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To invest in energetically demanding life history stages, individuals require a substantial amount of resources. Physiological traits, particularly those related to energetics, can be useful for examining variation in life history decisions and trade-offs because they result from individual responses to environmental variation. Leptin is a protein hormone found in mammals that is proportional to the amount of endogenous fat stores within an individual. Recently, researchers have confirmed that a mammalian leptin analogue (MLA), based on the mammalian sequence of leptin, is present with associated receptors and proteins in avian species, with an inhibitory effect on foraging and body mass gain at high circulating levels. While MLA has been both quantified and manipulated in avian species, little is currently known regarding whether plasma MLA in wild-living species and individuals is associated with key reproductive decisions. We quantified plasma MLA in wild, Arctic-nesting female common eiders ( Somateria mollissima ) at arrival on the breeding grounds and followed them to determine subsequent breeding propensity, and reproductive phenology, investment, and success. Common eiders are capital-income breeding birds that require the accumulation of substantial fat stores to initiate laying and successfully complete incubation. We found that females with lower plasma MLA initiated breeding earlier and in a shorter period of time. However, we found no links between plasma MLA levels and breeding propensity, clutch size, or reproductive success. Although little is still known about plasma MLA, based on these results and its role in influencing foraging behaviors and condition gain, plasma MLA appears to be closely linked to reproductive timing and is therefore likely to underlie trade-offs surrounding life history decisions.

This study explored the trajectory of patients who remained on a general unit after medical emergency team activation. Of those who had a second activation within 24 hours, 80% occurred within 12 hours of the baseline activation. Chest pain and recent intensive care unit discharge were associated with having a second activation. There were statistically, not clinically, significant associations between mean vital signs and second activations; however, the patterns of change may be clinically useful.

Clinical research to identify effective interventions for decreasing nonactionable alarms has been limited. The objective of this study was to determine if a staff educational program on customizing alarm settings on bedside monitors decreased alarms in a medical intensive care unit (MICU). A preintervention, postintervention, nonequivalent group design was used to evaluate an educational program on alarm management in a convenience sample of MICU nurses. A 15-minute session was provided in a 1-week period. The outcome variable (number of alarms for low oxygen saturation via pulse oximetry [SpO 2 ]) was determined from monitor log files adjusted by patient census. Data were collected for 15 days before and after the intervention. χ 2 analysis was used, with P less than .05 considered significant. After 1 week of education, low SpO 2 alarms decreased from 502 to 306 alarms per patient monitored per day, a 39% reduction (P < .001). Instructions for nurses in the medical intensive care unit on individualizing alarm settings to patients' clinical condition decreased common monitor alarms by 39%., (©2016 American Association of Critical-Care Nurses.)

On average, avian blood glucose concentrations are 1.5-2 times those of mammals of similar mass and high concentrations of insulin are required to lower blood glucose. Whereas considerable data exist for granivorous species, few data are available for plasma metabolic substrate and glucoregulatory hormone concentrations for carnivorous birds and alligators. Birds and mammals with carnivorous diets have higher metabolic rates than animals consuming diets with less protein whereas alligators have low metabolic rates. Therefore, the present study was designed to compare substrate and glucoregulatory hormone concentrations in several birds of prey and a phylogenetically close relative of birds, the alligator. The hypothesis was that the combination of carnivorous diets and high metabolic rates favored the evolution of greater protein and fatty acid utilization leading to insulin resistance and high plasma glucose concentrations in carnivorous birds. In contrast, it was hypothesized that alligators would have low substrate utilization attributable to a low metabolic rate. Fasting plasma substrate and glucoregulatory hormone concentrations were compared for bald eagles (Haliaeetus leucocephalus), great horned owls (Bubo virginianus), red-tailed hawks (Buteo jamaicensis), and American alligators (Alligator mississippiensis). Avian species had high circulating β-hydroxybutyrate (10-21 mg/dl) compared to alligators (2.81 ± 0.16 mg/dl). In mammals high concentrations of this byproduct of fatty acid utilization are correlated with insulin resistance. Fasting glucose and insulin concentrations were positively correlated in eagles whereas no relationship was found between these variables for owls, hawks or alligators. Additionally, β-hydroxybutyrate concentrations were low in alligators. Similar to carnivorous mammals, ingestion of a high protein diet may have favored the utilization of fatty acids and protein for energy thereby promoting the development of insulin resistance and gluconeogenesis-induced high plasma glucose concentrations during periods of fasting in birds of prey., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

1. The present study compared the effects of fasting on circulating concentrations of glucose, insulin and glucagon in male and female modern meat-type chickens (Ross 708) at three ages (19 d, 33 d and 47 d). 2. Plasma concentrations of glucose were reduced by fasting with reductions of 24.9% (19-d-old), 22.6% (33-d-old) and 17.9% (47-d-old) in broiler chickens fasted for 12 h. 3. Plasma concentrations of insulin decreased with fasting. For instance, circulating concentrations of insulin declined after 6 h of fasting by 45.7%, 54.7% and 50.0%, respectively, in 19-d-old, 33-d-old and 47-d-old broiler chickens. 4. Plasma concentrations of glucagon were increased by fasting. Plasma concentrations of glucagon were elevated by 3.79% (19-d-old), 3.51% (33-d-old) and 3.79% (47-d-old) with 6 h of fasting and remained elevated with 12 h, 18 h and 24 h of fasting.

The sperm storage tubules (SST) of the turkey hen, which are located in the uterovaginal junction (UVJ) of the oviduct, maintain viable sperm for up to 10 wk after a single insemination. The mechanisms of this in vivo sperm storage are poorly understood. Our objective was to evaluate mRNA and protein expression of avidin and 2 avidin-associated factors, avidin-related protein-2 (AVR2) and progesterone receptor, in the oviducts of 2 different lines to determine the extent to which they were sperm responsive and tissue specific. At 38 wk of age, Hybrid Grade Maker and Converter turkey hens were artificially inseminated with diluted semen (AI) or were sham-inseminated with extender alone (SI). Forty-eight hours after insemination, total RNA was extracted from the UVJ epithelium (containing SST) and vaginal epithelium (VGE) of SI and AI hens. Real time-polymerase chain reaction data showed a clear tissue region-specific effect on gene expression in the turkey hen oviduct, with much greater (P < 0.0001) expression in the UVJ compared with VGE region for avidin and AVR2 mRNA in both lines and for progesterone receptor mRNA in the Converter line. In contrast to real-time PCR data, in situ hybridization of SI and AI tissues showed that the presence of sperm increased avidin mRNA in the SST and UVJ surface epithelium in the Converter hens. Immunohistochemistry confirmed the presence of avidin protein in the epithelium of the UVJ in both lines; however, whereas avidin protein was localized in the SST of SI-Grade Maker hens, this protein was not detected in the SST of Converter hens. The upregulation of avidin and AVR2 mRNA within the sperm storage region indicates the involvement of avidin, and perhaps avidin analogs, in the sustained storage of sperm in the SST, possibly through the binding of biotin to avidin. The absence of avidin protein in the SST and VGE of Converter hens in the presence of increased mRNA may indicate a rapid turnover of protein.

