Recombinant bovine somatotropin stimulates short term increases in growth rate and insulin-like growth factor I (IGF-I) in chickens

Recombinant bovine somatotropin (rbGH) was administered by subcutaneous injection at daily doses of 0.5 or 2.5 mg/kg for a two week period in female broiler chicks between 4 and 6 weeks of age. Half of the chicks received dietary corticosterone at a 1 ppm level. Growth rate was significantly increased 6.1% and 6.9% following one week of treatment with 0.5 or 2.5 mg/kg rbGH respectively. Treatment with the same respective doses of rbGH in the presence of 1 ppm corticosterone, supplied to suppress any possible immune response elicited by the heterologous somatotropin, resulted in an 8.0% and 7.8% increase (P less than .05) in growth rate during the first week of treatment. The rbGH-associated increase in growth rate was accompanied by a significant increase in food intake, higher circulating levels of IGF-I, and lower plasma T4 concentrations, while plasma T3 levels were unchanged. All effects were attenuated during the second week of treatment, concomitant with the development of high antibody titer against rbGH regardless of dietary corticosterone administration. Carcass parameters relating to bone, muscle and fat were not different between rbGH-treated and control chickens at the end of the two week treatment period. Thus rbGH is capable of stimulating a short-term improvement in growth rate, which is related to increased feed consumption and is of limited duration.     

Growth hormone response to growth hormone-releasing hormone in beef cows divergently selected for milk production

In dairy cattle, increased circulating growth hormone has been associated with selection for greater milk yield. This study tested the hypothesis that beef cows divergently selected for milk production would have differing GH responses to a challenge dose of GHRH. Growth hormone response to a challenge of GHRH was measured in 36 Angus-sired cows ranging from 6 to 10 yr of age. The cows were classified as high milking (n = 16) or low milking (n = 20), on the basis of their sires' milk EPD. Mean milk EPD (in kilograms) were 16.6 and -14.4 for high and low milking cows, respectively. Milk production was estimated by the weigh-suckle-weigh procedure. Blood samples were taken immediately before and 10 min after a clearance dose of 4.5 microg of GHRH/100 kg BW (injected i.v.) and, 3 h later, immediately before and 10 min after a challenge dose of either 1.5 or 4.5 microg of GHRH/100 kg BW. Each animal received both challenge doses, and the doses were randomly assigned across 2 d of blood collection. Serum concentrations of GH and IGF-I were measured by RIA. Serum IGF-I was measured in the baseline blood sample on d 1 of blood collection. A positive relationship (r = 0.35; P = 0.03) was observed between the cows' rankings for each dose of GHRH; that is, high responders to the low dose were high responders to the high dose. Growth hormone response to the 4.5 microg/100 kg BW challenge dose of GHRH was positively related to sire milk EPD (R2 = 0.09; P = 0.03). Response of GH to the 1.5 microg GHRH/100 kg BW challenge dose also tended to be related (P = 0.08) to sire milk EPD of high milking cows. In addition, IGF-I concentrations of high milking cows were inversely related (R2 = 0.24; P = 0.04) to sire milk EPD. Growth hormone response to GHRH challenge may have potential as an additional tool in the evaluation of milk production in beef cattle.     

Cortisone arrests growth but enhances the inductive effect of porcine growth hormone on plasma IGF-I concentrations in female rats

