Effects Of Ractopamine Research Articles

Effect of ractopamine on the release of dopamine from the striatum dissected from mice.

In the past two decades, ractopamine has been used as a feed additive to increase protein synthesis in farmed animals (swine, cattle, and turkeys) and to produce high-quality meat. However, the excessive feeding of animals with ractopamine may result in its accumulation in animal and human tissues after consuming the meat. Ractopamine is a trace amine-associated receptor1 and β-adrenoceptor agonist banned in the EU but approved in the USA, and it may pose a potential risk to human health. In this paper, the authors, for the first time, provide neurochemical evidence that ractopamine leads to the release of dopamine from nerve terminals of the nigrostriatal pathway in the striatum.

Ractopamine residues in meat might reduce the risk of type 2 diabetes.

Background: The overall prevalence of diabetes in the world has risen substantially in the past several decades, so have complications and mortalities associated with it. Aim: Prevention strategies for diabetes thus become an urgent public health need for reducing the burden of diabetes. Methods: Ractopamine, a β1/2-adrenergic receptor agonist, has been approved for use in finishing swine, cattle, and turkey in countries where meat exporting brings tremendous economic benefits. This leanness enhancer is recently found to be a full agonist at trace amine-associated receptor 1 also. A thorough literature review was performed to assess possible effects of ractopamine on glucose metabolism. Results: Activating β-adrenoceptor could lead to glucose-lowering effects independent of insulin while activation on trace amine-associated receptor 1 induces an incretin-like signaling on insulin-secreting pancreatic β-cells. Conclusion: Accordingly, it is hypothesized that long-term consuming meat containing ractopamine might lower the risk of type 2 diabetes.

Effect of ractopamine and conjugated linoleic acid on performance of late finishing pigs

The dietary inclusion of feed additives to improve the carcass characteristics of the final product is of great importance for the pork production chain. The aim of our study was to evaluate the effects of the association of ractopamine (RAC) and conjugated linoleic acid (CLA) on the performance traits of finishing pigs during the last 26 days prior to slaughter. In total, 810 commercial hybrid barrows were used. Animals were distributed among treatments according to a randomised block design in a 3 × 3 factorial arrangement, with three RAC levels (0, 5 or 10 ppm) and three CLA levels (0, 0.3 or 0.6%). Pigs fed the diet with 5 ppm RAC had higher average daily feed intake (ADFI) (2.83 kg; P < 0.05) when compared with those fed 10 ppm RAC and the control diet (2.75 and 2.74 kg, respectively). Lower ADFI values (P < 0.01) were observed with the diets containing CLA compared with the control diet with no CLA (2.73 and 2.75 v. 2.85 kg/day, respectively). The average daily weight gain of pigs fed 5 and 10 ppm RAC was +148 and +173 g/dayhigher (P < 0.001), respectively, than those fed the control diet. Dietary RAC levels influenced (P < 0.001) feed conversion ratio (FCR), which was reduced as RAC levels increased, with the pigs fed 10, 5 and 0 ppm RAC presenting FCR values of 2.57, 2.71 and 3.05, respectively. FCR also improved (P < 0.05) with the inclusion of 0.6% CLA relative to the control diet (2.70 v. 2.84, respectively). There was a significant interaction between CLA × RAC levels (P < 0.01) for final BW, loin eye area (LEA) (P < 0.05) and backfat thickness (BT) (P < 0.05). The treatments containing 10 ppm RAC + 0.6% or 0.3% CLA increased LEA and reduced BT. In conclusion, the level of 10 ppm inclusion of RAC increased the overall performance parameters of pigs and therefore improved production efficiency. The combined use of RAC and CLA promoted a lower feed conversion ratio as well as better quantitative carcass traits, as demonstrated by the higher LEA and lower BT. The dietary inclusion of CLA at 0.3% improved feed efficiency, however, without affecting LEA or BT yields.

Ractopamine-Induced Changes in the Mitochondrial Proteome of Postmortem Beef Longissimus Lumborum

