Effects of oxidized corn oil and a synthetic antioxidant blend on performance, oxidative status of tissues, and fresh meat quality in finishing barrows.

The objective was to evaluate the effect of feeding oxidized corn oil with or without a dietary antioxidant (AOX) on performance, tissue oxidative status, and meat quality in barrows. One hundred sixty barrows were arranged in a 2 × 2 factorial of treatments in a complete randomized block design with 8 pens per treatment and 5 pigs per pen. Diets contained 5.0 mg/kg of 1 of 2 types of corn oil (fresh or oxidized) with or without antioxidant. Final oxidized oil was produced in a heated container by continuously bubbling air heated to 95°C at a rate of 80 L/min to reach a target peroxide value of approximately 150 and 7.5 mEq/kg in the final diet. After 56 d, barrows fed diets formulated with fresh oil had increased ADG (P = 0.03) and ADFI (P = 0.04) and heavier final BW (P = 0.03) than barrows fed oxidized oil. Increased G:F (P = 0.07) was observed for barrows fed diets with AOX after 28 d of feeding but not after 56 d of feeding (P = 0.67) when compared with barrows not fed AOX. An increase (P = 0.06) in plasma thiobarbituric acid reactive substances (TBARS) values, a decrease (P = 0.03) in plasma glutathione peroxidase (GPx) enzyme activity, and a decrease (P = 0.01) in liver vitamin E concentrations were observed in barrows fed diets with oxidized oil. Dietary AOX reduced plasma protein carbonyl content regardless of oil type (P = 0.04). Barrows fed fresh oil had 4.4% heavier HCW (P = 0.01) and 0.7 percentage units increase in dressing percentage (P = 0.01) compared with barrows fed oxidized oil. Loin TBARS values from barrows fed AOX were lower (P < 0.001) after 14 and 21 d of storage in both fresh and oxidized oil groups. In summary, oxidized oil impaired growth performance and caused oxidation stress. Dietary AOX partially ameliorated the negative effects of oxidized oil in finishing pigs by reducing protein oxidation and improving shelf life.

Effects of increasing lysine on carcass composition and cutting yields of immunologically castrated male pigs.

The objective of this experiment was to determine if increasing lysine in the diets of immunologically castrated (IC) male pigs would increase percentage fat free lean and carcass cutting yields when compared with physical castrates. The anti-gonadotropin-releasing factor (GnRF) immunological product (Improvest, Pfizer Animal Health) is used worldwide to immunologically castrate entire male pigs to control boar taint and take advantage of the inherent ability of the entire male to deposit more muscle, less fat, and grow more efficiently than physically castrated males. The immunization process essentially allows the pig to grow as an entire male pig for most of its life and then removes any boar odor (boar taint) before slaughter. Reported lean meat advantages may also provide economic benefits to the domestic meat industry. Approximately 1,200 male pigs [physical castrates, IC males, and entire males] were each assigned to 1 of 4 diet programs which differed in lysine content. In each case, lysine was fed in a conventional step-down program that culminated with the following concentrations in the late finishing diet: physical castrates fed low lysine (0.7%), IC fed low lysine (0.7%), IC fed low/medium lysine (0.8%), IC fed medium/high lysine (0.9%), IC fed high lysine (1.0%), and entire males fed high lysine (1.0%). At 25 wk of age (5 wk post-second injection), pigs were individually weighed and the 2 pigs (n=96) in each pen closest to the median pig BW were selected and slaughtered. The right side of each carcass was dissected into soft tissue, skin, and bone. Proximate composition was determined on the soft tissue to determine percentage fat-free lean. The left side of each carcass was weighed and initially fabricated into ham, loin, belly, and whole shoulder. Each primal piece was weighed again and further fabricated into respective subprimal cuts. Immunological castration did not change (P>0.05) shear force values or ultimate pH when compared with either physical castrates or entire males. Marbling appeared to decrease as dietary lysine was increased among IC males. As expected, IC males had a greater (P<0.05) percentage fat-free lean than physical castrates but less (P<0.05) than entire males. Immunologically castrated males fed diets with medium/high and high lysine had greater (P<0.05) lean cutting yields and carcass cutting yields than physical castrates. Lean cutting yield and carcass cutting yields appeared to increase as dietary lysine was increased among IC males. Overall, immunological castration improved carcass cutability, increased percentage fat free lean, and had no effect on pork quality when compared with physical castrates.

