Effects of L-carnitine on fetal growth and the IGF system in pigs

The effects of L-carnitine on porcine fetal growth traits and the IGF system were determined. Fourth-parity sows were fed a gestation diet with either a 50-g top dress containing 0 (control, n = 6) or 100 mg of L-carnitine (n = 6). At midgestation, fetuses were removed for growth measurements, and porcine embryonic myoblasts (PEM) were isolated from semitendinosus. Real-time quantitative PCR was used to measure growth factor messenger RNA (mRNA) levels in the uterus, placenta, muscle, hepatic tissue, and cultured PEM. A treatment x day interaction (P = 0.02) was observed for maternal circulating total carnitine. Sows fed L-carnitine had a greater (P = 0.01) concentration of total carnitine at d 57 than control sows. Circulating IGF-I was not affected (P = 0.55) by treatment. Supplementing sows with L-carnitine resulted in larger (P = 0.02) litters (15.5 vs. 10.8 fetuses) without affecting litter weight (P = 0.07; 1,449.6 vs. 989.4 g) or individual fetal weight (P = 0.88) compared with controls. No treatment effect was found for muscle IGF-I (P = 0.36), IGF-II (P = 0.51), IGFBP-3 (P = 0.70), or IGFBP-5 (P = 0.51) mRNA abundance. The abundance of IGF-I (P = 0.72), IGF-II (P = 0.34), and IGFBP-3 (P = 0.99) in hepatic tissue was not influenced by treatment. Uterine IGF-I (P = 0.46), IGF-II (P = 0.40), IGFBP-3 (P = 0.29), and IGFBP-5 (P = 0.35) mRNA abundance did not differ between treatments. Placental IGF-I (P = 0.30), IGF-II (P = 0.18), IGFBP-3 (P = 0.94), and IGFBP-5 (P = 0.42) mRNA abundance did not differ between treatments. There was an effect of side of the uterus for IGF-I (P = 0.04) and IGF-II (P = 0.007) mRNA abundance; IGF-I mRNA abundance was greater in the left uterine horn than in the right uterine horn (0.14 and 0.07 relative units, respectively). Placental IGF-II mRNA abundance was greater (P = 0.007) in the left than in the right uterine horn (483.5 and 219.59, respectively). The abundance of IGFBP-3 was not affected by uterine horns in either uterine (P = 0.66) or placental (P = 0.13) tissue. There was no treatment difference for IGF-I (P = 0.31) or IGFBP-5 (P = 0.13) in PEM. The PEM isolated from sows fed L-carnitine had decreased IGF-II (P = 0.02), IGFBP-3 (P = 0.03), and myogenin (P = 0.04; 61, 59, and 67%, respectively) mRNA abundance compared with controls. These data suggest that L-carnitine supplemented to gestating sows altered the IGF system and may affect fetal growth and development.     

Effects of recombinant bovine somatotropin on growth and abundance of mRNA for IGF-I and IGF-II in channel catfish (Ictalurus punctatus)