ObjectivesRactopamine is a β-adrenergic agonist approved as growth promotant in beef cattle, and it increases muscle deposition while limiting fat deposition. Dietary ractopamine causes a muscle fiber shift in cattle, and the biochemistry of mitochondria in postmortem beef skeletal muscles is influenced by fiber type. Therefore, dietary ractopamine may potentially affect mitochondrial functionality. Nonetheless, the influence of ractopamine on beef skeletal muscle mitochondrial proteome has not been evaluated. Therefore, the objective of this study was to examine the effects of ractopamine on mitochondrial proteome of postmortem longissimus lumborum (LL) from beef cattle.Materials and MethodsPen-housed crossbred steers were fed either a corn-based basal diet (CON) or a diet top-dressed with Optaflexx 45 (Elanco Animal Health) to provide 400 mg of ractopamine hydrochloride/steer per day (RAC). Ractopamine was fed the last 28 d prior to the harvest. The animals were harvested, and carcasses were chilled for 24 h. The LL muscle samples were obtained from nine (n = 9) RAC and nine (n = 9) CON carcasses. Mitochondrial proteome was analyzed using two-dimensional electrophoresis, and the digital gel images were analyzed. The protein spots exhibiting more than 1.5-fold intensity differences (P &lt; 0.10) between RAC and CON were subjected to in-gel tryptic digestion and were identified by tandem mass spectrometry.ResultsSeven differentially abundant proteins were identified in the mitochondrial proteome. Three proteins were over-abundant (P &lt; 0.10) in RAC, whereas four spots were over-abundant in CON. The proteins over-abundant in RAC mitochondrial proteome was complement component 1 Q subcomponent-binding protein, very long-chain specific acyl-CoA dehydrogenase, and aconitate hydratase. On the other hand, ATP synthase subunit β, prohibitin, Cytochrome b-c1 complex subunit, and thioredoxin-dependent peroxide reductase were over-abundant in CON samples. The differentially abundant proteins belong to four functional groups; i.e., energy metabolism (ATP synthase subunit β, Cytochrome b-c1 complex subunit 1, and aconitate hydratase), chaperone activity (complement component 1 Q subcomponent-binding protein and prohibitin), antioxidant activity (thioredoxin-dependent peroxide reductase), and lipid metabolism (very long-chain specific acyl-CoA dehydrogenase).ConclusionDietary ractopamine impacts mitochondrial proteome in postmortem beef LL muscle and influences the abundance of proteins involved in cellular metabolism and protective mechanisms. The increased protein synthesis and leanness previously reported in ractopamine-fed cattle may be attributed to the decreased expression of enzymes involved in respiratory electron transport pathways and the increased expression of enzymes involved in lipolysis.

Effect of ractopamine on digestible-lysine requirement for finishing barrows under thermoneutral conditions

The purpose of the present study was to determine the digestible-lysine (Lys) requirement in diets supplemented or not with ractopamine (RAC), so as to maximise performance and carcass characteristics for finishing barrows reared at thermoneutral conditions. In total, 128 high-lean commercial hybrid barrows with an initial bodyweight of 78.2 ± 4.3 kg were distributed in a completely randomised block design, in a 4 × 2 factorial arrangement (four Lys concentrations: 0.730%, 0.830%, 0.930% and 1.030% and two RAC inclusions: 0 and 10 mg/kg), with two animals per pen and eight pens per treatment. Lys concentrations tested significantly (P &amp;lt; 0.05) affected digestible-lysine intake, and the absolute (g) and relative (%) lean meat content, regardless of RAC inclusion. When diets were RAC-supplemented, feed conversion rate of animals was improved and, in addition, final bodyweight, daily bodyweight gain, loin eye area, loin eye depth, and absolute (g) and relative (%) carcass lean meat content increased (P &amp;lt; 0.05). RAC inclusion also decreased (P &amp;lt; 0.05) backfat thickness and the colour values a* and b* of finishing pigs. Therefore, on the basis of our results, it can be inferred that the best performance and carcass characteristics for finishing barrows reared at thermoneutral conditions were obtained at 1.030% and 0.730% Lys respectively, corresponding to an estimated daily Lys intake of 34.3 g and 24.2 g, independently of the diet RAC concentration.

Effect of ractopamine on physicochemical characteristics and collagen solubility in finishing pigs

The objective of this study was to investigate physicochemical characteristics and collagen solubility of pigs fed with dietary ractopamine (RAC) during finishing period. Thirty of three-way crossbred pigs (Large White × Landrace × Duroc) with an initial bodyweight (BW) of 18.0 ± 0.5 kg were randomly assigned to one to three dietary RAC inclusions (0, 20, or 40 mg/kg) fed during finishing period (60-100 kg BW). Each group consisted of five gilts and five barrows. After 109 day of raising period, all pigs were slaughtered at the average weight of 100 kg. Longissimus dorsi muscle (LD) was taken from each carcass after overnight chill and analyzed for physical characteristics, chemical composition, and collagen solubility. The LD from pigs fed 40 mg/kg of RAC had lower a* value (p &lt; 0.01) than others. Pigs fed with 40 mg/kg of RAC had higher Warner-Bratzler shear force (p &lt; 0.05) than pigs fed without RAC. Pigs fed with dietary RAC had lower glycogen content than control (p &lt; 0.01). While other chemical compositions and collagen solubility of LD were not affected by dietary RAC (p &gt; 0.05). Gilts had larger muscle fibers (p &lt; 0.01), lower glycogen content (p &lt; 0.05), higher content of insoluble collagen (p &lt; 0.05), total collagen (p = 0.054), and collagen solubility (p = 0.054) than barrows.

