg/kg 25-OH-D3). Each dietary treatment had 50 replicate pens of 10 ducks per pen. During the feed restriction phase, 30 replicate pens selected from Group A and Group B, repetitively, were redivided into 5 different dietary VD regimes to form a 2 × 5 experimental design. Each group consisted of 6 replicates, each with 10 ducks. During the feed restriction phase, we evaluated 5 different dietary VD combinations were as follows: T1: 2,000 IU/kg VD3 ; T2: 5,000 IU/kg VD3; T3: 3,620 IU/kg VD3 + 34.5 μg/kg 25-OH-D3; T4: 2,240 IU/kg VD3 + 69 μg/kg 25-OH-D3; T5: 1,800 IU/kg VD3 + 80 μg/kg 25-OH-D3). Results showed that Group B combinations with T5 had a better growth performance and breast meat deposition (P < 0.1). Regardless of 5 dietary VD regimes during the feed restriction phase, Group B significantly increased (P < 0.05) 52 d sternal depth and tended to increase (P < 0.1) 52 d sternal defatted weight, ash content, and phosphate (P) content of ducks. A significant interactive effect (P < 0.05) was observed on the mRNA abundance of DMP1 and Sost1 as well as RANKL/OPG in sternum and of VDR in duodenal mucosa of ducks at 52 d of age between dietary VD combinations during 2 phases. These results indicated that dietary VD regimes during the grower phase could affect the effectiveness of dietary VD regimes during the feed restriction phases; Dietary VD combinations of both phases could affect the genes expression of bone formation and the absorption as well as reabsorption of calcium and phosphorus in duodenum and kidney.

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.

Heat stress and poultry production: a comprehensive review

The impact of global warming on poultry production has gained significant attention over the years. However, our current knowledge and understanding of the mechanisms through which heat stress (HS) resulting from global warming affects the welfare, behavior, immune response, production performance, and even transgenerational effects in poultry are still incomplete. Further research is needed to delve deeper into these mechanisms to gain a comprehensive understanding. Numerous studies have investigated various biomarkers of stress in poultry, aiming to identify reliable markers that can accurately assess the physiological status and well-being of birds. However, there is a significant amount of variation and inconsistency in the results reported across different studies. This inconsistency highlights the need for more standardized methods and assays and a clearer understanding of the factors that influence these biomarkers in poultry. This review article specifically focuses on 3 main aspects: 1) the neuroendocrine and behavioral responses of poultry to HS, 2) the biomarkers of HS and 3) the impact of HS on poultry production that have been studied in poultry. By examining the neuroendocrine and behavioral changes exhibited by poultry under HS, we aim to gain insights into the physiological impact of elevated temperatures in poultry.

Chronic treatment with glucocorticoids does not affect egg quality but increases cortisol deposition into egg albumen and elicits changes to the heterophil to lymphocyte ratio in a sex-dependent manner

During chronic stress, there is an initial increase in glucocorticoid (GC) levels, but they then return to low, albeit not baseline, levels. Recent studies have renewed interest in cortisol in that it may also have important roles in the stress response. The purpose of our study was to test the hypothesis that chronic treatment with low levels of either corticosterone or cortisol would alter HLR and immune organ morphometrics. Further, we wanted to determine if chronic treatment with either GC would elicit an increase in cortisol levels in egg albumen. To test our hypotheses, we implanted silastic capsules that contained corticosterone, cortisol, or empty capsules as controls (N = 5/sex/treatment). Blood serum, smears, body weights, and egg quality data were collected. Ducks were then euthanized and body weight, weights of spleens, livers, and the number of active follicles were recorded. Albumen GC levels were assessed using mass spectrometry. Data were analyzed using a 2- or 3-way ANOVA as appropriate and post-hoc with Fishers PLSD. No treatment elicited differences in egg quality measures or body weight compared to controls. Corticosterone treatment did elicit an increase in serum corticosterone (p &lt; 0.05), but not cortisol, levels compared to controls in both sexes. Both cortisol and corticosterone treatments increased (p &lt; 0.05) serum levels of cortisol compared to controls. Relative spleen weights were higher (p &lt; 0.05) in hens following corticosterone but not cortisol treatment. No other organs showed any differences among the treatment groups. Both GCs elicited an increase (p &lt; 0.001) in HLR in hens at all time-points over the 2-week treatment period compared to controls. Cortisol, not corticosterone, only elicited an increase in HLR for drakes (p &lt; 0.05) compared to controls but only at day 1 after implants. Chronic treatment with cortisol, but not corticosterone, elicited an increase (p &lt; 0.01) in egg albumen cortisol levels compared to other groups. Corticosterone was not detected in any albumen samples. Our results suggest that glucocorticoids elicit differential effects and although corticosterone has been stated to be the predominant GC in avian species, cortisol may provide critical information to further understand bird welfare.

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.

