Marbofloxacin for the treatment of experimentally induced Mycoplasma haemofelis infection in cats.

BACKGROUND: Administration of tetracyclines or fluoroquinolones is associated with improvement in clinical and laboratory abnormalities in cats infected with Mycoplasma haemofelis. No treatment protocol has consistently eliminated the organism, and antimicrobial susceptibility may vary among M. haemofelis isolates. Continued search for effective therapies is warranted. HYPOTHESIS: Marbofloxacin administered at the onset of clinical illness will be safe and effective for the treatment of M. haemofelis. ANIMALS: Fourteen young adult, laboratory-reared cats housed together in a specific pathogen-free facility. METHODS: Twelve cats were inoculated IV with 2.0 mL of blood from 2 M. haemofelis positive cats. Clinical parameters were assessed daily. CBC and hemoplasma polymerase chain reaction (PCR) assay were performed before inoculation, weekly for 1-3 weeks postinoculation (PI) and twice weekly 3-6 weeks PI. Treatment with marbofloxacin (2.75 mg/kg PO daily for 14 days) was initiated in 6 randomly selected cats when PCV was <30% or fever was >102.5 degrees F (39.2 degrees C). Cats that were PCR positive on day 7 of therapy were treated for 28 days. Cats that were PCR negative on day 42 PI were treated with 20 mg/kg methylprednisolone acetate IM on day 50 PI. RESULTS: Significant differences between groups on some days after inoculation included higher PCV and red blood cell counts, lower mean cell volume, and higher mean cell hemoglobin content in marbofloxacin-treated cats. No differences in PCR assay results were noted between groups. CONCLUSIONS AND CLINICAL IMPORTANCE: Marbofloxacin was safe and resulted in more rapid hematologic improvement in M. haemofelis-infected cats, but did not change clinical scores and did not consistently eliminate infection.

Relaxin increases insulin-like growth factors (IGFs) and IGF-binding proteins of the pig uterus in vivo.

Relaxin promotes growth of reproductive tissues, including the uterus. Although we have evidence of a role for insulin-like growth factor I (IGF-I) in mediating relaxin-induced growth of porcine granulosa cells in vitro, the mechanism of action by which relaxin enhances uterine growth has not been identified. To investigate a role for the uterine insulin-like growth factor (IGF) system in relaxin-induced uterine growth, we monitored the effects of relaxin on porcine IGFs and IGF-binding proteins (IGFBPs) in vivo. The trophic effects of relaxin on the uterus were elicited by administering relaxin or saline to prepubertal gilts every 6 h for 54 h. Three hours after the last injection, uterine flushes, uteri, follicular fluid, and ovaries were collected. Estradiol was measured in plasma and follicular fluid to confirm the prepubertal status of each animal. Significantly higher concentrations of uterine lumen IGF-I (P < 0.05) and IGF-II (P < 0.01) were observed in animals treated with relaxin. However, relaxin administration did not affect uterine IGF-I and -II gene expression, as determined by a ribonuclease protection assay and Northern analysis, respectively. In uterine flushes, relaxin treatment increased an IGFBP doublet (33 and 34.5 kDa) and IGFBP-3. The uterine IGFBP doublet was identified as IGFBP-2 by immunoprecipitation. Plasma or follicular fluid IGFs and IGFBPs were unaffected by relaxin administration. In addition, relaxin did not influence IGF-I binding to its uterine receptor. This is the first study to demonstrate regulation of the pig uterine IGF system by relaxin. In conclusion, the data point to IGF-I, IGF-II, IGFBP-2, and IGFBP-3 as putative mediators of relaxin-induced uterine growth in the pig.

Hypoglycemia, enteritis, and spiking mortality in Georgia broiler chickens: experimental reproduction in broiler breeder chicks.

The clinical signs, hypoglycemia, and mortality of "spiking mortality syndrome" were experimentally reproduced. Seven groups of day-old male primary broiler breeder chicks were orally inoculated with tissue and/or fecal-urate homogenates taken from field broilers with spiking mortality syndrome and from field broilers with enteritis and/or runting-stunting syndrome. All homogenates used as inocula were shown by transmission electron microscopy and negative staining to contain arenavirus-like particles. Inocula produced from field broilers with spiking mortality syndrome contained the highest numbers of the arena-virus-like particles and produced the highest percentage of hypoglycemic chicks 13-15 days postinoculation after a 5-to-9-hour fast. These homogenates also produced the most significant differences in mean plasma growth hormone and insulin-like growth factor-1 levels. The significance of the arenavirus-like particles is unknown but is currently being investigated.