Ractopamine-induced changes in sarcoplasmic proteome profile of post-rigor pork &lt;i&gt;semimembranosus&lt;/i&gt; muscle

Ractopamine is a beta-adrenergic agonist that increases leanness and carcass weight in finishing pigs. Our previous study observed that dietary ractopamine increased the abundance of several glycolytic enzymes in the sarcoplasmic proteome of post-rigor pork longissimus thoracis muscle. Pork semimembranosus is an economically important muscle and demonstrates differences in biochemistry compared with longissimus thoracis. Nonetheless, the effects of ractopamine on sarcoplasmic proteome of semimembranosus have not been evaluated yet. Therefore, this study examined the influence of ractopamine on sarcoplasmic proteome of post-rigor pork semimembranosus. Analyses of sarcoplasmic proteome of semimembranosus muscles from control (CON; diet without ractopamine) and ractopamine-fed (RAC; 7.4 mg/kg for 14 days followed by 10.0 mg/kg for 14 days) barrows revealed that haemoglobin subunit beta, alpha-crystallin B, and titin fragments were over-abundant in CON. In contrast, myosin light chain 1/3 and tripartite motif-containing protein 72 were over-abundant in RAC. The low abundance of haemoglobin subunit beta and alpha crystallin B in RAC could be attributed to fibre type shift (from oxidative to glycolytic) in response to ractopamine. The over-abundance of MLC 1/3 and tripartite motif-containing protein 72 in RAC could be due to the increased myofibrillar protein synthesis and muscle mass in ractopamine-fed pigs. Dietary ractopamine decreased the abundance of sarcoplasmic proteins involved in oxygen transport and chaperone activity, but increased the abundance of proteins involved in muscle contraction and plasma membrane repair in pork semimembranosus muscle. Keywords : Pork, ractopamine, sarcoplasmic proteome, semimembranosus

Effect of ractopamine on Nile tilapia in the end of grow-out period

ABSTRACT This experiment was conducted in outdoor tanks to evaluate the effect of inclusion of ractopamine at increasing levels (0, 4, 8, 12, and 16 mg kg−1) as additive in Nile tilapia (Oreochromis niloticus) diet in the final grow-out period (750-920 g) during 31 days. Therefore, 400 fish were housed into 20 experimental tanks, in a completely randomized design with five treatments and four replications. Growth performance, body yield, and chemical composition of fish muscle and organs were evaluated. Fish [...]

A multivariate approach to determine the factors affecting response level of growth, carcass, and meat quality traits in finishing pigs fed ractopamine.

The effect of ractopamine (RAC) supplementation on growth, carcass, and meat quality traits of finishing pigs was studied using a meta-analytical approach. The database was composed of 57 studies published from 2004 to 2016. The dependent variables extracted for the meta-analysis included final BW, ADG, ADFI, feed:gain ratio, HCW, dressing percentage, carcass length, lean yield, back fat thickness, loin muscle area, loin depth, postmortem pH, meat brightness, redness, and yellowness. The studies were grouped by similarity in 3 clusters (C1, C2, and C3) by hierarchical clustering on principle components. The main differences observed between clusters were those of animal initial weight, which increased from C1 through C3. Linear mixed models were used to analyze the data, where studies were assumed as random effect, whereas the total amount of RAC in the diet, cluster, and sex category were considered fixed effects. The interactions between cluster and sex category (barrows, gilts, and mixed sex) and RAC level were also evaluated. Dietary RAC was effective in improving final weight ( < 0.0001), ADG ( < 0.0001), and feed:gain ratio ( < 0.0001) and had a positive effect on HCW ( < 0.0001), lean yield ( = 0.0081), loin muscle area ( = 0.0190), and loin depth ( < 0.0001). In addition, a relatively limited effect on pork quality was observed in the current study. The RAC supplementation was more effective, mainly when pigs started supplementation with higher initial weight, although different responses were observed according to sex category ( < 0.05). There is ample indication that growth and carcass traits could be improved by dietary RAC supplementation. Ractopamine supplementation did not influence the pork quality.