Research was conducted to examine growth rates, circulating concentrations of IGF-I, and mRNA abundance levels of IGF-I and IGF-II in channel catfish (Ictalurus punctatus) given recombinant bovine ST (rbST; Posilac, Monsanto Co., St. Louis MO). In the first study, juvenile catfish (5.5 +/- 0.5 g) were randomly assigned to one of three treatments: 1) sham-injected control (one needle puncture per week); 2) rbST (30 microg x g BW(-1) x wk(-1); Posilac); and 3) nonhandled control (control). At the end of the 6-wk study, the fish were weighed, measured for length, and G:F was determined. Compared with sham and control treatments, rbST-treated fish had 48% greater final BW, 14% greater total length, and 52% greater G:F (P < 0.001). In the second study, juvenile catfish (41.1 +/- 1.5 g) were assigned randomly to one of two treatments: 1) sham or 2) rbST. Eight fish per treatment were sampled on d 0, 1, 2, 7, 14, and 21 for blood, muscle, and liver. Relative expression of IGF-I and IGF-II mRNA was determined by real-time PCR and plasma concentrations of IGF-I were measured using a validated fluoroimmunoassay. Circulating concentrations of IGF-I were increased (37.9 +/- 5.5 vs. 22.0 +/- 6.6 ng/mL; P < 0.05) in rbST-injected fish compared with sham-injected controls by d 14. Liver IGF-I and IGF-II mRNA was increased 4.3-and 14.4-fold, respectively, by d 1 in rbST-injected fish compared with controls (P < 0.05); however, abundance of liver IGF-I and IGF-II mRNA did not differ from controls on d 0, 2, 7, 14, and 21. Abundance of muscle IGF-I and IGF-II mRNA did not differ in rbST-injected fish compared with controls throughout the study. Results of the first study demonstrated that rbST improves growth performance of channel catfish. Results of the second study showed that the growth-promoting effects of rbST were not mediated by the expression of IGF-I or IGF-II mRNA in the muscle. Instead, the results suggest that rbST promotes growth by stimulating plasma IGF-I release, possibly through its direct effect on the liver or on local tissues to synthesize IGF-I. The changes in mRNA abundance and plasma concentrations of IGF-I support the role of IGF-I in growth regulation of channel catfish.     

Follicular Dominance in Cattle Is Associated With Divergent Patterns of Ovarian Gene Expression for Insulin-Like Growth Factor (IGF)-I,IGF-II,and IGF Binding Protein-2 in Dominant and Subordinate Follicles

A decrease in insulin-like growth factor (IGF) binding protein (BP) amount occurs within the follicular fluid of dominant ovarian follicles. At the same time, concentrations of follicular fluid IGF-I do not change. The mRNA for IGF-I, IGF-II, IGFBP-2, and IGFBP-3 in dominant and subordinate follicles were measured to determine if changes in IGF or IGFBP gene expression are associated with follicular dominance. Heifers were ovariectomized during a follicular wave, either during early-dominance (emerging dominant follicle, 9 mm diameter) or mid-dominance (established dominant follicle, 14–16 mm diameter). Follicles were classified as either dominant (DF), subordinate (SF), or not-recruited (NRF; small antral follicles). mRNA was localized by in situ hybridization and measured by image analyses. The IGF-I mRNA (granulosa cells) was greatest in DF and increased in DF, SF, and NRF from early- to mid-dominance. Likewise, IGF-II mRNA (theca cells) was greatest in DF compared with SF or NRF. The IGFBP-2 mRNA (granulosa cells), however, was nearly undetectable in DF, whereas adjacent SF expressed abundant IGFBP-2 mRNA. The NRF were not uniform in their IGFBP-2 expression because only 5 of 13 NRF had IGFBP-2 mRNA. The IGFBP-3 mRNA (granulosa cells) was found only in two NRF, suggesting that local synthesis is not a predominant source of follicular fluid IGFBP-3. These data show that changes in gene expression for IGFBP-2 are opposite to those for IGF-I or IGF-II. Increased IGF-I and IGF-II mRNA and decreased IGFBP-2 mRNA within the DF may be one mechanism leading to follicular dominance. The opposite pattern of IGFBP-2 gene expression in SF and some NRF may lead to follicular atresia.     

