Abstracts presented at the Poultry Science Association Annual Meeting, Edmonton, Canada, July 2006:
Expression of 5-HT1A and 5-HT2C receptors in the hypothalamus during the turkey reproductive cycle: Colocalization with tyrosine hydroxylase
T. Bakken1, S.W. Kang1, A. Thayananuphat1, J.A. Proudman2, and M.E. El Halawani1
Serotonin (5-HT) acts through dopamine (DA) and vasoactive intestinal peptide (VIP) to stimulate prolactin (PRL) release when infused into the third ventricle of the turkey brain. Dopamine also inhibits PRL release by antagonizing the stimulatory effect of VIP at the pituitary level. Recent studies have shown that a 5-HT2A/2C receptor agonist stimulates and a 5-HT1A receptor agonist inhibits PRL secretion. The stimulatory effect of 5-HT2A/2C receptor agonist appears to be mediated via DA cells in the nucleus premamillaris (PMN) and nucleus mamillaris lateralis (ML). The site of the inhibitory action of the 5-HT1A receptor agonist needs to be clarified. To clarify the involvement of 5-HT1A and 5-HT2C receptors in PRL regulation, in situ hybridization experiments were performed on tissue sections from the turkey hypothalamus. The nucleus preopticus medialis (POM), ML and PMN showed strong expression of 5-HT1A receptors, while 5-HT2C receptors were concentrated in the nucleus paraventricularis hypothalami (PVN), PMN and ML. The relative density of receptor expression in each hypothalamic region was compared between birds from different reproductive stages. A significant difference in 5-HT1A receptor expression was seen in the ML, PMN, and POM in birds of different stages, with photorefractory birds showing the highest and incubating birds the lowest expression. In the ML, 5-HT2C receptors density was significantly higher in incubating birds than short day birds. In the ML and PMN, 5-HT1A receptors were colocalized with tyrosine hydroxylase (TH) immunoreactive cells. The data presented, taken together with our previous findings showing that the two receptor subtypes are antagonistic to each other supports the notion that 5-HT, like DA, can both stimulate and inhibit PRL secretion, depending on the relative abundance of the two receptor subtypes.
1University of Minnesota, St. Paul
2USDA, Beltsville, MD
Characterization of the serotonergic system in the brainstem during the turkey reproductive cycle
S.W. Kang, T. Bakken, and M.E. El Halawani
University of Minnesota, St. Paul
The serotonergic system is an important regulator of the avian reproductive cycle. Our earlier studies indicated that serotonin (5-HT) played a pivotal role in the regulation of prolactin secretion. This regulatory effect of 5-HT was mediated via the DAergic system which expressed 5-HT receptors and with which 5-HT immunoreactive fibers were intermingled. However, little is known about the neuroanatomical distribution of the 5-HTergic system and its neuronal activity across the turkey reproductive cycle. These were investigated in the present study utilizing the expression of tryptophan hydroxylase 2 mRNA (TPH2), the rate limiting enzyme in the neuronal 5-HT biosynthesis. We identified three 5-HTergic neuronal groups in the brainstem of the turkey using in situ hybridization technique for TPH2 expression including: 1) A ventro-rostral mesencephalic group located in the area ventralis of Tsai (AVT), dorsal to the nucleus interpeduncularis (IP). 2) A dorsal mesencephalo-pontine group located in the dorsal and ventral to the nucleus linearis caudalis (LC), and 3) A ventro-caudal ponto-medullary group, occupying the raphe nucleus (R). Significant differences in TPH2 expression across reproductive states were observed within the ventro-rostral mesencephalic and dorsal mesenphalo-pontine groups. TPH2 expression was markedly less in reproductively quiescent non photostimulated hens as compared with laying and incubating hens. Photorefractory hens displayed intermediate TPH2 expression. However, 5-HT neurons of raphe nucleus group in the ventro-caudal ponto-medullary region did not show significant alterations in TPH2 expression during the turkey reproductive cycle. These findings indicate that the variations in reproductive hormones expression and secretion observed across the turkey reproductive cycle may be explained, in part, by changes in neuronal serotonergic activity in the turkey brainstem. This is the first study to show alterations in neuronal 5-HT synthesis and the 5-HT neuronal group involved during the different reproductive stages in avian species.