Ractopamine hydrochloride and immunological castration in pigs. Part 1: fresh belly characteristics for bacon processing and quality

Abstract The effects of ractopamine and immunological castration on belly characteristics, processing yield, physicochemical and sensory quality of bacon were investigated from two crossbred pigs under different conditions of animal production, diet, management and slaughter arranged in factorial design using 2 ractopamine levels (0 and 7.5 ppm) and 3 genders (barrows, immunocastrated and gilts). Before processing, belly firmness, weight, length, width and thickness were measured, and then, bacon processing yield evaluated. After processing, bacon slices were digitally imaged and analyzed for lean meat and fat areas, pH, instrumental color of meat and fat, cooking loss and sensory quality. The ractopamine did not alter belly characteristics, but significantly increased the process yield and decreased cooking loss. Barrows and immunocastrated pigs showed firmer bellies, which could be advantageous for bacon processing and slicing. Barrows presented the highest total area of bacon slices. The results of this study indicate that both techniques ractopamine in the finishing diets and immunocastration of pigs can be combined with no further consequences for belly processing and to bacon quality and with some advantages.

The Effects of Ractopamine and Hormonal Growth Promotants on Growth and Meat Quality of Crossbred Angus Steers

ObjectivesMeat tenderness is an important quality parameter that influences consumer preference. The cattle industry has over the years seen the emergence of feed additives and hormonal growth promotants in the form of β-adrenergic agonists (β-AA) and steroids, respectively. The objective of this study was to analyze the effect of hormonal growth implants and ractopamine on slaughter weight and meat quality parameters of steers selected for high (inefficient) and low (efficient) residual feed intake (RFI) performance.Materials and MethodsForty-eight crossbred Angus steers identified from individual GrowSafe data as high (n = 21) or low (n = 27) RFI cattle were randomly assigned to pens according to treatment (n = 12). Treatments included control (no ractopamine hydrochloride (RAC)/no steroids), RAC and steroids, steroids only, and RAC only in a 2x2x2 factorial design. Steers on steroid treatment received a first implant (200mg progesterone, 20mg estradiol benzoate and 29mg tylosin tartrate) at about 350 d of age and 450kg live weight and a terminal implant (120 mg trenbolone acetate and 24mg estradiol) at about 100 d before slaughter. RAC was fed to the appropriate group 28 d before slaughter at a rate of 200mg head–1d–1. Cattle were slaughtered at about 16 mo of age over 6 consecutive weeks by weight and back fat, with 1 animal per treatment represented in each kill for a total of 8 animals slaughtered per week. Hot carcass weights (HCW) were recorded. Gluteus medius (GM) muscles were obtained from the carcasses 3 d post mortem and halved for ageing, with one half aged a further 12 d under vacuum. After ageing at 4°C, muscle halves were assessed for pH, color, drip loss and Warner-Bratzler shear force (WBSF). For all data the experimental unit was the steer as the effect of ageing was not considered. Data was analyzed using the General Linear Model procedure in SAS (SAS Inst. Inc., Cary, NC) with RFI, steroids, RAC and their interactions as fixed factors with slaughter day used as a covariate. Mean differences were determined using Least Square Means and Tukey’s multiple comparisons.ResultsResults revealed no effect (P > 0.05) of RFI and RAC on slaughter weight (SW) but steroids increased (P < 0.0001) SW of steers. An interaction effect (P = 0.0381) was seen between RFI, steroids and RAC on HCW, where high RFI steers that were implanted with steroids and fed RAC had a higher HCW at 389.64 ± 8.70 kg than low RFI steers that were neither implanted nor fed RAC (325.68 ± 7.05kg). An interaction between RFI, steroids and RAC (P = 0.045) for drip loss was observed on muscles aged for 12 d, where high RFI steers that were implanted but not fed RAC had a higher drip loss (1.93 ± 0.23 g) than low RFI steers that were not implanted but feed RAC (0.63 ± 0.19g). Muscles from implanted steers had a higher mean WBSF value than muscles from non-implanted steers on d 12 post-mortem (P = 0.039), while high RFI steers that received RAC had the lowest mean WBSF (P = 0.015).ConclusionResults indicated that steroids compromised the development of tenderness during post mortem ageing in the GM. This suggests that the benefit of steroid use on slaughter and hot carcass weights will compromise tenderness of this muscle. Additional post mortem ageing beyond 12 d may be required. Conversely, the use of the β-AA RAC showed potential for decreasing cooked GM toughness in high RFI steers regardless of the ageing period.