Effects of colostrum feeding and dexamethasone treatment on mRNA levels of insulin-like growth factors (IGF)-I and -II, IGF binding proteins-2 and -3, and on receptors for growth hormone, IGF-I, IGF-II, and insulin in the gastrointestinal tract of neonatal calves

The somatotropic axis regulates growth of the gastrointestinal tract (GIT). In addition, colostrum feeding and glucocorticoids affect maturation of the GIT around birth in mammals. We have measured mRNA levels of members of the somatotropic axis to test the hypothesis that colostrum intake and dexamethasone treatment affect respective gene expression in the GIT. Calves were fed either colostrum or an isoenergetic milk-based formula, and in each feeding group, half of the calves were treated with dexamethasone (DEXA; 30 microg/kg body weight per day). Individual parameters of the somatotropic axis differed (P < 0.05) among different GIT sections and formula feeding increased (P < 0.05) mRNA levels of individual parameters at various sites of the GIT. Effects of DEXA on the somatotropic axis in the GIT partly depended on different feeding. In colostrum-fed calves, DEXA decreased (P < 0.05) mRNA levels of IGF-I (esophagus, fundus, duodenum, and ileum), IGF-II (fundus), IGFBP-2 (fundus), IGFBP-3 (fundus), IGF1R (esophagus, ileum, and colon), IGF2R (fundus), GHR (fundus), and InsR (esophagus, fundus), but in formula-fed calves DEXA increased mRNA levels of IGF-I (esophagus, rumen, jejunum, and colon). Furthermore, DEXA increased (P < 0.05) mRNA levels of IGF-II (pylorus), IGFBP-3 (duodenum), IGF2R (pylorus), and GHR (ileum), but decreased mRNA levels of IGFBP-2 (ileum), and IGF1R (fundus). Whereas formula feeding had stimulating effects, effects of DEXA treatment on the gene expression of parameters of the somatotropic axis varied among GIT sites and partly depended on feeding.     

Maternal l-arginine supplementation during early gestation affects foetal skeletal myogenesis in pigs

To study the impact of maternal l-arginine supplementation during early gestation on skeletal muscle formation in the offspring, gilts were fed 3 kg of a standard diet (control group, n=10) or standard diet and additionally 26 g/d l-arginine from d 14 to 28 of gestation (arginine group, n=10). The gilts were sacrificed at d 75 of gestation. From each litter the lightest, the heaviest, and one medium-weight foetus per sex were selected and three different muscle samples were collected. In the longissimus dorsi muscle of all foetuses (n=99) biochemical properties were assessed. In the same muscle of a subset of the lightest and heaviest female foetuses (n=28), mRNA expression of selected genes involved in myogenesis were measured. In all three muscles, myosin heavy chain (MyHC) expression analyses (n=99) were performed. The protein/DNA ratio tended to be lower (P=0.08) in the offspring of the arginine group. Treatment×sex interactions revealed lower creatine kinase activity (P<0.05) and protein concentration (P=0.07) in female's of the arginine group. The MYF5 mRNA expression was lower (P<0.01) in the lightest, whereas IGF2 and IGFBP5 expressions (P<0.001) were lower in the heaviest females of the arginine group. The proportion of MyHC mRNA expression revealed an increase in the embryonic isoform (P=0.05) and a decrease by tendency in the Slow/I and IIx isoforms (P<0.10) in response to arginine supplementation. The results suggest that arginine supplementation during early gestation stimulates myogenic proliferation and delays muscular differentiation at d 75 of gestation.     

Investigation of the insulin-like growth factor system in the avian epiphyseal growth plate