Compensatory growth in runt pigs is not mediated by insulin-like growth factor I.

Runt pigs grow more slowly and never reach the same body weight as age-matched littermates. We hypothesized that IGF-I would be reduced in the runts and that postnatal nutrition would alter IGF-I concentration and tissue expression. Runt and control littermates were removed from 20 crossbred sows 20 to 28 h after birth. Tissues were collected from a baseline group (n = 4). The remaining pigs were fed porcine milk replacer at either 70 or 120 g/kg BW for 14 d (n = 8). Feed intake and body weight were measured daily, with plasma samples collected by jugular venipuncture throughout the experiment. Expression of IGF-I mRNA was measured in the liver and gastrocnemius with an RNase protection assay. At d 0, runts were significantly smaller than controls in all measurements, except brain weight. During the 14 d, the relative rate of growth was significantly faster and more efficient in runts than in controls; however, runts never attained the same absolute body weight as controls. Circulating IGF-I was significantly reduced at d 0 but was similar to that in controls by d 2 of feeding. The IGF-I mRNA expression in liver or gastrocnemius muscle was not different between control and runts at d 0 or 14 and was not affected by dietary intake. This study has shown that runt pigs grow in a compensatory manner for at least the first 2 wk of life. However, this growth response does not seem to be mediated by IGF-I.

Fumaric and citric acids as feed additives in starter pig diets: effect on performance and nutrient balance.

The effect of dietary citric acid (CA) and fumaric acid (FA) on pig weight gain (ADG) and gain/feed (G/F) was studied in two trials using 192 crossbred, 4-wk-old weaning pigs. Three dietary levels (0, 1.5 or 3.0%) of either FA (Trial 1) or CA (Trial 2) with or without an antibiotic supplement (110 mg chlortetracycline, 110 mg sulfamethazine and 55 mg penicillin/kg diet) formed six treatment combinations in each trial. These six diets were fed to two replicate pens of eight pigs each for a 4-wk period. In Trial 1, ADG was improved (P less than .01) during wk 1, and G/F was improved during wk 1 (P less than .01) as well as during wk 1 to 2 (P less than .05) for pigs consuming FA-supplemented diets. In Trial 2, CA had no beneficial influence on ADG during the 4-wk trial. However, feed intake during wk 1 was depressed (P less than .05) by adding CA, as was G/F during wk 1 to 2 (P less than .05). Based on these results, FA was selected to be used in a nutrient balance study. Twelve 4-wk-old weanling pigs were fed one of three diets: control (C), C + 1.5% FA, or C + antibiotic supplement (A). Diet digestible energy (DE), ME and N-corrected ME (MEN) were not different among treatments. Nitrogen balance, percentage N retained and apparent N digestibility were not affected by dietary treatment. Calcium balance and percentage of Ca retained were unaffected by diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dietary copper on intestinal mucosa enzyme activity, morphology, and turnover rates in weanling pigs.

Twenty-four pigs from four litters weaned at 21 d of age (6.6 kg of BW) were used to evaluate the influence of 250 ppm of dietary Cu on intestinal mucosa glucose-6-phosphatase (GP), alkaline phosphatase (AP), and adenosine triphosphatase (ATPase) activity; mucosal morphology; and the turnover rate of the intestinal mucosa throughout the gastrointestinal tract. Pigs were allotted into four pens of six pigs each based on sex, litter, and weight. Pens were then assigned to one of two treatments: 1) corn-soybean meal-whey diet with no antimicrobials (CO), or 2) CO + 250 ppm of Cu. Pigs were fed twice daily an amount approximately equal to ad libitum intake for 14 d. On d 14, pigs were injected i.p. with [3H]thymidine (50 microCi/kg of BW) 10 h after the morning meal. One pig from each pen was euthanatized at 1, 6, 12, 20, 32, and 44 h postinjection, and intestinal tissue was collected from the duodenum, two jejunum sites (upper and lower), ileum, cecum, and colon. The activity of GP and AP in the lower jejunum tended to decrease in pigs fed Cu (P less than .11, P less than .08, respectively). The ATPase activity was not affected by treatment (P greater than .10). Crypt death, villus height, or epithelial cell size (P greater than .10) were not affected by feeding Cu. Migration rate of epithelial cells up the villus was also not affected by treatment (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of adding fat to the sow lactation diet on lactation and rebreeding performance.