Animal production--a longstanding biotechnological success.

Biotechnology has been practiced in one form or another under many banners since the beginning of the domestication of animal species. Many of the previously used tools of animal breeding have played and will continue to play an important role in the selection and propagation of desirable and economically important characteristics in livestock. From this viewpoint, animal production practices have been a long-standing biotechnological success. We now produce more animal products with fewer animals than was imagined even 10 y ago. These animal products are produced more efficiently and with less competition with humans for high-quality cereal grains. However, improvements are still needed in product composition and production efficiency, especially in growth, disease resistance, and reproduction. The attainment of such improvements will depend heavily on our ability to quantify desirable traits, to identify markers linked to gene(s) responsible for those traits, to select or redesign populations of superior individuals, and to propagate those animals.

Effect of genetic background on the developmental expression of c-fos and c-myc in chicken.

The developmental expression of the protooncogenes, c-fos and c-myc, in muscle and liver of 14- and 19-day embryos and 1-, 6-, 8- and 28-day-old chicks of Athens Canadian Random Bred (ACRB) Single Comb White Leghorn (SCWL) and Peterson X Arbor Acres commercial broiler (PXAA) was determined. For the three stocks of chicken, significant differences were found in c-fos and c-myc expression. For both muscle and liver, averaged across ages, abundance of c-fos RNA was highest in PXAA and lowest in ACRB with differences significant at the P less than 0.01 level. c-myc RNA levels were significantly higher (P less than 0.01) in PXAA than in ACRB or SCWL liver. Taken over the developmental period, expression of c-fos RNA in muscle increased at different rates between breeds from 14-day embryo levels to peak levels in 6- to 8-day-old chicks and declined in 28-day-old chicks. Levels of c-fos were much lower in liver and showed no consistent differences related to developmental stage. A steady decline in c-myc from 14-day embryo levels to 28-day-old chicks was found in both muscle and liver. This decline in c-myc levels generally parallels the decline in relative growth rates which occurs in all breeds over the developmental period. In liver, the fast growing PXAA had the highest levels of c-myc, c-fos, on the other hand, showed elevated levels in PXAA for both muscle and liver and distinctly different patterns between these two tissues over the developmental period, suggesting tissue-specific involvement in growth.

Effect of dietary manipulation on c-myc RNA expression in adipose tissue, muscle and liver of broiler chickens.

The effects of dietary restriction on the relative steady state levels of cellular myc (c-myc) mRNA in abdominal adipose tissue, breast muscle and liver of chickens were determined. Fasting was found to increase c-myc RNA expression in adipose tissue (p less than 0.01). This increase returned to normal levels after refeeding. Muscle and liver in fasted birds did not show changes in c-myc that differed from controls. Serum concentrations of glucose, triglyceride (TG), free fatty acids (FFA) and insulin-like growth factor (IGF-I) were compared to levels of c-myc found in control birds. In adipose tissue, c-myc levels were negatively correlated with serum glucose, TG and IGF-I, while in muscle a positive correlation with serum glucose and TG was found. Data suggest that c-myc is involved in the metabolic changes occurring in fat cells under fasting conditions.

Concentration of insulin-like growth factors (IGF-I and IGF-II) in tissues of developing lean and obese pig fetuses.

An ontogeny study of lean and pre-obese pig fetuses was conducted to evaluate the temporal and genetic influence on the relationship between growth and IGF production. At 70, 90 and 110 days of gestation, three fetal pigs were obtained from each of three obese and lean dams. The heart, kidneys, lungs, liver and one biceps femoris muscle were removed, weighed, frozen and extracts prepared. For all the organ and tissue weights, there were significant (P less than .001) main effects of genotype (G) and fetal age (A). At each fetal age, pre-obese fetuses had lighter organ and tissue weights. The content of IGF's in serum and various tissues and/or organs was also determined. Main effects of A and G were significant (P less than .05) for liver and lung IGF-I and muscle IGF-II concentrations. Main effects of G were significant (P less than .01) for liver IGF-II whereas muscle IGF-I and lung IGF-II concentrations were only affected by fetal age (P less than .01). Overall, liver IGF-I and II and muscle IGF-II concentrations were higher in lean fetuses (P less than .01). Serum IGF-I concentration increased (P less than .01) with fetal age and was independent of fetal strain. Serum IGF-II concentration increased with age (P less than .01) in lean but not pre-obese fetuses. Therefore, these studies demonstrate genotype dependent growth factor concentrations in tissues and organs of developing fetuses. Finally, serum concentration of IGF's were strongly correlated (positive) with overall growth but were not strongly correlated with tissue and organ concentration of IGFs.

