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Insulin-like growth factor-I in conjunction with gonadotropins are important stimulators of mitosis and ovarian steroid production by granulosa and thecal cells, which are required for normal oocyte development and hormonal feedback signaling to the hypothalamus and pituitary. However, a comprehensive evaluation of the changes in gene expression induced by IGF-I has not been conducted. Our objective was to characterize granulosa cell gene expression in response to IGF-I treatment. Porcine granulosa cells were pooled in 4 biological replicates and treated with FSH (baseline) or FSH+IGF-I for 24 h in vitro. The RNA was collected and hybridized to 8 Affymetrix Porcine GeneChips (Affymetrix, Santa Clara, CA) in a paired design. Differentially regulated gene sequence element sets (P < 0.01) were used as queries in the UniGene database searching for annotated genes. Abundance of messenger RNA (mRNA) for genes differentially expressed in the microarray analysis was determined through multiplex assays of one-step real-time reverse transcription-PCR and further analyzed under a statistical model including the fixed effect of treatment. A total of 388 gene sequence element sets were differentially expressed, and 42 matched annotated genes in the UniGene database. Of the 3 upregulated target genes selected for further quantitative reverse transcription-PCR analysis, only FGF receptor 2 III c (FGFR2IIIc) mRNA abundance was significantly increased by IGF-I. Of the 3 downregulated target genes selected for further analysis, only thrombospondin-1 (THBS1) mRNA abundance was significantly decreased by IGF-I. Further study revealed that neither FSH nor estradiol affected the IGF-I-induced suppression of THBS1 mRNA abundance. These results provide the first comprehensive assessment of IGF-I-induced gene expression in granulosa cells and will contribute to a better understanding of the molecular mechanisms of IGF-I regulation of follicular development. Involvement of FGFR2IIIc and THBS1 in mediating IGF-I-induced granulosa cell steroidogenesis and proliferation during follicular development is novel, but their specific roles will require further elucidation. Key words: gene expression, granulosa cell, insulin-like growth factor-I, pig, thrombospondin-1

The objective of this study was to determine the effects of BCS at calving and the amount of postpartum protein supplementation on the dominant follicle (DF) and behavioral characteristics at the first postpartum estrus of mature beef cows. Multiparous Angus x Hereford cows (n = 45) were fed to calve in thin (T; < 5) or moderate (M; [greater than or equal to] 5) BCS. Cows were stratified by BCS and calving date, and randomly assigned to receive lesser (L; 1.2 kg/d) or greater (G; 2.5 kg/d) amounts of a 42% CP supplement. All cows grazed the same native grass pasture and were fed in individual stalls for 49 [+ or -] 2 d. Beginning 20 d after calving, blood samples were collected from each cow thrice weekly, and estrous behavior was monitored continuously with a radiotelemetry system. At 4 to 16 h after the onset of estrus, size of the DF was determined by ultrasonography. Body condition score of T cows was less (P < 0.01) at calving than M cows; L and G cows had similar BCS at calving and at the end of the feeding period. Body weight gains during treatment did not differ for L or G cows. Duration from calving to first estrus was greater (P < 0.01) for T than M cows. The incidence of a short luteal phase before first estrus was not influenced by BCS or protein supplement. Concentrations of IGF-I in plasma tended (P < 0.07) to be greater and size of the DF was greater (P < 0.01) for M than T cows. Size of the DF tended (P < 0.06) to be greater for G than L cows. Duration and number of mounts received at the first estrus were not influenced by BCS or supplement. Pregnancy rate of M cows during the breeding season was greater (P < 0.05) than T cows. Postpartum protein intake and BCS at calving influenced the size of the DF at the first postpartum estrus in mature suckled beef cows. Cows should be managed to calve in moderate BCS and maintain BW after parturition to decrease the interval to first estrus, increase follicular development, and maximize pregnancy rate. Key words: beef cow, body condition, estrus, follicle, postpartum, protein

Our objective was to determine if prolonged exposure to various durations of light (i.e., photoperiod) would affect serum IGF-I concentrations in heifers. Thus, 16 Holstein heifers, 2 to 4 mo of age, were exposed during a 5-wk pretreatment period to 12 h of cool-white fluorescent light (L) at an intensity of 1200 lux and 12 h of dark (D). At 5 wk, photoperiods were adjusted to 24 L: 0 D (24 L), 20 L: 4 d (20 L), 16 L: 8 D (16 L) or 8 L: 16 D (8 L) per 24 h (n=4 heifers per photoperiod treatment). Blood was sampled at 5 wk and monthly for 4 mo. During each sampling period, blood was collected at 16-h intervals for 48 h and serum IGF-I was determined by RIA. Photoperiod treatment, month of experiment and their interactions affected serum IGF-I concentrations. Averaged over months, concentrations of serum IGF-I was greatest in heifers on 16 L; heifers on 20 L had IGF-I concentrations similar to 8 L, 16 L and 24 L and heifers on 24 L had concentrations similar to that of heifers on 8 L. Heifers in all treatment groups exhibited an increase in serum IGF-I concentration during the 4 mo of treatment. Heifers on 16 L and 20 L exhibited the greatest difference in serum IGF-I concentrations compared with 8L heifers after 3 mo of treatment. In conclusion, 16 L increases concentrations of serum IGF-I above that seen for heifers treated with 8 L or 24 L. Key words: Photoperiod, heifers, growth factor, prepubertal, INTRODUCTION Increased duration of light (i.e., photoperiod) increases body growth in dairy heifers [1,2] and milk production in lactating dairy cows [3,4]. Of the hormones that are affected by photoperiod [...]