One-hundred-three multiparous sows were randomly assigned to one of two lactation diets containing either no supplemental animal fat (C) or 10% added fat (F) during two seasons, summer (S) and winter (W), in a 2 X 2 factorial arrangement of treatments. Sows were placed on their respective dietary treatments 1 wk prior to farrowing and were fed these diets ad libitum throughout the 28-d lactation period. Weekly feed intake and total feed intake were not affected by diet or season, while weekly metabolizable energy (ME) intake tended to be higher during week 1 and 3, and was higher (P less than .04) during wk 2 for sows fed diet F. Sow weight loss from farrowing to 21 d of lactation and to weaning (28 d) were unaffected by diet or season. Average pig birth weight was .15 kg higher (P less than .01) for pigs born during S compared with those born in W. Sows receiving diet F had heavier litters at 21 d (P less than .01) and heavier average pig 21-d weights (P less than .01). This was primarily due to the 13.1% increase (P less than .04) in estimated milk yield and the higher fat concentration (P less than .001) of milk consumed by the pigs nursing sows fed diet F. Interval between weaning and rebreeding was shortened by 5.9 d (P less than .01) for sows during W than during S, and tended to be lower for sows fed diet F (7.3 d) compared with that of sows fed diet C (9.7 d).(ABSTRACT TRUNCATED AT 250 WORDS)

Inoculation of two genotypes of Hemobartonella felis (California and Ohio variants) to induce infection in cats and the response to treatment with azithromycin.

OBJECTIVES: To describe clinical and laboratory findings associated with cats experimentally infected by inoculation with the 2 recognized genotypes of Hemobartonella felis (small variant, Hfsm; large variant, Hflg) and to determine the response of cats to treatment with azithromycin. ANIMALS: 18 young adult domestic shorthair cats of both sexes. PROCEDURES: Cats were inoculated with H felis and monitored weekly, using CBC counts and a polymerase chain reaction (PCR) designed to detect both genetic variants of H felis. Beginning 26 days after inoculation, 11 cats were administered azithromycin (15 mg/kg of body weight, PO, q 12 h, for 7 days). RESULTS: Inoculation resulted in coinfection with Hflg and Hfsm, and both variants were detected by PCR. Clinical abnormalities and anemia were most severe in Hflg- and dual-infected cats. Results of PCR and CBC were positive for H felis in 112/112 (100%) and 42/112 (37.5%), respectively, samples collected after inoculation. Administration of azithromycin had little effect on clinical variables, including anemia. All cats, regardless of treatment with azithromycin, had positive results for the PCR at the end of the study period. CONCLUSIONS AND CLINICAL RELEVANCE: In these cats, Hflg was more pathogenic than Hfsm, and coinfection with both variants was detected. Results of the PCR were superior to results of CBC for detecting infection with H felis. Azithromycin administered at the dose and duration reported here was not efficacious for the treatment of cats with hemobartonellosis.

Safety, efficacy, and immunogenicity of a modified-live equine influenza virus vaccine in ponies after induction of exercise-induced immunosuppression.

OBJECTIVE: To determine safety, efficacy, and immunogenicity of an intranasal cold-adapted modified-live equine influenza virus vaccine administered to ponies following induction of exercise-induced immunosuppression. DESIGN: Prospective study. ANIMALS: Fifteen 9- to 15-month old ponies that had not had influenza. PROCEDURE: Five ponies were vaccinated after 5 days of strenuous exercise on a high-speed treadmill, 5 were vaccinated without undergoing exercise, and 5 were not vaccinated or exercised and served as controls. Three months later, all ponies were challenged by nebulization of homologous equine influenza virus. Clinical and hematologic responses and viral shedding were monitored, and serum and nasal secretions were collected for determination of influenza-virus-specific antibody isotype responses. RESULTS: Exercise caused immunosuppression, as indicated by depression of lymphocyte proliferation in response to pokeweed mitogen. Vaccination did not result in adverse clinical effects, and none of the vaccinated ponies developed clinical signs of infection following challenge exposure. In contrast, challenge exposure caused marked clinical signs of respiratory tract disease in 4 control ponies. Vaccinated and control ponies shed virus after challenge exposure. Antibody responses to vaccination were restricted to serum IgGa and IgGb responses in both vaccination groups. After challenge exposure, ponies in all groups generated serum IgGa and IgGb and nasal IgA responses. Patterns of serum hemagglutination inhibition titers were similar to patterns of IgGa and IgGb responses. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that administration of this MLV vaccine to ponies with exercise-induced immunosuppression was safe and that administration of a single dose to ponies provided clinical protection 3 months later.

