Response of C2C12 mouse and turkey skeletal muscle cells to the beta-adrenergic agonist ractopamine

The effects of ractopamine (RAC) and ractopamine stereoisomers (RR, RS, SR, and SS) on cyclic AMP (cAMP) production, total protein, and DNA concentrations in mouse skeletal muscle cells (C2C12) were evaluated. The RAC (10 microM) caused an approximately 30% increase in cell number, protein, and DNA concentrations in myoblasts after 48 h; no differences were found in myotubes. The RAC-stimulated increase of these variables in myoblasts was blocked by the presence of equimolar concentrations of propranolol. At a later passage, myoblasts failed to exhibit an increase in cell number, protein, or DNA upon exposure to RAC. Both myoblasts and myotubes increased cAMP production in response to 10 microM RAC. The RAC isomers ranked RR > SR > RS approximately SS in ability to stimulate cAMP production, with essentially no response to SS. The SR produced about 50% of the RR response. Coincubation of propranolol (10 microM) and RAC (10 microM) prevented RAC-stimulated cAMP production in myotubes but not in myoblasts (approximately 35% of cAMP produced by RAC alone). Turkey satellite cells (derived from biceps femoris of 12-wk-old toms) produced essentially no increased cAMP when exposed to 10 microM RAC stereoisomers. Stability of RAC was evaluated under laboratory storage and culture conditions. The RAC was stable for more than 4 mo when stored in deuterated DMSO (>98% purity) at room temperature or in aqueous solutions at -80 degrees C, as determined from sequential nuclear magnetic resonance studies. Radiolabeled RAC was incubated for 72 h in the presence of serum-containing medium, with or without C2C12 cells. Ninety-eight percent of the parent compound found in the medium at time zero was present in the medium as parent at the end of 72 h. The cellular cAMP response to RAC through beta-adrenergic receptors seems to be stereospecific. If the state of myoblasts and myotubes in vitro reflects the in vivo state, then the ractopamine effect in vivo on cellular processes (including cell division and protein and DNA accumulation) may be independent of beta-adrenergic receptors in muscle.     

美国详细调查生长肥育猪的饲养面积

美国消费者对于舍饲肉用动物健康和福利的关注度日益增长,这使得生产者考虑提高动物的饲养面积。在Allen D.Leman养猪大会上,与会代表对这一主题进行了详细讨论。     

Tissue residues of ractopamine and urinary excretion of ractopamine and metabolites in animals treated for 7 days with dietary ractopamine

Ractopamine HCl is a beta-adrenergic leanness-enhancing agent recently approved for use in swine. Depletion of ractopamine in tissues, and elimination of ractopamine and its metabolites in urine, is of interest for the detection of off-label use. The objectives of this study were to measure the residues of ractopamine in livers and kidneys of cattle (n = 6), sheep (n = 6), and ducks (n = 9) after treatment with dietary ractopamine for seven (sheep, ducks) or eight (cattle) consecutive days and to measure the depletion of ractopamine from urine of cattle and sheep. Two cattle and sheep and three ducks were each slaughtered with withdrawal periods of 0, 3, and 7 d. Urine samples were collected daily from cattle and sheep. Tissue ractopamine concentrations were determined using the regulatory method (FDA approved) for ractopamine in swine tissues. Ractopamine residues in urine samples were measured before and after hydrolysis of conjugates. Analysis was performed with HPLC using fluorescence detection after liquid- (hydrolyzed samples) and(or) solid-phase extraction. No residues were detected in duck tissues. Liver residues in sheep averaged 24.0 and 2.6 ppb after 0- and 3-d withdrawal periods, respectively. Sheep liver residues after a 7-d withdrawal period were less than the limit of quantification (2.5 ppb). Sheep kidney residues were 65.1 and undetectable at 0- and at 3- and 7-d, withdrawal periods, respectively. Cattle liver residues were 9.3, 2.5, and undetectable after 0-, 3-, and 7-d withdrawal periods, respectively; kidney residues were 97.5, 3.4, and undetectable at the same respective withdrawal periods. Concentrations of parent ractopamine in sheep urine were 9.8+/-3.3 ppb on withdrawal d 0 and were below the LOQ (5 ppb) beyond the 2-d withdrawal period. After the hydrolysis of conjugates, ractopamine concentrations were 5,272+/-1,361 ppb on withdrawal d 0 and 178+/-78 ppb on withdrawal d 7. Ractopamine concentrations in cattle urine ranged from 164+/-61.7 ng/mL (withdrawal d 0) to below the LOQ (50 ppb) on withdrawal d 4. After the hydrolysis of conjugates in cattle urine, ractopamine concentrations were 4,129+/-2,351 ppb (withdrawal d 0) to below the LOQ (withdrawal d 6). These data indicate that after the hydrolysis of conjugates, ractopamine should be detectable in urine of sheep as long as 7 d after the last exposure to ractopamine and as long as 5 d after withdrawal in cattle.     