Pregnant Angus x Hereford cows (n = 73) were used to determine the effects of amount of nutrient intake and BCS on concentrations of IGF-I, insulin, leptin, and thyroxine in plasma. At 2 to 4 mo of gestation, cows were blocked by BCS and assigned to one of four nutritional treatments: high (H = a 50% concentrate diet fed ad libitum in a drylot) or adequate native grass pastures and one of three amounts of a 40% CP supplement each day (M = moderate, 1.6 kg; L = low, 1.1 kg; or VL = very low, 0.5 kg; as-fed basis). After 110 d of treatment, all cows grazed dormant native grass pasture and received 1.6 kg/d of a 40% CP supplement. At 68, 109, and 123 d of treatment, cows were gathered, and plasma samples were collected by tail venipuncture (fed sample). After 18 h without feed and water, a second plasma sample was collected (fasted sample). At 109 d of treatment, BCS was great est (P < 0.05) for H cows, similar for M and L cows, and least for VL cows. Concentrations of insulin and leptin were greater (P < 0.05) for H cows than for M and VL cows at 68 and 109 d, but similar for all groups at 123 d. Thyroxine in plasma was greatest (P < 0.05) for H cows at 68 d and similar for cows on all treatments at 123 d. Concentrations of IGF-I, insulin, and leptin in fed and fasted cows were positively correlated with BCS at 109 d. Body condition was predictive of concentrations of IGF-I, insulin, and leptin when cows had different nutrient intakes, but BCS accounted for less than 12% of the variation in plasma concentrations of IGFI, insulin, and leptin when nutrient intake was the same for all cows. We conclude that amount of nutrient intake has a greater influence than body energy reserves on IGF-I, insulin, and leptin concentrations in the plasma of gestating beef cows. Key Words: Beef Cows, Body Condition, Insulin, Insulin-Like Growth Factor I, Leptin, Nutrition

Comparisons of numbers of antral ovarian follicles and corpora lutea (CL), of blood hormone concentrations, and of follicular fluid steroid concentrations and IGFBP activity were conducted between cows selected (twinner) and unselected (control) for twin births to elucidate genetic differences in the regulation of ovarian follicular development. Ovarian follicular development was synchronized among cows by a single i.m. injection of PG[F.sub.2[alpha]] on d 18 of the estrous cycle; six cows per population were slaughtered at 0, 24, 48, and 72 h after PG[F.sub.2[alpha]], Jugular vein blood was collected from each animal at PG[F.sub.2[alpha]] injection and at 24-h intervals until slaughter. Ovaries of twinner cows contained more small ([less than or equal to] 5 mm in diameter, P < 0.05), medium (5.1 to 9.9 mm, P < 0.05), and large ([greater than or equal to] 10.0 mm, P < 0.01) follicles and more (P < 0.01) CL than ovaries of controls. Follicular fluid concentrations of estradiol, androstenedione, testosterone, and progesterone reflected the stage of follicular development and were similar for twinner and control follicles at the same stage. Earlier initiation of follicular development and/or selection of twin-dominant follicles in some twinner cows resulted in greater concentrations of estradiol in plasma at 0, 24, and 48 h and of estradiol, androstenedione, and testosterone in follicular fluid of large follicles at 0 h after PG[F.sub.2[alpha]] for twinner vs. control cows (follicular status x time x population, P < 0.01). Binding activities of IGFBP-5 and -4 were absent or reduced (P < 0.01) in follicular fluid of developing medium and large estrogen-active (estradiol:progesterone ratio > 1) follicles but increased with atresia. Only preovulatory Graafian follicles lacked IGFBP-2 binding, suggesting a possible role for IGFBP-2 in selection of the dominant follicle. Concentrations of IGF-I were twofold greater (P < 0.01), but GH (P = 0.10) and cholesterol (P < 0.05) were less in blood of twinners. Three generations of selection of cattle for twin ovulations and births enhanced ovarian follicular development as manifested by increased numbers of follicles within a follicular wave and subsequent selection of twin dominant follicles. Because gonadotropin secretion and ovarian steroidogenesis were similar for control and twinner cattle, enhanced follicular development in twinners may result from decreased inhibition by the dominant follicle(s), increased ovarian sensitivity to gonadotropins, and/or increased intragonadal stimulation, possibly by increased IGF-I. Key Words: Cattle, Gonadotropins, Insulin-Like Growth Factor Binding Proteins, Ovarian Folliculogenesis, Steroids, Twins

The influences of body condition score (BCS) at calving and postpartum nutrition on endocrine and ovarian functions, and reproductive performance, were determined by randomly allocating thin (mean BCS = 4.4 [+ or -] 0.1) or moderate condition (mean BCS = 5.1 [+ or -] 0.1) Angus x Hereford primiparous cows to receive one of two nutritional treatments after calving. Cows were fed to gain either 0.45 kg/d (M, n = 17) or 0.90 kg/ d (H, n = 17) for the first 71 [+ or -] 3 d postpartum. All cows were then fed the M diet until 21 d after the first estrus. A replication (yr 2; M, n = 25; H, n = 23) was also used to evaluate reproductive characteristics. Concentrations of IGF-I, leptin, insulin, glucose, NEFA, and thyroxine were quantified in plasma samples collected weekly during treatment and during 7 wk before the first estrus. Estrous behavior was detected by radiotelemetry, and luteal activity was determined based on concentrations of progesterone in plasma. All cows were bred by AI between 14 and 20 h after onset of estrus, and pregnancy was assessed at 35 to 55 d after AI by ultrasonography. Cows that calved with a BCS of 4 or 5 had similar endocrine function and reproductive performance at the first estrus. During treatment, H cows gained BW and increased BCS (P < 0.01), and had greater (P < 0.05) concentrations of IGF-I, leptin, insulin, glucose, and thyroxine in plasma than M cows. However, during the 7 wk before the first estrus, plasma concentrations of IGF-I, leptin, insulin, glucose, NEFA, and thyroxine were not affected by time. Cows previously on the H treatment had a shorter (P < 0.01) interval to first postpartum estrus and ovulation, and a larger dominant follicle (P < 0.01) at first estrus, than M cows, but duration of estrus and the number of mounts received were not influenced by nutrient intake. Pregnancy rate at the first estrus was greater (P < 0.03) for H (76%, n = 38) than for M (58%, n = 33) cows. Increased nutrient intake after calving stimulated secretion of anabolic hormones, promoted fat deposition, shortened the postpartum interval to estrus, and increased pregnancy rate at the first estrus. Concentrations of IGF-I and leptin in plasma were constant during 7 wk before the first estrus, indicating that acute changes in these hormones are not associated with the resumption of ovarian function in primiparous beef cows. Key Words: Beef Cows, Fertility, Insulin-Like Growth Factor, Leptin, Nutrition, Postpartum