The suppressive effects of testosterone on growth in young chickens appears to be mediated via a peripheral androgen receptor; studies of the anti-androgen ICI 176,334.

ICI 176,334 is a nonsteroidal anti-androgen that has been shown to selectively block peripheral androgen receptors in rats and is presumed to do so in chickens. In chickens, androgens stimulate secondary sexual characteristics (e.g., comb), but inhibit growth and the immune tissues. The present study examined the effect of dietary ICI 176,334 (5 or 25 mg/kg body weight) on growth in chickens in the presence or absence of testosterone treatment (as 1-cm long silastic implants). Treatments began at 2 wk of age and continued through 6 wk of age. Testosterone alone reduced body growth (average daily gain and shank-toe length, together with weights of the body, skeletal muscle, and the bursa of Fabricius, an immune tissue), and stimulated comb development. At the low dose (5 mg/kg), ICI 176,334 alone had no effect on body growth or organ weight with the exception that comb weight was reduced. At the high dose (25 mg/kg), ICI 176,334 decreased growth (body weight, average daily gain, and shank-toe length) and organ weights (breast muscle, bursa of Fabricius, testis, and comb weights). This effect may represent a toxicity. As might be expected with an anti-androgen, ICI 176,334 (at either 5 or 25 mg/kg) completely suppressed the stimulation of comb growth evoked by testosterone. Similarly, ICI 176,334 (5 mg/kg) overcame, albeit partially, the growth-suppressive effects of testosterone (on body weight, average daily gain, shank-toe length, and breast muscle weight) and also had inhibitory effects on the weights of the testis and bursa of Fabricius. The anti-androgen, ICI 176,334, did not influence the reduction in circulating concentrations of luteinizing hormone occurring after testosterone treatment. The present data are consistent with the growth-suppressive effects of testosterone in chickens being mediated via a peripheral androgen receptor. No effects of either testosterone or ICI 176,334 were observed on circulating concentrations of insulin-like growth factor-I despite the marked changes in growth rate.

Bartonella species antibodies and hyperglobulinemia in privately owned cats.

BACKGROUND: Bartonella species are zoonotic agents and primary pathogens in cats. Hyperglobulinemia has been associated with bartonellosis in humans and cats. HYPOTHESIS/OBJECTIVES: To evaluate for associations between Bartonella species immunoglobulin G (IgG) antibodies and serum biochemistry panel results in privately owned cats. ANIMALS: 1,477 privately owned cats. METHODS: Residual sera were collected after biochemical evaluation for this prospective, cross-sectional serosurvey. Bartonella species IgG ELISA was performed with a cutoff value of ≥ 1 : 64. Stepwise logistic regression analysis was performed with the endpoint titer as the outcome variable. The final statistical model included age, albumin, ALP activity, ALT activity, bilirubin, creatinine, glucose, and globulin as covariates. Serum protein electrophoresis was performed with serum from 50 cats with and without antibodies to Bartonella species and hyperglobulinemia. Sera from cats seropositive to Bartonella species and with hyperglobulinemia were assessed for evidence of exposure to other infectious agents associated with hyperglobulinemia. RESULTS: Risk of seropositivity to Bartonella species was positively associated with the natural log of globulin concentration (OR = 11.90, 95% CI 6.15-23.02, P < .0001), and inversely associated with the natural log of glucose concentration (OR = 0.66, 95% CI 0.50-0.87, P = .004). Another explanation for hyperglobulinemia was not identified for most cats with Bartonella species antibodies. Hyperglobulinemia was primarily caused by polyclonal gammopathy in cats that were seronegative and seropositive for Bartonella species. CONCLUSIONS AND CLINICAL IMPORTANCE: Hyperglobulinemia was significantly associated with seropositivity to Bartonella species. Testing for bartonellosis is warranted in cats with unexplained hyperglobulinemia and clinical or laboratory findings suggestive of bartonellosis.

Effect of cocoa and green tea on biomarkers of glucose regulation, oxidative stress, inflammation and hemostasis in obese adults at risk for insulin resistance.

