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.     

The distribution of orally administered 14C-aniline HCl in tissues of dairy cattle, swine and laying pullets

Single or chronic daily (30 d) doses of 14C-aniline (an aromatic amine) were administered to dairy cattle, swine and laying pullets to determine the amount of an ingested synfuel-related chemical that would remain in consumable animal products. The 14C-residues were found in muscle, liver, other edible organs and fat, as well as in milk and eggs. The predominant site of deposition in acute- and chronic-exposed pullets was kidney, followed by internal yolk (immature ovum of ovary) and then liver. Egg yolk was the major site of 14C-radioactivity in whole eggs. Liver, then kidney, were the major sites of deposition in acutely exposed swine; when chronically exposed, only liver showed preferential deposition with other tissues surveyed yielding similar concentration values. Dairy cattle yielded tissue distribution patterns similar to chronic swine. Within 8 h after an acute exposure, 14C-residue was detected in milk which reached its maximum at 24 to 32 h. Our data demonstrate that derived concentration values of 14C-residue in tissues was dependent upon the species studied as well as on the mode of exposure, acute versus chronic. Although the concentration values were variable, sufficient amounts of 14C-aniline and (or) its metabolites were found in consumable products.     

Pasteurella multocida antigen-induced in vitro lymphocyte immunostimulation, using whole blood from cattle and turkeys.

A whole blood lymphocyte stimulation assay to study cell-mediated immune responses in bovine pasteurellosis was developed. Peripheral blood lymphocytes from cattle artificially immunised with three Asiatic haemorrhagic septicaemia strains of Pasteurella multocida exhibited higher stimulation indices when incubated with antigen preparations from homologous strains than with the heterologous shipping fever strain. Lymphocytes from cattle immunised with the shipping fever strain of P multocida exhibited a higher stimulation index when incubated with an antigen preparation from the homolgous strain than with antigen preparations from heterologous haemorrhagic septicaemia strains. These results suggest that immunogenic differences exist between the haemorrhagic septicaemia strains and the shipping fever strain of P multocida. An assay using turkey whole blood lymphocytes was also developed. The use of small amounts of whole blood, microtitre plates, either 125I iododeoxyuridine or 3H-thymidine as the labelling agent, and a multiple cell-culture harvester makes the method simple, rapid and suitable for the study of immune competence and cell-mediated immune responses in turkeys on a flock basis.     

莱克多巴胺残留检测方法研究进展

介绍了不同动物产品中莱克多巴胺残留检测方法的前处理方法及其差异;综述了色谱法的种类及其检测限、灵敏度、精密度,对其优缺点作了简单说明;着重对ELISA法的抗原合成方法及其对抗体质量的影响、抗体的特异性、与色谱法的相关性及检测质量等方面进行了较为详细的分析,并简单介绍了免疫传感器法.     

Effects of ractopamine HCl stereoisomers on growth, nitrogen retention, and carcass composition in rats

The objectives of this study were to determine the effects of ractopamine HCl (RAC) stereoisomers (RR, RS, SR, and SS) on performance, carcass composition, and nitrogen retention in growing female rats. Forty-eight rats (eight rats/treatment) were treated with 0 or 320 microg/d of RAC or with 80 microg/d of the RR, RS, SR, or SS stereoisomers of ractopamine. Rats had free access to feed and water before and during the experiment. Ractopamine and stereoisomers were delivered via i.p. implanted osmotic pumps for 14 d, and rats were then slaughtered. Control rats were fitted with osmotic pumps containing saline. Ractopamine increased (P < .05) feed intake (d 1 to 6); body weight; carcass CP; and intake, apparent absorption, retention, and retained:intake ratio of CP on d 1 to 6 of the study. Ractopamine decreased (P < .05) carcass lipid and visceral lipid. Rats dosed with the RR stereoisomer responded similarly to rats dosed with RAC, except for carcass lipid. Carcass lipid was decreased (P < .01) by RAC relative to controls, but it was not different from controls in rats treated with the RR isomer. Compared with controls, BW, carcass CP, and CP retention were increased by the RR stereoisomer, and visceral lipid was decreased. The RS isomer also decreased visceral lipid (P < .10), but variables measured in rats dosed with the RS, SR, and SS isomers generally did not differ from controls. Results of this study indicate that the RR isomer of RAC is responsible for a majority of the leanness-enhancing effects of RAC in rats.     