Research Note: Retinal cryptochrome gene expression is not altered by presence of light in incubators

Cryptochromes are blue-, or ultraviolet-, light-absorbing proteins involved in the circadian clock, blue/ultraviolet light perception and potentially magnetoreception. At least 4 separate cryptochrome genes have been identified in avian species. The purpose of this study was to first determine if cryptochrome genes are expressed in the developing duck retina, and second to determine if the presence of lights in incubators affects the expression of cryptochrome genes. To accomplish these goals, duck eggs were placed in one of 2 commercial incubators (Buckeye, Single Stage Incubator, Model, SS-112) at Maple Leaf Farms, Inc., one with "poultry" LEDs obtained from a commercial source (Once Innovation, Agrishift) and the other in the absence of light (dark). Eggs in the incubators were placed on a reciprocating tray, tilting to 45° to simulate the rotation of eggs; thus all eggs spent 50% facing the light source and the other 50% of time facing 45° away from light source. Temperature gradients and humidity were maintained at industry standards. Retinal tissue samples from light and dark incubators were collected on days 3, 7, 11, 16, and 21 of incubation (extraction day, ED) known to be anatomical hallmarks of visual system development (n = 9-18 treatment group/ED timepoint). Samples were prepped and assayed for Cry2 and GAPDH gene transcription using qRT-PCR. Data were analyzed by using 2^-ddCt method and a 2-way ANOVA was performed. No significant differences in Cry2 gene expression were observed between the lighted or dark incubator (P > 0.10). When combining light and dark treatment groups there is a significant 9 P < 0.05) increase in retinal Cry2 at ED 21, compared to ED 3 and 7. The presence of cryptochrome does not necessitate a migratory drive as evidenced by the fact that the Cry2 expression has been shown in non-migratory birds. However, since blue/ultraviolet wavelengths also activate the Cry2 photoreceptor, its presence could explain reports that suggest duck welfare can be improved if housed under lights that include ultraviolet wavelengths.

Research Note: Sex difference in changes in heterophil to lymphocyte ratios in response to acute exposure of both corticosterone and cortisol in the Pekin duck

Poultry scientists have utilized both direct and indirect measures of stress hormones for monitoring the state of avian welfare. For decades, it has been assumed that the mammalian and avian hypothalamic pituitary adrenal (HPA) function similarly to one another. However, there are considerable differences between the 2. Further, it has been assumed that the predominate glucocorticoid (GC) in birds was corticosterone, but recent studies have suggested that both corticosterone and cortisol are secreted. GC release is associated with an increase in blood heterophils due to increased migration from the lymph nodes and a decrease in lymphocytes due to marginalization. Both actions account for an increase in heterophil to lymphocyte ratios (HLR). The goal of this project was to determine the effect of each GC on HLR over time. To achieve this, we intramuscularly injected 2.0 mg/kg of corticosterone or cortisol, a lower dose cortisol treatment (0.5 mg/kg), or safflower oil as vehicle control. Blood was collected prior to intramuscular (IM) injections and blood collected 3 more times at every hour. Blood smears were also collected to assess HLR at the same four time points. HLR assays were completed by avian pathologists from an independent lab who were unaware of the treatments. Data were analyzed by 3-way repeated measures ANOVA with a P < 0.05 considered significant. We found significant sex (P < 0.001) x treatment (P < 0.001) x time (P < 0.001) effects with significant interactions (P = 0.0055). In hens, both GC resulted in significant increase in HLR at 1 h after injection compared to controls. In drakes, however, both GC showed a significant increase in HLR but not until 2 h after injection. The low dose cortisol had no significant effect on HLR in either sex. These data suggest that sex differences need to be considered when assessing duck welfare, and that cortisol may play a role in the HPA axis in ducks.

Sex differences in serum glucocorticoid levels and heterophil:lymphocyte ratios in adult pekin ducks (Anas platyrhynchos domesticus)

It is becoming more common for poultry scientists to utilize direct and indirect measures of stress hormones to monitor bird welfare. However, it has been clear that our understanding of the avian hypothalamic-pituitaryadrenal axis (HPA) is insufficient as evidenced by the many conflicting reports regarding stress responses, such as transportation stress, in poultry. It has long been assumed that the poultry HPA functions similarly to that of mammals, but now we know that there are considerable differences in the avian HPA compared to mammals. Synthesis and release of glucocorticoids (GC) are stimulated by adrenocorticotropin hormone (ACTH); GC are synthesized from a common pathway that begins with cholesterol and pregnenolone. The synthesis of one of the glucocorticoids does not depend upon the synthesis of the other. The purpose of our study was to test the hypothesis that ACTH will stimulate both corticosterone and cortisol release in ducks. To test this hypothesis, we injected artificial ACTH (cosyntropin; 0.0625 mg/kg, 0.031 mg/kg, or 0.016 mg/kg or saline as control) intramuscularly into adult drakes and hens (N = 10/sex/dose). Both glucocorticoids (GC) were assayed in serum using previously verified ELISAs. Blood smears were also assessed for heterophil to lymphocyte ratios (HLR). Data were analyzed by repeated measures 3-way ANOVA with Fishers PLSD as an ad hoc test. We observed that both GC were secreted in significantly (p = 0.0002) different patterns in a dose-dependent manner compared to controls, and that there was a significant (p = 0.0001) sex difference in both GC compared to saline controls. Further, we observed that all doses of ACTH elicited a significant (p = 0.004) sex difference in the HLR response compared to controls, but no dose-dependent effects were noted. Our data suggest that ducks, at least, may utilize more than just corticosterone to maintain physiological homeostasis in response to stress. Further, the time course of the stressor to release GC and subsequent HLR response may be dependent upon sex. More detailed analyses of the HPA are necessary in all avian species to better understand stress responses as we utilize biological bases for welfare assessments and stress responses.

