Acute changes in blood flow in pigs infused with beta-adrenergic agonists

Previous results indicate that clenbuterol decreases carcass adipose tissue accretion when administered to pigs but does not appear to stimulate the adipose tissue beta-adrenergic receptor. Clenbuterol increases plasma free fatty acid concentration when acutely infused in vivo, suggesting an indirect affect. One possible indirect effect is that clenbuterol could change blood flow to adipose tissue. Blood flow was measured with radiolabeled microspheres in tissues from pigs before and after infusion of a beta-adrenergic agonist for 30 min. High probability levels (up to P less than .2) were used to indicate trends due to extreme variability. Infusion of isoproterenol increased heart rate, plasma free fatty acid concentration and blood flow at many adipose tissue sites and at a few skeletal muscle sites. Infusion of isoproterenol decreased blood pressure. Infusion of clenbuterol increased heart rate and tended to increase blood flow to several skin and adipose tissue sites slightly. The results suggest that increased adipose tissue blood flow may contribute to the accelerated release of free fatty acids when clenbuterol is infused acutely in vivo.     

Effects of ractopamine on genetically obese and lean pigs

Twenty-eight genetically obese and 24 lean barrows (65.0 and 68.7 kg average BW, respectively) were allotted within genotype to a 16% CP corn-soybean meal basal diet or this basal diet + 20 ppm ractopamine (a phenethanolamine beta-adrenergic agonist) and allowed ad libitum access to feed for 48 d. Compared to lean pigs, obese pigs had lower ADG, gain to feed ratio, longissimus muscle area, predicted amount of muscle, and weights of trimmed loin and ham, ham lean, heart, spleen, kidney and gastrointestinal tract (P less than .05). Obese pigs also had shorter carcass but higher dressing percentage, backfat thickness, fat depth, fat area, untrimmed loin weight and fasting plasma urea N concentration (P less than .05). Dietary supplementation with 20 ppm ractopamine reduced daily feed intake and improved gain to feed ratio in both lean and obese pigs (P less than .05). Pigs fed ractopamine had shorter carcasses, less fat depth and fat area, smaller weights of stomach and colon plus rectum, but higher dressing percentages, longissimus muscle areas, weights of trimmed Boston butts, picnics and loins, ham lean and predicted amounts of muscle than pigs not fed ractopamine (P less than .05). Supplemental ractopamine had no effect on fasting plasma concentrations of urea N, nonesterified fatty acids, triglyceride or glucose (P greater than .05). No genotype x ractopamine interactions for the criteria described above were detected (P greater than .05). These results suggest that ractopamine will improve the efficiency of feed utilization and carcass leanness in swine with different propensities for body fat deposition.     

Responses to cimaterol in genetically obese and lean pigs

Twenty-four genetically obese and 24 lean barrows were allotted within genotype to either a 16% CP corn-soybean meal basal diet, the basal + .69 ppm cimaterol or the basal + 1.38 ppm cimaterol. Pigs had ad libitum access to their diets from 59.3 kg to 104.5 kg body weight. No genotype x cimaterol interactions were detected (P greater than .05). Neither genotype nor cimaterol supplementation had any effect (P greater than .05) on average daily weight gain or gain-to-feed ratio. Compared with lean pigs, obese pigs had higher fasting plasma urea nitrogen (BUN), a smaller gastrointestinal tract and a greater dressing percentage with a shorter and fatter carcass (P less than .05). Cimaterol produced a higher fasting plasma BUN, a greater dressing percentage with a leaner carcass and a higher shear force value for loin chops (P less than .05). Cimaterol also tended (P less than .10) to increase heart weight. However, no difference was observed in these measurements between pigs fed .69 or 1.38 ppm cimaterol. In lean pigs fed the basal or .69 ppm cimaterol diet, there was no difference (P greater than .05) in the 8 to 24 h postprandial whole-animal heat production. Cimaterol effectively decreased fat deposition and increased lean accretion both in genetically obese and in lean pigs; there were no differential responses to cimaterol in pigs with different propensities to deposit body fat.     