BACKGROUND/OBJECTIVES: Flavanols may provide protection against insulin resistance, but little is known about the amounts and types of flavanols that may be efficacious. SUBJECTS/METHODS: This study was designed to determine whether cocoa flavanols, over a range of intakes, improve biomarkers of glucose regulation, inflammation and hemostasis in obese adults at risk for insulin resistance. As an adjunct, green tea and cocoa flavanols were compared for their ability to modulate these biomarkers. In a randomized crossover design, 20 adults consumed a controlled diet for 5 days along with four cocoa beverages containing 30-900 mg flavanol per day, or tea matched to a cocoa beverage for monomeric flavanol content. RESULTS: Cocoa beverages produced no significant changes in glucose, insulin, total area under the concentration-time curve (AUC) for glucose or total insulin AUC. As the dose of cocoa flavanols increased, total 8-isoprostane concentrations were lowered (linear contrast, P=0.02), as were C-reactive protein (CRP) concentrations (linear contrast, P=0.01). The relationship between cocoa flavanol levels and interleukin-6 (IL-6) concentrations was quadratic, suggesting that a maximum effective dose was achieved (quadratic contrast, P=0.01). There were no significant effects on measured indices of glucose regulation, nor on those of total 8-isoprostane, CRP and IL-6 concentrations, when cocoa and green tea were compared. However, relative to cocoa, green tea lowered fibrinogen concentrations (P=0.0003). CONCLUSIONS: Short-term intake of cocoa and green tea flavanols does not appear to improve glucose metabolism; they do affect selected markers of one or more measures of oxidative stress, inflammation or hemostasis in obese adults at risk for insulin resistance.

Triiodothyronine reduces growth hormone secretion and pituitary growth hormone mRNA in the chicken, in vivo and in vitro.

The influence of triiodothyronine (T3) on growth hormone (GH) mRNA and GH secretion has been examined in the chicken. Initially T3 treatment in the diet for three days did not alter plasma concentrations of GH. Plasma concentrations of GH were depressed with seven and 14 days of T3 treatment (1 or 5 ppm in the diet). There was a concomitant decline in pituitary GH mRNA with T3 treatment. Pituitary GH content was reduced with 14 but not seven days of T3 treatment. No effect of T3 was observed on the percentage by somatotroph cells in the anterior pituitary gland by fluorescence flow cytometry analysis. While exposure of pituitary cells in vitro from young chickens to GHRF for 2 hr increased GH mRNA, no effect was observed with T3. The presence of T3, for 48 hr in vitro, tended to reduce GH mRNA in adenohypophyseal cells from young chickens and decreased GH mRNA with anterior pituitary cells from adult chicks. It is concluded that T3 chronic administration of T3 depresses circulating concentrations of GH, at least in part, by decreasing GH mRNA and hence GH synthesis.

Influence of continuous growth hormone or insulin-like growth factor I administration in adult female chickens.

A series of studies was conducted to determine whether growth hormone (GH) exerts effects on adult female chickens. Recombinant chicken GH (rcGH) was administered continuously via osmotic minipumps. No consistent effects of rcGH treatment were observed on reproductive indices. Hens receiving rcGH treatment for 10 days exhibited hepatomegaly and showed a tendency (P < 0.1) for increased spleen and thymus weights. Moreover, there were increases in the circulating concentrations of insulin-like growth factor-I (IGF-I) and IGF-binding proteins (IGF-BPs) (22-kDa IGF-BP after 2, 5, and 10 days; 28-kDa IGF-BP after 5 and 10 days; and 36-kDa IGF-BP after 10 days) with rcGH treatment. To determine whether the changes in IGF-BPs were due directly to GH or indirectly via IGF-I, the effects of the continuous administration of rcGH or recombinant human IGF-I (rhIGF-I) were compared. While rcGH again elevated the circulating levels of 28- and 36-kDa IGF-BPs, no such effect was observed with rhIGF-I treatment. However, both treatments exerted similar effects in depressing pituitary GH mRNA levels and elevating plasma concentrations of IGF-I. It is concluded that GH directly elevates circulating concentrations of IGF-I and IGF-BPs, but the negative feedback effect on GH synthesis is mediated via IGF-I.

Ontogeny of insulin-like growth factors (IGF-I and IGF-II) and IGF-binding proteins in the chicken following hatching.