Economical evaluation of ractopamine inclusion in diets of finishing gilts

The use of adrenergic agonists such as ractopamine leads to lean carcasses due to an increasein muscle deposition. The effects of ractopamine on performance and carcass traits in pigsmay be varied depending on the level of agonist and amino acids, especially lysine, on diet,sex and age of the animals at the beginning of the additive supply. These factors, as well asthe feed cost and the adoption or not the carcass classification influence the economicviability of the use of ractopamine. The economic analysis, therefore, is necessary to evaluatethe feasibility of ractopamine inclusion in diets of finishing gilts. This study aimed to evaluatethe addition of ractopamine at 0, 5, 10 and 15 mg/kg of diets for gilts slaughtered with 110 kg,on feed cost, gross and net incomes, considering or not the carcass rewarding. A total of 468gilts were used and fed for 28 days. There was an increase in feed cost and linear decrease innet income without carcass rewarding with raising level of additive. For net income withcarcass rewarding, there was a linear effect with higher income for the level of 15 mg/kg.Considering the carcass classification, the inclusion of ractopamine at the level of 15 mg/kgpromotes higher income.

Effects of ractopamine on growth performance and carcass characteristics of immunologically and physically castrated barrows and gilts.

The study was performed to evaluate the effect of feeding ractopamine (RAC) to physically castrated barrows (PC), immunologically castrated barrows (IC), and gilts (gilts) using a randomized complete block design with a 3 × 3 factorial arrangement of treatments: 1) sex (PC, IC, and gilts) and 2) RAC inclusion level (0, 5, and 7.5 mg/kg). The IC received 2 doses of gonadotropin releasing factor analog-diphtheria toxoid conjugate (Improvest; Zoetis, Kalamazoo, MI) at the start of the study (wk 16 of age; 69.6 ± 2.96 kg BW) and 4 wk later. The study used 180 pigs housed in groups of 4 (5 groups/sex × RAC subclass) and was performed over a fixed time of 61 d with RAC being fed for the final 26 d of study. Diets were formulated to meet requirements of intact males for the first 35 d and of intact males fed 7.5 mg/kg RAC for the remainder of the study. Pigs had ad libitum access to feed and water throughout the study period. At the end of the study, pigs were harvested at a commercial facility and HCW and last rib backfat thickness were measured. There were no treatment interactions (P > 0.05) for any variables. For the overall study period, IC had greater (P ≤ 0.05) overall ADG compared to PC, which grew faster (P ≤ 0.05) than gilts (1,246, 1,083, and 1,025 g/d for IC, PC, and gilts, respectively; SEM = 20.3); ADFI was lower (P ≤ 0.05) for gilts than IC and PC, which had similar ADFI (3.36, 3.37, and 2.87 kg/d, respectively; SEM = 0.051); and G:F was greater (P ≤ 0.05) for IC than gilts and greater for gilts than PC (0.371, 0.322, and 0.358 kg/kg, respectively; SEM = 0.0039). For the period from the second dose to the end of study, IC had greater (P ≤ 0.05) ADG (28.6%), ADFI (12.3%), and G:F (14.3%) than PC. Carcass yield was lower (P ≤ 0.05) for IC compared to PC and gilts (72.8, 75.0, and 74.6%, respectively; SEM = 0.25). Feeding RAC increased (P ≤ 0.05) ADG (15.7 and 14.5% for 5 and 7.5 mg/kg, respectively), G:F (17.1 and 16.4%, respectively), carcass weight (3.7 and 3.2 kg, respectively), and carcass yield (1.0 and 1.0 percentage unit, respectively) compared to the control. These results highlight sex differences in and effects of RAC on growth and carcass characteristics and suggest that the relative response to RAC is similar in IC and PC.

Growth performance of immunologically castrated (with Improvest) barrows (with or without ractopamine) compared to gilt, physically castrated barrow, and intact male pigs