The effect of pulsatile infusion of gonadotropin-releasing hormone (GnRH) on follicular function was evaluated in nutritionally induced anovulatory beef cows. After 4 (short; n = 12) or 18 wk (long; n = 12) of anovulation, cows were randomly assigned within anovulatory group to either 2 [micro]g of GnRH treatment or saline (control; i.v.) every hour for 5 d. Ovarian structures were monitored by daily ultrasonography. Growth rate of the largest follicle (P < 0.01) and maximal size of the largest follicle during treatment were greater (P < 0.01) for GnRH vs control cows. At exsanguination after 5 d of GnRH treatment, the size of the second-largest follicle was greater (P < 0.05) in short (i.e., 4 wk) anovulatory cows than in long (i.e., 18 wk) anovulatory cows and the largest follicle tended (P < 0.10) to be larger in long vs short anovulatory cows. Short anovulatory GnRH-treated cows had more small follicles than short anovulatory control cows or long anovulatory GnRH-treated or control cows (anovulation x GnRH; P < 0.10). Follicular fluid (FFL) concentrations of estradiol (P < 0.01) and androstenedione (P < 0.05) were greater in GnRH vs control cows. Concentrations of insulin-like growth factor-I were greater (P < 0.10) in large vs small follicles in cows that were anovulatory for 4 wk, but not in cows that were anovulatory for 18 wk. The amount of insulin-like growth factor-binding protein (IGFBP)-3 in FFL was greater (P < 0.05) in 4vs 18-wk anovulatory cows. Amounts of IGFBP-2, -4, and -5 were greater (P < 0.001) in FFL of small ( Key Words: Anovulation, Beef Cows, Follicles, Gonadotropin-Releasing Hormone, Insulin-Like Growth Factor, Nutrition

The objective of this study was to determine the effect of genotype and week postpartum on serum concentrations of IGF-I, body condition score (BCS), BW, and ovarian function in beef cows. Cows from the following genotypes were utilized in two consecutive years: Angus (A x A; n = 9), Brahman (B x B; n = 10), Charolais (C x C; n = 12), Angus x Brahman (A x B; n = 22), Brahman x Charolais (B x C; n = 19) and Angus x Charolais (A x C; n = 24). Serum concentrations of IGF-I, BCS, and BW were determined between wk 2 and 9 postpartum. Rectal ultrasound was used to determine days postpartum to first medium (6 to 9 mm) and first large ([greater than or equal to] 10 mm) follicle. Averaged across genotype, BCS decreased (P < 0.05) from 5.0 [+ or -] 0.1 on wk 3 to 4.8 [+ or -] 0.1 on wk 6 postpartum, and BW decreased (P < 0.05) between wk 2 and 3 and again between wk 4 and 9 postpartum. Averaged over year and week postpartum, serum IGF-I concentrations were greatest (P < 0.05) in B x B cows (46 [+ or -] 5 ng/mL) compared with all other genotypes; lowest in A x A (12 [+ or -] 4 ng/mL), C x C (13 [+ or -] 4 ng/mL), and A x C cows (18 [+ or -] 3 ng/mL); and intermediate (P < 0.05) in A x B (28 [+ or -] 3 ng/mL) and B x C (26 [+ or -] 3 ng/mL) cows compared with all other genotypes. Serum IGF-I concentrations did not change (P > 0.10) with week postpartum in C x C, A x A, and A x C cows, but increased (P < 0.05) between wk 2 and 7 postpartum in B x C, A x B, and B x B cows. Average interval to first medium (16 [+ or -] 2 d) and first large (35 [+ or -] 2 d) follicle did not differ (P > 0.10) among genotypes. Serum IGF-I concentrations correlated with BCS (r = 0.53 to 0.72, P < 0.001) but not with days to first large follicle (r = -0.19 to -0.22, P > 0.10). Averaged across genotypes, cows that lost BCS postpartum had lower (P < 0.01) serum IGF-I concentrations. Cows that calved with adequate BCS (i.e., > 5) had greater (P < 0.01) serum IGF-I concentrations postpartum than cows that calved with inadequate BCS (i.e., < 5) but days to first large and medium follicle did not differ (P > 0.10). In conclusion, concentrations of IGF-I in serum differed among genotypes and were associated with BCS but not days to first large or medium follicle in postpartum beef cows. Key Words: Beef Cows, Follicles, Genotypes, Insulin-Like Growth Factor, Tropics