The aim of this study is to elucidate whether insulin acts differentially within the central nervous system (CNS) of two types of commercial chicks to control ingestive behavior. Male layer and broiler chicks (4-day-old) were intracerebroventricularly (ICV) injected with saline or insulin under satiated and starved conditions. Feed intake was measured at 30, 60 and 120 min after treatment. Secondly, blood and hypothalamus were collected from both chick types under ad libitum feeding and fasting for 24 h. Plasma insulin concentration was measured by time-resolved fluoro-immunoassay. Hypothalamic insulin receptor mRNA expression levels were measured by quantitative RT-PCR. The ICV injection of insulin significantly inhibited feed consumption in layer chicks when compared with saline (P<0.05), but not broiler chicks (P>0.1). Plasma insulin concentration of both chick types significantly decreased following 24 h of fasting, while insulin concentrations in the broiler chicks were significantly higher compared to the layers fed under ad libitum conditions. Hypothalamic insulin receptor mRNA expression levels were significantly lower (P<0.05) in broiler chicks than in layer ones under ad libitum feeding. Feed deprivation significantly decreased insulin receptor mRNA levels in layer chicks (P<0.01), but not in broiler chicks (P>0.1). Moreover, plasma insulin concentrations correlated negatively with hypothalamic insulin receptor protein expression in the two types of chicks fed ad libitum (P<0.05). These results suggest that insulin resistance exists in the CNS of broiler chicks, possibly due to persistent hyperinsulinemia, which results in a down-regulation of CNS insulin receptor expression compared to that in layer chicks., (Copyright © 2011 Elsevier Inc. All rights reserved.)

The embryo to neonate transition is a critical period of development that has significant impact on broiler production. During this time important genetic programs governing metabolism and growth are established. The goal of this work was to study the effects of early post-hatch (PH) development and the time of initiation of feeding on activation of the genetic program regulating hepatic lipogenesis. A comparison of liver total RNA samples at hatch and 7 days PH was performed using oligonucleotide-based (Affymetrix GeneChip®) chicken genome microarrays. During the first week PH there was significant up-regulation of key lipogenic genes including: ATP citrate lyase (ACL), malic enzyme (ME), fatty acid synthase (FAS), acetyl-CoA carboxylase alpha (ACCα), stearoyl-CoA desaturase-1 (SCD-1), sterol regulatory element binding protein-2 (SREBP-2) and thyroid hormone responsive spot 14α (Spot 14α) among others. These findings were confirmed using gene-specific RT-PCR assays. In a follow-up study, we investigated the effects of withholding feed for the first 48 h PH (delayed feeding, DF) on lipogenic gene expression through 8 days PH. Body weight gain was significantly depressed by DF. Plasma levels of the major metabolic hormones that regulate lipogenic gene expression (insulin, glucagon and T(3)) changed significantly during PH development, but were largely unaffected by DF. Plasma glucose was significantly lower in the DF group at 24h PH but recovered thereafter. In general, DF inhibited the up-regulation of lipogenic genes until feeding was initiated. Delayed up-regulation was also observed for the lipogenic transcription factor genes, SREBP-1, SREBP-2 and peroxisome proliferator-activated receptor gamma (PPARγ), but not for carbohydrate response element binding protein (ChREB) or liver X receptor (LXR). Our results offer additional insight into the transcriptional programming of hepatic lipogenesis in response to the transition from high fat (yolk) to high carbohydrate (feed) nutrition that occurs during early PH development., (Published by Elsevier Inc.)

Research addressing digestible Lys requirement data of modern broilers from 4 to 6 wk of age is limited. Male broilers (1,632 Ross×Ross TP16 and 3,000 Cobb×Cobb 700) were used in separate experiments to determine the digestible Lys requirements from 28 to 42 d. In each experiment, 2 diets (dilution and summit) consisting of corn, soybean meal, animal protein meal, and peanut meal were formulated to be adequate in all other amino acids. The dilution and summit diets were blended to create 9 titration diets. A control diet formulated to contain corn, soybean meal, and animal protein meal as the primary ingredients was used for comparison with the titration diets. Body weight gain, feed intake, digestible Lys intake, digestible Lys intake:BW gain, feed conversion, mortality, carcass yields, and physiological measurements were assessed during experimentation. Digestible Lys requirements were estimated using a quadratic broken-line model. In experiment 1, the digestible Lys requirement for male Ross×Ross TP16 broilers was determined at 0.988, 1.053, 0.939, and 0.962%, respectively, for BW gain, feed conversion, carcass weight, and total breast meat weight. In experiment 2, the digestible Lys requirement for male Cobb×Cobb 700 broilers ranged from 0.965, 1.012, 1.029, 0.987, and 0.981%, respectively, for 28- to 42-d BW gain, feed conversion, carcass weight, total breast meat weight, and total breast meat yield. Digestible Lys requirements for male Ross×Ross TP16 and Cobb×Cobb 700 broilers were estimated at 1.001 and 0.995%, respectively, based upon averages of live performance and meat yield responses. Both strains required the highest requirement estimate of digestible Lys to optimize feed conversion.

A trial was conducted to determine the effects of different rearing feed regimens on plasma hormone and metabolite levels and hepatic lipid metabolism and gene expression on sexually mature broiler breeders. Cobb 500 birds were divided into 2 groups at 4 wk and fed either an everyday (ED) or skip-a-day (SKP) regimen. At 24 wk of age, all birds were switched over to an ED regimen. At 26.4 wk, breeder hens were randomly selected and killed at intervals after feeding. Livers were sampled from 4 hens at 4-h intervals for 24 h for a total of 28 samples per treatment. Blood was sampled from 4 hens per sampling time; sampling times were 0, 30, and 60 min and 2 and 4 h after feeding and then every 4 h up to 24 h for a total of 36 samples per treatment. Main feeding regimen, time, and interaction effects were analyzed. Significant interaction effects were found between time and feeding regimen for acetyl-coenzyme A carboxylase and malic enzyme mRNA expression. The peak for acetyl-coenzyme A carboxylase expression was higher in ED-reared birds, whereas the peak for malic enzyme expression was higher in SKP-reared birds. Overall, plasma levels of insulin-like growth factor-II were higher in SKP-reared birds. Overall, plasma corticosterone levels were also higher in SKP-reared birds and significant interaction effects between time and feeding regimen were seen. The expression of apolipoprotein A1 was significantly higher in ED-reared birds: significant interaction effects were also noted. Other researchers also found some of the differences observed in the present study in 16-wk-old pullets. In summary, different feeding regimens alter metabolic responses, some of which carry over into sexual maturity.

Leptin, a protein hormone secreted by fat cells, is best known for its role as an adiposity signal; however, leptin has diverse physiological roles ranging from regulation of feeding behavior and body weight, to effects on reproduction and immune function. Although leptin has been extensively studied in mammals, the identification and function of leptin in birds remains controversial, and studies have focused on captive or domesticated species. Here, we describe changes in plasma leptin-like immunoreactivity during the reproductive and non-reproductive seasons in free-living female European starlings (Sturnus vulgaris). Plasma leptin-like immunoreactivity was high during egg-laying (27.8+/-2.4 ng/mL) and clutch completion (23.8+/-1.6 ng/mL), decreased during incubation (13.0+/-1.6 ng/mL) and chick-rearing (12.0+/-1.3 ng/mL), but was elevated again in non-breeders in November (23.7+/-1.1 ng/mL). Although there was marked and consistent variation in total body mass and body composition with breeding stage and season in this population, plasma leptin-like immunoreactivity did not parallel changes in body mass or body composition. These data suggest that the strong positive relationship between plasma leptin-like immunoreactivity and body mass reported for captive birds and mammals does not hold for free-living birds. Rather, among free-living female European starlings, variation in plasma leptin-like immunoreactivity is associated with breeding stage or seasonal variation per se, and we discuss possible mechanisms underlying this variation, focusing on ovarian function and egg production., (Copyright 2009 Elsevier Inc. All rights reserved.)