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

Ontogenic maturation of the somatotropin/insulin-like growth factor axis

The ontogeny of the somatotropin/insulin-like growth factor system was examined in well-fed pigs under basal conditions and during a short-term challenge of porcine ST (pST). The study was conducted with two replicates of eight castrate male pigs from 3.8 kg BW (10 d of age) to 92 kg BW (129 d of age). Pigs were reared individually with ad libitum access to milk replacer through 23 d of age. Thereafter, pigs were fed a corn, soybean meal, and dry skim milk diet formulated to exceed nutrient requirements by approximately 30%. Pigs were randomly assigned to receive daily i.m. injections of either 0 (buffer) or 120 microg/kg BW of pST for a duration of 4 d starting at 10, 19, 33, 43, 63, 83, and 125 d of age. Blood was collected via jugular venipuncture on d 0 and 4 of the challenge. Circulating levels of IGF-I were not dramatically affected by age, but levels of IGF-II were low from 10 to 19 d of age and then increased through later stages of growth. Circulating concentrations of IGF binding protein (BP)-3 increased with age (P < .05), but levels of IGFBP-2, a 30-kDa IGFBP, and IGFBP-4 were unchanged (P > .10). The pST challenge reduced plasma urea nitrogen at all ages, but the magnitude of the response was less in younger pigs compared with the maximum response in pigs greater than 30 kg BW (63 d of age). The IGF-I response to the pST challenge also increased from approximately 30% in young pigs to a threefold increase in older pigs. Regardless of age, concentrations of IGF-II were minimally affected by the pST challenge. Circulating levels of IGFBP-3 increased and IGFBP-2 levels decreased in response to the pST challenge, and the magnitude increased with age. The high nutritional status of pigs in the early phases of growth diminished the postnatal changes in IGF-I and IGFBP-2, but not IGF-II or IGFBP-3. Overall, data demonstrate a developmental regulation of the ST/IGF system, with pST challenges altering circulating concentrations of IGF-I, IGFBP-3, and IGFBP-2 coincident with changes in amino acid metabolism.     

Endometrial expression of the insulin-like growth factor system during uterine involution in the postpartum dairy cow

Rapid uterine involution in the postpartum period of dairy cows is important to achieve a short interval to conception. Expression patterns for members of the insulin-like growth factor (IGF) family were determined by in situ hybridisation at day 14 ± 0.4 postpartum (n = 12 cows) to investigate a potential role for IGFs in modulating uterine involution. Expression in each uterine tissue region was measured as optical density units and data were analysed according to region and horn. IGF-I mRNA was localized to the sub-epithelial stroma (SES) of inter-caruncular and caruncular endometrium. Both IGF-II and IGF-1R expression was detected in the deep endometrial stroma (DES), the caruncular stroma and myometrium. IGFBP-2, IGFBP-4 and IGFBP-6 mRNAs were all localised to the SES of inter-caruncular and caruncular uterine tissue, and in the DES and caruncular stroma, with IGFBP-4 mRNA additionally expressed in myometrium. IGFBP-3 mRNA was only detectable in luminal epithelium. IGFBP-5 mRNA was found in myometrium, inter-caruncular and caruncular SES and caruncular stroma. These data support a role for IGF-I and IGF-II in the extensive tissue remodelling and repair which the postpartum uterus undergoes to return to its non-pregnant state. The differential expression of binding proteins between tissues (IGFBP-3 in epithelium, IGFBP-2, -4, -5 and -6 in stroma and IGFBP-4 and -5 in myometrium) suggest tight control of IGF activity within each compartment. Differential expression of many members of the IGF family between the significantly larger previously gravid horn and the previously non-gravid horn may relate to differences in their rate of tissue remodelling.     

Exogenous somatotropin alters IGF axis in porcine endometrium and placenta

The aim of this study was to examine whether exogenous somatotropin (ST) can alter the insulin-like growth factor (IGF) axis in the porcine epitheliochorial placenta. Crossbred gilts were injected either 6 mg of recombinant porcine ST or vehicle from days 10 to 27 after artificial insemination (term day 116). Control and ST-treated gilts were euthanized on day 28 (8 control/5 treated), day 37 (4 control/6 treated), and day 62 (4 control/6 treated) of gestation. Endometrium and placental tissue samples were collected and subjected to mRNA analyses. In control gilts, somatotropin receptor (STR) and IGF-I mRNA abundance in the endometrium decreased with gestation. Conversely, the amounts of IGF-II mRNA and of IGF binding protein (BP)-2 and -3 mRNA, which were analyzed in endometrium and placental chorion, increased with gestation. The endometrium contained less IGF-II mRNA but more IGFBP-2 and-3 mRNA than the placental chorion. In response to pST treatment, the amounts of endometrial STR and IGF-I mRNA were lower at days 28 and 37, but higher at day 62 of gestation. The content of IGF-II mRNA was higher in the endometrium of pST-treated than control gilts on day 37. The amount of IGFBP-2 mRNA was increased on day 37 in endometrium and placenta of pST-treated gilts, whereas no changes in IGFBP-3 mRNA were observed. The IGF-II/IGFBP-2 ratio was higher in the placenta in response to pST on day 28 of gestation. Results show that pST treatment of pregnant gilts during early gestation alters IGF axis in maternal and fetal placental tissues and suggest pST may exert an effect on fetal growth by altering the relative amount of IGFBPs and IGFs at the fetal-maternal interface.     