The objective of the present study was to evaluate changes in equine follicular fluid insulin-like growth factor binding protein (IGFBP) proteolytic activity as well as steroid, IGF, and IGFBP concentrations during follicular development in the mare. Mares (n = 14) were classified as either in the follicular phase (n = 8) or luteal phase (n = 6). Follicles (n = 92) were categorized as small (6 to 15 mm; n = 54), medium (16 to 25 mm; n = 23), or large (> 25 mm; n = 15), and follicular fluid was collected. Estradiol and androstenedione levels in follicular fluid were greater (P < 0.05), and IGFBP-3 concentrations tended to be greater (P < 0.10) in large than in small or medium follicles, whereas IGFBP-2, -4, and -5 levels were less (P < 0.05) in large than in small or medium follicles. Estradiol and androstenedione concentrations were negatively correlated (P < 0.01) with IGFBP-2, -4, and -5 but not IGFBP-3 concentrations. To evaluate proteolysis of IGFBP, follicular fluid was incubated with human [sup.125]I-labeled IGFBP-2, -3, and -5 and protein separated by 12% SDS-PAGE. Follicular fluid caused little or no proteolysis of [sup.125]I-lableled IGFBP-2 or -3, and the small amount of proteolysis of IGFBP-2 and -3 did not differ (P > 0.10) among follicle classes. However, more [sup.125]I-labeled IGFBP-5 was cleaved (P < 0.05) by follicular fluid from large follicles collected during the follicular phase than large follicles during the luteal phase, and small or medium follicles from follicular and luteal phase mares indicating that a protease to IGFBP-5 exists in estrogen-dominant equine follicles. This IGFBP-5 protease was inhibited by kallikrein/serine protease and metalloprotease inhibitors. We conclude that the tendency of estrogen-dominant follicles of mares to have greater levels of IGFBP-3 and lesser levels of IGFBP-2 does not appear to be due to differences in proteolysis, whereas changes in IGFBP-5 levels are likely due to changes in activity of a serine protease or metalloprotease. Changes in IGFBP may alter levels of bioavailable IGF that stimulate steroidogenesis and mitogenesis in developing mare follicles. Key Words: Follicles, Insulin-like Growth Factor, Mares

Chromium (Cr) depletion may exacerbate hyperglycemia and negative outcomes of pregnancy in the streptozotocin (STZ) diabetic pregnant rat model through the regulation of the insulin-like growth factor (IGF) system. To test this hypothesis, 40 female rats, all fed a low Cr diet (i.e., 70 [[micro]gram] Cr/kg diet) from 21 d of age, were randomly assigned one of four treatments, applied on Day 1 of pregnancy, in a 2 x 2 factorial design: 1) very low Cr diet (40 [[micro]gram] Cr/kg diet) + citrate buffer injection, 2) very low Cr diet + STZ injection (30 mg STZ/kg body wt in citrate buffer), 3) adequate Cr diet (2 mg Cr [from added CrK[([SO.sub.4]).sub.2]]/kg diet) + citrate buffer injectionand 4) adequate Cr diet + STZ injection. Blood and tissues were collected on Day 20 of pregnancy. Chromium depletion increased (P < 0.05) urinary hydroxyproline excretion, 22-kDa IGF binding protein (IGFBP) concentration and litter size but decreased (P < 0.05) placental wt, percentage of protein per fetus, and fetal IGF-I and -II concentrations. Chromium had no effect (P > 0.10) on maternal hormones, 32-kDa IGFBP, glucose, or placental and fetal hydroxyproline concentrations. Diabetes decreased (P < 0.05) maternal wt gain, embryonic survival, litter size, mean pup wt and maternal insulin concentrations, increased (P < 0.05) maternal blood glucose, IGF-I concentrations and maternal hydroxyproline excretion but did not affect fetal concentrations of hormones, IGFBP, glucose or hydroxyproline. Interaction between chromium and diabetes tended (P < 0.10) to affect maternal IGF-II concentrations, but had no effect on other maternal or fetal variables. In conclusion, maternal chromium depletion did not exacerbate hyperglycemia or pregnancy outcome in STZ-induced diabetic rats, but may negatively affect fetal protein content by decreasing fetal IGF-II concentrations. Diabetes may negatively affect fetal growth through its effect on maternal glucose, insulin and IGF-I. KEY WORDS: * Chromium * diabetes * insulin-like growth factors * pregnancy * rats

Angus x Hereford heifers were used to determine whether the ovaries of heifers immunized against GnRH would respond to exogenous gonadotropins. Heifers (n = 23; 24 mo; 491 [+ or -]23 kg) were assigned to a 2 x 2 factorial experiment: immunization against GnRH conjugated to human serum albumin (GnRH-IMM) or human serum albumin alone (HSA-IMM), and treatment with gonadotropins (GTH) or saline. The GTH treatment was 2,000 IU PMSG + 1,000 IU hCG, and control heifers were given saline (s.c.). Immunization against GnRH (GnRH-IMM) caused cessation of ovulation (progesterone < 1 ng/mL plasma for 3 wk) and GTH treatment began within 3 to 5 wk after heifers became anovulatory. Heifers immunized against HSA (HSA-IMM) were treated between d 9 and 11 of the estrous cycle. All heifers were given PGF (i.m.) on d 2 (d 0 = start of GTH treatment) and 2,000 IU of hCG (i.m.) on d 4. Ovaries of heifers were evaluated by ultra-sound. Blood was sampled daily from d 0 to d 8 and every second day through d 24 to quantify progester-one and estradiol. Concentrations of estradiol increased with time after GTH but the response was reduced by GnRH-IMM (IMM x GTH x day, P < .01). Number of follicles [greater than or equal to] 6 mm (d 0 to 14) was increased after GTH (GTH x day, P < .001) but was decreased (P < .03) by GnRH-IMM. Immunization against GnRH reduced total follicles [greater than or equal to] 6 mm on d 4 in heifers on both saline and GTH treatments. Treatment with gonadotropins increased the number of follicles [greater than or equal to] 16 mm on d 14 compared with control heifers. The number of CL was increased by GTH (GTH x day, P < .001) but the response was reduced (P < .03) in GnRH-IMM heifers compared with HSA-IMM heifers. We conclude that treatment with gonadotropins will induce follicular growth and ovulation in heifers that are anovulatory due to immunization against GnRH. Key Words: GnRH, Gonadotropins, Heifers, Immunization