To understand how the proghrelin system functions in regulating growth hormone release and food intake as well as defining its pleiotropic roles in such diverse physiological processes as energy homeostasis, gastrointestinal tract function and reproduction require detailed knowledge of the structure and function of the components that comprise this system. These include the preproghrelin gene that encodes the proghrelin precursor protein from which two peptide hormones, ghrelin and obestatin, are derived and the cognate receptors that bind proghrelin-derived peptides to mediate their physiological actions in different tissues. Also key to the functioning of this system is the posttranslational processing of the proghrelin precursor protein and the individual peptides derived from it. While this system has been intensively studied in a variety of animal species and humans over the last decade, there has been considerably less investigation of the avian proghrelin system which exhibits some unique differences compared to mammals. This review summarizes what is currently known about the proghrelin system in birds and offers new insights into the nature and function of this important endocrine system. Such information facilitates cross-species comparisons and contributes to our understanding of the evolution of the proghrelin system.

This study investigated the effects of fasting and refeeding on AMP-activated protein kinase (AMPK) and carbohydrate response element binding protein (ChREBP) mRNA, protein and activity levels; as well as the expression of lipogenic genes involved in regulating lipid synthesis in broiler chicken (Gallus gallus) liver. Fasting for 24 or 48 h produced significant declines in plasma glucose (at 24 h), insulin and thyroid hormone (T3) levels that were accompanied by changes in mRNA expression levels of hepatic lipogenic genes. The mRNA levels of malic enzyme (ME), ATP-citrate lyase (ACL), acetyl-CoA carboxylase alpha (ACCalpha), fatty acid synthase (FAS), stearoyl-CoA desaturase-1 (SCD-1) and thyroid hormone responsive Spot 14 (Spot 14) declined in response to fasting. Refeeding for 24 h increased mRNA levels for each of these genes, characterized by a significant increase ('overshoot') above fed control values. No change in mRNA expression of the two AMPK alpha subunit genes was observed in response to fasting or refeeding. In contrast, ChREBP and sterol regulatory element binding protein-1 (SREBP-1) mRNA levels decreased during fasting and increased with refeeding. Phosphorylation of AMPK alpha subunits increased modestly after a 48 h fast. However, there was no corresponding change in the phosphorylation of ACC, a major downstream target of AMPK. Protein level and DNA-binding activity of ChREBP increased during fasting and declined upon refeeding as measured in whole liver tissue extracts. In general, evidence was found for coordinate transcriptional regulation of lipogenic program genes in broiler chicken liver, but specific regulatory roles for AMPK and ChREBP in that process remain to be further characterized.

Understanding how the proglucagon system functions in maintaining glycemic control and energy balance in birds, as well as defining its specific roles in regulating metabolism, gastrointestinal tract function and food intake requires detailed knowledge of the components that comprise this system. These include proglucagon, a precursor protein from which glucagon and two glucagon-like peptide hormones (GLP-1 and GLP-2) are derived, and the membrane bound G-protein-coupled receptors that specifically bind glucagon, GLP-1 and GLP-2 to mediate their individual physiological actions. Another key feature of the proglucagon system that is important for regulating its activity in different tissues involves post-translational processing of the proglucagon precursor protein and the individual peptide hormones derived from it. Currently, there is limited information about the proglucagon system in birds with the majority of that coming from studies involving chickens. By summarizing what is currently known about the proglucagon system in birds, this review aims to provide useful background information for future investigations that will explore the nature and actions of this important hormonal system in different avian species.

An investigation was conducted to study insulin-like growth factor (IGF)-I, IGF-II, insulin, glucagon, leptin, triiodothyronine (T(3)), and thyroxine (T(4)) levels in a chicken population divergently selected for P bioavailability (PBA). There were differences in growth and feed efficiency between the 2 lines. Concentrations of IGF-I, IGF-II, and T(3) were significantly greater in the high PBA line compared with the low PBA line, whereas the reverse was true for glucagon. There were no correlations between IGF-I and II and PBA in either line, suggesting that the line differences may be the result of factors other than PBA. Glucagon and IGF-I have different relationships with feed conversion ratio in the high PBA line compared with the low PBA line. There was a significant correlation between PBA and T(3) in the low line and between PBA and T(4) in the high PBA line. Thyroid hormone levels may be an indirect indicator of PBA in growing chickens. The genes in the thyroid hormone pathway may be key in the identification of genes associated with PBA.

To better understand how the proglucagon system functions in birds, we utilized a molecular cloning strategy to sequence and characterize the chicken proglucagon gene that encodes glucagon, glucagon-like peptide (GLP)-1 and GLP-2. This gene has seven exons and six introns with evidence for an additional (alternate) first exon and two promoter regions. We identified two distinct classes of proglucagon mRNA transcripts (PGA and PGB) produced by alternative splicing at their 3'-ends. These were co-expressed in all tissues examined with pancreas and proventriculus showing the highest levels of each. Although both mRNA classes contained coding sequence for glucagon and GLP-1, class A mRNA lacked that portion of the coding region (CDS) containing GLP-2; whereas, class B mRNA had a larger CDS that included GLP-2. Both classes of mRNA transcripts exhibited two variants, each with a different 5'-end arising from alternate promoter and alternate first exon usage. Fasting and refeeding had no effect on proglucagon mRNA expression despite significant changes in plasma glucagon levels. To investigate potential differences in proglucagon precursor processing among tissues, mRNA expression for two prohormone convertase (PC) genes was analyzed. PC2 mRNA was predominantly expressed in pancreas and proventriculus, whereas PC1/3 mRNA was more highly expressed in duodenum and brain. We also determined mRNA expression of the specific receptor genes for glucagon, GLP-1 and GLP-2 to help define major sites of hormone action. Glucagon receptor mRNA was most highly expressed in liver and abdominal fat, whereas GLP-1 and GLP-2 receptor genes were highly expressed in the gastrointestinal tract, brain, pancreas and abdominal fat. These results offer new insights into structure and function of the chicken proglucagon gene, processing of the precursor proteins produced from it and potential activity sites for proglucagon-derived peptide hormones mediated by their cognate receptors.

A trial was conducted to determine the effects of different feeding regimens on plasma hormone and metabolite levels in 16-wk-old broiler breeder pullets. A flock of 350 Cobb 500 breeder pullets was divided in 2 at 28 d of age and fed either every day (ED, 5 pens of 35 birds) or skip-a-day (SKIP, 5 pens of 35 birds) from 28 to 112 d of age. Total feed intake did not differ between the 2 groups. At 112 d, 52 randomly selected pullets from the larger flock of ED-fed pullets, and 76 from the SKIP-fed pullets were individually caged and fed a meal of 74 g (ED) or 148 g (SKIP). Blood samples were collected from 4 pullets in each group by cardiac puncture at intervals after feeding. Plasma was analyzed for insulin, glucagon, insulin-like growth factor-I and insulin-like growth factor-II, triiodothyronine and thyroxine, corticosterone, leptin, glucose, nonesterified fatty acids, triglycerides, and uric acid. Feed retention in the crop was also noted at each interval. In ED birds, the crop was empty by 12 h and in SKIP birds, the crop was empty by 24 h after feeding. The physiological responses to fasting, such as increased glucagon and corticosterone and reduced plasma triglyceride, occurred at times coincidental with crop emptying in both ED and SKIP birds. Overall, mean insulin-like growth factor-I levels were higher (P < 0.05) in ED birds. Triiodothyronine was higher (P = 0.09) in SKIP birds. Overall mean plasma corticosterone was 2-fold higher in SKIP-fed birds, which may be related to the increased length of fasting periods, hunger, and stress. Plasma leptin was consistently higher in ED-fed birds, which was indicative of their more consistent food supply and more stable energy status. In summary, the experiment reported here shows that different feeding regimens can alter hormone and metabolite profiles, in spite of total feed intakes being equal.