In vivo mechanical and in vitro electromagnetic side-effects of a ruminal transponder in cattle

This work was undertaken to assess the long-term impacts of a ruminal transponder, used for electronic identification, on ruminal motility and on health and performance of cattle, as well as to study the electromagnetic effects on ruminal bacteria in vitro. A passive transponder (51.4 g, 67 x 17 mm) was delivered into the forestomachs of 8 calves, 32 bulls, 10 heifers, and 40 dairy cows. Final readability was 87.5% in calves, 96.9% in bulls, 90% in heifers, and 100% in cows at 481, 360, 650, and 601 d, respectively, after transponder administration. The transponder did not affect production or reproduction of cows over a 2-yr period, or performance of bulls, or mortality compared with control animals. Chewing movements per bolus were lower (P <0.01) in treated animals than in controls (49.6 vs. 52.2, 51.2 vs. 63.6, and 57.0 vs. 59.7 for bulls, heifers, and cows, respectively). Regurgitation frequency (number of boluses/10 min) tended to be greater in treated cattle: 12.4 vs. 11.3 (P = 0.07), 11.3 vs. 10.6, and 11.3 vs. 10.7 (P = 0.08) for bulls, heifers, and cows, respectively. Rumination patterns of calves fitted with transponders within the first weeks of life were similar to controls. During the experiment, 43 treated animals (8 calves, 29 bulls, and 6 cows) were slaughtered. Thirty transponders were localized in the reticulum (3 calves, 24 bulls, and 3 cows), 11 in the rumen (4 calves, 4 bulls, and 3 cows), and 2 were not recovered (1 calf and 1 bull). Within the calves, 57% of the boluses were found in the rumen. In 8 reticula (2 calves and 6 bulls) and 1 rumen (1 cow), an impression left by physical contact of the transponder was observed, although histological examination did not reveal specific lesions in the mucosa of the dystrophic areas. In strained, whole ruminal contents incubated in vitro, pH values were lower after 24 and 48 h (P <0.001) of continuous exposure to an electromagnetic field induced by the transponder-reading system. After 48 h of incubation, total bacterial numbers and NH3-N concentration were greater (P <0.001) in exposed flasks than in controls. These data indicate that the transponder may alter, via mechanical action, the reticuloruminal mucosa and rumination patterns. Furthermore, the transponder may increase, via its electromagnetic action, the growth rate and metabolic activity of ruminal bacteria.     

Comparative distribution of ivermectin and doramectin to parasite location tissues in cattle