Thymidine and somatomedin-like activity of fetal pig sera: effect of fetal decapitation.

The effect of fetal decapitation on porcine serum thymidine and somatomedin activity was studied. Fetal decapitation, at 45 d of gestation, did not alter body weight when compared to controls at 110 d of gestation. Thymidine activity, measured as 3H-thymidine incorporation into rat L6 myoblasts in response to test sera, did not differ between decapitated (D) and control (C) fetal pig sera. Thymidine activity of fetal sera was low when compared to a postnatal normal pig serum pool (NPS) and approximately equal to that of a postnatal hypophysectomized pig serum pool (HPS). Somatomedin-like activity, measured as 35S-sulfate uptake into 110 d fetal costal cartilage, was similar in D and C sera and was low when compared to NPS. Postnatal cartilage, but not fetal cartilage, responded greater to NPS than to HPS when measuring somatomedin activity. This indicates that fetal cartilage may be sensitive to different factors than postnatal pig cartilage. Thymidine activity and somatomedin-like activity were also low in maternal sera when compared to NPS. The concentration of insulin-like growth factor-I (IGF-I) was lower in D sera when compared to C sera (0.26 +/- 0.03 vs 0.62 +/- 0.09 U/ml, respectively, p less than 0.05). It is postulated that locally produced growth factors, compared to circulating growth factors, may be more important determinants controlling the rapid growth rate of the fetus.

Transforming growth factor type beta (TGF-beta) and adipogenesis in pigs.

The present study was performed on s.c. adipose tissue of fetal pigs at 35 to 110 d of gestation to examine the distribution of TGF-beta-positive cells, to localize TGF-beta immunoreactivity at the cellular level using electron microscopy (EM), and to determine the effect of TGF-beta on primary cultures of pig adipose tissue cells. Tissues for EM were fixed and embedded in LR white resin. Sections then were incubated with a polyclonal antibody specific for TGF-beta and TGF-beta was located using 20 nm colloidal gold conjugated second antibody. Tissues were fixed and embedded in paraffin for localization of TGF-beta at the light microscope (LM) level. Tissues were incubated with anti-TGF-beta followed by localization using biotinylated second antibody. Using LM, only a few cells stained positively for TGF-beta within developing blood vessels at 35 d. By 50 d, more TGF-beta-positive cells were associated with forming capillary networks. Between 70 d and 110 d, positively stained adipocytes usually were clustered around blood vessels. Cells surrounding hair follicles stained positive for TGF-beta between 90 to 110 d. Electron microscopy revealed TGF-beta labeling within fat cells. Fibroblasts and endothelial cells did not exhibit TGF-beta immunoreactivity. The addition of TGF-beta to primary cultures of s.c. adipose tissue cells from newborn pigs prevented lipid filling in fat cells. This effect was dose-dependent, with half-maximal inhibition occurring at 3 pM maximum inhibition occurred at 40 pM. These results indicate that TGF-beta may regulate angiogenic activity and lipid filling in s.c. adipose tissue of fetal pigs. Although TGF-beta was present in adipocytes and in cells associated with developing capillary networks, the physiological role of TGF-beta during early adipose tissue development is not known.

Fetal hypophysectomy causes a decrease in preadipocyte growth and insulin like growth factor-1 in pigs.