Carcass, muscle and meat characteristics of lean and obese pigs

Six pigs obtained from a lean selected strain and six pigs obtained from an obese selected strain were slaughtered at about 110 kg live-animal weight. Carcasses were evaluated; hams were dissected into bone, skin, fat and lean, and loin samples were obtained for fiber type characteristics, percentage of fat and moisture, collagen analysis, sensory characteristics, textural properties and objective color analysis. Carcasses from lean pigs were longer, had less backfat and larger longissimus muscle cross-sectional areas than carcasses obtained from obese pigs. Hams from lean pigs had less fat, more bone and more lean than hams from carcasses of obese pigs. The percentages and cross-sectional areas of red and white muscle fibers of the longissimus muscle from lean and obese pigs were not different. However, lean pigs had intermediate fibers that were only 79% as large (P less than .10) as intermediate muscle fibers from obese pigs. Intermediate fibers represented only 7 and 10% of total fiber area, whereas white fibers represented 84 and 79% of total fiber area in longissimus muscle of lean and obese pigs, respectively. Overall, lean pigs tended to possess fewer fibers (-16%) per unit of area than obese pigs, indicating that total muscle fiber hypertrophy was partially responsible for the increased longissimus muscle area of the lean strain. Sensory properties of longissimus meat samples from lean and obese strains were not different. However, the shear force requirement of the longissimus samples from the lean strain were slightly, but significantly (P less than .10), higher than those from the obese strain. No differences were observed in meat color.     

Interactions between the beta-adrenergic agonist salbutamol and genotype on meat quality in pigs

Salbutamol (2.7 ppm) fed to pigs between weaning and slaughter increased ADG (5%), dressing percentage (2%) and cross-sectional area of the longissimus (LD) muscle (14%). In fatter, White-line-sired pigs, but not in leaner, Meat-line-sired animals, it reduced backfat thickness (25%). Liver weight and glycogen concentration also were decreased. In neither genotype were there effects of Salbutamol on pH45, drip loss or reflectance value of the LD, but ultimate pH was elevated in semimembranosus (SM), adductor (AD) and supraspinatus (SS) muscles, resulting in reduced color saturation values. Total muscle heme pigment concentrations were reduced by 10 (SS) to 19% (LD and SM) and the intramuscular fat concentration of the AD, but not the LD, was reduced by 21%. Treated pigs had LD and SM muscles that when measured instrumentally were 15 and 8% tougher, respectively, after cooking, but the texture of the SS was not significantly altered by treatment. Salbutamol increased plasma lactate and creatine phosphokinase (CPK) concentrations. Compared with White-line-sired animals, Meat-line-sired pigs had a higher dressing percentage (2%) and LD muscles with larger cross-sectional area (13%). They also had higher circulating CPK levels.     

The effects of the beta-adrenergic agonist salbutamol on meat quality in pigs

The beta-adrenergic agonist Salbutamol was administered to pigs at 3 ppm in the feed between weaning and slaughter at 85 kg. Growth rate was not affected by Salbutamol. Treated pigs had a higher dressing percentage (2.6%) and produced carcasses that were less fat (17%) and had longissimus (LD) muscles of larger (11%) cross-sectional area. They also had smaller livers that contained less glycogen. The thinner backfat in treated animals was less firm and tended to separate from the underlying lean. However, these changes were attributable solely to the reduced fatness and there was no direct effect of Salbutamol. There were no differences in pH 45 min postmortem, percentage drip loss during storage or reflectance value of the LD between the two groups, indicating no greater propensity for Salbutamol-treated pigs to develop pale, soft, exudative muscle. However, treated pigs had higher final pH values in the muscles; this was reflected in slightly reduced hue and saturation values. These results suggest that the propensity of the pigs to develop dark, firm, dry meat was slightly increased. Salbutamol-treated pigs produced LD muscles that were slightly tougher (22%), had reduced concentration of heme pigments in the muscle, reduced plasma glucose and increased plasma creatine phosphokinase activity. Salbutamol improved lean meat yield but slightly increased the potential to produce dark, firm, dry meat and reduced tenderness.     