Sex differences in glucocorticoid responses to shipping stress in Pekin ducks

Some concerns have been raised recently about the assay of corticosterone vs. cortisol in poultry species. Thus, we tested the hypothesis that ducks secrete both glucocorticoids. First, we validated two commercially ELISA kits for the two glucocorticoids by first charcoal stripping duck serum in order to remove all steroid hormones. We ran serial dilutions of spiked, charcoal-stripped serum on kits of opposite glucocorticoid as well as a serial dilution using the respective ELISA buffer of the opposite assay kit. We found that the glucocorticoid standard curve in duck serum matched the respective curve in that kit's own buffer. However, when the opposite hormone was run in each kit in both duck serum or ELISA buffer, a near zero slope was obtained. Second, we further validated the presence of both glucocorticoids using mass spectrometry. Third, we tested the hypothesis that exogenous ACTH would stimulate the release of both corticosterone and cortisol. And, fourth, we tested the hypothesis that each glucocorticoid would have different serum levels in response to shipping stress. To test this hypothesis, we collected serum from 10 drakes and 10 hens from 2 flocks (N = 20 per time point per sex): 24 h prior to shipping, at shipping as ducks were walked off the truck, 24 h after shipping, and 1 wk after shipping. Data were analyzed by 2-way repeated measures ANOVA. Surprisingly, we also observed a sex difference in both glucocorticoid levels in that hens showed higher (P < 0.01) serum levels than did drakes at all-time points in response to either ACTH or transportation. Finally, no differences were observed in either glucocorticoid levels associated with shipping in either sex. The fact that both glucocorticoids are released in measurable amounts lends to the possibility that they may be differentially regulated, or at least there is a sex difference in the neural pathways associated with glucocorticoid release in ducks. Although corticosterone is the likely predominate glucocorticoid in ducks, serious attention should be given to the role of cortisol in poultry. Further consideration of sex, age, and timing of blood collection to stressor needs to be considered when assessing glucocorticoid levels in any avian species.

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

By some accounts, ducks were domesticated between 400 and 10,000 yr ago and have been a growing portion of the poultry industry for decades. Ducks specifically, and waterfowl in general, have unique health, housing, nutrition and welfare concerns compared to their galliform counterparts. Although there have been many research publications in regards to health, nutrition, behavior, and welfare of ducks there have been very few reviews to provide an overview of these numerous studies, and only one text has attempted to review all aspects of the duck industry, from breeders to meat ducks. This review covers incubation, hatching, housing, welfare, nutrition, and euthanasia and highlights the needs for additional research at all levels of duck production. The purpose of this review is to provide guidelines to raise and house ducks for research as specifically related to industry practices.

A feed restriction milieu for Pekin meat ducks that may improve gait characteristics but also affects gut leakiness

In a previous study, we demonstrated that a 15% feed restriction (FR) during the first 2 wk after hatch could improve gait in Pekin meat ducks, but did result in reduced breast mass. We hypothesized that feed restriction after day 5 following muscle satellite cell development would allow the full growth of the breast meat. To accomplish this goal, 300 1-day-old ducklings (Maple Leaf Farms Inc.) were randomly allocated to 1 of the 3 groups (n = 4 pens, 25 ducks per pen): (1) Control group fed to ad libitum; (2) 85% daily feed intake from days 1 to 14 (FR 85% 1-14); 85% daily feed intake from days 5 to 14 (FR 85% 5-14). All ducks were vaccinated with inactivated Salmonella enteritidis on day 14 and boosted on day 26. The FR 85% 5-14 did show similar production standards to controls, and improved gait characteristics (P < 0.05). To determine if the partial feed restriction would have an impact on intestinal epithelial tight junction integrity, we treated ducks on days 7, 14, 21, 28, and 35 with 8.32 mg/kg FITC-d in water per os and blood samples were obtained via the tibial vein 1 h later. Serum samples were analyzed for presence and quantification of FITC-d. Feed restriction elicited a significant increase in FITC-d permeability at all points of evaluation. Anti-S. enteritidis specific IgY responses were assessed by ELISA from serum collected at 14 D, 28 D, and 35 D. Although all ducks showed an increase humoral immune response to the S. enteritidis, both feed restricted groups showed reduced IgY production compared to ad lib controls. Our data suggest that although the FR 5-14 feed restriction paradigm may reduce gait abnormalities without affecting production rates, some challenges exist due to increased gut leakiness or decreased acquired immune activity. Future studies will look at altering the feed restriction milieu to ameliorate these challenges.