The study used a randomized complete block design (blocking factor was date of start on test) with 5 treatments: 1) physically castrated barrows (PC), 2) intact males (IM), 3) gilts (G), 4) immunologically castrated barrows (IC), and 5) immunologically castrated barrows fed ractopamine at 5 mg/kg (IC+RAC). The study used 192 pigs and was performed from the 16 wk of age (67.2 ± 2.52 kg BW) to a pen mean BW of 132.5 ± 3.60 kg. For IC+RAC, ractopamine was fed for the final 23 d of the study. Pigs were housed in groups of 4 (10 groups for PC, IM, G, and IC and 8 groups for IC+RAC) in a finishing building at a floor space of 1.18 m(2)/pig. Diets were formulated to meet requirements of IM except that the diet for the IC+RAC fed during the ractopamine feeding period was formulated to meet requirements of pigs on that treatment. Pigs had ad libitum access to feed and water throughout the study period and were individually weighed at the start, wk 2 and 4, and subsequently every week until the end of study. For the overall study period, IC had greater (P ≤ 0.05) ADG than the other genders (1,150, 1,024, 1,064, and 954 g/d for IC, PC, IM, and G, respectively; SEM = 25.8) and required fewer days to reach slaughter weight than the other genders (58.1, 61.6, 61.6, and 66.5 d for IC, PC, IM, and G, respectively; SEM = 1.26). Overall ADFI was less (P ≤ 0.05) for IM and G than IC and PC, which were similar (P > 0.05) in this respect (3.11, 3.06, 2.68, and 2.75 kg/d for IC, PC, IM, and G, respectively; SEM = 0.061). Overall G:F was greater (P ≤ 0.05) for IM than the other genders; IC had greater overall G:F than PC and G, which were similar in this respect (0.371, 0.335, 0.397, and 0.347 kg/kg for IC, PC, IM, and G, respectively; SEM = 0.0068). Immunologically castrated barrows had greater (P ≤ 0.05) ADG (30.7%) and ADFI (22.5%) than PC from the second week following the second Improvest dose to the end of the study. During the ractopamine feeding period, IC+RAC had greater (P ≤ 0.05) ADG (11.6%) and G:F (17.3%) than IC. The results of this study confirmed previously observed gender differences and effects of ractopamine on growth performance and that IC grew faster and had greater feed efficiency than PC during the study period.

Effects of ractopamine plus amino acids on growth performance, carcass characteristics, meat quality, and ractopamine residues of finishing pigs

The aim of the study was to evaluate the effects of adding ractopamine (RAC) and amino acids (AA) to the diet on growth performance, carcass characteristics, commercial cuts yield, meat quality and residues in liver and muscle. Ninety-two crossbred castrated pigs (97.96 + 2.32 kg) were randomly assigned to one of two dietary treatments: a Control diet with 0 mg kg -1 of RAC and a RAC+AA diet with 10 mg RAC kg -1 , for the last 27 days. Pigs of RAC+AA group had greater average daily gain (ADG), gain to feed ratio (G:F) and final bodyweight (P≤0.05) and tended to have lower average daily feed intake (ADFI) (p=0.084) than Control pigs. Carcasses from RAC+AA animals were heavier than controls (P≤0.05). Dressing percentage and backfat depth were not affected (P>0.05) by diet. Weights of head and skin were not different between treatments, but RAC+AA pigs had greater weights of boneless center loin, ribs, boneless ham and shoulders, tenderloin, neck, rear shank and trimmings (P≤0.05). The addition of RAC+AA did not affect crude protein and water content of loins but tended to reduce ether extract (p=0.08). Drip loss, pH, and cooking loss in pork were not different. Shear force tended (p=0.092) to be higher in RAC+AA. No differences in L* and b* color coordinates were found but a* values were lower in RAC+AA. Hue angle and chroma did not differ. Confidence limits at 90% were determined for residues in muscle and liver, obtaining values from -2.7 to 3.4 μg kg -1 and -6.7 to 10.6 μg kg -1 , respectively, both below the limits established by Codex Alimentarius. Dietary inclusion of RAC+AA at 10 mg RAC kg -1 in the diet of finishing pigs improved growth performance and produced heavier carcasses and commercial cuts, had minimal effects in pork characteristics and produced pork and liver with RAC residues below limits from Codex Alimentarius . El objetivo de este estudio fue medir el efecto de la adicion de ractopamina (RAC) y aminoacidos (AA) en la dieta sobre el crecimiento, caracteristicas de la canal, rendimiento de cortes comerciales, caracteristicas de la carne y residuos en higado y musculo. Noventa y dos cerdos castrados (97,96 + 2,32 kg) fueron asignados aleatoriamente a dos dietas: un Control con 0 mg kg -1 de RAC y a una dieta RAC+AA con 10 mg RAC kg -1 , durante los ultimos 27 dias de engorda. Los cerdos RAC+AA tuvieron mayor ganancia diaria de peso (GDP), eficiencia de conversion alimenticia (ECA) y peso final (P≤0,05) y tendieron a comer menos (P=0,084). Las canales del grupo RAC+AA fueron mas pesadas (P≤0,05), pero son diferencias en rendimiento y espesor de grasa dorsal. El peso de cabeza y plancha no fue diferente, pero el grupo RAC+AA tuvo pesos mayores en el lomo de centro, lomo vetado, costillar, pulpa paleta, pulpa pierna, pernil y sobras (P≤0,05). La adicion de RAC+AA no afecto la proteina cruda y materia seca del lomo, pero redujo el extracto etereo (P=0,08). No hubo diferencia en la perdida por goteo, y por coccion, ni en pH, pero la fuerza de corte tendio (P=0,092) a ser mayor en RAC+AA. No hubo diferencias en L * y b * pero si en a *, siendo mas bajo en RAC+AA. El angulo Hue y Chroma no difirieron. El intervalo de confianza al 90% determino que los residuos en musculo e higado fueron de -2,7 a 3,4 mg kg -1 y -6,7 a 10,6 mg kg -1 , respectivamente. La inclusion de RAC+AA en la dieta de cerdos de engorda, produjo canales y cortes comerciales mas pesados, con efectos minimos en caracteristicas de la carne y con residuos de RAC bajo el limite del Codex Alimentarius.