Distribution of vasoactive intestinal peptide-expressing neurons in the brain of the native Thai chicken (Gallus domesticus)
S. Kosonsiriluk1, N. Sartsoongnoen1, N. Prakobsaeng1, T. Bakken2, T. Songserm3, M.E. El Halawani2, and Y. Chaiseha1
Avian prolactin (PRL) secretion is under stimulatory control by vasoactive intestinal peptide (VIP), the PRL-releasing factor, residing in nucleus infundibuli hypothalami (IN). The release and expression of VIP/PRL system is photo-periodically regulated by gonad stimulatory photoperiod in temperate zone birds. The distribution of VIP-immunoreactivity (VIP-ir) in several brain areas of these species has been reported. This study was designed to characterize the distribution of VIP system in the native Thai chicken brain, a non-photoperiodic species. The differential VIP expression may give us insight into the mechanism(s) underlying the regulation of the reproductive cycle in this species. Immunohistochemistry technique with quantitative analysis was performed throughout the brain of laying hens. The results revealed that VIP-ir cells and fibers were found throughout the brain and predominantly located within the diencephalon; nucleus preopticus medialis, nucleus anterior medialis hypothalami, regio lateralis hypothalami, nucleus paraventricularis magnocellularis, nucleus ventromedialis hypothalami, IN, and median eminence. The greatest staining was found within the IN. VIP-ir neurons were also observed within nucleus accumbens, cerebellum, nucleus septalis lateralis, nucleus commissurae pallii, etc. The pattern of VIP-ir distributions in this study is similar to that reported previously in several avian species. The abundance of VIP neuronal network in hypothalamus of the native Thai chicken suggests of its importance in the regulation of reproductive behavior in equatorial birds.
1Suranaree University of Technology, Thailand
2University of Minnesota, St. Paul
3Kasetsart University, Thailand
The role of the retinal and extra retinal photoreceptors in reproductive activities of broiler breeder hens
I. Rozenboim1, N. Mobarkey1, and M.E. El Halawani2
The role of light in biological activities associated with egg production is well known. The decline in the rate of egg production during the reproductive season of the hen can be the result of incubation behavior as well as photorefractoriness both connected to photostimulation. Determining the role of the eye and the brain photoreception in the decline in reproductive activities was the objective of this study. Animals: 130 broiler breeder hens at 23 wk of age were divided into nine environmental and light controlled rooms (n=15), equipped with individual battery cages. Three rooms were photostimulated (14L:10D) with full light spectrum (white light; 29 lux; 0.16 W/m2), and served as control. Six rooms were equipped with two lighting systems provided; red (0.16 W/m2) and green (27.5 lux). Upon photostimulation three rooms were photostimulated by increasing red light to 14 h of light (green light remained on 6 h) and the last 3 rooms were photostimulated by increasing green light to 14 h of light (red light remained on 6 h). Reproductive activities were recorded daily, monthly blood samples were collected and plasma level of ovarian steroids, as well as LH was recorded. At 65 wk of age birds were killed, hypothalamic tissue and pituitary were removed and assay for GnRH, GnIH, VIP mRNA levels. Photostimulation with green light caused a significant delay in the reproductive activities manifested by low egg production and plasma gonadal steroid levels during the 12 wk of photostimulation. Cumulative eggs were the lowest during all the period of experiment. Hens photostimulated with red light had higher egg production, compare to white control and green light treated birds. Photostimulation with red light caused significant elevation in both GnRH and GnIH mRNA level. Retinal photostimulation (green light) together with non-photostimulation of extra-retinal photoreceptors (red light) delayed reproductive activities; where as extra-retinal photostimulation (red light) together with retinal non-photostimulation (green light) accelerated reproductive activities.