Inheritance of embryo thyroid function was measured in lines of turkeys. Two lines that had been selected for either increased egg production (E) or increased 16-wk BW (F) and their respective randombred controls (i.e., RBC1 and RBC2) were examined. Reciprocal crosses of dams and sires from each selected line and its randombred control were made to estimate sire line and dam line effects. Orthogonal contrasts were used to determine if the differences found were due to the presence of additive, nonadditive, or maternal, sex-linked, or both, gene effects. With the data involved, sex-linkage and maternal effects could not be separated. Embryo survival was measured for all lines and their reciprocal crosses. Crossing the RBC1 sire and E dam also resulted in better embryo survival and lower death losses at pipping than for the other cross- or purelines. Reciprocal crosses of the F and RBC2 lines showed better total embryo survival, and they survived pipping better than the F or RBC2 purelines. Thyroxine (T(4)) and triiodothyronine (T(3)) concentrations differed between the reciprocal crosses at external pipping, but the effects were inconsistent for the 2 data sets. Reciprocal tests indicated that maternal, sex-linked, or both, effects were present for T(3) concentrations at internal pipping in the E and RBC1 lines and at external pipping for the F and RBC2 lines. Reciprocal effects were significant for T(4) at internal pipping for both data sets. The RBC1 sire embryos had significantly higher T(3):T(4) ratios than the E line sire embryos at internal and external pipping, and the pureline RBC1 embryos had consistently higher ratios than the pureline E embryos. The differences for the T(3):T(4) ratios between these 2 lines at internal pipping, external pipping, and hatch appeared to be consistently additive in nature, although significant nonadditive or heterotic effects were present for the ratio at external pipping. Similar effects on the T(3):T(4) ratio were observed for the F and RBC2 lines at external pipping.

Components of the insulin-like growth factor (IGF) system were investigated in chondrocytes isolated from the avian growth plate. The genes for IGF-I, IGF-II, type 1 IGF receptor (IGF-R), IGF binding protein-2 (IGFBP-2), IGFBP-3, IGFBP-5 and IGFBP-7 were found to be expressed in both proliferative and hypertrophic chondrocytes. The expression of IGF-II in proliferative chondrocytes was extremely high relative to IGF-I. Although IGF-I expression was significantly increased in hypertrophic chondrocytes, the level was still low relative to IGF-II. In cell culture, IGF-I stimulated proteoglycan synthesis and increased the expression of Indian hedgehog (Ihh) and type X collagen, markers of chondrocyte differentiation. IGF-II was found to be equally efficacious in stimulating proteoglycan biosynthesis. These observations suggest that IGF-II may play a significant role in avian growth plate physiology, which is consistent with several reports on mammalian endochondral bone growth.

Treatment of fetal rats and embryonic chickens with exogenous glucocorticoids induces premature GH cell differentiation. However, it is unknown whether the developing adrenal gland is capable of mounting this response autonomously. The present study determined whether stimulation of the adrenal gland in developing chicken embryos through administration of ACTH could induce a premature increase in GH cells. We found that plasma corticosterone and ACTH levels increased between embryonic day (e) 11 and e17, consistent with GH cell (somatotroph) ontogeny. Injection of ACTH into eggs on e9, e10, or e11 increased somatotrophs on e14. In contrast, thyroid-stimulating hormone, CRH, alpha-MSH, GHRH, and TRH were ineffective. Culture of e11 pituitary cells with ACTH failed to induce somatotrophs, suggesting an indirect action of ACTH on GH cells in vivo. Intravenous administration of ACTH dramatically increased plasma levels of corticosterone within 1 h and increased the percentage of pituitary somatotrophs within 24 h. Although ACTH administration increased the relative abundance of pituitary GH cells, there was no effect on plasma levels of GH, IGF-I, or IGF-II, or in hepatic expression of IGF-I or IGF-II mRNA. We conclude that ACTH administration can increase the population of GH cells in the embryonic pituitary. However, this treatment alone does not lead to downstream activation of hepatic IGF production. These findings indicate that the embryonic adrenal gland, and ultimately anterior pituitary corticotrophs, may function to regulate pituitary GH cell differentiation during embryonic development.

Developmental hormonal changes in Cobb 500 chick embryos and hatched chicks were determined by measuring plasma insulin, glucagon, insulin-like growth factor (IGF)-I, IGF-II, triiodothyronine, thyroxine, and glucose concentrations at different ages of embryogenesis and posthatch development. Plasma samples were obtained daily from 10 d of embryogenesis (10E) through 13 d posthatch and also at 17 and 21 d posthatch. A significant increase in plasma insulin was observed with increasing age from 10E to hatch. Plasma glucagon levels remained low until 17E, and then significantly increased approximately 3-fold at hatch, which corresponded with increasing plasma glucose levels during late embryo development. The plasma insulin to glucagon molar ratio of incubation from 14E to 17E ranged from 2 to 4, and was significantly higher than at any other time during incubation. These results indicate that insulin may be an important promoter of chick embryonic growth by the anabolic drive to promote protein deposition. Insulin and glucagon increased after hatch, which may be due to increased feed consumption and increased utilization of carbohydrates as the key energy source, compared with nutrients obtained through lipolysis and proteolysis in the embryos. Plasma triiodothyronine increased 4-fold from 18E to 20E, and thyroxine increased 3-fold from 16E to 19E. Insulin-like growth factor-I and IGF-II peaked at 14E. Insulin-like growth factor-I steadily increased above embryonic levels during the 3 wk of the posthatch period, whereas IGF-II levels steadily declined. These results suggest that IGF-II may be a more important functionary for chick embryonic development than IGF-I, and that IGF-I may be more important than IGF-II after hatch. The profile of metabolic hormones in the present study may help support an understanding of significant changes that occur in embryonic development and posthatch growth in chicks.

The current study is a comprehensive genome analysis to detect QTL affecting metabolic traits in chickens. Two unique F(2) crosses generated from a commercial broiler male line and 2 genetically distinct inbred lines (Leghorn and Fayoumi) were used in the present study. The plasma glucagon, insulin, lactate, glucose, tri-iodothyronine, thyroxine, insulin-like growth factor I, and insulin-like growth factor II concentrations at 8 wk were measured in the 2 F(2) crosses. Birds were genotyped for 269 microsatellite markers across the entire genome. The program QTL Express was used for QTL detection. Significance levels were obtained using the permutation test. For the 10 traits, a total of 6 and 9 significant QTL were detected at a 1% chromosome-wise significance level, of which 1 and 6 were significant at the 5% genome-wise level for the broiler-Leghorn cross and broiler-Fayoumi cross, respectively. Most QTL for metabolic traits in the present study were detected in Gga 2, 6, 8, 9, 13, and Z for the broiler-Leghorn cross and Gga 1, 2, 4, 7, 8, 13, 17, and E47 for the broiler-Fayoumi cross. Phenotypic variation for each trait explained by all QTL across genome ranged from 2.73 to 14.08% in the broiler-Leghorn cross and from 6.93 to 21.15% in the broiler-Fayoumi cross. Several positional candidate genes within the QTL region for metabolic traits at the 1% chromosome-wise significance level are biologically associated with the regulation of metabolic pathways of insulin, triiodothyronine, and thyroxine.