The present study was conducted to determine whether corticosteroids influence the inductive effect of growth hormone (GH) on plasma concentrations of insulin-like growth factor I (IGF-I). The first experiment was designed to determine the effects of corticosterone alone on basal concentrations of IGF-I. Rats were treated daily for 4 d with 0, 50, 100, 250, or 500 mg of corticosterone/kg of BW. There was a close positive relationship between the dose of steroid injected and plasma concentrations of corticosterone and a close negative relationship between plasma corticosterone and growth. Plasma concentrations of IGF-I showed a positive relationship to dose and plasma concentrations of corticosterone and a negative relationship to growth rate. In the second experiment, rats were treated daily for 21 d with either porcine growth hormone (10 mg of pGH/kg of BW), pGH plus corticosteroid, or vehicle. The dose of steroid administered was increased every 3 d until the mean weight gain of the group was zero. Animals treated with pGH alone gained significantly more weight than controls. This growth response was not impaired significantly by corticosterone acetate at doses up to 500 mg/kg of BW. The more potent corticosteroid, cortisone, arrested the growth of pGH-treated rats at a dose of 80 mg/kg of BW, however. Plasma concentrations of IGF-I were increased by pGH treatment (57%) and increased further by concurrent cortisone treatment (212%). In summary, corticosteroids increase plasma concentrations of IGF-I and enhance the inductive effect of pGH on this hormone despite their catabolic actions.     

Response of young broiler chickens to chronic injection of recombinant-derived human insulin-like growth factor-I

The purpose of this study was to determine if exogenous insulin-like growth factor-I (IGF-I) would improve growth rate or body composition of young broiler chickens. Broiler cockerels were given a daily intramuscular (im) injection of sodium acetate buffer (buffer control), 100 or 200 μg recombinant-derived human IGF-I (rhIGF-I) per kg body weight from 11 to 24 days of age. Exogenous IGF-I did not affect the average daily gain, average daily feed consumption, or the gain-to-feed ratio of broiler chickens. Although daily injection of 200 μg/kg of rhIGF-I reduced (P<0.05) body ash content, there was no significant effect of IGF-I treatment on either body fat or protein content. Plasma GH levels were depressed (P<0.05) by chronic treatment with rhIGF-I. In contrast, plasma levels of T₃ and T₄ were not affected by rhIGF-I treatment. The half-life of rhIGF-I in plasma was determined at 25 days of age in naive control or chronically-injected chickens after a single intravenous dose of 50 μg rhIGF-I/kg. We found a single compartment, first-order disappearance pattern of rhIGF-I from chicken plasma. The half-life (t_1/2) of rhIGF-I in plasma was similar (t_1/2 = 32.5 min) for naive controls (injected once) or chronically-treated chickens which had received a daily injection of rhIGF-I (100 or 200 μg/kg) for 14 d. These data indicate that daily injection of IGF-I cannot be used to enhance growth performance or body composition of broiler chickens when given during the early growth period. The depression of plasma GH levels in rhIGF-I-injected chickens supports a negative-feedback role of IGF-I on pituitary GH secretion.     

Effects of isulin-like growth factor-I on maternal and fetal plasma amino acid levels in pregnant rats

Pregnant rats were subcutaneously administered with recombinant human insulin-like growth factor-I (rhIGF-I) in doses of 0 (control), 1, 2, and 4 microg/g body weight per day from day 18 to 21 of pregnancy. On day 21 of pregnancy, maternal and fetal plasma samples were collected and those amino acid levels were measured. The ratios of fetal/maternal plasma amino acids, especially leucine, isoleucine, tryptophan, phenylalanine and tyrosine, increased in 2 microg rhIGF-I treated group. Both total fetal weight and total placental weight were also higher than those in the control group. These results suggested that IGF-I enhanced fetal growth by, as one of its possible mechanisms, promoting placental amino acid supplies from the mother to fetuses.     