The objective of the present study was to determine the effects of IGF-I and insulin on cell proliferation, LH receptors, and basal and LH-induced progesterone and androstenedione production by bovine thecal cells. Cells from large ([greater than or equal to] 8 mm) bovine follicles were cultured for 1 or 2 d in medium containing 10% fetal calf serum (FCS) and treated for 1 or 2 d in serum-free medium with IGF-I, insulin, and(or) LH. Treatment with 30 and 100 ng/mL of IGF-I for 1 or 2 d increased thecal cell numbers in the absence of LH regardless of whether treatments were initiated after 1 or 2 d of exposure to 10% FCS. Co-treatment with LH reduced the stimulatory effect of IGF-I on thecal cell numbers. Insulin at 10 and 100 ng/mL increased cell numbers in the presence of LH. Both IGF-I and insulin were ineffective at stimulating thecal cell progesterone or androstenedione production in the absence of LH. However, IGF-I and insulin increased (P < .05) androstenedione and progesterone production in the presence of LH. Alone, LH had little or no effect on androstenedione and progesterone production, whereas in the presence of 30 and 100 ng/mL IGF-I or 1 to 100 ng/mL insulin, LH stimulated (P < .05) androstenedione production. The stimulatory effects of IGF-I on cell proliferation and progesterone production were not detected in the presence of 100 ng/mL insulin. However, co-treatment with various doses of IGF-I and 100 ng/mL insulin further increased androstenedione production above that seen with insulin alone. In glucose-deficient medium, 25 to 75 mg/dL of glucose increased (P < .05) thecal cell proliferation, progesterone production, and androstenedione production. In the absence or presence of glucose, insulin (100 ng/mL) increased (P < .05) thecal cell proliferation, progesterone production, and androstenedione production. Treatment with 3, 10, or 100 ng/mL LH had no effect (P > .10) on the numbers of IGF-I binding sites on thecal cells but increased (P < .05) androstenedione production. Treatment with 10 and 100 ng/mL IGF-I increased (P < .01) numbers of LH/hCG binding sites. These results indicate that IGF-I and insulin may each play a significant role in thecal cell mitogenesis and LH-induced thecal cell steroidogenesis during follicular development in cattle and that glucose enhances these effects. Furthermore, the synergism between IGF-I and LH on increasing steroidogenesis does not seem to be mediated through increased binding sites for IGF-I in bovine thecal cells but rather, in part, through increased binding sites for LH. Key Words: IGF-I, Insulin, Thecal Cells, Steroidogenesis, Receptors, Cattle

Three experiments were conducted to evaluate spray-dried porcine plasma (SDPP) protein in diets for early-weaned pigs. In Exp. 1, 144 weanling pigs (24 [+ or -] 4 d of age) were used to determine the effects of replacing dried skim milk (DSM) with either 4% SDPP or 2.75% spray-dried blood meal (SDBM) in Phase 1 diets (d 0 to 14 postweaning). During d 0 to 14, pigs fed SDPP or SDBM had higher ADG (P < .05) and ADFI (P < .1) than those fed DSM. Pigs fed SDPP had greater (P < .05) ADG and ADFI (P < .1) than those fed SDBM. In Exp. 2, performance was similar in pigs fed two plasma protein sources (AP-820 and MP-722). In Exp. 3, 18 weanling pigs (19 to 20 d of age) were used to determine the effects of feeding high levels of SDPP on performance and on plasma IGF-I, growth hormone, insulin, and glucose concentrations. Pigs were fed either a control diet containing 21.5% soybean meal (SBM) or a diet containing 14% SDPP. Treatments were applied for 14 d (Phase 1). During d 0 to 14, pigs fed a SDPP had greater ADG and ADFI (P < .05) than pigs fed SBM. Replacing SBM with SDPP did not affect plasma IGF-I and glucose concentrations. However, SDPP replacement increased (P < .06) plasma growth hormone concentrations. Insulin levels were greater (P < .06) in pigs fed SBM than in those fed SDPP. These results indicate that SDPP and SDBM are effective alternatives to DSM or SBM in Phase I diets and the two plasma protein sources will produce similar performance. The factor(s) responsible for this improved performance does not seem to involve a change in plasma IGF-I. Key Words: Pigs, Blood Protein, Performance, Insulin-like Growth Factor, Somatotropin, Insulin