Abundance of message for insulin-like growth factors-I and -II and for receptors for growth hormone,insulin-like growth factors-I and -II,and insulin in the intestine and liver of pre- and full-term calves

The somatotropic axis and insulin are involved in pre- and postnatal development. In pre- and full-term calves (GrP0 and GrN0; born after 277 and 290 d of pregnancy, respectively) and in preterm calves on d 8 of life after being fed for 7 d (GrP8), we studied whether there are differences in the abundance of messenger RNA (mRNA) of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II, and insulin among different intestinal sites (duodenum, jejunum, ileum, and colon) and whether there are ontogenetic differences during the perinatal period in intestine and liver. Intestinal site differences (P < 0.05) existed in mRNA levels of IGF-I and IGF-II and receptors for GH, IGF-I, IGF-II, and insulin. Abundance of mRNA of IGF-I and -II and of receptors for IGF-I and GH was highest (P < 0.05) in the colon, abundance of the receptor for IGF-II was comparably high in the colon and ileum, and that of the receptor for insulin was similarly high in colon, ileum, and jejunum. Among GrP0, GrN0, and GrP8 groups, there were differences (P < 0.05) in mRNA levels of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II and insulin. Abundance of mRNA of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II and insulin was highest (P < 0.05) in GrP0 calves immediately after birth and was primarily seen in the ileum. In liver, the mRNA levels differed (P < 0.05) among groups for IGF-II and receptors for IGF-I, IGF-II, and insulin, and were highest (P < 0.05) for IGF-II in GrP0, for receptors of IGF-I in GrN0, and were higher (P < 0.05) in GrP0 than GrP8 for receptors of IGF-II. In conclusion, mRNA levels of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II, and insulin were different at different intestinal sites and in intestine and liver and changed during the perinatal period.     

Meat colour,fatty acid profile and carcass characteristics of Hereford bulls finished on grazed pasture or grass silage-based diets with similar concentrate allowance

The objective of this study was to determine the impact of grazed grass (PAS bulls) and grass silage-based (UB bulls) diets on muscle colour, intramuscular fatty acid composition and carcass characteristics of Hereford bulls with similar concentrate allowances, ages, growth rates and carcass weights. The carcass fat score of the UB bulls was 14% higher than that of the PAS bulls (P < 0.05). Muscle lightness was 5%, redness 5% and yellowness 8% higher in the UB bulls than in the PAS bulls (P < 0.05). The Longissimus muscle (LM) of the UB bulls contained a higher proportion of 14:1 and 16:0 fatty acids compared to that of the PAS bulls (P < 0.05). In contrast, the LM of the PAS bulls contained a higher proportion of 18:3n-3 fatty acid and 18:2 cis-9 trans-11 CLA compared to that of the UB bulls (P < 0.01). There were no differences in saturated fatty acid, monounsaturated fatty acid or polyunsaturated fatty acid proportions of the LM muscle between treatments.     