Influence of diet on basal and growth hormone-stimulated plasma concentrations of IGF-I in beef cattle

The effects of nutrition on plasma concentrations of insulin-like growth factor-I (IGF-I) were characterized in steers under basal conditions and following single i.m. injection of bovine growth hormone (bGH, .1 mg/kg BW). Nutritional effects on IGF-I were studied in three trials. In all trials steers were individually fed and penned Angus or Hereford x Angus (280 kg). In the first trial, two diets (LPLE1: 8% CP and 1.96 Mcal ME/kg, 4.5 kg.hd-1.d-1; MPHE1: 11% CP, 2.67 Mcal ME/kg, 6.5 kg.hd-1.d-1) were fed (n = 5/diet). Plasma IGF-I concentrations averaged 74 (LPLE1) and 152 (MPHE1) ng/ml (P less than .02). Following bGH injection, IGF-I increased to peak concentrations between 12 and 24 h (averaging 105 and 208 ng/ml at peak for LPLE and MPLE, respectively, P less than .01). In the second trial, steers were fed diets composed of 8, 11 or 14% CP and 1.96 or 2.67 Mcal ME/kg dry matter (6.35 kg.hd-1.d-1 in a factorial arrangement for 84 d, n = 4/diet). Within the low ME diet groups, plasma IGF-I was similar in steers fed 11 and 14% CP but greater at these two CP levels than in steers fed 8% CP (P less than .05). Within the high ME diet groups, plasma IGF-I increased linearly with CP (P less than .01). In the third trial, steers were fed diets to result in a negative N status. Insulin-like growth factor-I was lower (P less than .02) during feed restriction than when steers were full-fed. The IGF-I response to bGH was diminished or absent in underfed steers (P less than .01). These data are interpreted to suggest that diet composition and intake affect plasma concentrations of IGF-I in steers. In cattle, CP may be the primary nutritional determinant of basal IGF-I, but the IGF-I response to CP may be affected by the available ME. Undernutrition can attenuate the IGF-I response to GH and uncouple the regulation of IGF-I normally ascribed to GH.     

Dietary L-carnitine increases plasma insulin-like growth factor-I concentration in chicks fed a diet with adequate dietary protein level

1. The effect of L-carnitine supplemented into experimental diets with varying dietary protein concentrations (50, 200 and 400 g/kg) on body weight gain and plasma insulin-like growth factor-I (IGF-I) concentration in chicks was examined. 2. Dietary L-carnitine supplementation provided 0, 200, 500 and 1000 mg/kg. Chicks were given the diet ad libitum for 10 d. 3. When L-carnitine was provided as 500 or 1000 mg/kg, body weight gain was significantly improved in birds receiving the 200 and 400 g protein/kg diets. 4. There was an interaction between dietary L-carnitine and protein content on plasma IGF-I concentration. L-carnitine supplementation had little influence on plasma IGF-I concentrations in birds receiving the low protein (50 g/kg) diet. When dietary L-carnitine concentrations were increased from 0 to 1000 mg/kg in the adequate protein (200 g/kg) diet, plasma IGF-I concentrations were also increased. However, when dietary L-carnitine content was more than 500 mg/kg in the 400 g/kg protein group, plasma IGF-I concentration decreased with increasing dietary L-carnitine content. 5. Body weight change correlated significantly with the alteration in plasma IGF-I concentrations in chicks given diets with adequate dietary protein. 6. In conclusion, the improvement in body weight gain caused by dietary L-carnitine supplementation was achieved when chicks were given their dietary protein requirement, which may be partially explained by an increase in plasma IGF-I concentration.     

The effect of three different doses of sodium pentosan polysulphate on haematological and haemostatic variables in adult horses