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)     

The effect of space allocation on barrow and gilt performance

Two experiments were conducted to determine the variation in response to space allocation between barrows and gilts and to examine an alternative allocation regimen for barrows and gilts. Experimental space allocations in both experiments were achieved by varying the number of pigs per pen in a fully slatted facility. In Exp. 1, barrows were given 0.58 and 0.65 m2/pig (nine and eight pigs per pen, respectively) and gilts were given 0.65 and 0.74 m2/pig (eight and seven pigs per pen, respectively). In addition, barrows at 0.58 m2/pig were fed diets formulated for barrows or diets formulated for gilts. Barrows grew 4.8% slower (P = 0.031) and ate 3.1% less feed daily (P = 0.062) at 0.58 vs. 0.65 m2/pig from 22 to 115 kg BW, with no difference in feed conversion, daily lean gain, carcass lean percent, or variation in weight within the pen at time of first pig removal to slaughter. There was no improvement in daily gain, feed intake, feed efficiency, lean gain, or carcass lean percent when gilts were given 0.74 vs. 0.65 m2/pig from 22 to 115 kg BW. There was no difference in performance between the population that consisted of barrows and gilts at 0.65 m2/pig vs. the population of barrows at 0.58 m2/pig and gilts at 0.74 m2/pig. There was no difference in performance by barrows at 0.58 m2/pig when fed either barrow or gilt diets, except for a slight increase (P = 0.078) in within-pen weight variation when the first pig was removed for slaughter for the barrows fed gilt diets. In Exp. 2, barrows and gilts were given 0.58 m2/pig or 0.74 m2/pig (18 vs. 14 pigs per pen) from weaning (mean age 17 d) to slaughter on d 168 postweaning. There were no interactions between space allocation and gender. Daily gain and feed intake were decreased by 2.8% (P = 0.037) and 2.9% (P = 0.084), respectively, with no effect on feed conversion or standardized fat-free lean daily gain for the 0.58 vs. the 0.74 m2/pig treatment, whereas total live weight gain per pen was increased 20.8% (P < 0.001). Results of Exp. 1 suggest that space allocation can be used to achieve similar growth rates between barrows and gilts, and results of Exp. 2 suggest that the response to space allocation is similar for barrows and gilts. The difference in magnitude of response to space allocation between experiments may be due in part to when the social group was formed, with a smaller difference in performance in Exp. 2 associated with a stable social group from weaning to slaughter.     

紫穗槐表型可塑性及植株资源分配对高寒生境的响应

对在西藏拉萨市和甘肃玛曲县青藏高原区种植的紫穗槐（Amorpha fruticosa）17项形态特征指标及其5个不同构件11种营养元素含量进行比较分析。结果表明,1）两地区紫穗槐表型特征存在差异,特别是地下部分形态指标差异显著;2）紫穗槐不同构件生物量比重、各个营养元素含量存在不同程度差异,且地区间相应指标也存在差异,是植株资源分配对高寒生境的响应所引起的;3）两地区紫穗槐形态指标与其营养元素含量均存在复杂的相关关系。     

莱克多巴胺人工抗原的合成与鉴定

用戊二酸酐将盐酸莱克多巴胺活化成莱克多巴胺-戊二酸酐半醛,用混合酸酐法将莱克多巴胺-戊二酸酐半醛与KLH和BSA偶联,合成免疫原和包被抗原,经核磁共振法和紫外吸收法鉴定,偶联成功.用紫外吸收法测定免疫原和包被抗原的偶联比分别为24：1和2.5：1.用免疫原免疫新西兰白兔,采用间接ELISA法检测抗体效价,采用间接竞争ELISA法检测IC50值,获得了效价为1：6 000以上、IC50值为10 ng/mL的多克隆抗体,证明合成的人工免疫原具有免疫原性.     