Sera-controlled preadipocyte growth in culture: an ontogeny study with sera from lean and obese pigs

Genetically lean and obese swine were used to investigate the control of preadipocyte growth in culture by porcine serum. Sera were collected from fetuses from obese and lean strains at 70, 90 and 110 d of gestation. Postnatal serum samples were collected from both lines of pigs at 23 to 27 kg. Rat preadipocytes were isolated and grown in culture. Preadipocyte and stromal-vascular cell proliferation was greater in cultures grown in sera obtained postnatally than in cultures grown in sera from fetuses. Sera from lean and obese fetuses were equipotent in promoting cell proliferation. Glycerol-phosphate dehydrogenase (GPDH) activity was higher in cultures fed serum from obese pigs and fetuses than in cultures fed serum from lean pigs and fetuses. Cultures grown in serum from obese fetuses and pigs had soluble protein levels similar to cultures grown with serum from lean pigs and fetuses. These results demonstrate that serum from genetically obese swine, in the pre-obese (fetal) and obese (postnatal) state, caused increased adipogenic activity in adipocytes in culture.     

Effects of the beta-adrenergic agonist isoproterenol on protein accretion, synthesis, and degradation in primary chicken muscle cell cultures

Seven-day-old primary myotube cultures derived from embryonic chicken limb muscles were used to determine the effects of the beta-adrenergic agonist isoproterenol (ISO) on muscle protein metabolism in vitro. Isoproterenol increased (P less than .05) total protein accumulation after 2 h of acute exposure and after chronic exposure for 24 and 48 h. Isoproterenol did not consistently retard rate of protein degradation of the total protein (TP), myofibrillar protein (MFP) pools, and myosin heavy-chain subunit (MHC); degradation of these protein pools tended to be slowed by inclusion of ISO in the culture medium. After acute treatment of 1 X 10(-4) M ISO for 2 h, TP, but not MFP and MHC, synthesis rate was increased, and after chronic exposure to 1 X 10(-4), 1 X 10(-5), and 1 X 10(-6) M ISO, TP, MFP, and MHC synthesis rates and net accumulation of TP, cytoplasmic protein, and MHC fractions were enhanced (P less than .05). The beta-adrenergic antagonist propranolol (1 X 10(-5) M) blocked chronic stimulatory effects of ISO. Furthermore, after 48 h of exposure to ISO, effects on protein synthesis were less pronounced than those observed after 24 h of exposure. Isoproterenol imparted a more pronounced effect on protein synthesis than on protein degradation, indicating that increased muscle protein accretion observed in animals after ISO treatment is likely a function of enhanced protein synthesis.     

Plasma thyroid hormones, growth and carcass measurements of genetically obese and lean pigs as influenced by thyroprotein supplementation

A 2 X 2 factorial arrangement with two genotypes of pigs (genetically obese and lean) and two dietary treatments (basal, a 16% protein corn-soybean meal standard grower diet, and basal +220 ppm thyroprotein as iodinated casein) was used. The 28 gilts were housed individually and fed ad libitum from 121 d of age until slaughtered at 99 kg body weight. Compared with lean pigs, genetically obese pigs had significantly lower average daily gain and gain/feed, greater backfat thickness, smaller loin eye area, shorter carcass length and lower circulating plasma triiodothyronine (T3) concentration. However, both total plasma and free thyroxine (T4) concentrations were similar comparing obese and lean pigs. Supplementation with thyroprotein increased circulating plasma concentration of both total and free T4 and produced interactions with genotype in affecting daily gain and gain/feed of pigs. Thyroprotein reduced both daily gain and gain/feed in obese pigs, but increased daily gain and gain/feed in lean pigs. It is suggested, similar to the case with obese mice, that heat production of our genetically obese pigs may be more sensitive to thyroprotein administration compared with similar treatment of lean animals.     