Fetal pigs in one uterine horn of each of five gilts were hypophysectomized (HX) in utero by electrical cauterization at 72-74 days of gestation and sera collected at 110 days of gestation. Sera from HX fetuses had lower levels of insulin-like growth factor-1 compared to control littermates (P less than .05). Sera were tested for their effects on primary cultures of stromal-vascular cells from adipose tissue. The soluble protein concentration/dish was lower when pig cells were cultured in sera from HX fetuses compared to sera from control fetuses (P less than .01). Sera from HX fetuses inadequately supported growth of stromal-vascular cells so subsequent experiments utilized pooled sera from normal and HX adult pigs. Sera from HX and control fetuses were mixed with sera from the two adult pools and tested for incorporation of tritiated thymidine into rat preadipocytes and the appearance of adipocytes (determined histochemically) in pig stromal-vascular cultures. In cultures fed sera from HX fetuses there was a lower (P less than .05) number of pig fat cells/culture and a lower level (P less than .06) of preadipocyte proliferation in rat cell cultures when compared to control fetal sera. Fetal pig serum contains factors (adipogenic) which promote the proliferation and differentiation of adipocytes in culture. Serum from HX fetuses has a lower level of adipogenic factors.

The insulin-like growth factor-binding proteins of porcine serum: endocrine and nutritional regulation.

Several studies have shown that insulin-like growth factor-binding proteins (IGF-BPs) modify IGF activity. To investigate their role in regulating growth, the number and size of IGF-BPs in porcine serum and the role of nutritional and endocrine factors in controlling their relative abundance were determined. IGF-BPs were analyzed by ligand blotting; sera were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, then the separated proteins were transferred to nitrocellulose filters and probed with [125I]IGF-I or -II. The band intensities of various forms of IGF-BPs were quantified by scanning densitometry. Fetal and postnatal sera contained six IGF-BPs of 220,000, 43,000, 39,000, 34,000, 29,000, and 24,000 mol wt (Mr). The band intensity of all forms of IGF-BPs increased with advancing gestational age. Specifically, the intensities of the 43,000, 39,000, 34,000, 29,000, and 24,000 Mr IGF-BP bands were 2.8-, 2.7-, 4.3-, 4.4-, and 3.1-fold higher, respectively, in fetal plasma at 110 than at 45 days gestation. In fetal plasma the 34,000 and 29,000 Mr forms predominated, whereas postnatally, the 43,000 and 39,000 Mr IGF-BPs predominated. Fasting of newborn pigs for 24 h reduced the intensity of the 43,000, 39,000, 34,000, and 24,000 Mr forms to 11.5%, 7.2%, 69.8%, and 5.2% of control levels, respectively. However, the 29,000 Mr IGF-BP was 1.8-fold higher in fasted pig serum than in that of fed controls. The band intensities of the 34,000 and 29,000 Mr forms were increased in postnatal animals after hypophysectomy. In contrast, fetal decapitation resulted in a preferential decrease in only the 34,000 Mr form, which was reduced by 30% compared to that in age-matched controls. These studies indicate that porcine serum contains six IGF-BPs that can be detected by ligand blotting. The level of each of these proteins increases with advancing gestational age, although the increases are not uniform, suggesting that the proteins may be regulated differentially. In the postnatal animal both endocrine and nutritional factors modulate the levels of IGF-BPs by distinct controlling mechanisms.

Effect of dietary energy source and level on serum growth hormone, insulin-like growth factor 1, growth and body composition in beef heifers.

Effects of fiber vs starch energy supplements on endogenous growth hormone (GH), insulin-like growth factor (IGF-1) and animal performance from weaning to breeding age were evaluated in 18, 9-mo-old beef heifers. Heifers had ad libitum access to wheat silage plus an average daily supplement intake of 1) 4.08 kg corn-soybean meal (SBM) (high energy-starch, HS), 2) 4.54 kg soyhulls (SH)-SBM (high energy-fiber, HF) or 3) 1.36 kg SH-SBM (low energy-fiber, LE). Serum samples were collected via jugular puncture every 10 d and were analyzed for IGF-1 by RIA. On d 45 and d 176, four heifers per treatment were fasted 18 h and serial blood samples collected via jugular cannulas every 15 min for 6.5 h. Arginine (.5 g/kg BW) was administered intravenously (ARG) to induce release of GH, and four additional samples of blood were collected. Samples were analyzed by RIA for GH. Mean fasted GH (6.4 +/- .4, 8.3 +/- .4 and 13.8 +/- .4 ng/ml for HS, HF and LE, respectively) varied with energy source and level (P less than .01). Mean GH following ARG was higher (P less than .01) in heifers receiving LE (46.2 +/- 4.7) than in those receiving HS and HF (23.5 +/- 4.4 and 24.1 +/- 4.6 ng/ml). Basal GH concentration and peak amplitude were higher (P less than .05) in LE than in HS and HF treatments. Diet did not influence number or frequency of GH peaks.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for inhibitory activity against cell proliferation in bovine liver.