The 5'-AMP-activated protein kinase (AMPK) plays a key role in regulating cellular energy homeostasis. The AMPK is a heterotrimeric enzyme complex that consists of 1 catalytic (alpha) and 2 regulatory (beta and gamma) subunits. Mutations of the gamma subunit genes are known to affect AMPK functioning. In this study, we characterized the genomic organization and expression of 3 chicken AMPK gamma subunit genes (cPRKAG). Alternative splicing of the second exon of the cPRKAG1 gene resulted in 2 transcript variants that code for predicted proteins of 298 and 276 amino acids. Use of an alternate promoter and alternative splicing of the cPRKAG2 gene resulted in 4 transcript variants that code for predicted proteins of 567, 452, 328, and 158 amino acids. Alternative splicing of exon 3 of the cPRKAG3 gene resulted in the production of "long" and "short" transcript variants that code for predicted proteins of 382 and 378 amino acids, respectively. We found evidence for differential expression of individual gamma subunit gene transcript variants and, in some cases, tissue-specific expression was observed. The cPRKAG subunit genes displayed similar structural features and high sequence homology compared with corresponding mammalian gamma subunit gene homologues.

Three hundred twenty Cobb 500 broiler breeder pullets at 21 wk of age were selected from a flock fed according to Cobb Breeder Management Guide specifications. One hundred sixty pullets at 21 wk of age were switched to ad libitum feeding, and the remaining 160 pullets continued to be control-fed. The pullets were photostimulated at 22 wk and maintained until 36.5 wk. Plasma samples were obtained, BW was determined, and hens were killed for determination of body composition at the following periods: 24 h prior to photostimulation, 2.5 wk after photostimulation, 24 h after first egg, and 36.5 wk following peak egg production. Compared with ad libitum-fed breeders, the restricted breeders had a higher percentage carcass protein and lower percentage carcass fat at all sampling periods. Total egg numbers were greater, and abnormal eggs were less for the restricted pullets compared with the ad libitum-fed pullets at 36.5 wk. Carcass percentage fat of ad libitum-fed pullets was positively related to plasma glucagon, insulin-like growth factor-II (IGF-II), and 17beta-estradiol but negatively related to plasma insulin, insulin/glucagon M ratio, insulin-like growth factor-I (IGF-I), thyroxine (T4), and triiodothyronine (T3). Carcass percentage fat of feed-restricted pullets was negatively related to IGF-I, IGF-II, and T4. The T4 was the most important hormone for predicting the percentage carcass fat in ad libitum-fed pullets, and IGF-I was the most important hormone for predicting the percentage carcass fat in feed-restricted pullets. The percentage carcass protein for ad libitum-fed breeders was positively correlated to IGF-I, T4, T3, insulin/glucagon M ratio, and insulin. Carcass percentage protein for feed-restricted breeders was positively correlated to IGF-I, IGF-II, T4, and glucagon. Stepwise regressions for predicting percentage carcass protein for breeders fed by both systems shows that T3 and IGF-I concentrations were the most important for ad libitum-fed breeders, whereas IGF-II and T4 were best for feed-restricted breeders. The hormone status of breeders may be a key indicator to help predict the body composition and thus support management decisions for maintaining optimum production.

Birds have much higher plasma glucose and fatty acid levels compared to mammals. In addition, they are resistant to insulin-induced decreases in blood glucose. Recent studies have demonstrated that decreasing fatty acid utilization alleviates insulin resistance in mammals, thereby decreasing plasma glucose levels. This has yet to be examined in birds. In the present study, the levels of glucose and beta-hydroxybutyrate (BOHB), a major ketone body and indicator of fatty acid utilization, were measured after the administration of chicken insulin, acipimox (an anti-lipolytic agent), or insulin and acipimox in mourning doves (Zenaidura macroura). Insulin significantly decreased whole blood glucose levels (19%), but had no effect on BOHB concentrations. In contrast, acipimox decreased blood BOHB levels by 41%, but had no effect on whole blood glucose. In addition to changes in blood composition, levels of glucose uptake by various tissues were measured after the individual and combined administration of insulin and acipimox. Under basal conditions, the uptake of glucose appeared to be greatest in the kidney followed by the brain and skeletal muscle with negligible uptake by heart, liver and adipose tissues. Acipimox significantly decreased glucose uptake by brain (58% in cortex and 55% in cerebellum). No significant effect of acipimox was observed in other tissues. In summary, the acute inhibition of lipolysis had no effect on glucose uptake in the presence or absence of insulin. This suggests that free fatty acids alone may not be contributing to insulin resistance in birds.

Ghrelin, a peptide hormone produced by the stomach in mammals, stimulates growth hormone release and food intake. Recently, ghrelin was identified and characterized in chicken proventriculus and shown to stimulate growth hormone release but inhibit feed intake. The purpose of this work was to identify and further characterize the ghrelin gene in chickens and in turkeys. Using molecular cloning techniques we have sequenced cDNAs corresponding to chicken (White Leghorn) and turkey ghrelin mRNAs. A total of 844 (chicken) or 869 (turkey) bases including the complete coding regions (CDS), and the 5'- and 3'-untranslated regions (UTRs) were determined. Nucleotide sequence (CDS) predicted a 116 amino acid precursor protein (preproghrelin) for both the chicken and the turkey that demonstrated complete conservation of an N-terminal 'active core' (GSSF) including a serine (position 3 of the mature hormone) known to be a modification (acylation) site important for ghrelin bioactivity. Additional nucleotide sequence was found in the 5'-UTRs of both Leghorn and turkey cDNAs that was not present in broilers or the red jungle fowl. The turkey ghrelin gene, sequenced from genomic DNA templates, contained five exons and four introns, a structure similar to mammalian and chicken ghrelin genes. Ghrelin was highly expressed in proventriculus with much lower levels of expression in other tissues such as pancreas, brain, and intestine. RT-PCR was used to quantify ghrelin mRNA levels relative to 18S rRNA in 3-week-old male broiler chickens. The level of ghrelin mRNA increased in proventriculus in response to fasting but did not decline with subsequent refeeding. Plasma ghrelin levels did not change significantly in response to fasting or refeeding and did not appear to reflect changes in proventriculus ghrelin mRNA levels. Ghrelin mRNA levels declined in broiler pancreas after a 48 h fast and increased upon refeeding. Expression of the gene encoding the receptor for ghrelin (growth hormone secretagogue receptor, GHS-R) and a variant form was detected in a variety of tissues collected from 3-week-old male broiler chickens possibly suggesting autocrine/paracrine effects. These results offer new information about the avian ghrelin and ghrelin receptor genes and the potential role that this system might play in regulating feed intake and energy balance in poultry.