OBJECTIVE: To evaluate the effects of three different doses of sodium pentosan polysulphate (PPS) on haematological and haemostatic variables in adult horses. DESIGN: Eight adult standardbred horses were used. All horses received a single injection of 0, 3, 6, and 10 mg/kg of PPS at the beginning of each treatment week for 4 weeks so that by the end of the study all horses had received all four doses of PPS. Blood samples were collected at 0, 1, 2, 3, 4, 6, 8, 12, 24, 48, and 168 h after each weekly injection of PPS. Variables measured were packed cell volume, haemoglobin, red blood cell count, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, platelet count, white cell count, neutrophil count, lymphocyte count, eosinophil count, monocyte count, serum protein, fibrinogen, prothrombin time, and activated partial thromboplastin time (PTT). Data were analysed using an ANOVA. Significance was set at P < 0.05. RESULTS: There was a dose-dependent increase in PTT. A significant increase in PTT occurrred in all treatment groups when compared to horses receiving 0 mg/kg in which there was no change over time. The PTT values all returned to baseline by 48 h after treatment. The mean neutrophil count was higher 3 h after treatment when compared to time 0. Horses receiving 3 mg/kg of PPS had a higher lymphocyte count 4 h after injection, and those receiving 6 and 10 mg/kg had higher counts at 3,4,6 and 8 h after injection when compared to time 0. At 8 h after injection horses receiving 6 and 10 mg PPS had higher lymphocyte counts than horses not receiving PPS. CONCLUSIONS: PPS causes a dose-dependent prolongation of PTT in horses. At the dose rates currently recommended for treatment of joint problems in horses this increase was small and remained elevated from baseline for up to 24 h. Based on these findings doses of PPS up to 3 mg/kg should not be administered to horses within 24 h of high stress activities or where physical injury may occur.     

Origin of plasma insulin-like growth factor-I (IGF-I) during estrus in goats

The objective of this study was to clarify the origin of the increase in plasma insulin-like growth factor-I (IGF-I) during estrus in goats. Focusing on the uterus, the effect of estradiol-17 beta (E2) on the secretion of IGF-I was examined using ovariectomized and hysterectomized animals. A single 5 microg/kg BW of E2 was injected intramuscularly into ovariectomized and hysterectomized goats for 3 consecutive days, and plasma IGF-I concentrations in the two groups were compared. The concentrations of IGF-I rose after the treatments in both groups. The concentrations were significantly higher from 3 to 8 days after the treatment than before the treatment in ovariectomized goats (P<0.05), and from 1 to 3 days after the treatment than before in hysterectomized goats (P<0.05). Thus higher concentrations of plasma IGF-I tended to last longer in ovariectomized than hysterectomized goats. The area under the IGF-I response curve for the 8-day period after the first injection of E2 tended to be greater in ovariectomized than in hysterectomized goats. The results show that E2 increases plasma IGF-I concentrations in goats, and suggest that E2-stimulated IGF-I in plasma may originate mainly from the uterus.     

Biological activity of insulin-like growth factor-I purified from chicken serum

This study describes a rapid purification of insulin-like growth factor-I from chicken serum and the immunological, biological and receptor binding activity of the peptide. It was purified after initial extraction, by cation exchange chromatography, hydrophobic interaction chromatography and reverse phase chromatography up to 1.4 x 10(6)-fold with an overall yield ranging from 10-30%. The N-terminal amino acid sequence was the same as predicted from the nucleotide sequence of a chicken IGF-I cDNA and the partial sequence obtained from a previously reported purification. The material was both immunologically and biologically active. It had a 50% potency compared to human IGF-I in a radioimmunoassay using an antiserum raised against human IGF-I, stimulated the incorporation of [3H]-thymidine into DNA in cultured chick embryo myoblasts with a half-maximum effective dose of 5 ng/ml and displaced [125I]-labelled human IGF-I and IGF-II from binding sites in microsomal membranes prepared from both the chicken liver and the lactating rabbit mammary gland in a dose dependent manner.     

Insulin-like growth factor-I concentration in Holstein female cattle: variations with age, stage of lactation and growth hormone-releasing factor administration