Bovine calf liver was homogenized in 0.1M NH4Ac, pH 7.4, and centrifuged. The supernatant was lyophilized and resuspended in 44 mM NaHCO3. After size exclusion chromatography on sephacryl S-300, a fraction of approximately 100 to 160 kDa was shown to inhibit the proliferation of rat L6 myoblasts in culture. The inhibitory activity was abolished when the resuspended preparation was heated at 70 C for 30 min before testing in L6 cell proliferation assay. Addition of 10(-9)M IGF-I did not influence the inhibitory response. Two IGF-I-binding proteins, 30 and 36 kDa, were identifiable in this fraction. These two proteins were more evident in other fractions in which no inhibitory activity was found. Inhibitory activity was not associated with IGF-I binding proteins.

Determination of circulating levels of insulin-like growth factor II (IGF-II) in swine.

A heterologous radioimmunoassay system was developed for the determination of circulating IGF-II concentrations in swine. The assay utilized a monoclonal antibody against human IGF-II (Amano Intl. Ez, VA) and bovine IGF-II (Monsanto Co., MO) as the cold standard and iodinated ligand. Serial dilutions of acid-ethanol extracted normal swine sera resulted in a curve which was parallel to the bovine IGF-II standard curve. Recovery of unlabeled standard added to extracted swine sera was 101%. Neither IGF-I nor insulin were capable of cross-reacting in this assay at levels up to 100-fold excess. Using this assay, serum IGF-II levels were determined to be significantly lower when subnormal growth hormone (GH) levels existed such as in hypophysectomized swine. However, in contrast to serum IGF-I concentrations, supranormal levels of porcine GH (pGH) did not elevate serum IGF-II concentrations after 13 wk of treatment in 25 kg hogs (initial body wt). In addition, serum IGF-II levels were reduced in fasted swine, despite a significant increase in circulating GH concentrations. Thus, although normal concentrations of GH are required for maintenance of physiological levels of IGF-II in swine, the mechanism for stimulation of IGF-II secretion is less GH-dependent than IGF-I.

Glycosylated prolactin in porcine plasma: immunoblotic measurement from birth to one year of age.

As much as 40% of PRL in the pituitary gland of the pig is glycosylated. To help determine the physiological significance of this structural variant of PRL, we have measured glycosylated PRL (G-PRL) in the plasma of growing pigs from birth to 1 yr of age. An immunoblotting method developed originally for human plasma was used. With some modifications, the method could detect G-PRL in as little as 0.2 ml porcine plasma. Concanavalin-A affinity chromatography confirmed the glycoprotein nature of the plasma G-PRL band. Quantitative estimates of the immunoblotting results revealed marked differences with age in the secretion of the two monomeric forms of PRL. G-PRL concentrations averaged 138% higher than those of non-G-PRL between birth and 2 months of age, but lower thereafter. Chronologically, both forms displayed similar patterns between birth and 2 months, the concentration remaining unchanged or decreasing slightly. After 2 months, however, concentrations of non-G-PRL increased markedly; the increase was characterized by great fluctuations. G-PRL concentrations, on the other hand, increased only moderately, but the increase was consistent until the end of the study period. The results demonstrate the circulating nature of G-PRL in the pig and suggest that the variant may play a physiological role in the growth and development of the animal.

Adipose cellularity in nonselected and selected broiler stocks: measurements at equal weights and ages.