We designed three experiments to determine both the optimal dose of and time on experiment for methimazole (MMI; 1-methyl-2-mercaptimidazole). Our goals were to determine if chicken growth was related to thyroid hormone levels and if intermediary metabolism changed along with changes in thyroid hormone levels. Initiating MMI at one week of age decreased (P<0.01) plasma thyroid levels and growth in four-week old birds. In contrast, initiating MMI at two and three weeks of age decreased (P<0.05) hormone levels without affecting growth as severely. Although initiating MMI at two weeks of age depressed (P<0.05) plasma thyroid hormones at four weeks, there was little change in vitro lipogenesis at four weeks. Again, initiating MMI at one week of age decreased body weight, plasma thyroid hormones and in vitro lipogenesis at four weeks of age. In addition, this treatment also decreased (P<0.05) malic enzyme activity at this same age period. The second experiment showed that MMI, initiated at 14 days, had no significant effect on 28-day body weight and again decreased both plasma T(3) and T(4) but T(3) replacement increased plasma T(3) in both 14-28-day treatment groups. All body weights were similar at 30 days, however. Lastly, diets containing graded levels of MMI decreased thyroid hormones and body weight (0>0.25>0.5>1 g MMI/kg). In contrast, only the two higher levels (0.5 and 1 g MMI/kg) decreased in vitro lipogenesis. Growth depression, caused by MMI feeding, can occur without changes in lipid metabolism. The length of MMI administration may be as important as dose level in obtaining effects (growth, thyroid hormone depression and inhibition of lipogenesis).

In mammals, AMP-activated protein kinase (AMPK) is involved in the regulation of cellular energy homeostasis and, on the whole animal level, in regulating energy balance and food intake. Because the chicken is a valuable experimental animal model and considering that a first draft of the chicken genome sequence has recently been completed, we were interested in verifying the genetic basis for the LKB1/AMPK pathway in chickens. We identified distinct gene homologues for AMPK alpha, beta and gamma subunits and for LKB1, MO25 and STRAD. Analysis of gene expression by RT-PCR showed that liver, brain, kidney, spleen, pancreas, duodenum, abdominal fat and hypothalamus from 3 wk-old broiler chickens preferentially expressed AMPK alpha-1, beta-2 and gamma-1 subunit isoforms. Heart predominantly expressed alpha-2, beta-2 and gamma-1, whereas skeletal muscle expressed alpha-2, beta-2 and gamma-3 preferentially. Moreover, the AMPK gamma-3 gene was only expressed in heart and skeletal muscle. Genes encoding LKB1, MO25 alpha, MO25 beta, and STRAD beta were expressed in all examined tissues, whereas STRAD alpha was expressed exclusively in brain, hypothalamus, heart and skeletal muscle. Alterations in energy status (fasting and refeeding) produced little significant change in AMPK subunit gene transcription. We also determined the level of phosphorylated (active) AMPK in different tissues and in different states of energy balance. Immunocytochemical analysis of the chicken hypothalamus showed that activated AMPK was present in hypothalamic nuclei involved in regulation of food intake and energy balance. Together, these findings suggest a functional LKB1/AMPK pathway exists in chickens similar to that observed in mammals.

In mammals, triacylglycerol (TAG) accumulation in nonadipose tissue, termed lipotoxicity, develops with obesity and can provoke insulin resistance, overt diabetes, and ovarian dysfunction. Leptin, an adipose tissue hormone, may mediate these effects. Feed-satiated broiler breeder hens manifest lipotoxicity-like symptoms. Changes in body and organ weights, hepatic and plasma TAG, nonesterified fatty acids (NEFA), ovarian morphology, and egg production in response to acute voluntary increases of feed intake were measured in 2 studies with Cobb 500 broiler breeder hens provided with either 145 or > or = 290 g of feed/d per hen for 10 d. In both studies, no hen fed 145 g of feed/d exhibited ovarian abnormalities, whereas approximately 50% of feed-satiated hens did. Egg production in feed-satiated hens was reduced from 73.3 to 55.8% (P = 0.001). Morphology indicated that apoptosis-induced atresia occurred in the hierarchical follicles. Fractional weight of yolk increased from 29.3 to 30.6% (P = 0.016) and no longer correlated to egg weight. Body, liver, and abdominal adipose weights were significantly greater (P < 0.05) in feed-satiated hens, as were plasma concentrations of glucose, NEFA, TAG, insulin, and leptin (P < 0.05). Feed-satiated hens with abnormal ovaries had significantly more liver and abdominal fat, greater plasma leptin and TAG concentrations, and more saturated fatty acids in plasma NEFA than did feed-satiated hens with normal ovaries. Differences in severity of lipotoxic metabolic and hormonal responses among feed-satiated hens were closely linked to the incidence of ovarian abnormalities and granulosa cell susceptibility to apoptosis and necrosis.

In the literature, IGFs in the developing embryo are usually determined by blood serum concentrations. For this study, IGF-I/-II was quantified in the amniotic and allantoic fluids of fertile commercial broiler chicken (Gallus domesticus) (n=222), Pekin duck (Anas platyrhyncha) (n=250), and turkey (Meleagridis gallopavo) eggs (n= 200) during incubation. Amniotic and allantoic fluids were collected from embryos starting at 6 days of incubation for chickens and 8 days of incubation for ducks and turkeys. IGF concentrations within the fluids were determined by radioimmunoassay. Chicken amniotic IGF-I concentration at stage 29 of development was significantly higher (P< or =0.05) than the duck or turkey. At stage 36 of development the concentration of IGF-II in the amniotic fluid was 2.8 times greater in the chicken versus the duck (P< or =0.05) and 2 times greater than in the turkey (P< or =0.05). Within species, chicken IGF-I concentration in the amniotic fluid had a cubic trend (P< or =0.001), duck IGF-I increased linearly (P< or =0.001), and turkey concentrations declined quadratically (P< or =0.001) throughout development. In all species, the IGF-II concentration was higher than the IGF-I concentration in the amniotic and allantoic fluids.

This study investigated changes in bone integrity and circulating concentrations of insulin-like growth factor-I (IGF-I) of hens subjected to 2 distinct molting regimens and fed pre- and postmolt diets high in n-3 or n-6 fatty acids. A dual-energy x-ray absorptiometer determined bone mineral density (BMD) of the tibia and humerus of 45 live hens from 62 to 76 wk of age. Densitometric scans were also conducted in excised tibia and humerus at 66, 71, and 76 wk of age. Concentrations of IGF-I were monitored using an homologous RIA at the same ages. The molting treatments consisted of 10 d of fasting + cracked corn for 7 d + pullet developer diet for 10 d or a nonfasting molt (wheat-middlings-based diet for 27 d). Five weeks prior to and after either molt treatment, birds were fed 1 of 2 diets containing dietary n-6/ n-3 fatty acids ratios of 0.6 or 8.0. At the end of the molt (71 wk of age), tibial BMD decreased 30% in fasted and 11% in nonfasted molt regimens, and the fatty acid content of the premolt diet had no effect on the decline in BMD. The BMD of the humerus also decreased during molt with the exception of hens subjected to a nonfasted molt and fed n-3 fatty acid diets in which their BMD values were similar to or greater (at 73 wk of age) than those of controls during the entire experimental period (treatment by bone by age, P < or = 0.0001). Induced molt affected circulating IGF-I concentrations (treatment by age interaction, P < or = 0.0001), and the response was the same regardless of molt regimen (fasting vs. nonfasting) or diet (n-3 vs. n-6 fatty acids). A decrease in IGF-I 54 h postmolt was noted; however, from 13 to 43 d postmolt, all molted birds had elevated IGF-I as compared with controls. In conclusion, a nonfasted molt as compared with fasted molt was less detrimental to bone mineralization; dietary n-6/n-3 fatty acid ratios in the pre- and postmolt diets had little effect on the decline of skeletal integrity during molt, and circulating IGF-I concentrations were affected by molt.