Influence of infused beta-adrenergic agonists on porcine blood metabolites and catecholamines

Anesthetized pigs were infused sequentially with increased concentrations of beta-adrenergic agonists. At selected times during infusion, blood pressure, heart rate and plasma concentrations of free fatty acids (FFA), glycerol, glucose, lactate, norepinephrine, epinephrine and dopamine were measured. Azaperone, a drug used to calm the pigs before anesthesia, caused hypotension and bradycardia but did not affect plasma metabolites. Infusion of norepinephrine, epinephrine, isoproterenol or clenbuterol produced changes in plasma metabolites and plasma catecholamines. These changes during norepinephrine infusion were attributed to the infused agonist, whereas those during epinephrine infusion might have resulted to some extent from release of norepinephrine. Plasma isoproterenol was not quantified because it interfered with the assay of epinephrine and dopamine so that it was not possible to distinguish between infused isoproterenol and release of endogenous epinephrine and dopamine. Infusion of clenbuterol caused a small increase in plasma norepinephrine so that some of the increase in plasma FFA, glycerol and lactate during clenbuterol infusion may result from release of endogenous norepinephrine.     

Response of low and high protein select lines of pigs to the feeding of the beta-adrenergic agonist ractopamine (phenethanolamine)

The effect of ractopamine, a phenethanolamine beta-adrenergic agonist, on growth, nutrient utilization and carcass composition was studied in two lines of pigs that were fed high (24%) or low (12%) protein diets. Of the two lines of pigs that had been selected for seven generations for rapid lean growth when fed either the higher (HS line) or low (LS line) protein diet, the HS line tended to exhibit a leaner carcass when fed either diet. Ractopamine, at 20 ppm in the diet, was fed from 60 kg live body weight until slaughter at 90 kg. When compared with their respective line-diet control group, the greatest response to ractopamine treatment was observed in the LS-12 group; at 90 kg, that group had 31% less carcass lipid (P less than .05) and 17% more carcass protein (P less than .05). Considering the change that took place only between 60 and 90 kg live body weight, this translated into 57% less lipid and 59% more protein deposited in the carcasses with ractopamine treatment. This group also was 73% more efficient (P less than .05) in converting dietary protein to carcass protein but 39% less efficient (P less than .05) in energy utilization. Response to ractopamine treatment was least by the LS-24 group, followed by the HS-12 and HS-24 groups. A line x diet x treatment interaction (P less than .05) was noted for whole-carcass lipid, backfat, longissimus muscle area and efficiency of protein utilization.(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of carbohydrate and fat as energy source by obese and lean swine

Genetically obese and lean pigs were fed isonitrogenous-isoenergetic (digestible energy) amounts of a high or low fat diet from 25 kg body weight. Obese pigs gained less and required more feed per unit gain than lean pigs. Lean pigs were more muscular with less fat than obese pigs. Obese pigs utilized more dietary amino acids for energy (greater plasma urea N) than did lean pigs. Weight gain was similar at all intermediate periods in obese pigs fed the two diets. However, gain tended (P less than or equal to .10) to be greater and the ratio of dietary energy intake to gain tended (P less than or equal to .10) to be less in obese pigs fed high compared with low fat diets. Similar results were observed in lean pigs fed the two diets. The high fat diet produced more carcass adipose tissue deposition in both strains after 20 wk of feeding (detectable by ultrasound at 14, but not at 7 wk). Adipose tissue lipogenic rate (glucose incorporation) was similarly depressed by fat feeding in both obese and lean pigs. Obese and lean pigs both utilized dietary carbohydrate and fat differentially but there was no indication of genetic divergence regarding this utilization. In both strains of pigs, energy from the fat-enriched diet was preferentially partitioned into carcass adipose tissue.     