High vitamin levels ameliorate negative effect of rapeseed meal in meat ducks by improving antioxidant activity

The purpose of this study was to test the hypothesis that a high level of a vitamin premix would prevent the deleterious effects of rapeseed meal (RSM) when added to the diet of Pekin meat ducks. A total of 674 fifteen-day-old ducks were randomly allocated to 6 treatments with 7 cages of 16 ducks each. Three diets were formulated that contained 5, 10, or 20% RSM to compensate for reducing levels of soybean meal. Each RSM level diet was then supplemented with either a low level (low) or a high level (high) of a vitamin premix providing a total of 6 experimental diets. Ducks were fed one of the 6 experimental diets (N = 7 pens per diet) from days 15 to 35 at which time they were euthanized. Ducks were analyzed for antioxidant activity, liver biochemistry, thyroid hormone levels, and liver and thyroid histopathology. Addition of the high vitamin premixes to the 5 or 10% RSM diets improved BW (P < 0.05), BW gain (BWG; P < 0.05), and feed to gain ratio (F/G; P < 0.05) compared to the low vitamin premix; however, neither vitamin premix level had effects on production variables of ducks fed the 20% RSM diet. The high vitamin premix level also improved antioxidant capacity as evidenced by increased (P < 0.05) serum and liver superoxide dismutase activities over that of the low vitamin premix diets. Furthermore, the high level of vitamin premix prevented liver and thyroid pathologies in diets that contain RSM compared to diets with the low vitamin premix. These results suggested that high vitamin premix could prevent the negative effects of a 5 or 10% RSM diet in ducks by improving antioxidative capacities and alleviating liver and thyroid damage.

Study on the morphology and mineralization of the tibia in meat ducks from 1 to 56 d

The objective of this current study was to characterize the basic physiological data on morphological and mineralized properties of the tibia from 1 to 56 days, as well as the interrelationships of body weight (BW) and bone traits for meat ducks. A total of 176 1-d-old ducks was allocated into eight pens and fed with the same diet until the age of 56 d. Eight birds (1 ducks/pen) were randomly selected weekly for measuring BW and tibia characteristics. The BW of duck was increased with age throughout the whole study. Tibial length and width rapidly grew from 1 to 35 d, when it leveled off. The fat-free weight, ash, calcium (Ca) and phosphorus (P) content of tibia increased rapidly from 1 to 42 d and reached its plateau from 42 d onward. Tibial density and tibia-breaking strength increased in a regular manner with age until 42 d. Serum alkaline phosphatase activity was higher between 1 to 7 d in the duck. Regression and ontogenetic scaling analysis showed the age of maximal growth rate in tibia dimension and mineralization was earlier than that in BW; when compared with BW, tibial fat-free weight and tibia-breaking strength increased isometrically, tibia length displayed a negative allometry, and tibial width showed a positive allometric growth. Results indicate that the tibia displayed rapid bone growth (1 to 35 d) and mineralization (1 to 42 d), and alkaline phosphatase (ALP) plays a critical role in the early stage of tibia mineralization of meat duck. Intensive selection for growth rate in ducks has resulted in tibial morphology changes, which represents an interesting compromise of adaptation for increasing BW.

Effects of supplementation with different rapeseed oil sources and levels on production performance, egg quality, and serum parameters in laying hens

This study was to determine the effects of rapeseed oil on production performance, egg quality, and serum parameters in laying hens. A total of 1,080 hens (33-wk-old) were randomly divided into a 1 plus 4 × 2 factorial design including four different rapeseed oil sources [high erucic acid of Mianyang city (MH); high erucic acid of Deyang city (DH); low erucic acid of Mianyang (ML); low erucic acid of Deyang (DL)] at two levels (2% and 4%) for 12 wk. The egg production and egg weight were decreased (P < 0.05) during 9 to 12 wk and 1 to 12 wk, while the average daily feed intake (ADFI) and feed conversion ratio were decreased (P < 0.01) in all phases compared to the control group. Adding ML as oil source had higher (P < 0.05) egg weight compared to DH in all periods in spite of levels. Meanwhile, layers fed 4% rapeseed oil decreased (P < 0.01) egg production compared with 2% in all phases except 1 to 4 wk. Regardless of rapeseed oil sources, hens fed 4% oil decreased (P < 0.05) egg weight in contrast to 2% during the whole experiment except 5 to 8 wk. The ADFI was lower (P < 0.01) in 4% oil inclusion groups compared with 2% during overall phase. Rapeseed oil decreased the yolk color (P < 0.01) and yolk ratio (P = 0.02) and increased (P < 0.01) the albumen height and Haugh unit at 12 wk. Dietary rapeseed oil supplementation resulted in a decreased total triglyceride (TG; P < 0.01) and increased high-density lipoprotein cholesterol (P = 0.02). Regardless of rapeseed oil levels, layers fed MH had higher TG (P < 0.01), TC (P < 0.05), low-density lipoprotein cholesterol (P < 0.05), alanine transaminase (P < 0.01) than those fed other sources. Taken together, the addition of rapeseed oil decreased laying performance, reduced TC and TG in the serum, and increased Haugh unit, with low erucic acid or 2% group showed more pronounced results among all treatments.