The effect of three rates of gain on carcass composition, lipid partitioning, age and BW at puberty, and concentrations of growth hormone (GH), IGF-I, insulin, glucose, and NEFA in plasma were evaluated in 38 Angus x Hereford heifers. Heifers were allotted by BW and age to three treatments with a replication in each of 2 yr: full-fed (n = 13; FF) to gain 1.36 kg/d; limit-fed (n = 12; LF) to gain .68 kg/d; maintenance-full-fed (n = 13; MFF) to gain .23 kg/d for 16 wk, then full-fed to gain 1.36 kg/d. Heifers were slaughtered within 10 d after the onset of puberty. At slaughter, kidney, pelvic, and heart fat (KPH) and udder (UDDER) were separated from carcass, as was fat surrounding viscera (OM). After 48 h at 4 [degrees] C a carcass side was dissected into subcutaneous fat (SC), intermuscular fat (SEAM), soft tissue (SFT = inseparable lean and fat), LEAN, and BONE. In yr 1, LF heifers (431 d) were older (P < .05) than MFF heifers (371 d) at puberty, but age of FF heifers (389 d) did not differ (P > .10) from that of LF and MFF heifers. In yr 2, FF heifers (351 d) were younger (P < .05) than LF and MFF heifers (398 and 434 d, respectively). The FF heifers had greater (P < .05) BW and a greater (P < .01) percentage of lipid in the carcass at puberty than LF and MFF heifers. During the first 16 wk of treatment, concentrations of NEFA were greater in heifers with slower daily gains (MFF > LF > FF; P < .01). Concentrations of NEFA were lesser and concentrations of IGF-I and insulin were greater in plasma of FF than in that of MFF heifers during the 10 wk before puberty. Treatment significantly altered age, BW, carcass composition, and lipid partitioning at puberty in beef heifers. We conclude that the percentage of body fat is not the sole regulator of puberty, and age may be an important modulator in determining the onset of puberty in beef heifers. Key Words: Carcass Composition, Heifers, Lipid, Nutrition, Puberty

Characteristics of growth hormone (GH), IGF-I, and IGF-binding proteins (IGFBP) were studied in gilts sampled from lines of pigs selected for either fast (line F, n = 14) or slow (line S, n = 14) postweaning ADG. Repeated blood samples were obtained from gilts (approximately 55 kg BW) during a period of feed deprivation and again during refeeding. Averaged across time, the difference in mean plasma GH concentrations of F and S gilts was not significant (7.7 vs 6.4 ng/mL; P > .20) during feed deprivation, and frequency, height, and amplitude of GH pulses did not differ (P > .25) for F and S pigs. Overall, F gilts had greater concentrations of plasma IGF-I than S gilts during feed deprivation (217.3 vs 145.1 ng/mL; P < .03). Across line, plasma IGF-I decreased (P < .01) during feed deprivation. Average GH did not differ (P > .40) for F and S gilts during the refeeding period. Average plasma IGF-I tended (P = .05) to be greater in F gilts than in S gilts during refeeding. Consistent with changes over time during feed deprivation, plasma IGF-I averaged across line increased (P < .01) in response to refeeding. Averaged across time (0 and 48 h refeeding), activity of IGFBP-2 (singlet band at 34 kDa) did not differ significantly (P = .17) in F and S gilts. However, there was a tendency (P = .13) for a line x time interaction. At time 0, the lines did not differ for IGFBP-2 activity, but S gilts had greater (P < .01) activity than F gilts at 48 h after refeeding. Similarly, the lines did not differ for activity of IGFBP-3 (doublet band at 40 and 44 kDa) when averaged across time, but there was a tendency (P = .12) for a line x time interaction. At 0 h, the lines were not different, but at 48 h after refeeding, the S gilts expressed greater (P = .05) IGFBP-3 activity than F gilts. Response to divergent selection for postweaning ADG has occurred, to some extent, through changes in the growth hormone/IGF axis. Throughout periods of feed deprivation and refeeding, pigs selected for fast gain expressed greater concentrations of circulating IGF-I than their contemporaries selected for slow gain. Key Words: Selection, Somatotropin, Insulin-Like Growth Factor, Pigs

Ovulation rate, serum hormone concentrations, follicular fluid (FFL) concentrations of steroids and IGF, IGF binding protein (IGFBP) activity in FFL, and follicular IGF-I and -II mRNA were compared during the follicular phase among five genotypes of ewes: Finn (F), Composite III (C), 1/2 Booroola Merino (B) X 1/2 F (BXF), 1/2 F X 1/2 C (FXC), 1/2 B X 1/2 C (BXC). Composite III ewes were a Columbia X Suffolk X Hampshire crossbred. Ovulation rates for F (n = 7), C (n = 5), BXF (n = 6), FXC (n = 3), and BXC (n = 8) ewes were 3.1, 1.6, 3.8, 2.9, and 2.9 (Pooled SEM = .5), respectively. Concentrations of IGF-I in FFL were 53% greater (P < .05) in large ([greater than or equal to] 4.1 mm) than in small (< 4.1 mm) follicles but did not differ (P > .10) among genotypes. In contrast, FFL IGF-II concentrations were greater (P < .05) in BXC and BXF ewes than in C or FXC ewes but did not differ between small and large follicles. Ligand blotting revealed that IGFBP activity of three species (34, 27 to 29, and 24 kDa) were lower (P < .05) in FFL of large than in FFL of small follicles but did not differ (P > .10) among genotypes. Follicular wall IGF-I mRNA and IGF-II mRNA was detected in 5 and 32% of the samples from preovulatory follicles, respectively, using reverse transcriptase-PCR and ethidium-bromide staining. Ovarian IGF-I mRNA levels, assessed by Northern analysis, in BXF and BXC ewes were greater (P < .05) than those in C ewes; ovarian IGF-I mRNA levels in F and FXC ewes were intermediate and did not differ (P > .10) from those in C ewes. Small follicles from BXC and BXF ewes had severalfold greater (P < .05) estradiol concentrations than those from F or C ewes, whereas large follicles from BXF ewes had twice (P < .05) the estradiol concentrations of follicles from F or C ewes. Progesterone in FFL did not differ among genotypes. Serum LH, FSH, inhibin, IGF-I, and progesterone did not differ (P > .10) among genotypes. In conclusion, higher ovulation rates in B-cross ewes (i.e., BXF and BXC vs C ) were associated with greater levels of FFL IGF-II, FFL estradiol, and ovarian IGF-I mRNA but were not associated with differences in FFL progesterone, IGF-I, or IGFBP. Key Words: Insulin-Like Growth Factor, Ovulation Rate, Follicular Fluid, Ovaries, Sheep, Binding Proteins