1Hebrew University of Jerusalem, Rehovot, Israel
2University of Minnesota, St. Paul
Distribution of cGnRH-I immunoreactive neurons and fibers in the brain of native Thai chicken (Gallus domesticus)
N. Sartsoongnoen1, S. Kosonsiriluk1, S.W. Kang2, J.R. Millam3, M.E. El Halawani2, and Y. Chaiseha1
Avian reproduction is primarily regulated by gonadotropin releasing hormone-I (GnRH-I) which is synthesized by neurosecretory cells in the hypothalamus. This decaneuropeptide stimulates the synthesis and release of pituitary gonadotropins. However, the data of the neuroendocrine regulation of native Thai chicken, a non-seasonally breeding tropical species are limited. The distribution of GnRH-I neurons has been reported in many temperate zone species. The GnRH-I neuronal system needs to be clarified in the native Thai chicken. The distribution of GnRH-I neurons of native Thai chicken brain was elucidated utilizing immunohistochemical technique. The results revealed that cGnRH-I-immunoreactive (cGnRH-I-ir)-cells and fibers were found mainly in the hypothalamus; nucleus preopticus medialis (POM), nucleus septalis lateralis, nucleus septalis medialis, nucleus accumbens, nucleus paraventricularis magnocellularis, nucleus periventricularis hypothalami, nucleus suprachiasmaticus, pars medialis, regio lateralis hypothalami, nucleus commissurae pallii (nCPa), nucleus habenularis medialis, nucleus habenularis lateralis, nucleus subhabenularis lateralis, and nucleus mesencephalicus nervi trigemini. The most abundance of cGnRH-I-ir neurons was found within the POM and nCPa. cGnRH-I-ir-fibers were mainly bilaterally located along the third ventricle with more abundance around the organum vasculosum lamina terminalis and very dense fibers were observed in the external layer of the median eminence as has been reported for other avian species. This present study confirms a pivotal role in the control of avian reproduction of non-seasonally breeding tropical species.
1Suranaree University of Technology, Thailand
2University of Minnesota, St. Paul
3University of California, Davis
Immunohistochemical localization of dopamine neurons in the brain of the native Thai chicken (Gallus domesticus)
N. Sartsoongnoen1, S. Kosonsiriluk1, N. Prakobsaeng1, A. Thayananuphat2, T. Songserm3, M.E. El Halawani2, and Y. Chaiseha1
Avian prolactin (PRL) secretion is regulated by vasoactive intestinal peptide (VIP). Dopamine (DA) acts centrally through D1 DA receptors to stimulate PRL secretion via an intact VIPergic system and activates D2 DA receptors and subsequently prevents VIP from stimulating the PRL release at the pituitary. The present study was aimed to characterize the distribution of the DAergic system in the native Thai chicken, a non-seasonally breeding tropical species, with paucity of information about its reproductive neuroendocrine regulation. An immunohistochemical method to localize tyrosine hydroxylase (TH) as a marker of the DAergic neuronal system was elucidated in the brain of laying hens. The results revealed that TH immunoreactive (TH-ir) cells and/or fibers were found throughout the brain and predominantly located within the diencephalon; nucleus preopticus medialis, nucleus paraventricularis magnocellularis, nucleus intramedialis, nucleus mamillaris medialis (MM), nucleus mamillaris lateralis (ML), and area ventralis (AVT). The greatest density was found within MM, ML, and AVT. The staining of TH-ir cells and fibers was also observed within nucleus accumbens, nucleus septalis lateralis, nucleus suprachiasmaticus, pars medialis, regio lateralis hypothalami, nucleus commissurae pallii, median eminence, etc. The distributions pattern of TH-ir observed in the present study is consistent with that reported previously in several avian species. It is suggested that DA may play a pivotal role in the regulation of reproduction activity in tropical species as in the case of temperate zone birds.