Plasma insulin-like growth factor-I (IGF-I) concentrations were monitored in Holstein females through different periods of their growth, lactation and after acute or chronic growth hormone-releasing factor (GRF) administration. Plasma samples were radioimmunoassayed using a human IGF-I antibody after a 24 hr incubation in a HCl(.1N)-glycine(.2M) buffer (pH 2). In a first study, IGF-I concentrations were measured in Holstein females of different ages and(or) stages of lactation (n = 6 per group). The IGF-I concentrations in newborn calves (102.0 +/- 11.3 ng/ml) markedly decreased (P less than .01) in 1 mo old animals (50.2 +/- 7.1 ng/ml), then increased (P less than .01) to 137.0 +/- 5.1 and 137.4 +/- 11.0 ng/ml in 6 and 10 mo old heifers, respectively. In dairy cows, IGF-I concentrations were low 24 hr post-partum (44.7 +/- 7.6 ng/ml) and then increased (P less than .05) to remain stable throughout lactation (91.3 +/- 4.9, 92.8 +/- 12.9, 96.1 +/- 7.6, 90.7 +/- 8.8 ng/ml at 2, 3, 6 and 9 mo of lactation, respectively). There was a further increase (P less than .05) to 113.7 +/- 3.1 ng/ml during the dry period. In a second trial, blood samples were collected from lactating dairy cows every 2 hr for 24 hr following a sc injection of saline (n = 4) or human (h) GRF (1-29)NH2 (10 micrograms/kg BW, n = 4). The IGF-I peak concentration was reached on average 10 hr after the GRF injection and was higher (P less than .01) in treated cows than in control cows (135.4 vs 86.9 +/- 16.2 ng/ml). In the last trial, daily sc injections of 10 micrograms of hGRF(1-29)NH2 per kg BW to dairy cows (252 days of lactation) for 57 days, which increased milk production by 14% (2 kg/day), also increased (P less than .01) IGF-I concentration: 127.1 +/- 5.3 and 118.0 +/- 1.6 vs 90.7 +/- 4.7 and 96.0 +/- 5.0 ng/ml on days 29 and 57 of treatment for treated (n = 9) and control (n = 8) cows, respectively. Thus, the IGF-I concentration in dairy cattle varies with age and stage of lactation, and is increased by GRF administration in lactating dairy cows.     

In vitro effect of leptin on growth hormone (GH)- and insulin-like growth factor-I (IGF-I)-stimulated progesterone secretion and apoptosis in developing and mature corpora lutea of pig ovaries

This study was designed to determine whether leptin modulates growth hormone (GH)- and insulin like growth factor-I (IGF-I)-stimulated progesterone (P4) production by corpora lutea (CL). Luteal cells were recovered from early developing (ELP) and mature (MLP) corpora lutea and cultured in defined medium with various combinations of GH, IGF-I, and leptin (0-200 ng/ml). P4 concentrations in the media were determined after 48 h of culture. During the early luteal phase, leptin at all used doses had no effect on basal P4 secretion, but it did suppress caspase-3 activity. When added in combination with GH, it had no effect on either GH-stimulated P4 secretion or apoptosis. Concomitant treatment with IGF-I and leptin decreased P4 secretion and parallelly increased the apoptosis rate. In mature corpora lutea of full secreting capacity, leptin at all doses had no effect on basal and GH-stimulated P4 secretion and caspase-3 activity. Only at the highest dose (200 ng/ml) when leptin was added with IGF-I did P4 secretion decrease with no effect on the caspase-3 activity. We conclude that the role of leptin is to restrict the stage of CL formation. During this luteal phase, leptin acts as an antiapoptotic factor and, at the same time, reverses antiapoptotic action of IGF-I, thereby protecting cells from excessive apoptosis and supporting retention of appropriate cell numbers, which is necessary for maintenance of homeostasis in developing CL.     