Effect of ractopamine on lipid metabolism in vivo - a systematic review

ABSTRACT The aim of this article was to evaluate the in vivo mechanism of action through which ractopamine reduces the amount of adipose tissue in carcass of animals fed diets supplemented with this drug. Literature search was carried out, using the keywords Ractopamine, lipogenesis, lipolysis, fatty acid and adipose tissue. The scoring system was designed for the adequacy of the methodology. A total of eight papers were found – all published in the English language. The determination of lipolysis and lipogenesis was carried out using different methods – from the quantification of non-esterified fatty acids in the blood to molecular analyses of adipose tissue. The review analysis suggested that, at least in the pigs, the use of this drug reduced lipid deposition in the carcass due to a greater inhibition of lipogenesis than an increase in lipolysis. Key words: β-adrenergic agonist, Lipogenesis, Lipolysis * Author for correspondence: mfmv433@gmail.com INTRODUCTION In the global context of the increase in human populations and the demand for food as well as the scarcity of large areas for livestock farming and the need to preserve environmental resources (Hejnfelt and Angelidaki 2009; Petersen 2010), the use of substances that increase the efficiency of animal production and the use of dietary nutrients may be viable alternatives for the modern world (Ferreira et al. 2011). The β-adrenergic agonist (BAA) pharmaceutical class has been widely used for the modification of carcass in some species of animals in different countries. Among this class of drugs, ractopamine is a synthetic β-agonist with proven efficiency in the production of meat with a lower fat content and greater utilization of nutrients from the diets (Mitchell et al. 2009; Gonzales et al. 2010). BAAs act through specific metabolic pathways, especially in the metabolism of proteins, lipids and carbohydrates, redirecting nutrients from the diet to metabolic pathways that favor protein synthesis over the deposition of fat in the carcass (Gunawan et al. 2007; Carr et al. 2009). A reduction in the deposition of adipose tissue in the carcass of pigs fed the diets containing ractopamine has been reported by many authors (Uttaro et al. 1993; See et al. 2004; Mimbs et al. 2005). Apparently, this effect occurs through two metabolic pathways: reduction in lipogenesis and/or increase in lipolysis. Analyzing the adipocytes isolated from pigs fed the diets containing ractopamine, Liu et al. (1989) determined the lipolytic rate of these cells through the formation of glycerol and found that the

Effects of ractopamine and gender on protein turnover in skeletal muscle of implanted steers and heifers

Effects of the β-agonist, ractopamine-HCl (ractopamine), on skeletal muscle protein turnover were evaluated in 16 steers (512 kg) and 16 heifers (473 kg). Treatments were arranged in a 2 × 2 factorial design and included gender (steer vs. heifer) and ractopamine (0 or 200 mg/d). Steers were implanted with 120 mg trenbolone acetate and 24 mg estradiol-17β, heifers with 140 mg trenbolone acetate and 14 mg estradiol-17β. Cattle were fed a diet based on steam-flaked maize. Muscle biopsy samples were collected from m. longissimus and m. biceps femoris on day 0 (prior to ractopamine feeding) and after 14 and 28 d of ractopamine feeding. In vitro protein synthesis rates in m. longissimus tended to be greater for steers than for heifers, but no effect of gender was observed in m. biceps femoris. Gender did not affect in vitro protein degradation rates for either muscle. Ractopamine significantly decreased rates of in vitro protein degradation in m. longissimus, but rates in m. biceps femoris were not affected by ractopamine. Ractopamine did not affect in vitro protein synthesis rates. In general, there were no striking differences between steers and heifers in response to ractopamine, indicating that its effectiveness should be similar between genders. Keywords: Cattle, β-agonist, protein turnover, ractopamine

Comparative effects of zilpaterol hydrochloride and ractopamine hydrochloride on growth performance, carcass characteristics, and longissimus tenderness of feedlot heifers fed barley-based diets