Adipose tissue lipolytic rate in genetically obese and lean swine

In vitro lipolytic rate was determined in adipose tissue from genetically obese and lean pigs. There were about 20 pigs/genetic strain at 25 and 80 kg and 10 pigs/strain at 50 kg body weight. When expressed on a cellular basis, the in vitro adipose tissue basal (no exogenous hormone) lipolytic rate was similar in obese and lean pigs at 25 and 50 kg body weight. At 80 kg body weight the basal rate was greater in obese than in lean pigs. The in vitro adipose tissue epinephrine-stimulated lipolytic rate expressed on a cell basis was greater at 25 kg, was similar at 50 kg body weight and tended (P less than or equal to .1) to be greater at 80 kg in obese compared with lean pigs. The in vitro sensitivity of lipolysis to epinephrine was slightly greater in lean compared with obese pigs. The data obtained in vitro indicate that obese pigs do not have low adipose tissue lipolytic rates compared with lean pigs. Consequently, adipose tissue lipolysis does not appear to be a major metabolic factor leading to the excessive fat accretion in these obese pigs.     

Effects of dietary fiber of young adult genetically lean, obese and contemporary pigs: rate of passage, digestibility and microbiological data

Twenty-one genetically lean, obese or contemporary slaughter weight castrated male pigs (6 mo old; seven of each genotype) were assigned to individual tether stalls and fed either a control diet (low fiber) or a diet containing 80% alfalfa meal (high fiber) at 1.50% of initial body weight for 71 d (1.75% for d 1 to 4). Apparent dry matter digestibility of the diets was estimated by determining acid insoluble ash in fecal samples. Fecal cellulolytic bacteria and total viable bacteria were enumerated at d 0, 14, 35, 49 and 70. Fecal inocula were used to determine 48-h in vitro digestibility of alfalfa meal fractions on the same days. Digesta rate of passage was determined by feeding a pulse dose of chromium-mordanted alfalfa fiber to the pigs fed the high-fiber diet. In vivo digestibility of both diets was less for the obese pigs than for the lean or contemporary genotypes. In vitro digestibility of alfalfa fiber fractions was not different between the genotypes fed either diet. When the high-fiber diet was fed, in vitro digestibility increased for all genotypes from d 0 to d 14, but not thereafter. The numbers of cellulolytic bacteria for all three genotypes were greater when pigs were fed the high-fiber diet (23.0 X 10(8), 51.6 X 10(8), 37.2 X 10(8) per gram fecal dry weight; obese, lean and contemporary, respectively) compared to the low-fiber diet (3.0 X 10(8), 3.2 X 10(8), 3.4 X 10(8), respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Triiodothyronine differentially regulates key metabolic factors in lean and obese cats

The effect of a 2-week administration of 75microg triiodothyronine (T3) on substrate oxidation, heat production, non-esterified fatty acids, and leptin was evaluated in eight lean (three females and five males) and eight obese (five females and three males) age-matched adult neutered cats. In addition, using real-time RT-PCR, expression of muscle and adipose tissue uncoupling proteins (UCP2 and UCP3), deiodinase 1 and 2 (D1; D2), and peroxisome proliferator-activated receptor (PPAR) alpha and gamma and peroxisome-proliferator-activator receptor-gamma co-activator 1alpha (PGC1) was examined. Compared to lean cats, obese cats had increased NEFA, leptin, UCP2, and D1mRNA in muscle and UCP3mRNA levels in fat, but lower heat production, and fat PPARs and PGC1. T3 administration increased thermogenesis and NEFA in lean and obese cats, and adipose tissue PPARgamma in lean cats. It also increased muscle D1 in lean and D2 in obese cats. The increase in muscle D2 was interpreted to be reflective of the reduced serum total T4 concentration following T3 suppression of the pituitary. No effect was seen on leptin, or UCP2 and 3. This shows that T3 regulates thermogenesis but not through changes in uncoupling protein expression. It also indicates that PPARs have an important role in the pathogenesis of obesity in cats.     