1Suranaree University of Technology, Thailand
2University of Minnesota, St. Paul
3Kasetsart University, Thailand
Dopamine and gondotrophin releasing hormone-I neuronal activation following photostimulation in the turkey
A. Thayananuphat1, S.W. Kang1, T. Bakken1, J.R. Millam2, and M.E. El Halawani1
Photoperiod plays a critical role in the regulation of turkey reproduction, but the precise neural pathways through which day length is detected, measured, and transduced into a reproductive neuroendocrine response have yet to be elucidated. Dopamine (DA) has been shown to play a regulatory role in prolactin (PRL) and luteinizing hormone-follicle stimulating hormone (LH-FSH) secretion. However the neuroanatomical interrelationship between DA and Gonadotrophin Releasing Hormone-I (GnRH-I)-LH/FSH and vasoactive intestinal peptide (VIP)-PRL systems in avian species is still unclear. In the present study, we used the photo-induced activation of c-fos mRNA expression and double in situ hybridization/ immunocytochemistry (ISH/ICC) to identify the DAergic neural group or subgroup that became active following photostimulation. In order to establish reproductive neuroendocrine system activation, double ISH/ICC was also conducted on c-fos-GnRH-I and c-fos-VIP. In addition, we investigated the optimal length of light required to induce c-fos mRNA expression. C-fos mRNA expression was observed in DA neurons within the nucleus premamillaris (PMN) and in GnRH-I neurons in nucleus commissurae pallii (nCPA), nucleus preopticus medialis (POM), and nucleus paraventricularis hypothalami (PVN) of short day birds exposed to a 30 minute of light period at 14 hours after first light. No c-fos expression was observed in nucleus infundibularis (IN) where VIP neurons secreting the PRL-releasing factor are located. c-fos mRNA expression in the PMN was higher in hens exposed to a 30 min light period at 14 or 16 hours after first light than at 8 and 20 hours, or in short day non-treated controls. The results revealed several brain areas which were activated by light and suggested that DA neurons in the PMN might contribute to the initiation of avian sexual reproduction.
1University of Minnesota, St Paul
2University of California, Davis
PSA Poster Presentations:
Inclusion levels of corn distillers grains with solubles and poultry byproduct meal in market turkey diets
S.L. Noll and J. Brannon
University of Minnesota, St. Paul
In the Midwestern U.S., animal protein and corn derived distillers grains with solubles (DDGS) are often priced favorably to enter diets at levels considered “excessive”. A feeding trial was conducted to examine different inclusion levels of poultry byproduct meal (PBM) and DDGS and their combined effect on market tom performance during 5-19 wks of age. Large White male turkey poults (Nicholas strain) were randomly assigned to pens (10/pen) at 5 wks age and fed one of the following diet treatments (T): 1. Corn and soybean meal control; 2. As T1 with PBM (8% ); 3. As T1 with PBM (12%); 4. As T1 with DDGS (10%); 5. As T1 with DDGS (20%); 6. As T 2 and T4; 7. As T2 and T5; 8. As T3 and T4; and, 9. As T3 and T5. Diets were formulated using digestible amino acids. Diet protein level was established by using intact protein to meet the digestible thr at 100% of the NRC recommendation. All diets were supplemented as needed with lys and met to meet the NRC recommendations. The ratio of calcium: phosphorus was maintained at 2:1 to accommodate higher levels of phosphorus. Each diet was fed to 10 replicate pens. The experimental design was a completely randomized block design with a factorial arrangement of PBM and DDGS inclusion levels. At 19 wks of age, dietary treatment affected 19-wk body weight and feed efficiency (5-19 wks) (P < 0.001). The BW of the corn-soy control diet (T1) averaged 20.18 kg. Diets containing PBM (8 or 12%) or DDGS (10 or 20%) were not significantly different from the control. BW of turkeys fed diets containing PBM (8 or 12%) in combination with 20% DDGS was less than that of the control by 3.3%. A significant interaction existed for inclusion of PBM and DDGS (P < 0.02) for feed efficiency. Feed/gain of turkeys fed diets containing PBM (8 or 12%) or DDGS (10 or 20%) were not different from the control. However, the feed/gain increased for turkeys fed diets containing PBM (8 or 12%) in combination with 20% DDGS and were different from the control by 5 to 6 points. In summary, performance of turkeys fed 20% DDGS diets was not different from the control except when used in combination with high levels of PBM.