Expression of deep brain photoreceptors in the Pekin drake: a possible role in the maintenance of testicular function

Several putative deep brain photoreceptors (DBPs) have been identified, such as melanopsin, opsin 5, and vertebrate ancient opsin. The aim of this study was to elucidate the role of DBPs in gonadal regulation in the Pekin drake. As previously reported, we observed opsin-like immunoreactivity (-ir) in the lateral septum (LS), melanopsin-ir in the premammillary nucleus (PMM), and opsin 5-ir in the periventricular organ. To determine the sensitivity of the DBPs to specific wavelengths of light, drakes were given an acute exposure to red, blue, or white light. Blue light stimulated an increase (P < 0.01) in the immediate early gene fra-2-ir co-expression in melanopsin-ir neurons in the PMM, and red light increased (P < 0.05) fra-2-ir co-expression in opsin-ir neurons, suggesting these neurons are blue- and red-receptive, respectively. To further investigate this photoperiodic response, we exposed drakes to chronic red, long-day white, short-day white, or blue light. Blue light elicited gonadal regression, as testes weight (P < 0.001) and plasma luteinizing hormone (LH) levels (P < 0.001) were lower compared to drakes housed under long-day white light. Photo-regressed drakes experienced complete gonadal recrudescence when housed under long-day red and blue light. qRT-PCR analyses showed that gonadally regressed drakes showed reduced levels (P < 0.01) of gonadotropin releasing hormone (GnRH) mRNA but not photoreceptor or GnIH mRNAs compared to gonadally functional drakes. Our data suggest DBP in the LS may be rhodosin and multiple DBPs are required to fully maintain gonadal function in Pekin drakes.

Immunolesion of melanopsin neurons causes gonadal regression in Pekin drakes (Anas platyrhynchos domesticus)

Several light sensitive receptors have been described in the avian brain that are thought to regulate the reproductive axis independently from the eyes and pineal gland. Recently, our lab has described the presence of three of these photoneuroendocrine systems in the Pekin duck: opsin, opsin 5, & melanopsin. We set out to test the hypothesis that melanopsin receptive neurons are necessary to maintain seasonal reproductive status along with growth and development in the Pekin drake. To accomplish these goals we first investigated 50-week-old Pekin drakes that were housed in the aviary at Hope College under long day length (18h lights on) conditions in floor pens. To specifically lesion melanopsin-receptive neurons, 3μl of an anti-melanopsin-saporin conjugate (MSAP, 100ng/ul) was injected into the lateral ventricle (n=10). Control drakes were injected with 3μl of equimolar unconjugated anti-melanopsin and saporin (SAP, n=10). Reproductive behaviors were analyzed weekly in a test pen with adult hens and MSAP drakes showed a significant (p<0.01) reduction in reproductive behaviors after week 2. After 5weeks, drakes were euthanized and body weights were measured, and brains, pituitaries, and testes collected and stored for analyses. Mature MSAP-treated drakes had significantly (p<0.001) reduced relative teste weights compared to SAP controls. qRT-PCR analyses of hypothalamus showed a significant reduction (p<0.001) in GnRH and melanopsin mRNA levels, but not opsin 5, vertebrate ancient opsin, or opsin 2 (rhodopsin). Immunocytochemical analyses showed a significant reduction (p<0.01) in tyrosine hydroxylase-immunoreactivity in the PMM. These data suggest that although blue light alone is not able to maintain testicular function, the blue-light sensitive melanopsin activity is critical to maintain gonadal function.

Increased water contamination and grow-out Pekin duck mortality when raised with water troughs compared to pin-metered water lines using a United States management system

Controversy has developed as to whether or not pin-metered water lines or water troughs are more appropriate for Pekin ducks. We hypothesized that water troughs would show improved duck body conditions and environmental quality compared to pin-metered water lines. To test this hypothesis, we housed ducks in 2 barns, one with water lines and one with water troughs. Water troughs were constructed to meet RSPCA guidelines for number and density of ducks and with recently described verandas. Ducks were divided into 4 pens per barn (n=1,000 ducks/pen). The study was then repeated (n=8 pens per water source) in a cross-over design so the barns each contained the opposite water source to the first experiment. We scored the ducks' body condition using an established scoring rubric and analyzed using SAS Proc GLM-Mix as binomial data. Ducks housed with water troughs showed higher (thus worse condition; P<0.001) scores for eyes, nostrils, feather quality, feather cleanliness, and foot pads. We also compared water condition, water quality, and duck mortality using a Student t test for both water sources each week. We found that the water troughs showed higher iron (P<0.001), nitrites (P<0.001), pH (P<0.01), and bacterial growth (P<0.001). The bacterial growth was shown to have higher (P<0.001)E. coli, coliforms, and Staphylococcusin the water troughs. Water lines typically showed no bacterial growth in culture-based assays. Ducks housed with water troughs used greater (P=0.001) volumes of water compared to ducks housed with water lines. Ducks with water troughs also showed a greater percent (P=0.008) mortality at all ages compared to ducks with water lines. These data suggest that water troughs may not be beneficial for duck welfare and could adversely impact both environment and duck or human health.