A population of nonselected broilers (AC) and a stock of commercial broilers (C) differ in growth characteristics. The two stocks of broilers were examined for differences in adipose tissue at equal ages at 28 and 54 days of age and at equal body weights. Body composition and abdominal adipose tissue were measured. Total adipocyte number, adipocyte size distributions, and DNA content of the abdominal fat pad were determined. Partial correlations of abdominal fat, expressed as a percentage of body weight, with mean adipocyte volume and abdominal adipocyte number were calculated. Body weights of C birds were greater than body weights of AC birds at 28 days of age (903 +/- 21 and 355 +/- 12 g; X +/- SE) and at 54 days of age (2,410 +/- 45 and 892 +/- 31 g). Abdominal fat pads were heavier in C birds than in AC birds on an absolute basis (P less than .01) and as a proportion of body weight (P less than .01). The C birds had more and larger adipocytes than AC birds at equal weights (P less than .05) and equal ages (P less than .01). Age did not significantly affect adipocyte size in AC birds, but adipocytes were larger in C birds at 28 days of age (117.3 vs. 78.8 pL, P less than .01) and further increased in size at 54 days (177.3 vs. 79.1 pL, P less than .01) when compared with those in AC birds at the same age.(ABSTRACT TRUNCATED AT 250 WORDS)

The ontogeny and regulation of a 31,000 molecular weight insulin-like growth factor-binding protein in fetal porcine plasma and sera.

Studies were conducted to determine the presence, quantity, and regulation of insulin-like growth factor (IGF)-binding proteins in porcine plasma and sera. The size distribution of IGF-binding protein was determined by affinity cross-linking to [125I]IGF-I, and the binding activity was quantified by a polyethylene glycol precipitation procedure. The major [125I]IGF-I-binding protein complex was of 38,000 mol wt (Mr) in all porcine sera or plasma tested. Binding to this protein was inhibited by excess unlabeled IGF-I, but not by insulin. When plasma samples from fetuses at 45, 70, 90, and 110 days gestation were cross-linked to [125I]IGF-I, there was an increase in the concentration of the 38,000 Mr complex with advancing gestational age, whereas plasma from the mothers of the age-matched fetuses showed little change in the amount of the 38,000 Mr complex. When the binding activity of the fetal plasma was quantified, there was a significant increase in binding activity between 45 and 110 days gestation from 30.5 +/- 3.3% to 77.5 +/- 3.6% (+/- SE) of the assay maximum. This increase was not due to a decrease in binding protein saturation, since the endogenous IGF-I levels (quantified after acid gel filtration chromatography) also increased with advancing gestational age, from 176 to 458 mU/ml. Blood samples were collected from porcine fetuses at 110 days gestation that had either been decapitated or spinal cauterized at 45 days gestation. Decapitation decreased the amount of the 38,000 Mr complex that could be detected by affinity labeling. In contrast, spinal cauterization had no effect on the amount of the 38,000 Mr complex in fetal plasma compared to that in control fetal plasma. These results were verified in the polyethylene glycol assay. These studies show that the amount of the 38,000 Mr IGF-binding protein complex in pig plasma is developmentally regulated and suggest that a pituitary or neural factor may be an important variable in the control of its plasma concentrations.

Adhesion, proliferation, and adipogenesis in primary rat cell cultures: effects of collagenous substrata, fibronectin, and serum.

The effects of collagenous substrata, fibronectin, and fetal bovine serum on the adhesion, proliferation, and adipogenesis of rat stromal-vascular cells are reported. There was no effect on initial stromal-vascular cell-attachment by fetal bovine serum or fibronectin. The number of cells attached to a hydrated collagen-gel was almost twice (P less than 0.04) the number attached to dried collagen-gel or dried denatured collagen-gel. Total number of cells after 5 days in culture was similar among the collagenous substrata and among the treatments with or without fibronectin in the growth media. Total number of cells increased significantly (P less than 0.02) with 10% FBS. Adipocytic formation was inhibited by hydrated collagen-gel (P less than 0.02) compared to dried collagen-gel or dried, denatured collagenous substrata. An interaction occurred between dried, denatured gel and fetal bovine serum so that total formation of adipocytes increased by increasing the level of fetal bovine serum (P less than 0.07). Adipocytic formation was inhibited by hydrated collagen-gel at all levels of fetal bovine serum. The percentage of cells that converted to adipocytes was significantly lower (P less than 0.01) on hydrated collagen-gel compared to dried, denatured or dried collagen-gel. Percentage of conversion was not significantly different among levels of fetal bovine serum, although this percentage increased as fetal bovine serum level increased. Adipocytic conversion was not different between fibronectin-treated or untreated cells. Morphology of stromal vascular cells was similar on dried collagen and dried, denatured collagen-gel, but tended to remain bipolar on hydrated collagen-gel.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of maternal obesity on fetal development in pigs.