Establishment of a time-resolved fluoroimmunoassay for measuring plasma insulin-like growth factor I (IGF-I) in fish: effect of fasting on plasma concentrations and tissue mRNA expression of IGF-I and growth hormone (GH) in channel catfish (Ictalurus punctatus)

A time-resolved fluoroimmunoassay (TR-FIA) was established and validated that allows for the determination of plasma concentrations of insulin-like growth factor I (IGF-I) in three domestically cultured fishes: channel catfish (Ictalurus punctatus), hybrid striped bass (Morone chrysopsxM. saxatilis), and rainbow trout (Oncorhynchus mykiss). Sensitivity of the assay was 0.20 ng/ml. Intra- and inter-assay coefficients of variation (CV) were <7 and <12%, respectively. Serial dilutions of plasma from each species were parallel to the standard curve. Recovery of IGF-I from spiked plasma samples was >90% for all three species of fishes. The IGF-I TR-FIA was biologically validated via its use to determine the effect of fasting on circulating IGF-I levels in channel catfish. Fasting-induced changes in plasma growth hormone (GH), hepatic IGF-I mRNA expression, and pituitary GH mRNA expression were also determined. Fasted channel catfish lost 5.6 and 15.6% body mass after 2 and 4 weeks of fasting, respectively. Plasma IGF-I concentrations were depressed (P<0.05) relative to fed controls following 2 and 4 weeks of fasting. Plasma GH concentrations were not different (P>0.05) in fasted fish after 2 weeks, but significantly increased (P<0.05) by 4 weeks of fasting. Hepatic IGF-I mRNA expression after 2 and 4 weeks of fasting was reduced (P<0.05) relative to fed controls. Pituitary GH mRNA expression was similar (P>0.05) between 2-week-fasted catfish and fed controls, but was increased (P<0.05) in 4-week-fasted catfish. The IGF-I TR-FIA was sensitive, accurate, and precise for all three species of fishes, and provided a low-cost, and non-radioisotopic method for quantifying plasma IGF-I levels in fed and fasted channel catfish.     

Evaluation of circulating IGF-I and IGFBP-3 as biomarkers for tumors in dogs

BackgroundSerum-based parameters are considered non-invasive biomarkers for cancer detection. In human studies, insulin-like growth factor-I and II (IGF-I and IGF-II) and insulin-like growth factor binding protein-3 (IGFBP-3) are useful as diagnostic or prognostic markers and potential therapeutic targets.ObjectivesThis study examined the diagnostic utility of circulating IGF-I, IGF-II, and IGFBP-3 levels in healthy dogs and dogs with tumors.MethodsThe serum concentrations of these biomarkers in 86 dogs with tumors were compared with those in 30 healthy dogs using an enzyme-linked immunosorbent assay (ELISA).ResultsThe ELISA results showed no difference between healthy dogs and dogs with tumors in the serum IGF-II concentrations. On the other hand, there was a significant difference in the circulating IGF-I and IGFBP-3 levels between healthy dogs and dogs with tumors. The concentrations of serum IGF-I (median [interquartile range], 103.4 [59.5–175] ng/mL) in dogs with epithelial tumors were higher than those (58.4 ng/mL [43.5–79.9]) in healthy dogs. Thus, the concentrations of serum IGFBP-3 (43.4 ng/mL [33.2–57.2]) in dogs with malignant mesenchymal tumors were lower than those (60.8 ng/mL [47.6–70.5]) in healthy dogs.ConclusionsThe serum IGF-I and IGFBP-3 levels can be used as diagnostic biomarkers in dogs with tumors.     

Moderate doses of porcine somatotropin do not increase plasma insulin-like growth factor-I (IGF-I) or IGF binding protein-3.