Temporal pattern of insulin-like growth factor-I response to exogenous bovine somatotropin in lactating cows

The effect of exogenous bovine somatotropin (bST) treatment on the temporal pattern of insulin-like growth factor-I (IGF-I) in serum of four multiparous Holstein cows was examined. Cows (190 +/- 24 days postpartum) were treated with daily subcutaneous injections of recombinant bST (40 mg) or excipient for 12-day periods in a crossover experimental design. During excipient treatment, concentrations of IGF-I in serum were relatively constant throughout the day and averaged 70 ng/ml. Following the first bST injection, serum IGF-I began increasing after a lag of 5 to 7 hr and progressively increased over the first 2 days of treatment. Serum IGF-I levels were approximately 2-fold greater than control values at the end of day 1 of bST treatment, with a 3-fold elevation observed at the end of day 2. Concentrations of IGF-I in serum plateaued by day 3 of bST treatment. Serum concentrations of IGF-I did not follow the oscillating pattern of bST in serum resulting from daily bST injections. Milk yield (3.5% fat-corrected) plateaued after 6 days of bST treatment and was increased 61% (+15.3 kg). Both IGF-I and milk yield remained essentially constant across days for the remainder of treatment. Following cessation of treatment, serum IGF-I and milk yield gradually declined, returning to control values after approximately 4 days. The temporal pattern of circulating concentrations of IGF-I is consistent with a role for IGF-I in mediating a portion of the effects of exogenous bST in lactating cows.     

Use of growth hormone response to growth hormone-releasing hormone to determine growth potential in beef heifers.

The response of GH to GHRH at weaning is known to predict postweaning growth and body composition in beef bulls. The objective of this study was to determine whether GH response to a challenge of GHRH and plasma IGF-I can predict growth rate and body composition in the beef heifer. Growth hormone response to a challenge with two doses of GHRH was measured in 67 Angus heifers averaging 225 d of age (SD = 21) and 217 kg BW (SD = 32). Blood samples were collected at 0 and 10 min relative to an initial "clearance dose" (4.5 micrograms GHRH/100 kg BW) and again, 3 h later, relative to a challenge dose (1.5 or 4.5 micrograms GHRH/100 kg BW). Each animal received each of the two challenge doses, which were randomly assigned across 2 d of blood collection. Serum GH concentration was measured by RIA. Plasma was collected every 28 d during a 140-d growth test and assayed for IGF-I by RIA. Body weight was measured every 28 d and hip height was measured at weaning and at the end of a 140-d growth test. Average daily gain was calculated on d 140 of the growth test and body composition measurements were estimated by ultrasound 2 wk after completion of the growth test. Responses to the two GHRH challenges were dose-dependent (P < 0.05). Average daily gain tended to be related to GH response to the 1.5 micrograms GHRH/100 kg BW dose (R2 = 0.05; P = 0.06), but no relationship was observed at the 4.5 micrograms GHRH/100 kg BW dose (R2 = 0.00; P = 0.93). An inverse relationship (R2 = 0.06; P = 0.02) was observed between response to the 1.5 micrograms GHRH/100 kg BW dose and intramuscular fat percentage. Mean plasma IGF-I concentration was positively associated with ADG (R2 = 0.06; P < 0.01). Growth hormone response to GHRH is modestly related to body composition but not to ADG in weanling beef heifers and likely has limited use in evaluation of growth performance in replacement beef heifers.     

Effect of epidermal growth factor and insulin-like growth factor I on porcine preantral follicular growth, antrum formation, and stimulation of granulosal cell proliferation and suppression of apoptosis in vitro