Distribution and sequence of gonadotropin-inhibitory hormone and its potential role as a molecular link between feeding and reproductive systems in the Pekin duck (Anas platyrhynchos domestica)

The reproductive status of adult Pekin drakes is very sensitive to nutritional status. Thus, the purpose of this study was to increase our understanding of the neurobiology underlying the depressive effect of fasting on the secretion of reproductive hormones. It was hypothesized that this effect was mediated by gonadotropin-inhibitory hormone (GnIH). Networks of GnIH fibers were present throughout the diencephalon, and cell bodies were present primarily, in the hypothalamic paraventricular nucleus (PVN). The duck GnIH gene was cloned and sequenced and found to encode GnIH and two GnIH-related peptides (GnIH-RP1, GnIH-RP2) which have a similar identity to those found in other avian species. Intracerebroventricular injection of GnIH, but not of GnIH-RP1, depressed plasma LH and stimulated feeding. Fasting for 48h depressed plasma LH and induced fos expression in about half the population of GnIH-ir neurons. These data suggest that GnIH neurons are mediators between feeding and reproductive systems in Pekin drakes.

Hypothalamic galanin-like peptide rescues the onset of puberty in food-restricted weanling rats

Galanin-like peptide (GALP) is a known mediator of metabolism and reproduction; however, the role that GALP plays in the onset of puberty is unknown. First, we tested the hypothesis that central GALP administration could rescue puberty in food-restricted weanling rats. GALP treatment in food-restricted rats of both sexes rescued the timing of the onset of puberty to that seen in ad lib. fed controls. Second, we tested whether GALP translation knocked-down in ad lib. fed, prepubertal rats would alter the timing of puberty. Knock-down females, but not males, showed a significant (P < 0.01) delay in the onset of puberty compared to controls. Third, we sought evidence that the role of GALP in pubertal onset is mediated by the kisspeptin system. In situ hybridisation analyses showed a significant (P < 0.01) reduction in Kiss1 mRNA within the hypothalamic arcuate nucleus in food-restricted rats compared to ad lib. fed controls and this reduction was prevented with i.c.v. GALP administration. Furthermore, analyses of Fos-immunoreactivity (-IR) after i.c.v. GALP treatment did not elicit Fos-IR within any kisspeptin neurones, nor are GALP and kisspeptin peptides or mRNA colocalised. These data demonstrate that hypothalamic GALP infusion maintained the onset of puberty in food-restricted weanling rats, although probably not via direct innervation of kisspeptin neurones.

Resveratrol protects neurons from cannulae implantation injury: implications for deep brain stimulation

Brain-implantable electrodes such as those used in deep brain stimulation (DBS) have a promising future in end-stage Parkinson's disease therapy. However, there is considerable injury when electrodes penetrate brain tissue. For instance, broken blood vessels and glial scar formation may impede continual DBS or electrical recording from specific neurons. To begin addressing this key safety issue, we tested the therapeutic potential of resveratrol in reducing brain trauma caused by DBS-like surgery. Microinfusion of resveratrol (10 μM) directly applied to the sub-thalamic nucleus (STN) of the rat brain significantly minimized the formation of astrocytic gliosis in response to a 27-G precision-glide cannula implant. The therapeutic effects of resveratrol extended to the "kill zone", a boundary zone of about 100 μm comprising the cannula implant and surrounding neurons. We also found that resveratrol not only provided almost complete protection from mechanical injury to the brain, but that it also prevented undesirable motor deficits often seen in animals with lesions to the STN. Lastly, continuous infusion of resveratrol over a 4-week period led to the inhibition of pro-apoptotic, neurodegenerative and cell division cycle genes that may be associated with a reduction in astrocytic gliosis and glial scar formation within the STN. Taken together, these data suggest that application of resveratrol to the brain is an effective adjunct surgical procedure for minimizing acute neuronal injury when electrodes are implanted directly into the STN.

Sex differences in the effect of prepubertal GALP infusion on growth, metabolism and LH secretion

The hypothalamic neuropeptide, galanin-like peptide (GALP), is known to have an effect on energy expenditure and reproduction in adult male rats, but little work has been done on prepubertal rats. We hypothesized that hypothalamic GALP is involved in physiological changes associated with the onset of puberty. To test this hypothesis, we first determined the postnatal ontogeny of GALP gene expression via in situ hybridization of developing male and female rat pups through adulthood. GALP gene expression was not observed in either male or female rat pups until after postnatal day (PND) 10 and did not reach adult-like levels until after weaning (PND25). To determine if exogenous GALP could induce the onset of puberty, PND25 male and female rats were implanted with lateral ventricular cannulas connected to an osmotic minipump that delivered either GALP or vehicle. GALP infusion significantly (p<0.05) increased body weight, food intake, and metabolic rate in male but not female rats compared to control infusion. After 2 weeks, GALP infusion had no significant effect on the onset of puberty, percent body fat, nor plasma levels of insulin, FSH or gonadal steroids in either sex; however, GALP did significantly (p<0.05) increase plasma levels of LH and leptin in male but not female rats and increased plasma growth hormone (GH) in both sexes. Our observations further demonstrate a sex difference in GALP responsiveness in prepubertal rats. These data suggest that GALP may be involved with the prepubertal increase in circulating leptin, LH, and GH resulting in an increase in metabolic rate and lean growth associated with puberty.