Turkey beak trim and feed form.
1. Effect on turkey performance
S.L. Noll1 and H. Xin2
Commercial turkeys undergo beak trimming at the hatchery prior to placement on the farm. The practice has come under scrutiny as an animal welfare issue. The research was conducted to assess methods of beak trimming and feed form on early tom poult performance and subsequent performance to market. Large White male turkey poults (1600 total, Hybrid strain) were obtained. At the hatchery, poults were beak trimmed via methods of electric arc (E), hot blade (HB) or infrared (I). A non-trimmed control (C) was also obtained from the same lot of poults. Turkeys within each beak trim treatment were fed a commercially prepared diet. Diets were fed either in mash (M) or as crumbles/pellets(CP). Crumbles were fed to 6 wks of age with pellets fed to 18 wks of age. For each treatment combination there were 8 replicate pens. A completely randomized block design was used for assignment of treatments and a factorial model used in the analyses of variance. The level of statistical significance is set to 0.05 unless stated otherwise. Live weight at 18 wks of age was improved by the feeding of CP by 5.3% and cumulative feed efficiency by 9.5%. Beak trimming did not affect body weight. Feed efficiency was improved in beak trimmed birds as compared to the non-trimmed controls when fed mash feed only. Higher mortality to 6 wks of age was observed with the birds that had beaks trimmed by hot blade as compared to the non-trimmed control (P<.06). The greatest effect of beak trim treatment was the incidence of damage related to pecking and the amount of birds that were removed from the experiment due to pecking injuries. Removals averaged 19, 7, 11, and 21% for the untrimmed controls, and poults trimmed by E, I, and HB methods, respectively. Turkeys beak trimmed by HB exhibited more regrowth of the beak. The results indicate that beak trimming did not negatively affect production performance with the exception of the hot blade treatment. Beak trimming substantially reduced the incidence of pecking damage and culling when regrowth did not occur. Commercial market tom turkeys responded favorably to the feeding of pellets with increased body weight most likely as a result of increased early intake.
1University of Minnesota, St. Paul
2Iowa State University, Ames
Turkey beak trim and feed form. 2. Effect on turkey behavior
H.E. Kassube1, E. Hoerl Leone2, I. Estevez2, H. Xin3, and S. Noll1
Commercial market turkeys undergo beak trimming at the hatchery prior to farm placement in order to decrease aggressive activities, such as feather pecking and cannibalism, which lead to mortality. Limited research has been done to determine the effect this procedure has on turkey poults. The objectives of this study are to assess the method of beak trimming and feed form on turkey behavior. The hypothesis is that feed form and beak-trimming will modify feeding and aggression behavior. Male Large White commercial turkey poults were obtained from a hatchery following beak trimming by hot blade, electric arc, and infrared methods, along with a set of birds that were not beak-trimmed. The poults were randomly assigned to 16 replicate floor pens per beak treatment with eight pens each fed mash or crumbled pelleted feed to 18 wks of age. Behavior observations were conducted using Observer software package (Noldus) and a time budget was created for each focal bird. Three birds per pen were observed, for a total of 24 replicate focal birds per feed/beak-trim treatment combination. Statistical analyses were conducted with SAS (V.9). Feed form was found to modify the time budget. Results indicate that poults fed the mash feed spent a larger percentage of their time feeding than those fed pellets (9.3 vs. 2.9%), along with less time resting and standing. Beak trim treatment did not affect the time budget nor were there any interactions of beak trim treatment with feed form. No significant interaction between feed form and beak trim method was detected. However, there was a significant interaction between feed form and period for the percentage time spent standing and preening while sitting. There was also an interaction between beak-trim method and age period on the amount of time spent drinking and foraging. Finally, a three-way interaction of beak trim, feed form and observation period was observed for the time spent preening while standing. In conclusion, feed form was found to alter the time budget of the turkeys primarily by changing the amount of time spent eating.