The growth rate of the young pig is generally much less than its potential and may be constrained by endocrine status as well as by nutrient intake. The aim of this study was to determine whether porcine somatotropin (pST) could increase growth in the nursing pig. Fourteen sows nursing litters of 6 (n = 7) or 12 (n = 7) piglets were utilized to establish a high and low plane of nutrition for sucking pigs. On Day 4 of lactation, the median two male pigs from each litter were randomly allocated to one of two doses of pST (0 or 60 micrograms/kg/d) until weaning on Day 31. Pigs were bled on Days 4, 13, 22, and 31 of lactation and the plasma was analyzed for insulin-like growth factor (IGF)-I, IGF-II, and IGF binding protein-3 (IGFBP-3). Pigs were weaned into conventional accommodation and further weighed on Days 63, 91, and 119. Pigs from litters of 6 grew more quickly and weighed 2.2 kg (P = 0.01) and 3.5 kg (P = 0.04) more than pigs from litters of 12 at 31 and 63 d of age, respectively. There was no effect of pST on preweaning growth of sucking pigs (261 vs. 258 g/d, P = 0.68), although growth rate increased in the final 3 d before weaning at 31 d (241 vs. 294 g/d, P = 0.01). IGFBP-3 was greater (1.09 vs. 0.78 micrograms/ml, P < 0.001), whereas IGF-I tended to be greater (206 vs. 176 ng/ml, P = 0.14), in pigs from the small litters. There was no effect of pST on plasma IGF-I (182 vs. 195 ng/ml, P = 0.454) or IGFBP-3 (0.93 vs. 0.94 microgram/ml, P = 0.85) concentrations. Plasma IGF-I and IGFBP-3 were highly correlated with the growth rate of nursing pigs (R = 0.638 and 0.756, respectively). There were no effects of pST (340 vs. 328 ng/ml, P = 0.48) or litter size (336 vs. 333 ng/ml, P = 0.88) on IGF-II. In conclusion, pST had no little or no effect on growth performance or plasma IGF-I, IGF-II, or IGFBP-3 in sucking pigs on either a high or low plane of nutrition.     

Ovarian and endocrine characteristics during an estrous cycle in Angus, Brahman, and Senepol cows in a subtropical environment

To determine breed differences in ovarian function and endocrine secretion, daily rectal ultrasonography was conducted on multiparous lactating Angus (temperate Bos taurus; n = 12), Brahman (tropical Bos indicus; n = 12), and Senepol (tropical Bos taurus; n = 12) cows during an estrous cycle in summer. Blood was collected daily to quantify plasma concentrations of FSH, LH, progesterone, estradiol, GH, insulin-like growth factor (IGF)-I, IGF-II, IGF binding proteins (IGFBP), insulin, glucose, and plasma urea nitrogen (PUN). Numbers of small (2 to 5 mm), medium (6 to 8 mm), and large follicles (> or = 9 mm) were greater (P < .05) in Brahman than in Angus and(or) Senepol cows. Length of the estrous cycle (SEM = .6 d) was similar (P > .10) among Senepol (20.4 d), Angus (19.5 d), and Brahman (19.7 d) cows. Senepol cows had greater (P < .05) diameters of the corpus luteum (CL) and a delayed regression of the CL as compared with Angus cows. The secondary surge of FSH (between d 1 and 2; d 0 = estrus) was greater in Angus than Brahman or Senepol cows (breed x day, P < .05). Between d 2 and 14 of the estrous cycle, concentrations of progesterone, LH, IGF-II, and binding activities of IGFBP-3, IGFBP-2, and the 27- to 29-kDa IGFBP in plasma did not differ (P > .10) among breeds. Concentrations of GH, IGF-I, insulin, and PUN were greater (P < .001) and binding activities of the 22-kDa and 20-kDa IGFBP tended (P < .10) to be greater in plasma of Brahman than in Angus or Senepol cows. Plasma glucose concentrations were greater (P < .05) in Senepol than in Brahman or Angus cows. In conclusion, Brahman (Bos indicus) and Senepol cows (tropical Bos taurus) had greater numbers of follicles in all size categories and greater diameter of CL than Angus (temperate Bos taurus) cows. These ovarian differences may be due to changes in the pattern of secretion of FSH, insulin, IGF-I, and GH but not LH, IGF-II, or IGFBP-2 or -3.     