Stimulation of sexual behavior in the male rat by galanin-like peptide

Galanin-like peptide (GALP) is a recently described neuropeptide, which shares a partial sequence identity with galanin but is derived from a separate gene. Central injections of GALP stimulate the secretion of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) and induce the expression of Fos in several brain areas known to regulate male sexual behavior in the rat. We postulated that GALP may also stimulate sexual behavior in concert with its stimulatory effect on the hypothalamic-pituitary-gonadal (HPG) axis. To test this hypothesis, we administered GALP, galanin, or the vehicle (artificial cerebrospinal fluid, aCSF) alone to sexually experienced male rats and assessed the effects of these agents on sexual behavior. We observed that compared to aCSF alone, GALP significantly increased all aspects of male-typical sexual behavior, whereas galanin inhibited all of these same behaviors. To examine whether the stimulatory effects of GALP on sexual behavior were mediated by GALP's stimulatory effects on the HPG axis, we castrated the same male rats and repeated the behavioral experiment. We found that GALP maintained its inductive action on male-typical sexual behaviors in the castrated animals, suggesting that the effects of GALP on sexual behavior are not the result of GALP's ability to stimulate testosterone secretion. These observations suggest that GALP neurons are part of the hypothalamic circuitry controlling sexual behavior in the male rat.

Immunolesion of norepinephrine and epinephrine afferents to medial hypothalamus alters basal and 2-deoxy-D-glucose-induced neuropeptide Y and agouti gene-related protein messenger ribonucleic acid expression in the arcuate nucleus

Neuropeptide Y (NPY) and agouti gene-related protein (AGRP) are orexigenic peptides of special importance for control of food intake. In situ hybridization studies have shown that NPY and AGRP mRNAs are increased in the arcuate nucleus of the hypothalamus (ARC) by glucoprivation. Other work has shown that glucoprivation stimulates food intake by activation of hindbrain glucoreceptor cells and requires the participation of rostrally projecting norepinephrine (NE) or epinephrine (E) neurons. Here we determine the role of hindbrain catecholamine afferents in glucoprivation-induced increase in ARC NPY and AGRP gene expression. The selective NE/E immunotoxin saporin-conjugated antidopamine-beta-hydroxylase (anti-dbetah) was microinjected into the medial hypothalamus and expression of AGRP and NPY mRNA was analyzed subsequently in the ARC under basal and glucoprivic conditions using (33)P-labeled in situ hybridization. Saporin-conjugated anti-dbetah virtually eliminated dbetah-immunoreactive terminals in the ARC without causing nonspecific damage. These lesions significantly increased basal but eliminated 2-deoxy-D-glucose-induced increases in AGRP and NPY mRNA expression. Results indicate that hindbrain catecholaminergic neurons contribute to basal NPY and AGRP gene expression and mediate the responsiveness of NPY and AGRP neurons to glucose deficit. Our results also suggest that catecholamine neurons couple potent orexigenic neural circuitry within the hypothalamus with hindbrain glucose sensors that monitor brain glucose supply.

Immunotoxic catecholamine lesions attenuate 2DG-induced increase of AGRP mRNA

Injections of the immunotoxin, saporin conjugated to anti-dopamine-beta-hydroxylase (DSAP), into the hypothalamic paraventricular nucleus (PVH) selectively destroy norepinephrine (NE) and epinephrine (E) terminals in the medial hypothalamus and abolish glucoprivic feeding. We utilized PVH DSAP injections to examine the role of NE/E neurons in the previously reported 2-deoxy-D-glucose (2DG)-induced increases in mRNA levels for the orexigenic peptides, AGRP and NPY. Northern blot analysis revealed that DSAP lesions elevated basal but blocked 2DG-induced increases in AGRP mRNA levels. Changes in NPY mRNA were not detectable. AGRP neurons may contribute to circuitry activated by NE/E neurons for elicitation of glucoregulatory responses.

Immunolesion of hindbrain catecholaminergic projections to the medial hypothalamus attenuates penile reflexive erections and alters hypothalamic peptide mRNA

The central mechanisms underlying diabetes-associated impotence are currently unknown. This study utilized immunolesion techniques to eliminate hindbrain catecholaminergic projections to the medial hypothalamus which have been reported to be glucoresponsive. The immunolesioned male rats had an attenuated feeding response to glucoprivic challenge. Furthermore, these lesioned rats had significantly attenuated penile reflexes. Northern blot analyses of hypothalamic oxytocin mRNA expression showed a significant increase; however, neuropeptide Y mRNA expression did not. These results suggest that hindbrain catecholaminergic neurones may alter the expression of hypothalamic neuropeptides that stimulate penile erections based upon glucoregulatory signals from the periphery.

Sexual dimorphism in the number and size of SNB motoneurons: delayed development during normal ontogeny

The spinal nucleus of the bulbocavernosus (SNB) is a sexually dimorphic pool of motoneurons that innervates the perineal musculature. In the Mongolian gerbil, the SNB lies dorsolateral to the central canal within the lumbosacral spinal cord. Previously, no information was available on the normal development of the sexual dimorphism of this structure in the Mongolian gerbil, although evidence exists for a peripubertal development of the SNB in the gerbil. At each age from postnatal day 1 (PND1) through PND15 and at PND25, male and female gerbils were aldehyde perfused. Spinal cords were gelatin-embedded, cryoprotected, frozen and sectioned coronally through the lumbosacral transition zone and stained for Nissl substance with thionin. Examination by light microscopy revealed that the number of visible male and female SNB motoneurons significantly increased from PND1 through PND25. The size of the motoneurons also significantly increased in both sexes, however, until PND15 male gerbil SNB showed two significantly different sized populations of motoneurons. These data suggest the development of the SNB in the Mongolian gerbil is delayed, compared to the rat, and may continue well beyond the perinatal time period.