Progression of aflatoxicosis in growing barrows

The progression of aflatoxicosis was evaluated in growing crossbred barrows given 0, 1, 2, 3, or 4 mg of aflatoxin (AF)/kg of feed for 28 days (6 to 10 weeks of age). On day 28, pigs were euthanatized and necropsied, and tissues were removed for histologic examination. Body weight gains were decreased in barrows fed 2 mg of AF/kg after 7 days and in barrows fed 1 mg of AF/Kg after 14 days. By 28 days, all barrows fed AF had decreased body weights and weight gains. Compared with decreased in all barrows fed AF. Neither liver weights nor bone ash values were altered, although liver lipid values were increased in barrows fed AF. Serum aspartate transaminase, gamma-glutamyl transferase, and alkaline phosphatase activities were increased in barrows fed AF, whereas creatine kinase activity was decreased. Aflatoxin diets resulted in decreases in serum concentrations of urea nitrogen, phosphorus, cholesterol, albumin, and total protein. Histologic alterations in liver included interlobular fibrosis, periportal lipidosis, bile duct hyperplasia, and periportal lymphocytic infiltration. Lymphocytes in the thymus were depleted, and numbers of granulocytic cells in the bone marrow were reduced. The frequency and severity of lesions increased with increased doses of AF.     

The tryptophan requirement of growing and finishing barrows

Five experiments were conducted to determine the true ileal digestible Trp (tidTrp) requirement of growing and finishing pigs fed diets (as-fed basis) containing 0.87% (Exp. 3), 0.70% (Exp. 4), 0.61% (Exp. 5), and 0.52% (Exp. 1 and 2) tidLys during the early-grower, late-grower, early-finisher, and late-finisher periods, respectively. Treatments were replicated with three or four replications, with three or four pigs per replicate pen. Treatment differences were considered significant at P = 0.10. Experiment 1 was conducted with 27 pigs (initial and final BW of 78.3 +/- 0.5 and 109.8 +/- 1.9 kg) to validate whether a corn-feather meal (FM) tidTrp-deficient (0.07%) diet, when supplemented with 0.07% crystalline l-Trp, would result in growth performance and carcass traits similar to a conventional corn-soybean meal (C-SBM) diet. Pigs fed the corn-FM diet without Trp supplementation had decreased growth performance and carcass traits, and increased plasma urea N (PUN) concentration. Supplementing the corn-FM diet with Trp resulted in greater ADG and G:F than pigs fed the positive control C-SBM diet. Pigs fed the corn-FM diet had similar carcass traits as pigs fed the C-SBM diet, but loin muscle area was decreased and fat thickness was increased. In Exp. 2, 60 pigs (initial and final BW of 74.6 +/- 0.50 and 104.5 +/- 1.64 kg) were used to estimate the tidTrp requirement of finishing pigs. The levels of tidTrp used in Exp. 2 were 0.06, 0.08, 0.10, 0.12, or 0.14% (as-fed basis). Response variables were growth performance, PUN concentrations, and carcass traits and quality. For Exp. 2, the average of the estimates calculated by broken-line regression was 0.104% tidTrp. In Exp. 3, 4, and 5, barrows (n = 60, 60, or 80, respectively) were allotted to five dietary treatments supplemented with crystalline l-Trp at increments of 0.02%. The basal diets contained 0.13, 0.09, and 0.07% tidTrp (as-fed basis) in Exp. 3, 4, and 5, and initial BW of the pigs in these experiments were 30.9 +/- 0.7, 51.3 +/- 1.1, and 69.4 +/- 3.0 kg, respectively. The response variable was PUN, and the basal diet used in Exp. 3 and 4 contained corn, SBM, and Canadian field peas. The tidTrp requirements were estimated to be 0.167% for pigs weighing 30.9 kg, 0.134% for pigs weighing 51.3 kg, and 0.096% for pigs weighing 69.4 kg. Based on our data and a summary of the cited literature, we suggest the following total Trp and tidTrp requirement estimates (as-fed basis): 30-kg pigs, 0.21 and 0.18%; 50-kg pigs, 0.17 and 0.14%; 70-kg pigs, 0.13 and 0.11%; and in 90-kg pigs, 0.13 and 0.11%.     