The object of this study was to investigate the role of epidermal growth factor (EGF) and IGF-I in the regulation of preantral follicular growth, antrum formation, and granulosal cell proliferation/ apoptosis. Porcine preantral follicles were manually dissected and cultured for up to 8 d in Waymouth's (Exp. 1) or alpha-minimum Eagle's essential medium (Exp. 2 and 3) supplemented with 10 microg/mL of transferrin, 100 microg/mL of L-ascorbic acid, and 2 mU/mL of ovine FSH, in the presence (Exp. 1 and 3) or absence (Exp. 2) of 7.5% fetal calf serum. According to the experimental protocol, IGF-I (0, 1, 10, or 100 ng/mL; Exp. 1), or IGF-I (50 ng/mL), EGF (10 ng/mL) and EGF+IGF-I (Exp. 2 and 3) were added to the culture media. In Exp. 1, follicles exhibited a concentration-dependent response (P < 0.05) to IGF-I, with the highest rates of granulosal cell proliferation, follicular integrity, and recovery rate of cumulus cell-oocyte complexes and lowest incidence of apoptosis occurring at the highest IGF-I dose. In Exp. 2 serum-free medium, granulosal cell proliferation was low (1 to 5%), irrespective of whether EGF and/or IGF-I were present and cellular apoptosis was increased (P < 0.05) on d 4 and 8 in the EGF+IGF-I group compared with the addition of either factor alone. In Exp. 3, granulosal cell proliferation was high in all follicles cultured in serum-containing medium for the first 3 d, but fell sharply (P < 0.05) on d 4, except in media containing IGF-I. Collectively, EGF and IGF-I increased granulosal cell proliferation, decreased apoptosis, and promoted follicular antrum formation. These results may provide useful information for developing a preantral follicular culture system in which the oocytes are capable of fertilization and embryonic development.     

Association of single nucleotide polymorphisms in the growth hormone and growth hormone receptor genes with blood serum insulin-like growth factor I concentration and growth traits in Angus cattle

This study was conducted to identify polymorphisms in the promoter and coding regions of the bovine growth hormone and growth hormone receptor genes and to study association of polymorphisms identified in these genes with growth traits and serum insulin-like growth factor-I (IGF-I) concentration. The denaturing gradient gel electrophoresis method and sequencing were utilized to identify three new single nucleotide polymorphisms in the promoter region of the growth hormone gene in Angus cattle. Polymerase chain reaction-based restriction fragment length polymorphism procedures were developed for rapid determination of the single nucleotide polymorphism genotypes in the growth hormone and the growth hormone receptor genes among Angus calves from lines divergently selected for high or low blood serum IGF-I concentration. The IGF-I concentration and growth traits were analyzed using animal models. The single nucleotide polymorphism in the promoter region of the growth hormone receptor gene was associated with serum IGF-I concentration on d 42 of the postweaning test and with mean IGF-I concentration. The associated effects of the markers need to be verified in other populations.     

Regulation of in vitro growth of preantral follicles by growth factors in goats

Goat preantral follicles were cultured to investigate the effects of insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) on the in vitro growth and viability of oocytes. Preantral follicles were isolated mechanically and enzymatically (using collagenase and DNase) from prepuberal goat ovaries. The working medium was composed of Defined Eagle's Minimum Essential Medium (DMEM) supplemented with HEPES (20 mM), 10% fetal calf serum (FCS), hypoxanthine (2 mM), dibutyryl cyclic adenosine 3',5'-monophosphate (dbcAMP) (2 mM), penicillin (75 ng/ml) and streptomycin (50 ng/ml). The culture medium consisted of the working medium with follicle stimulating hormone (FSH) (100 ng/ml) and hydrocortisone (40 ng/ml) added. In the experiment, goat preantral follicles were cultured for 9 days in the culture medium and in the culture medium supplemented with either IGF-I (100 ng/ml), EGF (50 ng/ml), bFGF (50 ng/ml) or IGF-I (100 ng/ml)+EGF (50 ng/ml). The results indicated that IGF-I (100 ng/ml) effectively maintained the survival of oocytes and promoted their growth; EGF (50 ng/ml) enhanced the survival rate of oocytes but had a negative effect on oocyte growth; bFGF (50 ng/ml) stimulated oocyte survival but had no obvious effect on their growth while IGF-I (100 ng/ml) and EGF (50 ng/ml) in combination had a greater effect on both survival and growth rate of oocytes than IGF-I or EGF alone. The supplementation of IGF-1 and EGF to the culture medium is recommended in the culture of goat preantral follicles.     