ABSTRACT A randomized complete block design trial was conducted with 3,444 beef heifers housed in 10 pens per treatment and fed barley-based diets to evaluate the effects of ractopamine (Optaflexx, Elanco Animal Health, Greenfield, IN) and zilpaterol (Zilmax, Intervet/Schering-Plough Animal Health, De soto, KS) on health, performance, carcass traits, and longissimus muscle tenderness in a commercial feedlot in western Canada. Treatments consisted of feeding Optaflexx at 20 mg/kg (100% DM basis) for 29 d at the end of the feeding period or Zilmax at 8.3 mg/kg (100% DM basis) for 20 d at the end of the feeding period, followed by a 4-d withdrawal period before slaughter. No differences (P > 0.05) were detected in morbidity, mortality, number of salvaged animals, ADG, feed efficiency, or final BW between heifers fed Zilmax or Optaflexx. Dry matter intake was reduced (P

Effect of ractopamine on whole body and splanchnic energy metabolism in Holstein steers

This study was designed to examine the influence of ractopamine (RAC) on whole-body and splanchnic energy balance. Six growing Holstein steers [body weight (BW) = 402 ± 39.5 kg] surgically fitted with an arterial and portal, hepatic, and mesenteric venous indwelling catheters were used in a repeated measures study. Treatments were a basal diet of alfalfa cubes fed at approximately 1.5&amp;times maintenance energy requirements (days 1-21) and basal plus RAC (430 mg head d-1; days 22-42). On day 14 of each period, splanchnic and portal-drained viscera (PDV) energy balances were determined as the product of arterio-venous O2 difference and blood flow. Blood flow was determined using down-stream dilution of p-aminohippuric acid. Whole-body energy balance was determined on days 15-21 of each period, which included 7 d total excreta collection and 3 d of respiratory gas exchange measurements. Body weight and DM intake were greater (P &lt; 0.05) for steers receiving RAC compared with those receiving the control diet; however, no difference was observed in either BW or DMI when expressed on a BW0.75 basis. Similarly, as a function of BW0.75, whole-body heat production (691 kJ kg BW0.75 d-1; P = 0.96) and retained N (0.85 g kg BW0.75 d-1; P = 0.34) and energy (298 kJ kg BW0.75 d-1; P = 0.71) were unaffected by RAC. In contrast, RAC tended to decrease (P = 0.09) energy use by splanchnic tissues (191 vs. 156 kJ kg BW0.75 d-1), largely due to a reduction (P = 0.12) in energy use by the PDV (100 vs. 86 kJ kg BW0.75 d-1). These data indicate that although whole-body energy use is not affected by RAC, energy use by splanchnic tissues is decreased, thereby increasing energy use by peripheral tissues.Key words: Bovine, ractopamine, beta-agonist, energy balance, metabolism

Effects of ractopamine and sex on serum metabolites and skeletal muscle gene expression in finishing steers and heifers

We evaluated growth-related responses to ractopamine in steers and heifers. Sixteen Angus steers (512 kg) and 16 Angus heifers (473 kg) housed in individual pens were used in a complete block design. At 90 to 97 d before the experiment, steers were implanted with 120 mg of trenbolone acetate and 24 mg of estradiol-17beta (Component TE-S) and heifers were implanted with 140 mg of trenbolone acetate and 14 mg of estradiol-17beta (Component TE-H). Treatments were arranged as a 2 x 2 factorial and included sex (steer vs. heifer) and ractopamine-HCl (0 or 200 mg/d). Cattle were fed a diet based on steam-flaked corn once daily. Blood and LM and biceps femoris (BF) biopsy samples were collected on d 0 (before ractopamine feeding) and after 14 and 28 d of ractopamine feeding. Serum insulin concentrations were not affected by ractopamine or sex. Serum IGF-I concentrations were greater in steers than heifers (P < 0.001), and steers demonstrated greater IGF-I mRNA expression in BF than heifers (P = 0.05). Ractopamine decreased serum IGF-I concentrations in heifers on d 14, but increased serum IGF-I concentrations in steers on d 28 (sex x ractopamine x day interaction; P = 0.03). Ractopamine did not affect (P >or= 0.19) mRNA expression of IGF-I, IGFBP-3, or calpastatin in BF or LM. However, ractopamine led to increases in LM expression of IGFBP-5 in heifers, but to decreases in expression in steers (ractopamine x sex interaction; P = 0.04). Ractopamine decreased myosin heavy chain IIA mRNA expression in BF (P = 0.04) but not in LM (P = 0.99). Ractopamine decreased beta(2)-receptor mRNA expression in LM of steers on d 14, but not on d 28; in contrast, expression of beta(2)-receptor mRNA in LM of heifers was not affected by ractopamine (sex x ractopamine x day interaction; P = 0.03). Although there were a few criteria for which ractopamine led to differences in response between steers and heifers, there were no striking disparities to suggest that the effectiveness of ractopamine would markedly differ between sexes.