Immunodetection of Parkin protein in vertebrate and invertebrate brains: a comparative study using specific antibodies

Parkin is an intracellular protein that plays a significant role in the etiopathogenesis of autosomal recessive juvenile parkinsonism. Using immunoblot methods, we found Parkin isoforms varying from 54 to 58 kDa in rat, mouse, bird, frog and fruit-fly brains. Immunocytochemical studies carried out in rats, mice and birds demonstrated multiple cell types bearing the phenotype for Parkin throughout telencephalic, diencephalic, mesencephalic and metencephalic brain structures. While in some instances Parkin-containing neurons tended to be grouped into clusters, the majority of these labeled nerve cells were widely scattered throughout the neuraxis. The topographical distribution and organizational pattern of Parkin within major functional brain circuits was comparable in both rats and mice. However, the subcellular localization of Parkin was found to vary significantly as a function of antibody reactivity. A consistent cytoplasmic labeling for Parkin was observed in rodent tissue incubated with a polyclonal antibody raised against the human Parkin protein and having an identical amino-acid sequence with that of the rat. In contrast, rodent tissue alternately incubated with a polyclonal antibody raised against a different region of the same human Parkin protein but having 10 mismatched amino-acid sequence changes with those of the rat and mouse, resulted in nuclear labeling for Parkin in rat but not mouse neurons. This difference in epitope recognition, however, was reversed when mouse brain tissue was heated at 80 degrees C, apparently unmasking target epitopes against which the antisera were directed. Collectively, these results show a high degree of conservation in the cellular identity of Parkin in animals as different as drosophilids and mammals and points to the possibility that the biochemical specificities of Parkin, including analogous functional roles, may have been conserved during the course of evolution.

Immunocytochemical and histochemical analyses of gonadotrophin releasing hormone, tyrosine hydroxylase, and cytochrome oxidase reactivity within the hypothalamus of chicks showing early sexual maturation

In order to determine the changes in gonadotrophin releasing hormone (GnRH) and dopaminergic activity within the brain during the onset of sexual precocity, a Halasz-like knife was developed to produce discrete parasagittal cuts in 2-week-old male broiler chicks. At 5 weeks of age, sexually precocious respondents were selected on the basis of advanced secondary sex characteristics and randomly paired with sham-operated controls. Each pair of birds was perfused with heparinized saline followed by 4% paraformaldehyde. Sections 40 microns thick, obtained throughout the hypothalamus, were immunostained with either anti-GnRH or anti-tyrosine hydroxylase (TH) to ascertain dopaminergic activity. Alternate sections from each pair of brains were also treated with cytochrome oxidase to determine metabolic activity levels or with Nissl stain to localize the knife cuts. Analysis revealed an increase in GnRH immunoreactivity within the bed nucleus of the pallial commissure (nCPa) and paraventricular nucleus (PVN), as well as the median eminence (ME). An increase in TH immunoreactivity was observed in the nucleus intramedialis (nI). Also an increase in metabolic activity was seen in the PVN as revealed by cytochrome oxidase reactivity. It is hypothesized that during the onset of puberty there is an increase in immunoreactive GnRH cell numbers as a result of a decrease in the inhibition of the GnRH system, possibly involving the nI and PVN. The source of the dopamine reported in the ME could be from the nI and other nearby nuclei. Dopamine from the tubero-infundibular area may be one of the putative neurotransmitters responsible for the increased activity of GnRH within the ME of chicks showing precocious puberty.

Precocious puberty in chicks (Gallus domesticus) induced by central injections of neuropeptide Y

The objective of the study was to determine the role of neuropeptide Y (NPY) and biogenic amines on the onset of puberty in birds. Male broiler chicks were administered chronic intracerebroventricular (ICV) injections of 5 micrograms NPY which produced sexually precocious chicks, determined by advanced secondary sex characteristics. One or two weeks following the beginning of a series of NPY injections, the preoptic area (POA), bed nucleus of the pallial commissure (nCPa), paraventricular nucleus (PVN), and median eminence (ME) were analyzed for biogenic amines. Levels of L-dopa, the precursor of dopamine (DA) were increased within the ME of chicks that responded to treatments by showing advanced sexual maturation when an amino acid decarboxylase blocker was administered prior to sacrifice. The PVN of respondents showed several changes in biogenic amines, while the nCPa displayed a biogenic amine metabolite of unknown identity which was significantly lower in respondent chicks. In contrast to mammals, L-dopa was detectable within the nCPa, PVN, and ME regardless of whether an enzymatic blocker of amino acid decarboxylase was administered to chicks prior to sacrifice. Results suggest that increased brain levels of NPY and DA, the latter specifically occurring within the ME, are associated with the onset of puberty. Due to the several significant differences found in biogenic amino levels within the PVN of respondent chicks, this nucleus, similar to the ME may be a highly active and integrative neural structure during the onset of puberty in chicks.