Effect of chromium picolinate and chromium propionate on glucose and insulin kinetics of growing barrows and on growth and carcass traits of growing-finishing barrows

Two experiments were conducted to determine the effects of dietary Cr tripicolinate (CrPic) or Cr propionate (CrProp) on growth, carcass traits, plasma metabolites, glucose tolerance, and insulin sensitivity in pigs. In Exp. 1, 36 barrows (12 per treatment; initial and final BW were 20 and 38 kg) were allotted to the following treatments: 1) corn-soybean meal basal diet (control), 2) as 1 + 200 ppb Cr as CrPic, or 3) as 1 + 200 ppb Cr as CrProp. Growth performance data were collected for 28 d, and then 23 pigs (seven, eight, and eight pigs for treatments 1, 2, and 3, respectively) were fitted with jugular catheters and a glucose tolerance test (500 mg glucose/kg BW) and an insulin challenge test (0.1 IU of porcine insulin/kg BW) were conducted. Both CrPic and CrProp decreased (P < 0.05) ADG and ADFI but did not affect gain:feed (P > 0.10). Fasting plasma glucose, total cholesterol, urea N, insulin, and high-density lipoprotein cholesterol:total cholesterol concentrations were not affected (P > 0.10) by either Cr source. Pigs fed CrPic had lower (P < 0.02) fasting plasma NEFA concentrations than control pigs, but plasma NEFA concentrations of pigs fed CrProp were not affected (P > 0.10). During the glucose tolerance test, glucose and insulin kinetics were not affected by treatment (P > 0.10). During the insulin challenge test, glucose clearance was increased (P < 0.01) in pigs fed CrProp but not affected (P > 0.10) in pigs fed CrPic. Glucose half-life was decreased (P < 0.03) in pigs fed CrPic or CrProp, but insulin kinetics were not affected (P > 0.10). In Exp. 2, 48 barrows (four replicates of four pigs per replicate; initial and final BW were 23 and 115 kg) were allotted to the same dietary treatments in a growing-finishing study. Average daily gain, ADFI, and gain:feed were not affected (P > 0.10) by treatments. Carcass length tended (P = 0.10) to be greater in pigs fed CrPic than in pigs fed CrProp, but other carcass measurements were not affected (P > 0.10). Glucose kinetics from the insulin challenge test indicate that both CrPic and CrProp increase insulin sensitivity and that both Cr sources are bioavailable.     

Insulin binding to mouse adipocytes exposed to clenbuterol and ractopamine in vitro and in vivo

Insulin binding to mouse adipocytes was measured after in vitro (30 min) and in vivo (5 days) exposure to clenbuterol and ractopamine. At 10(-6) M, both agonists decreased insulin binding by 20-30% after a 30 min preincubation at each insulin concentration between 1 and 25 ng/ml. Binding was not decreased if propranolol was present. Scatchard plots suggested that decreased binding was due to a decrease in insulin receptor concentration. Insulin binding was decreased approximately 10% at agonist concentrations as low as 10(-13) M, but binding was not further decreased until concentrations exceeded 10(-9) M. Rate of gain was increased 2-fold by clenbuterol (10 mg/liter of drinking water) and 50% by 500 mg ractopamine/liter, but not by 50 mg ractopamine/liter. Clenbuterol and ractopamine (500 mg/liter) decreased fat pad weight but only clenbuterol increased hind limb muscle mass. Insulin binding following in vivo administration was not influenced by ractopamine at 50 mg/liter, but tended to be increased by clenbuterol and ractopamine at 500 mg/liter. The disparity in results between administering the beta-agonists in vitro or in vivo suggests that counter regulatory factors influenced insulin binding capacity in vivo. Results indicate that ractopamine and clenbuterol can decrease insulin binding to adipocytes but the relevance of this response to decreased fat accretion is not clear.     