Pharmacokinetic studies have been used traditionally to characterize drug concentration profiles achieved in the bloodstream. However, endectocide molecules exert their persistent and broad spectrum activity against parasites localized in many different tissues. The aim of this study was to compare the distribution of ivermectin (IVM) and doramectin (DRM) to different tissues in which parasites are found following subcutaneous administration to calves. Holstein calves weighing 120-140 kg were injected in the shoulder area with commercially available formulations of IVM (Ivomec 1% MSD AGVET, NJ, USA) (Group A) or DRM (Dectomax 1%, Pfizer, NY, USA) (Group B). Two treated calves were sacrificed at 1, 4, 8, 18, 28, 38, 48 or 58 days post-treatment. Plasma, abomasal and small intestinal fluids and mucosal tissues, bile, faeces, lung and skin samples were collected, extracted, derivatized and analyzed by high performance liquid chromatography (HPLC) with fluorescence detection to determine IVM and DRM concentrations. IVM and DRM were distributed to all the tissues and fluids analyzed. Concentrations >0.1 ng/ml (ng/g) were detected between 1 and 48 days post-treatment in all the tissues and fluids investigated. At 58 days post-treatment, IVM and DRM were detected only in bile and faeces, where large concentrations were excreted. Delayed Tmax values for DRM (4 days post-administration) compared to those for IVM (1 day) were observed in the different tissues and fluids. High IVM and DRM concentrations were measured in the most important target tissues, including skin. The highest IVM and DRM concentrations were measured in abomasal mucosa and lung tissue. Enhanced availabilities of both IVM (between 45 and 244%) and DRM (20-147%) were obtained in tissues compared to plasma. There was good correlation between concentration profiles of both compounds in plasma and target tissues (mucosal tissue, skin, and lung). Drug concentrations in target tissues remained above 1 ng/g for either 18 (IVM) or 38 (DRM) days post-treatment. The characterization of tissue distribution patterns contributes to our understanding of the basis for the broad-spectrum endectocide activity of avermectin-type compounds.     

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.     

The inheritance of ocular colobomata in Charolais cattle

The examination of approximately 800 pure bred and cross bred Charolais cattle indicated that ocular colobomata is inherited via an autosomal dominant gene in this breed. Penetrance was found to be complete in the male and partial (52 per cent) in the female. Inheritance in the crossbred animals was different to that in the pure bred.     

Experimental Cryptosporidium baileyi infections in chickens and turkeys produced by ocular inoculation of oocysts

Developmental stages of Cryptosporidium baileyi were observed on the conjunctival epithelium of 3 of 14 chicks and none of 7 turkeys following ocular inoculation of oocysts. No clinical signs of disease were observed in chicks or turkeys. All 14 chicks had developmental stages of C. baileyi in the cloaca, whereas 4 of the 7 turkeys were infected at this site.     

Characteristics of prolactin-releasing response to salsolinol in vivo in cattle

The aims of the present study were to clarify the effect of salsolinol (SAL), a dopamine (DA)-derived endogenous compound, on the secretion of prolactin (PRL) in cattle. The experiments were performed from April to June using calves and cows. A single intravenous (i.v.) injection of SAL (5 mg/kg body weight [BW]) or sulpiride (a DA receptor antagonist, 0.1 mg/kg BW) significantly stimulated the release of PRL in male and female calves (P < 0.05), though the response to SAL was smaller than that to sulpiride. The secretory pattern of PRL in response to SAL or sulpiride in female calves resembled that in male calves. A single i.v. injection of SAL or sulpiride significantly stimulated the release of PRL in cows (P < 0.05). There was no significant difference in the PRL-releasing response between the SAL- and sulpiride-injected groups in cows. A single intracerebroventricular injection of SAL (10 mg/head) also significantly stimulated the release of PRL in castrated calves (P < 0.05). These results show that SAL is involved in the regulatory process for the secretion of PRL, not only in male and female calves, but also in cows. The results also suggest that the potency of the PRL-releasing response to SAL differs with the physiological status of cattle.     

Response of barrows to space allocation and ractopamine

An experiment using 264 crossbred barrows was conducted to examine the interaction between space allocation and dietary ractopamine addition on pig performance and carcass characteristics using a 2 x 2 factorial arrangement of treatments. Treatments were 0.55 (19 pigs per pen) or 0.74 (14 pigs per pen) m2/pig from start (29.7 +/- 0.1 kg BW) to slaughter (108 kg BW) in a fully slatted facility and 0 or 10 ppm (as-fed basis) ractopamine for 28 d before slaughter. There were few treatment interactions. Pigs given 0.55 m2/pig had a lower ADG (P = 0.010), ADFI (P = 0.088), 10th-rib backfat depth on d 86 (P = 0.010), and carcass loin muscle depth (P = 0.011) than pigs given 0.74 m2/pig. There was no difference in feed conversion (P = 0.210) as a result of space allocation. Pigs fed diets containing 10 ppm ractopamine had decreased (P = 0.004) ADFI and improved (P = 0.001) feed conversion efficiencies for the 28-d feeding period, along with greater loin depth (P = 0.005) and carcass lean percent (P = 0.001). The improvements in 28-d carcass lean growth associated with feeding 10 ppm ractopamine resulted in an improvement in overall daily fat-free lean gain (P = 0.046). Under these experimental conditions, the response to dietary ractopamine was similar for crowded and uncrowded pigs.     