1University of Minnesota, St. Paul
2University of Maryland, College Park
3Iowa State University, Ames
Leptin and its neural effector can modulate long bone growth in the chick
M.R. Zillhardt, A. Undersander, C.S. Carlson, and L.J. Mauro
University of Minnesota, St. Paul
Leptin is a potent hormone that can regulate feed intake and energy balance in domesticated and wild birds. It can act centrally, through activation of hypothalamic nuclei and the sympathetic nervous system, or directly on peripheral tissues. Studies in mammals suggest that leptin also can be a potent modulator of the skeleton. It is not known if this function of leptin and its neuroendocrine circuitry exists in poultry. To explore this mechanism for linking nutritional status, energy balance and skeletal quality, a bone explant culture model was used to test effects of chicken leptin (cLEP) and the sympathetic neurotransmitter, norepinephrine (NE), on the growth of embryonic chick bones. Contralateral pairs of tibiotarsi bones were dissected from day 10 chick embryos and incubated individually with cLEP (1 µM), NE (10 µM) or transforming growth factor-β (TGFβ:10 ng/ml-control for tissue viability). After 5 days in culture, measurements were taken of the length of proximal condyles and width of the mineralized band at the diaphyseal-epiphyseal junction as estimates of longitudinal growth and chondrocyte maturation respectively. cLEP treatment resulted in an increase in condyle length (CO 3.96±0.06 mm; cLEP 4.21±0.07 mm;p=0.0003) as well as the mineralized band (CO 318±35 µm; cLEP 640±77 µm; p=0.006). Similar effects were observed with NE treatment on length (CO 4.65±0.08 mm;NE 5.04±0.11 mm;p=0.006) and mineralization (CO 514±57 µm; NE 680±52;p=0.04). In contrast, TGFβ had no effect on length and reduced mineralization (CO 510±81 µm; TGFβ 260±52 µm;p=0.0003), consistent with its role as an inhibitor of proliferation and maturation. Immunohistochemical and quantitative real time PCR analysis for the expression of Type X Collagen, a marker of chondrocyte maturation, further supported these results. For example, NE treatment resulted in a ~2-fold increase in Type X expression (f=2-∆∆Ct;f=2.13±0.29). In addition, analysis of BrdU incorporation suggest a positive effect of leptin and NE on chondrocyte proliferation. These results provide compelling evidence that leptin and its effectors may function to regulate skeletal growth and homeostasis in poultry.
Abstracts presented at the Annual Meeting of the American Society for Virology, Madison, WI, July 15-19, 2006:
Species specific deletion of the viral glycoprotein of avian metapneumovirus
B. Kong, L.K. Foster, and D.N. Foster
University of Minnesota, St. Paul
The avian metapneumovirus (AMPV) genome encodes the fusion (F), small hydrophobic (SH), and attachment glycoprotein (G) as envelop glycoproteins. The F and G proteins mainly function to allow viral entry into host cells during the early steps of the virus life cycle. The highly variable AMPV G protein is a major determinant for distinguishing virus subtypes. Different lengths of the variable G protein (and resulting changes in the predicted amino acid and nucleotide sequences) have been reported (Govindarajan and Samal; Virus Genes 30:331-3, 2005; Lwamba et al.; Virus Res 107:83-92, 2005). Sequence analysis was used to determine if any differences between avian or mammalian cell propagated subtype C AMPV could be detected for the 1.8kb G gene. In agreement with Govindarajan and Samal (2005) and Bennett et al. (J Virol 79:14834-42, 2005), the complete 1.8kb G gene was found when AMPV was propagated in our immortal turkey turbinate (TT-1) cell line. Surprisingly, mammalian Vero cell propagated AMPV revealed an essentially deleted G gene in the viral genome, resulting in no G gene mRNA expression. Although the Vero cell propagated AMPV genome contained a small 122bp fragment of the G gene, no splicing mRNA variants were detected from either mammalian or avian propagated AMPV. The G gene truncation might be caused by subcellular molecular mechanisms that are species specific. The antigenic changes together with the lack of viral gene deletions suggest that avian cell propagated AMPV will provide a better alternative host for live vaccine development. |