嘉峪关城市公园绿地的空间分布与服务范围分析

采用综合评价法对嘉峪关市的公园绿地进行评价,以遥感影像为基础,分析公园绿地面积变化和空间位置变化;利用缓冲区的方法分析公园绿地空间配置的合理性。结果表明:(1)自2004~2014年,城市公园绿地发展势头良好,2014年提升至"优"水平,政府公共财政投入的加大对城市公园绿地建设有巨大的推动作用;(2)地处内陆干旱地区的嘉峪关市十分重视公园绿地的建设,公园绿地作为公共服务用地的主要组成部分,在城市公共服务用地中所占比重始终保持在50%;(3)公园绿地在空间位置上呈现依居住区沿街道分布的特点,但部分公园绿地存在服务范围重叠,未能使城市公园绿地资源的服务功能最大化,在未来的城市建设中需考虑到公园绿地的服务范围,使其空间分布更加合理。     

饲料中莱克多巴胺检测前处理方法分析

饲料检测前处理时间几乎占整个分析时间的80%,是决定分析测定效果的关键。文中对饲料及饲料添加剂中莱克多巴胺检测的前期处理方法进行分析总结,探讨了各种检测方法在前处理中的注意事项。     

Effects of betaine, pen space, and slaughter handling method on growth performance, carcass traits, and pork quality of finishing barrows

An experiment was conducted to determine the effects of betaine, pen space, and preslaughter handling method on growth, carcass traits, and pork quality of finishing barrows. For the growth trial, a 2 x 2 factorial arrangement of treatments was used: betaine (0 or 0.250%) and(or) pen space (m2/pig; adequate, 0.035 BW0.67 kg, or inadequate, 0.025 BW0.67 kg). Each treatment was replicated five times with four barrows per replicate. At trial termination, two barrows from each pen were selected to receive either minimal or normal preslaughter handling. Reducing pen space decreased (P < 0.05) overall ADG and gain:feed and tended (P = 0.12) to decrease overall ADFI. Betaine had no affect (P > 0.10) on overall ADG, ADFI, or gain:feed. Pigs fed betaine had decreased (P < 0.10) carcass length. Other carcass and ham measurements were not affected (P > 0.10) by betaine. Pigs with inadequate pen space had increased (P < 0.10) ultimate pH, subjective color, cooking loss (fresh and frozen chop), and shear force but decreased rectal temperature, loin muscle CIE L*, biceps femoris CIE b*, and drip loss. Pigs subjected to minimal preslaughter handling had decreased (P < 0.10) rectal temperature, plasma cortisol, loin muscle CIE b*, and fresh chop total loss (drip + cooking loss). Pigs fed betaine had increased (P < 0.01) initial pH and decreased (P < 0.10) drip loss (fresh chop). Cooking loss and total loss (frozen chop) were decreased in pigs fed betaine with adequate pen space but increased in pigs fed betaine with inadequate pen space (betaine x pen space, P < 0.01). Pigs fed betaine may have improved pork quality.     

True ileal digestible tryptophan to lysine ratios in ninety- to one hundred twenty-five-kilogram barrows

Three experiments were conducted to determine the optimal true ileal digestible (TID) Trp:Lys ratio for 90- to 125-kg barrows. Basal diets contained 0.55% TID Lys and were either corn-based (Exp. 1) or corn- and soybean meal-based (Exp. 2 and 3) diets supplemented with crystalline AA. In addition, each experiment contained a corn-soybean meal control diet. The number of pigs per pen progressively increased, with pigs housed in 2 (n = 82; initial and final BW of 88.5 and 113.6 kg, respectively), 7 (n = 210, initial and final BW of 91.2 and 123.3 kg, respectively), or 20 to 22 (n = 759; initial and final BW of 98.8 and 123.4 kg, respectively) pigs per pen for each successive experiment. Pigs in Exp. 1 were fed 6 incremental additions of L-Trp, equating to TID Trp:Lys ratios of 0.109, 0.145, 0.182, 0.218, 0.255, and 0.290. For the 28-d period, there was a quadratic improvement in G:F (P = 0.05) and ADG (P = 0.08) with increasing TID Trp:Lys, characterized by an improvement in performance of pigs fed the basal diet compared with those consuming diets with a 0.145 TID Trp:Lys ratio, with a plateau thereafter as TID Trp:Lys increased. Pigs fed the control diet had less increase in backfat depth than the average of pigs fed the titration diets (1.30 vs. 4.09 mm, respectively; P = 0.02), but pork quality was unaffected by dietary treatment. Pigs in Exp. 2 were fed 4 incremental additions of L-Trp, equating to TID Trp:Lys ratios of 0.130, 0.165, 0.200, and 0.235. Average daily gain and ADFI increased in a linear fashion with increasing TID Trp:Lys for the 29-d trial (P < 0.01), with quadratic improvements in d-29 BW (P = 0.06) and G:F (P = 0.05). Pigs fed the diet containing a TID Trp:Lys ratio of 0.165 had greater d-29 BW, ADG, G:F, and lower serum urea N concentration than pigs fed the basal diet (P < 0.05), but were similar to pigs fed TID Trp:Lys ratios of 0.200 and 0.235 for all criteria measured. In Exp. 3, TID Trp:Lys ratios of 0.13, 0.15, 0.17, 0.19, and 0.21 were evaluated. The response to increasing TID Trp:Lys was limited to a quadratic (P < 0.10) improvement in G:F with increasing TID Trp:Lys ratios. Maximum G:F was noted at a TID Trp:Lys ratio of 0.17. No relationship was noted between TID Trp:Lys and carcass characteristics. These experiments demonstrate that the minimum TID Trp:Lys ratio for pigs from 90 to 125 kg of BW is at least 0.145, but not greater than 0.17.     