Heavy sarcocystosis in the ocular musculature of cattle and buffaloes

A high prevalence of 71.5 per cent and 69.7 per cent of sarcocystosis was observed in the ocular musculature of cattle and buffaloes respectively, in Bihar, India. The concentration of cysts in the eye muscle was also usually heavy. Ocular musculature appears to be a preferred site for the development ofSarcocystis in these intermediate hosts, second only to the heart muscle. The species ofSarcocystis involved in the present study were morphologically indistinguishable fromS. cruzi in cattle andS. levinei in buffaloes. This appears to be the first report on the occurrence ofS. cruzi andS. levinei in ocular musculature.     

Distribution of kanamycin in ocular tissues of calves

The ocular distribution of kanamycin following intramuscular, bulbar subconjunctival injection, or after constant rate intravenous infusion to calves was studied. Steady-state plasma concentrations of kanamycin were achieved in either normal calves, or in those experimentally infected with Moraxella bovis, and the concentrations of kanamycin in the serum, aqueous humor, vitreous body, tears, and the ocular tissues were measured. Kanamycin was not detected in the retina, lens, vitreous body, or the aqueous humor of any eyes, but the concentration of drug in the tears, conjunctiva, cornea and the orbital lacrimal gland of these calves ranged between 18 and 21% of that in serum. At steady-state plasma levels, the kanamycin concentrations in tears from eyes with keratoconjunctivitis and from normal eyes were similar. A study using lyophilized, powdered, ocular tissues in vitro showed that kanamycin was highly bound to the bovine retina and iris, and could be eluted using 0.2 N NaOH. The binding of kanamycin to other ocular tissues, including cornea, conjunctiva and lens, was significantly less. The concentration of kanamycin in the serum and the tears of calves was also measured after intramuscular or bulbar subconjunctival injection. After intramuscular administration of kanamycin (10 mg/kg of body-weight), the mean serum concentration was maximal at 1 h (32 micrograms/ml) and remained greater than or equal to 1.0 microgram/ml for 8 h. The mean tear concentration was maximal (3.1 micrograms/ml) at 30 min, and remained greater than or equal to 1.5 micrograms/ml for only 2.5 h. Following bulbar subjunctival administration of kanamycin (100 mg, single subconjunctival dose), the mean tear concentration was 1127 micrograms/ml at 30 min, less than or equal to 4.1 micrograms/ml at 4 h, and thereafter was less than or equal to 1.0 microgram/ml. It was concluded that kanamycin has limited distribution to the ocular tissues following parenteral administration. Binding of the drug to the ocular pigments may be responsible for its limited intraocular penetration.     

Nature and cause of bilateral ocular dermoids in Hereford cattle

Nature and cause of bilateral ocular dermoids were investigated by field studies, pedigree analysis, clinical examination, light microscopy, scanning electron microscopy, and transmission electron microscopy. It was determined that ocular dermoids in Hereford cattle are a genetically transmitted defect; characteristics of autosomal recessive and polygenic inheritance were observed. Calves typically were affected bilaterally with multiple, connected ocular growths that clinically, histologically, and ultrastructurally mimicked normal haired skin. Sites most commonly involved included ventro-lateral limbus, third eyelid, medial canthus, eyelid and conjunctiva. Centro-corneal and anterior segmental dermoids also were observed.