A molecular cloning strategy employing primer-directed reverse transcription polymerase chain reaction (RT-PCR) was devised to sequence 1300 bp of a turkey liver-derived cDNA corresponding to the complete coding region and the 5'- and 3'-untranslated regions of the insulin-like growth factor (IGF)-II mRNA transcript (GenBank accession no. ). The turkey IGF-II gene codes for a 187 amino acid precursor protein that includes a signal peptide, the mature IGF-II hormone, and a C-terminal extension peptide comprised of 24, 67 and 96 amino acids, respectively. Turkey IGF-II showed greater than 95% sequence identity at both the nucleotide and amino acid level with chicken IGF-II. Expression of IGF-I, IGF-II, IGF type-I receptor (IGF-IR), and IGF binding protein (IGFBP)-2 and -5 genes was quantified relative to an internal 18S rRNA standard by RT-PCR in liver and whole brain tissue on days 14, 16, 18, 20, 22, 24 and 26 of embryonic development, as well as at hatch (H, day 28) and at 3 weeks post-hatching (PH). Expression of liver IGF-I was low throughout embryonic development, but increased more than 8-fold by 3 weeks PH. In contrast, IGF-I was expressed in brain tissue at much higher levels than liver throughout development and this level of expression in brain increased gradually, reaching its highest point at 3 weeks PH. IGF-II was expressed at comparable levels in brain and liver tissue during embryonic development, except for transient increases in liver just prior to hatching (days 24 and 26) and at 3 weeks PH. Expression of IGF-IR declined in brain throughout development reaching its lowest level at 3 weeks PH. In liver, IGF-IR expression was lower than that of brain throughout development. An inverse relationship was observed for the expression of IGF-I and IGF-IR genes in brain, but not in liver, through 3 weeks PH. Expression of the IGFBP-2 gene increased in liver around the time of hatch (days 26-28) and declined by 3 weeks PH, whereas the level of expression of IGFBP-5, which was higher than IGFBP-2, remained fairly constant in both brain and liver throughout the developmental period studied. Our data indicates differential expression of selected genes that comprise the IGF system in the turkey during embryonic and PH growth and development.

Molecular genetic selection on individual genes is a promising method to genetically improve economically important traits in chickens. A resource population was developed to study the genetics of growth, body composition, skeletal integrity, and metabolism traits. Broiler sires were crossed to dams of 2 diverse, highly inbred lines (Leghorn and Fayoumi), and the F1 birds were intermated by dam line to produce broiler-Leghorn and broiler-Fayoumi F2 offspring. Growth, body composition, skeletal integrity, and hormonal and metabolic factors were measured in 713 F2 individuals. Insulin-like growth factor-I (IGF1) was selected for study as a biological and positional candidate gene. A single nucleotide polymorphism (SNP) was identified between the founder lines in the IGF1 promoter region, and a PCR-RFLP assay was developed. A mixed model was used to statistically analyze associations of IGF1-SNP1 with phenotypic traits. The IGF1-SNP1 had significant associations with most recorded traits, except metabolic traits. Strong interactions between the IGF1 gene and genetic background on growth traits in the 2 F2 populations suggest that genetic interaction is an important aspect for consideration before using the IGF1-SNP1 in marker-assisted selection programs. Several beneficial effects (improved growth, increased breast muscle weight, decreased abdominal fat, and enhanced skeletal integrity) associated with 1 allele indicate the presence of 1 or more loci near IGF1-SNP1 controlling biologically diverse and economically important traits in chickens.

Phosphorus in runoff from fields where poultry litter is surface-applied is an environmental concern. We investigated the effect of adding phytase and reducing supplemental P in poultry diets and composting poultry manures, with and without Fe and Al amendments, on P in manures, composts, and runoff. We used four diets: normal (no phytase) with 0.4% supplemental P, normal + phytase, phytase + 0.3% P, and phytase + 0.2% P. Adding phytase and decreasing supplemental P in diets reduced total P but increased water-extractable P in manure. Compared with manures, composting reduced both total P, due to dilution of manure with woodchips and straw, and water-extractable P, but beyond a dilution effect so that the ratio of water-extractable P to total P was less in compost than manure. Adding Fe and Al during composting did not consistently change total P or water-extractable P. Manures and composts were surface-applied to soil boxes at a rate of 50 kg total P ha(-1) and subjected to simulated rainfall, with runoff collected for 30 min. For manures, phytase and decreased P in diets had no significant effect on total P or molybdate-reactive P loads (kg ha(-1)) in runoff. Composting reduced total P and molybdate-reactive P loads in runoff, and adding Fe and Al to compost reduced total P but not molybdate-reactive P loads in runoff. Molybdate-reactive P in runoff (mg box(-1)) was well correlated to water-extractable P applied to boxes (mg box(-1)) in manures and composts. Therefore, the final environmental impact of dietary phytase will depend on the management of poultry diets, manure, and farm-scale P balances.

Although changes in dietary protein levels change metabolism in the broiler chicken, there is little information concerning the time course of the process of adaptation. Therefore, male Hubbard broiler chickens were fed diets containing either 12 or 30% crude protein from 7 to 28 d of age and then were switched to the opposite level for an additional 9 d. Birds were bled and killed at 0, 2, 5, 7and 9 d following the reversals. Data taken at these intervals included those involved in vitro lipogenesis (IVL), growth and feed consumption, hepatic enzyme activities and plasma hormones and metabolites. Birds fed the lower level of crude protein were smaller in growth from 7 to 28 d. Feeding these birds a higher protein diet from 28 to 37 d improved both growth and feed efficiency in comparison to controls. Lipogenesis was also greater and plasma insulin-like growth factor-I (IGF-I) less in birds fed the lower protein diet. Switching dietary treatments increased and decreased lipogenesis as birds were switched from high to low and low to high protein diets, respectively. Half-maximal changes were observed 2 d after the reversal and maximal changes 5 d after the reversal. In contrast, switching dietary treatments decreased and increased plasma IGF-I as birds were switched from high to low and low to high protein diets, respectively. Half-maximal changes were observed 2 d after the reversal. Of the three hepatic enzymes monitored, malic enzyme activity most closely followed the rapid changes in IVL. In the present study, plasma IGF-I may be a more sensitive indicator of changes in dietary protein than changes in intermediary metabolism.

The present study was conducted to determine if peripheral leptin administration can alter GH secretion or feed intake in young pigs. Six, 6 kg female pigs were fasted overnight and randomly chosen to receive porcine recombinant leptin or saline injections in a crossover design. Three leptin dosages were tested over a 10 day period, 100, 200 or 500 microg/kg body mass (L100, L200 or L500). Leptin was administered in 0.2% bovine serum albumin as a bolus injection into the carotid artery. Blood samples were obtained from the jugular vein over a 24 h period. Leptin delayed feeding in pigs treated with L200 and L500 (P<0.05), while reducing overall intake in pigs treated with L100 (P<0.05). L200 or L500 depressed blood glucose (P<0.05). Plasma insulin levels were elevated by feeding in control animals, while insulin levels were depressed in pigs treated with L200 or L500 (P<0.05). L200 elevated plasma growth hormone (P<0.05) with three peaks apparent at 5, 8, and 13 h post injection. The ability for a single injection of leptin to produce significant changes in hormone and metabolite levels suggests that this peptide has a role in regulation of peripheral metabolism.