贝加尔针茅草原主要植物地上生物量分配对放牧梯度的响应

通过对放牧梯度下贝加尔针茅草原主要植物不同器官(茎、叶、花或果)的生物量分配格局变化进行探索,结果表明:贝加尔针茅草原主要植物的繁殖分配随牧压梯度增加,表现出明显的规律性,中牧条件下,贝加尔针茅草原植物群落的繁殖分配与优势种羊草等较耐牧植物变化趋势一致,均较轻牧下显著增加,而优良禾草、豆科牧草等均显著减少;重牧条件下,植物群落的繁殖分配与优良禾草、豆科牧草等以及退化标志植物变化趋势一致,均较中牧下显著减少,而较耐牧植物羊草等均显著增加。     

National Meat Case Study 2004: Fresh product types and allocation of retail space

Fresh meat retail cases in 104 supermarkets across 5 regions of the United States were audited for product space allocation, percentage of space allocated to each fresh meat category and frequency of species among all stock keeping units (n = 14,863). The United States was divided into Mountain/Southwest, Midwest, Northeast, Southeast, and West Coast regions. Fresh meat categories for self-service cases included beef muscle cuts, ground beef, pork, veal, lamb, chicken, turkey, fresh sausage, value-added, heat and serve, ham-bone-in, ham-boneless, ham steak, other processed meats, seafood, and nonmeat items. Fresh meat categories for the full-service case included seafood, beef, pork, chicken, and other. Whole muscle beef, pork, and chicken products were available in all stores. Ground beef products and turkey were reported in almost all stores, 94.5 to 100%, respectively. The majority of the self-service meat case was dedicated to beef in all regions except for the Northeast, where chicken occupied the majority of the self-service case. Linear meters of self-service fresh meat case were greatest in the Northeast region, which was similar to Mountain and Midwest regions, but different (P = 0.003) than the Southeast and West Coast regions. However, the West Coast region best utilized the retail meat case by providing consumers with the greatest number of offerings per linear meter. The percentage of stores audited with a full-service meat case was 37.5%, and the percentage with a full-service seafood case was 60.6%. The full-service meat case was the smallest (number of linear meters, P = 0.039) in the Southeast and largest (number of linear meters, P = 0.039) in the Midwest.     

β_2兴奋剂莱克多巴胺及其检测技术研究进展

莱克多巴胺(RCT) 属苯酚胺类β肾上腺素激动剂, 因能增强运动员、动物运动肌肉, 提高运动成绩, 被国际奥委会列为禁用兴奋剂药物。同时RCT因具有营养再分配、促进蛋白质合成, 增加酮体瘦肉率, 提高饲料转化率的作用, 有可能作为饲料添加剂用于畜产品的生产, 而其残留对人类健康存在潜在的危害, 被禁止或限定在畜产品生产中使用。因此, 研究RCT的分析测定方法, 对于畜产品的安检和兴奋剂的检测都具有实际意义。本文对兴奋剂莱克多巴胺的药理、毒理性质以及检测方法和国内外研究状况进行了较详细的阐述及讨论。     

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.