The present study examined plasma concentrations of insulin-like growth factor (IGF)-I, IGF-II and IGF-binding proteins (IGFBPs) during posthatch growth and development in chickens. Three distinct proteins which bound 125I-IGF-I were observed irrespective of age or sex, these having apparent molecular weights of 22, 28, and 36 kDa. The major IGFBP present during much of the growth and development period was the 28-kDa form followed by the 36-kDa form. Plasma concentrations of IGF-II and of the 22-kDa IGFBP showed little ontogenic variation with the exception of elevated levels of the 22 kDa IGFBP in 1-day-old chicks. The circulating concentrations of IGF-I and of the 28-kDa IGFBP increased progressively between the time of hatching to reach a maximum at 6 weeks of age and subsequently declined to lower levels in adults. Somewhat similarly, the 36-kDa IGFBP increased during early pre- and posthatching growth to a maximum at 6 weeks of age. There were marked sex differences in circulating concentrations of IGF-I in young (4 week) and adult chickens and in the 36-kDa IGFBP in the adult, both being lower in females. Estrogen treatment of adult male chickens decreased the circulating concentrations of IGF-I together with the level of both the 28- and 36-kDa IGFBPs. Testosterone treatment had no effect on the circulating concentrations of either IGF-I or IGFBPs in adult female chickens. We conclude that the relative levels of IGF-I, IGF-II, and the IGFBPs change with age. In addition, circulating concentrations of estrogen may play a role in the regulation of IGF-I and IGFBPs.

Ontogeny of pituitary growth hormone and growth hormone mRNA in the chicken.

The changes in pituitary growth hormone (GH) mRNA levels have been determined by Northern blot analysis and laser densitometry during embryonic development and posthatch growth of white Leghorn cockerels. Pituitary GH mRNA levels were observed to progressively increase between 18 days of embryonic development to a maximum at 4 weeks of age (posthatch). Subsequently, pituitary GH mRNA levels declined between 4 and 8 weeks of age, and between 12 weeks of age and adulthood. Pituitary GH contents showed increases during embryonic development and posthatch growth that paralleled the rise in GH mRNA. The decline in pituitary GH mRNA levels between 4 weeks of age and adulthood occurs when GH secretion has been observed previously to decline.

Ontogenic changes in the circulating concentrations of insulin-like growth factor (IGF)-I, IGF-II, and IGF-binding proteins in the chicken embryo.

The ontogeny of circulating concentrations of insulin-like growth factor (IGF-)-I, IGF-II, and IGF-binding proteins (IGF-BPs) was examined in the chick embryo. Distinct ontogenic changes in the circulating concentrations of IGF-I and IGF-II were observed. The present study confirms the overall profile for circulating concentrations of IGF-I. During middevelopment, plasma concentrations of IGF-I increased to a maximum which was attained on Day 14.5 of incubation. Thereafter, plasma concentrations of IGF-I declined with decreases (P < 0.05) between Days 14.5 and 15.5 and between Days 16.5 and 17.5 of incubation. In contrast to the monophasic profile for IGF-I, plasma concentrations of IGF-II were maximal on Day 10.5 of incubation and declined to a nadir on Day 17.5 of incubation. In late developmental stages (17.5 or 18.5 days of incubation), three IGF-BPs, having molecular weights of 22, 28, and 36 kDa, were detected in the plasma of chick embryos. No significant ontogenic changes in the circulating levels of the 28- and 36-kDa IGF-BPs were observed. However, it should be noted that prior to Day 17.5 of incubation, the 22-kDa IGF-BP was nondetectable in the circulation. The role of these changes in the functioning of IGF in embryonic development is discussed.

Chronic administration of growth hormone (GH) to adult chickens exerts marked effects on circulating concentrations of insulin-like growth factor-I (IGF-I), IGF binding proteins, hepatic GH regulated gene I, and hepatic GH receptor mRNA.

In young birds, growth hormone (GH) administration has been found to have only a small or even no effect on circulating concentrations of insulin-like growth factor-I (IGF-I). This is in obvious contrast to the situation in mammals. The present study examines the effect of continuous administration of GH in adult male chickens. Plasma concentrations of IGF-I were markedly elevated (2.5-3.0-fold, p < 0.001) in GH-treated chickens. There were also some transient increases in the circulating levels of IGF binding proteins. Adult chickens showed other manifestations of increased responsiveness to GH, including elevated hepatic expression of GH-regulated gene-I (mRNA) with GH treatment (p < 0.05), and a tendency (p < 0.08) for decreased GH-receptor mRNA. In contrast to the changes in circulating concentrations of GH and IGF-I with GH treatment, no changes in plasma concentrations of thyroid hormones, reproductive hormones, glucose, or nonesterified fatty acids were evident.