Changes in the local regulation of insulin-like growth factors I and II and insulin-like growth factor-binding proteins in osteoarthritis of the canine stifle joint secondary to cruciate ligament rupture

OBJECTIVES: To investigate changes in concentrations of insulin-like growth factors I (IGF-I) and II (IGF-II) and the expression of IGF-binding proteins (IGFBP) in synovial fluids from dogs with naturally occurring osteoarthritis (OA) of the canine stifle joint secondary to cranial cruciate ligament (CCL) rupture. STUDY DESIGN: Prospective study with synovial fluid sampling from diseased and contralateral unaffected joints at 0, 1.5, and 5 months. SAMPLE POPULATION: Eleven dogs with unilateral CCL deficiency, with unaffected contralateral joints. METHODS: IGF-I and IGF-II concentrations in synovial fluids were estimated by radioimmunoassay at 0, 1.5, and 5 months; Western ligand blotting was performed for intact IGFBPs at 0, 1.5, 5, and 9 months. Both stifle joints were radiographed at 0, 7, and 13 months. RESULTS: The IGF system is altered after CCL rupture and during development of early OA. Mean IGF-I and IGF-II concentrations in index stifle joints at study entry were 201.6 microg/mL and 345.7 microg/mL, respectively, compared with 57.7 microg/mL and 79.4 microg/mL, respectively, for contralateral joints. Index joint IGF concentrations increased after surgical treatment and then declined, although they remained higher than contralateral joints. Index joints had increases in IGFBP-3 and -4, and a decrease in IGFBP-2 expression compared with contralateral joints. CONCLUSIONS: Although IGF concentrations are increased in canine OA, alterations in IGFBP profiles may limit the tissue availability of IGF. CLINICAL RELEVANCE: Manipulation of the IGF system may provide an opportunity for novel treatments of OA in dogs.     

Growth,carcass, fiber type,and meat quality characteristics in Large White pigs with different live weights

The aim of this study was to compare the growth, carcass, histochemical, and meat quality characteristics in Large White pig groups that were categorized by live weight (Heavy and Light) and type I fiber percentage (High and Low), a procedure which resulted in four groups (Heavy-High, Heavy-Low, Light-High, and Light-Low). As expected, the Heavy group showed heavier live weight (114 vs. 94.7 kg, P<0.001) and larger loin eye area (53.3 vs. 47.8 cm², P<0.001), as well as, higher total number (1,223,000 vs. 1,140,000, P<0.05) and greater mean value cross-sectional area (CSA; 4031 vs. 3798 μm²P<0.05) of muscle fibers than the Light group. However, there were no significant differences in start and finish days among the groups (P>0.05). Heavier pigs harboring a higher percentage of type I fibers (HH) exhibited a similar mean CSA (3894 vs. 4101 μm²) and total number (1,249,000 vs. 1,198,000) of muscle fibers, even though these pigs had a greater CSA of type I fibers (3181 vs. 2719 μm², P<0.05) and a smaller CSA of type IIB fibers (4048 vs. 4457 μm², P<0.05) compared to heavier pigs harboring a lower percentage of fiber type I (HL). Both the HL and Light-Low groups exhibited a rapid decline of muscle pH at the early postmortem period (5.90 and 5.85 vs. 6.08, P<0.05), paler surfaces (43.07 and 43.55 vs. 40.73_,P<0.05), and higher degrees of fluid loss by exudation (6.26 and 6.39 vs. 4.22%, P<0.05) compared to the HH group due to their muscle fiber type composition. Thus, the HH pigs showed better meat quality characteristics without significant differences in growth and carcass performance compared to the HL pigs. Therefore, selection for increased live weight at the same age and muscle fiber characteristics, especially the increased type I fiber CSA and proportion, is one of the relevant indicators to improve and control meat quality without reducing the growth and carcass performance.