The objectives of the present study were to determine the effect of and interaction between basic fibroblast growth factor (bFGF) and heparin, a major bFGF-binding protein, on bovine granulosa cell estradiol and progesterone production. Cells from small (1 to 5 mm) follicles were collected from cattle, cultured for 2 d in medium containing 10% fetal calf serum, and then treated for 1 d with bFGF and(or) heparin in serum-free medium. Treatment with .1 to 10 [[micro]gram]/mL of heparin for 1 d had no effect (P [is greater than] .05), whereas 100 [[micro]gram]/mL of heparin inhibited (P [is less than] .05) FSH-induced estradiol production by bovine granulosa cells. Treatment with .1 to 1.0 ng/mL of bFGF for 1 d, supplied with human serum albumin as a carrier protein, inhibited (P [is less than] .05) FSH-induced estradiol production by bovine granulosa cells, with the greatest inhibition detected at 1.0 ng/mL; coculture with 10 [[micro]gram]/mL of heparin did not influence these effects. In comparison, .1 ng/mL of bFGF supplied carrier-free had no effect (P [is greater than] .05) on FSH-induced estradiol production, whereas 1.0 to 100 ng/mL of carrier-free bFGF inhibited (P [is less than] .05) FSH-induced estradiol production, with the greatest inhibition detected at 100 ng/mL. The presence of heparin (10 [[micro]gram]/mL) had variable effects on granulosa cell estradiol and progesterone production inhibited by carrier-free bFGF. These results indicate that bFGF may play a significant role in FSH-modulated granulosa cell steroidogenesis during follicular development in cattle.

The influence of body energy reserves on the onset of luteal activity and concentrations of LH and IGF-I in serum was evaluated in postpartum anestrous beef cows after early weaning. Multiparous Hereford and Hereford x Angus cows (n = 24) were fed during gestation to establish body condition scores between 3 and 6 (BCS, 1 = emaciated; 9 = obese) at parturition. Concentrations of progesterone in plasma were determined weekly for 5 wk postpartum (PP). Anovulatory cows and their calves (n = 19) were confined in stalls on d 40 [+ or -] 3 PP. Jugular cannulas were inserted on d 44 [+ or -] 3 PP, and calves were weaned (d 0) the following day. Blood samples were collected from all cows for 4 h (every 10 min) before weaning and on d 1, 2, 4, 6, 8, and 10 after weaning and LH was quantified. Progesterone was quantified in daily blood samples until d 10, and in samples taken twice weekly until d 46. Within 25 d after weaning, 100% of the cows with a BCS [is greater than or equal to] 5 at weaning (n = 7) had initiated luteal activity, whereas only 43% (P [is less than] .01) of the cows with BCS [less than] 5 (n = 12) had luteal activity. Mean serum IGF-I concentrations were correlated with BCS (r = .50; P [is less than] .05). Frequency of LH pulses was influenced ( P [is less than] .01) by body condition at weaning but was not influenced by day after weaning. The number of LH pulses at weaning, serum IGF-I, and the interval to the onset of ovarian activity after early weaning of anestrous beef cows were influenced by BCS.

The objective of this study was to determine the effect of long-term administration of a growth hormone (GH)-releasing factor analog (GRFa) and(or) thyrotropin-releasing hormone (TRH) on growth, feed efficiency, carcass characteristics, and blood hormones and metabolites in beef heifers. Crossbred heifers (n = 48; 345.9 |+ or -~ 2.8 kg) were divided into four equal groups: control (vehicle), 1 ||micro~gram~ of GRFa (human GRF 1-29 analog) |center dot~ kg B|W.sup.-1~ |center dot~ |d.sup.-1~, 1 ||micro~gram~ of TRH |center dot~ kg B|W.sup.-1~ |center dot~ |d.sup.-1~, or GRFa + TRH. Daily s.c. injections continued for 86 d. Blood samples were collected from half of the heifers after injection on d 1, 36, and 78. On d 89, all heifers were slaughtered. Treatments did not affect (P |is greater than~ .05) ADG but GRFa + TRH decreased (P |is less than~ .05) ADFI relative to all other treatments. Feed conversion efficiency tended (P |is less than~ .10) to be improved in the groups given GRFa alone or TRH alone. Treatment with GRFa and(or) TRH did not affect carcass weight, dressing percentage, conformation score, backfat thickness, or weights of liver, kidneys, pituitary, and ovaries. The GRFa + TRH treatment reduced (P |is less than~ .05) fat score and increased (P |is less than~ .05) longissimus muscle area relative to other treatments. The GRFa treatments reduced (P |is less than~ .05) the weight and fat percentage of the mammary gland and increased (P |is less than~ .05) heart weight. Treatment with TRH alone failed to stimulate GH on d 1, 36, and 78. Treatment with GRFa alone increased (P |is less than~ .05) GH above controls on d 36, whereas GRFa + TRH increased (P |is less than~ .05) GH on d 1, 36, and 78. Treatment with GRFa alone increased (P |is less than~ .05) IGF-I only on d 1, whereas GRFa + TRH was without effect on all days. Across sampling days, treatments had little effect on blood concentrations of insulin, triiodothyronine, nonesterified fatty acids, urea nitrogen, and glucose. The GRFa alone and GRFa + TRH decreased (P |is less than~ .05) and TRH alone increased (P |is less than~ .05) thyroxine concentrations. In conclusion, with the dose and administration regimen used, GRFa and(or) TRH yielded small but positive improvements in animal performance.