Leptin is an adipose and liver tissue-derived secreted protein in chickens that has been implicated in the regulation of food intake and whole-body energy balance. In this study, the metabolic clearance and tissue uptake of leptin were examined in the chicken (Gallus gallus). Four-week-old broiler males were infused with (125)I-labeled mouse leptin. Chromatography of radiolabeled leptin in plasma produced two peaks, one at 16 kDa (free leptin) and a free iodine peak. No leptin binding protein in blood was detected. Leptin was cleared with a half-life estimate of 23 min. In order to investigate the tissue distribution and uptake of radiolabeled leptin, multiple tissues were removed from infused birds at 15 and 240 min post-infusion, and trichloroacetic acid (TCA)-precipitable radioactivity was determined. The amounts of radioactivity at 15 min post-infusion in the tissues in rank order were: kidney, testis, lung, spleen, heart, liver, small and large intestine, gizzard, pancreas, bursa, leg and breast muscle, adrenals, and brain. A slightly different pattern of distribution was observed at 240 min post-infusion. We conclude from these studies that unlike mammals, no circulating leptin binding protein is present in chickens. Leptin is metabolized and cleared very rapidly from blood by the kidney.

The goal of this research was to determine whether directing expression of an insulin-like growth factor I (IGF-I) transgene specifically to striated muscle would alter the growth characteristics in swine. Transgenic pigs were produced with a fusion gene composed of avian skeletal alpha-actin regulatory sequences and a cDNA encoding human IGF-I. Six founder transgenic pigs were mated to nontransgenic pigs to produce 11 litters of G1 transgenic and sibling control progeny. Birth weight, weaning weight, and proportion of pig survival did not differ between transgenic and control pigs. The ADG of pigs as they grew incrementally from 20 to 60 kg, 60 to 90 kg, and 90 to 120 kg, respectively, did not significantly differ between transgenic and control pigs. Efficiency of feed utilization (gain:feed) was also similar for transgenic and control pigs. Plasma IGF-I and porcine growth hormone (pGH) concentrations were determined at 60, 90, and 120 kg body weight. Plasma IGF-I concentrations were 19% higher in transgenic gilts than control gilts and 11.1% higher in transgenic boars than control boars (P=0.0005). Plasma IGF-I concentrations for boars were also higher than for gilts (P=0.0001). At 60, 90, and 120 kg body weight each pig was scanned by dual energy X-ray absorptiometry (DXA) to derive comparative estimates of carcass fat, lean, bone content of the live animal. Control pigs had more fat and less lean tissue than transgenic pigs at each of the scanning periods and the difference became more pronounced as the pigs grew heavier (P<0.005 at each weight). Transgenic pigs also had a slightly lower percentage of bone than control pigs (P<0.05 at each weight). While daily rates of lean tissue accretion did not differ for transgenic and control pigs, daily rates of fat accretion were lower in transgenic pigs than in control pigs (P<0.05). Based on these results we conclude that expression of IGF-I in the skeletal muscles gradually altered body composition as pigs became older but did not have a major affect on growth performance.

Seven-day-old chickens were fed diets containing 18% crude protein + 0 or 1g methimazole/kg to produce either euthyroid or hypothyroid groups of birds at 28 days of age. These two groups were then offered diets containing either 0 or 1mg triiodothyronine (T(3))/kg diet. Birds were sampled at 0, 2, 5, and 8 days following the onset of the T(3) treatment. Measurements taken at these intervals included in vitro hepatic lipogenesis (IVL), growth and feed consumption, hepatic enzyme activities (malic enzyme, ME; isocitrate dehydrogenase, ICD; and aspartate amino transferase, AAT), plasma hormones (T(3); thyroxine, T(4); insulin like growth factors I, IGF-I; and insulin like growth factors II, IGF-II) and metabolites (glucose; fatty acids, NEFA; triglyerides; uric acid). Hypothyroidism decreased IVL and ME at 28 days of age; however, T(3) supplementation for 2 days restored both IVL and ME. Paradoxically, continuing T(3) replenishment for an additional 3-6 days decreased IVL without affecting ME activity. In contrast, supplemental T(3) decreased IVL in euthyroid birds, regardless of the dosing interval, but had no effect on ME activity. Methimazole decreased plasma T(3), T(4), uric acid, and IGF-I, but did not affect IGF-II at 28 days. Giving T(3) to birds previously on methimazole increased plasma IGF-I as did feeding a control diet. Supplemental T(3) increased NEFA in both euthyroid and hypothyroid birds, but only for a short period following the initiation of supplementation (2 days post-supplementation). These data may help to explain some of the apparent reported dichotomies in lipid metabolism elicited by changes in the thyroid state of animals. In addition, most metabolic changes in response to feeding T(3) occurred within 2-5 days, suggesting that changes in intermediary metabolism preceded morphological changes. In conclusion, the thyroid state of the animal will determine responses to exogenous T(3)., (Copyright 2002 Elsevier Science Inc.)

Broiler breeder pullets were divided into two groups at 21 wk of age. One group was given free access to feed (ad libitum) and the other fed a limited amount of feed (restricted). At 22 wk, all birds were photostimulated and maintained throughout an egg-laying cycle ending at 36 wk. Samples of liver and abdominal fat pad were collected just before photostimulation (prelight), after photostimulation at first egg and at peak egg production (plateau). Hepatic expression of sterol regulatory element binding protein-1, ATP-citrate lyase, fatty acid synthase, malic enzyme, acetyl-CoA carboxylase and stearoyl-CoA (Delta9) desaturase 1 genes in ad libitum birds declined from their highest levels just before photostimulation as the birds came into and maintained egg production. In contrast, the restricted birds had significant (P < 0.05) increases in the expression of these genes after photostimulation at first egg with a subsequent decline as they reached peak egg production. Hepatic expression of fatty acid binding protein, VLDL apolipoprotein (apoVLDL-II) and apoB genes increased significantly (P < 0.05) in both ad libitum and restricted breeders after photostimulation, whereas apoA1 gene expression declined during this time. Abdominal fat pad weights were significantly (P < 0.05) higher in the ad libitum compared with restricted birds after photostimulation. Lipoprotein lipase in this tissue showed a pattern of expression similar to that observed for the hepatic lipogenic enzyme genes. In conclusion, feed restriction during the pullet-to-breeder transition period significantly (P < 0.05) altered hepatic lipogenic gene expression in broiler breeders.

An avian uncoupling protein (UCP) gene homolog was recently sequenced from skeletal muscle and was proposed to have a role in thermogenesis in chickens, ducks and hummingbirds. Since mammalian UCP 2 and UCP 3 also appear to have functions associated with energy and substrate partitioning and body weight regulation, the purpose of this study was to further characterize chicken UCP under conditions of nutritional stress and/or leptin administration. Male 3-week-old chickens were starved for 24 or 48 h and then half of each group was refed for an additional 24 h. In a follow-up experiment, chickens were fed or starved for 48 h with or without leptin administration. Feed deprivation increased UCP mRNA expression in skeletal muscle by up to 260% (P<0.001), and in a time-dependent manner in pectoralis muscle. Refeeding for 24 h normalized muscle UCP mRNA levels. Leptin administration had no effect on muscle UCP. Chicken muscle UCP mRNA levels were highly correlated with plasma triglyceride and non-esterified fatty acid (NEFA) concentrations, and with circulating levels of insulin, insulin-like growth factor (IGF)-I and IGF-II. These results suggest that, as in mammals, avian UCP is up-regulated during feed deprivation and is highly correlated with increased fatty acid oxidation and flux into skeletal muscle.