Effects of intraovarian infusion of insulin-like growth factor-I on ovarian follicular function in cattle

The objective of this study was to determine if increased secretion of intraovarian insulin-like growth factor-I (IGF-I), experimentally induced via minipumps, affects follicular function in cattle. Fourteen cycling Holstein cows were divided equally into two groups: Control, osmotic minipumps (containing vehicle) surgically inserted into each ovary, or IGF-I treated, osmotic minipumps as in Controls but pumping 2.0 microg of recombinant human IGF-I per hr for 7 days. All cows were synchronized with prostaglandin F(2alpha) 0.10) between Control and IGF-I-treated cows during Days 2 to 6 of treatment. IGF-I treatment increased (P<0.05) estradiol concentrations in follicular fluid of small follicles, but had no effect (P<0.10) on estradiol concentrations in follicular fluid of large follicles, or on progesterone, androstenedione, or IGF binding protein concentrations in small or large follicles. We conclude that a 7-day infusion of IGF-I directly into the stroma of the ovary altered follicular growth and follicular fluid estradiol concentrations.     

Effect of dietary supplementation of chitosan and galacto-mannan-oligosaccharide on serum parameters and the insulin-like growth factor-I mRNA expression in early-weaned piglets

The study was to determine effects of dietary supplementation of chitosan (COS) and galacto-mannan-oligosaccharids (GMOS) on some serum biochemical indices, serum growth hormone (GH) and insulin-like growth factor-I (IGF-I) levels, and hepatic and long gissimus muscle IGF-I mRNA expression in early-weaned piglets. Twenty six Duroc × Landrace × Yorkshire piglets at the age of 15 days were used. The piglets had access to creep feed during the suckling. Six piglets were sacrificed for sampling at the beginning of the study. The other 20 piglets were individually housed in metabolic cages and randomly allotted to four corn and soybean meal-based diets including the control group, the antibiotic group with 110 mg lincomycin/kg diet, the COS group containing 0.025% COS, and the GMOS group with 0.20% GMOS, respectively, in a 2-week feeding experiment. Blood urea nitrogen (BUN) level was reduced whereas serum total protein concentration was increased (P < 0.05) in responses to the COS and GMOS supplementation. Dietary supplementation of COS and GMOS also increased (P < 0.05) the serum GH and IGF-I levels along with enhanced hepatic and the muscle IGF-I mRNA abundance. Dietary supplementation of oligosaccharides such as COS and GMOS may improve growth and feed conversion efficiency by increasing plasma GH and IGF-I levels, in the early-weaned piglets.     

Endocrine and metabolic changes during altered growth rates in beef cattle

Eight steers from a group of 14 were fed ad libitum from 240 to 510 kg live weight, gaining at 1.4 +/- .2 kg/d. The six other steers were diet-restricted and grew at .37 +/- .09 kg/d from 240 to 307 kg, prior to ad libitum realimentation on the same diet to a final weight of 510 kg. Blood samples taken during the growth phases from both treatments were analyzed for insulin-like growth factor-I (IGF-I), triiodothyronine (T3), thyroxine (T4), glucose (GLU), nonesterified fatty acids (NEFA), and blood urea nitrogen (BUN) and (or) growth hormone (GH). During restricted growth, mean serum concentrations of GH were elevated (45.6 vs 23.4 ng/ml; P less than .05), serum concentrations of IGF-I decreased (108 vs 167 ng/ml; P less than .05) compared with control steers with ad libitum access to feed. Levels of T4 and GLU also were lower (P less than .05) during restricted than during normal growth. During early realimentation, levels of GLU (P less than .05), IGF-I (P less than .01), T4 and BUN (P less than .01) increased. Levels of T3 remained unchanged, whereas concentration of NEFA declined (P less than .001). Blood urea nitrogen decreased during early realimentation despite a large increase in diet protein intake and in protein storage, suggesting an increased efficiency of nitrogen use for protein synthesis. During realimentation, IGF-I levels rose above those of control steers and remained higher at the final weight of 510 kg (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)