Prepubertal gilts of obese (n = 24) or lean (n = 24) genetic lines were injected (s.c.) daily with 0, 2, or 4 mg of porcine somatotropin (pST) for 6 wk starting at 160 d of age to determine whether pST affects follicular function. Blood and ovaries were collected at slaughter 24 h after the last injection. Surface follicles is greater than or equal to 1.0 mm in diameter were counted, and pools of follicular fluid (FFL) and granulosa cells were collected from 1.0- to 3.9-mm (small) and 4.0- to 6.9-mm (medium) follicles. Oocytes were collected from small and medium follicles and evaluated for maturational stage and viability. Porcine somatotropin increased (P < .08) the numbers of small but not the numbers of medium follicles per gilt (P > .10). Oocyte maturation and viability were not affected by pST or genetic line. Porcine somatotropin increased (P < .05) concentrations of insulin-like growth factor I (IGF-I) in serum and FFL of both obese and lean gilts; IGF-I was lower (P < .01) in lean gilts. Treatment with pST decreased (P < .05) IGF-II in FFL of lean but not in that of obese gilts. Dose of pST and line had no effect on concentrations of progesterone in FFL of small or medium follicles or on concentrations of estradiol in FFL of small follicles. Concentrations of estradiol in FFL of medium follicles were decreased (P < .05) by pST (2 and 4 mg/d) in obese gilts, but estradiol was lower (P < .01) and unaffected (P > .10) by pST in lean gilts. The numbers of LH/hCG binding sites in granulosa cells were decreased (P < .05) by pST (4 mg/d) in medium follicles. The 4 mg/d dose of pST increased (P < .05) IGF-I binding protein activity only in serum of obese gilts. We conclude that 2 and(or) 4 mg/d of pST can increase concentrations of IGF-I in serum and FFL and stimulate growth of small follicles in two genetically divergent lines of gilts without affecting oocyte viability.

• Granulosa cell fibrillin 1 mRNA abundance was increased during follicle selection. • Granulosa cell fibrillin 1 mRNA abundance was decreased by insulin-like growth factor 1. • Olfactory receptor 4M1 mRNA abundance was increased by progesterone. • Asprosin production and its receptor are hormonally regulated in granulosa cells. Recent studies have reported hormonal regulation of expression of fibrillin 1 (FBN1) , the gene that encodes asprosin, in bovine theca cells, however, hormonal regulation of gene expression of FBN1 and the asprosin receptor, olfactory receptor 4M1 (OR4M1), has not been evaluated in granulosa cells (GC). This study was designed to characterize FBN1 and OR4M1 gene expression in GC during development of bovine dominant ovarian follicles, and to determine the hormonal regulation of FBN1 and OR4M1 mRNA expression in GC. GC FBN1 mRNA abundance was greater (P < 0.05) in medium (5.1–8 mm) estrogen inactive (EI) follicles than in large (>8.1 mm) or small (1–5 mm) EI follicles. In comparison, GC OR4M1 mRNA abundance was greater (P < 0.05) in small EI follicles than in large or medium EI follicles. Abundance of OR4M1 mRNA in GC of follicles collected on days 3 to 4 (early growth phase) and on days 5 to 6 (late growth phase) was similar, whereas FBN1 mRNA abundance was greater (P < 0.05) on days 5 to 6 vs days 3 to 4. Hormonal regulators for FBN1 mRNA abundance in cultured small-follicle GC were identified: TGFβ1 causing a 2.45-fold increase, WNT3A causing a 1.45-fold increase, and IGF1 causing a 65% decrease. Steroids, leptin, insulin, growth hormone, follicle stimulating hormone, fibroblast growth factor 9 and epidermal growth factor had no effect on FBN1 mRNA abundance. Abundance of OR4M1 mRNA in GC was regulated by progesterone with 3.55-fold increase, but other hormones did not affect GC OR4M1 mRNA abundance. Findings indicate that both FBN1 and OR4M1 gene expression are hormonally and developmentally regulated in bovine follicles, and thus may affect asprosin production and its subsequent role in ovarian follicular function in cattle. [ABSTRACT FROM AUTHOR]

A 2 x 4 factorial arrangement of treatments was used to determine the effects of dietary Zn concentration and endotoxin challenge in weanling pigs. Forty-eight weanling pigs (5.5 kg; 15 d) were housed individually and allotted randomly to four liquid diets. Dietary treatments were prepared by adding ZnS[O.sub.4] to a commercial milk replacer (MR, 5 ppm Zn) to provide 0, 100, 1,500, or 3,000 ppm added Zn. Diets were mixed prior to feeding by adding 12 g of MR to 100 mL of deionized water. The diets were fed 4 times/d for 14 d. On d 14, pigs were fasted 10 h and injected i.p. with saline or 25 ug LPS (E. coli. 0111:B4)/kg BW. Blood samples and temperature were collected at 0 h (before injection), and at 3, 6 and 24-h post injection (PI). Growth performance from d 0-14 was not affected (P>.10) by dietary Zn. On d 14 (prior to LPS), plasma Zn concentrations for the 4 dietary treatments were, respectively: .36, 1.09, 3.50, and 4.30 mg/L (linear, P Key Words: Weanling pigs, Zinc, Endotoxin