Fetuses from linebred lean (L) and linebred obese (O) and reciprocal crossmatings were examined at 110 d of gestation for line, maternal and heterotic effects. There was no significant heterotic effect for any trait measured. A significant maternal effect was observed for adipose tissue lipoprotein lipase (LPL) activity and for serum triglycerides. The enzyme activity and triglycerides concentration were higher in fetuses from O dams than in fetuses from L dams. In a lipid clearance test, no maternal effect was observed for changes in serum concentrations of triglycerides and free fatty acids or in optical density (associated with the disappearance of injected Liposyn). Linebred O fetuses exhibited higher LPL activity in both the biceps femoris muscle and sc adipose tissue compared with linebred L fetuses. The LPL activity of the adipose tissue was higher than that of the skeletal muscle. The percentage of dry matter, percentage of triglycerides and protein/DNA were higher in the muscle of linebred O fetuses than in that of linebred L fetuses. Based on tissue LPL activity and on muscle compositional traits, linebred O fetuses were more mature at 110 d of gestation than were the linebred L fetuses. Maternal obesity had little detectable influence on fetal development of the pig when measured at 110 d of gestation.

Metabolic characteristics of skeletal muscle from lean and obese Zucker rats.

The purpose of this study was to determine if the metabolic response to obesity and to pair feeding of obese Zucker rats to lean Zucker rats was similar across skeletal muscles. Oxidation of glucose, palmitate and isoleucine was studied in muscle strips in vitro using appropriate 14- carbon substrates as tracers. The plantaris muscle was subjected to histochemical analyses using an alkaline actomyosin ATPase, NADH-tetrazolium reductase and an oil red 0 stain. Soleus muscles from both ad libitum and pair fed obese rats oxidized less glucose to CO2, but released similar amounts of lactate when compared to the soleus muscles of lean rats. Oxidation of glucose was similar in the extensor digitorum longus (EDL) muscle of ad libitum fed obese rats, but lower when pair fed to the intake of lean rats. No differences were apparent in palmitate oxidation to CO2 or in incorporation into lipid (both soleus and EDL muscles), except in the EDL muscle of pair-fed obese rats which exhibited a higher rate for palmitate metabolism when compared with lean rats. Isoleucine oxidation to CO2 was higher in the EDL and plantaris muscles, but similar in the soleus muscle of ad libitum-fed obese rats when compared with lean rats. The magnitude of the difference in isoleucine oxidation was similar when the obese rats were pair fed. No differences in the percentage of plantaris muscle fibers sensitive to alkaline ATPase staining were observed. The plantaris muscle of obese rats, contained a higher proportion of oxidative fibers. These results indicate the great risk in generalizing about metabolic activity of the whole skeletal muscle mass based on observations made on one, or even two, distinct muscles in this animal model. Also, pair feeding of obese to lean Zucker rats did not result in uniform changes in metabolism between muscles of the obese rats.

Determination of insulin-like growth factor 1 (IGF1) and IGF binding protein levels in swine.

A heterologous radioimmunoassay system was validated for the determination of IGF1 concentrations in swine sera. Parallelism, accuracy and response to physiological stimuli were obtained following the incubation of serum samples with 1M glycine-glycine HC1 buffer at a pH of 3.5 +/- 0.2 for 24 hours at 37C. Following acidification and neutralization, circulating IGF1 concentrations were significantly (P less than .05) reduced in hypophysectomized swine and elevated in swine injected with porcine growth hormone (pGH) when compared to IGF1 levels in control hogs. IGF binding protein levels were also increased following GH administration and reduced by hypophysectomy. In addition, circulating IGF1 concentrations were significantly (P less than .05) correlated with body size in three types of swine which differ in growth rate and mature body weight. These data suggest that IGF1 is involved in the regulation of swine growth in vivo and that its physiologic regulation is similar to that in humans.