Pharmacokinetics of pioglitazone in lean and obese cats(1)

Clark, M. H., Hoenig, M., Ferguson, D. C., Dirikolu, L. Pharmacokinetics of pioglitazone in lean and obese cats. J. vet. Pharmacol. Therap.  35 , 428–436. Pioglitazone is a thiazolidinedione insulin sensitizer that has shown efficacy in Type 2 diabetes and nonalcoholic fatty liver disease in humans. It may be useful for treatment of similar conditions in cats. The purpose of this study was to investigate the pharmacokinetics of pioglitazone in lean and obese cats, to provide a foundation for assessment of its effects on insulin sensitivity and lipid metabolism. Pioglitazone was administered intravenously (median 0.2 mg/kg) or orally (3 mg/kg) to 6 healthy lean (3.96 ± 0.56 kg) and 6 obese (6.43 ± 0.48 kg) cats, in a two by two Latin Square design with a 4‐week washout period. Blood samples were collected over 24 h, and pioglitazone concentrations were measured via a validated high‐performance liquid chromatography assay. Pharmacokinetic parameters were determined using two‐compartmental analysis for IV data and noncompartmental analysis for oral data. After oral administration, mean bioavailability was 55%, t_1/2 was 3.5 h, T_max was 3.6 h, C_max was 2131 ng/mL, and AUC_0–∞ was 15 556 ng/mL·h. There were no statistically significant differences in pharmacokinetic parameters between lean and obese cats following either oral or intravenous administration. Systemic exposure to pioglitazone in cats after a 3 mg/kg oral dose approximates that observed in humans with therapeutic doses.     

Dietary B vitamin needs of strains of pigs with high and moderate lean growth

Ten sets of 5 littermate pigs from each of 2 genetic strains were utilized to determine the impact of the dietary concentration of 5 B vitamins (riboflavin, niacin, pantothenic acid, cobalamin, and folacin) on growth from 9 to 28 kg of BW in pigs with high or moderate capacity for lean growth. All pigs (penned individually) were reared via a segregated, early weaning scheme, so that the lean growth potential of each strain could be expressed. The basal diet provided the 5 test vitamins at concentrations of total and estimated bioavailability equivalent to a minimum of 100 and 70%, respectively, of their estimated requirements (NRC, 1998) for 5- to 10-kg pigs. At a BW of 9 +/- 0.9 kg, pigs within each litter were allotted to the basal diet supplemented with sources of the 5 test vitamins equivalent to an additional 0, 100, 200, 300, or 400% (bioavailable) of the NRC requirements. Pigs from the high lean strain consumed less feed (P < 0.05) and gained BW faster (P < 0.02) and more efficiently (P < 0.01) than pigs of the moderate lean strain. In both lean strains, the rate and efficiency of growth were improved (P < 0.01) as dietary B vitamin concentrations were increased. However, the dietary B vitamin concentrations needed to optimize G:F were greater (P < 0.03) in the high (>470% of NRC, 1998) vs. moderate (270%) lean strain. Based on these data, the dietary needs for 1 or more of the 5 B vitamins are greater than current NRC (1998) estimates, particularly in pigs expressing a high rate of lean tissue growth. The greater need for these vitamins is not associated with greater dietary energy intake or body energy accretion rate but is potentially due to shifts in the predominant metabolic pathways.     

Lipid mobilization and inflammatory responses during the transition period of dairy cows

The transition period of dairy cattle is characterized by dramatic changes in metabolism and host defense mechanisms that are associated with increased disease. Intense lipid mobilization from tissue stores is an important metabolic adaptation during the transition period that results in significant release of non-esterified fatty acids (NEFA) into the blood stream. Whereas these fatty acids are important sources of energy during times of increased metabolic demands, elevated concentrations of NEFA are known to disrupt several immune and inflammatory functions. This review will discuss the implications of lipid mobilization on inflammatory responses with special emphasis on leukocytes and endothelial cell functions during the transition period of dairy cows.