首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Using a monoclonal antibody raised against zeranol, a radioimmunoassay has been validated for the determination of zeranol residues in the faeces of treated steers. The limit of decision defined as the mean apparent concentration of zeranol in the faeces of untreated cattle + 3 SD was 1 ng/g faeces. In a trial in which 27 steers were implanted with zeranol (36 mg) at the base of the ear and six steers were sham implanted, the mean maximum concentration of zeranol in faeces was 5.8 ng/g on Day 15 following implanting, declining to 1.67 ng/g on Day 34 following implanting. During this period there was a marked variation between animals sampled on the same day following implanting. At no time during the trial did the apparent concentration of zeranol in the faeces of untreated animals rise above 0.91 ng/g, which is below the limit of decision for this assay.  相似文献   

2.
Rapid solvent extraction combined with a radioimmunoassay using a monoclonal antibody raised against a derivative of zeranol has been used to measure the residues of the anabolic agent zeranol in the edible tissues (muscle, liver, kidney and fat) of cattle treated with Ralgro. Calibration curves, both with and without, tissue extracts exhibit good parallelism. Regression analysis for the extraction of zeranol from tissues dosed with standard amounts of zeranol have correlation coefficients of 0.979, 0.991, 0.986 and 0.985 for muscle, liver, kidney and fat, respectively. The limits of decision defined as the mean value + 3 SD for the concentrations apparently observed (noise) in tissues from animals not treated with Ralgro were 278, 121, 373 and 110 ng/kg for muscle, fat, liver and kidney, respectively. In the tissues of 4 cows implanted with Ralgro (36 mg), and sampled 70 days after implanting, the highest concentration of zeranol in each tissue was 232 ng/kg (muscle), 391 ng/kg (liver), 287 ng/kg (kidney) and 293 ng/kg (fat), and residues were detected in all samples of fat (4), 3 kidney samples and 1 liver sample.  相似文献   

3.
A radioimmunoassay for zeranol has been validated and used to measure the concentration of zeranol in the urine of sheep and cattle treated with zeranol (Ralgro). The assay uses an antibody raised against zeranol-16-carboxy-propyl ether conjugated to human serum albumin. In sheep and cattle urine the limits of detection were approximately 2 ng/ml and 2.5 ng/ml, respectively. In two trials 13 sheep were implanted with 12 mg zeranol at the base of the ear. The mean maximum concentrations of zeranol observed in urine were 45 ng/ml (Trial I) on day 35 and 90 ng/ml (Trial II) on day 56, and had declined to 26 ng/ml 42 days after implantation (Trial I) and 11.7 ng/ml 70 days after implantation (Trial II). In four cattle implanted with 36 mg zeranol the concentrations of zeranol in urine reached a mean maximum concentration of 13.5 ng/ml 22 days after implantation and had declined to 2.9 ng/ml 69 days after implantation.  相似文献   

4.
A fast, reliable and sensitive radioimmunoassay method using either 3H-hexoestrol or a 125I-hexoestrol derivative as the competitive radioligand has been developed for the measurement of residues of hexoestrol in faeces. The blank value for untreated cattle was 113 +/- 98 pg/g faeces, the intra-assay coefficient of variation 10.8 per cent, interassay coefficient of variation 11.1 per cent and recovery of 3H-hexoestrol added to faeces was 58.7 per cent. The concentration of hexoestrol in faeces was measured in 18 steers and 14 bulls at regular intervals after implantation of 36, 45 and 60 mg of hexoestrol. Residues were detected in all samples up to 104 days after implantation and in nine out of 13 samples taken 111 to 153 days after implantation. Residues of hexoestrol were also measured in edible tissues and body fluids of 14 bulls and eight steers slaughtered between 90 and 153 days after implantation of 45 mg hexoestrol. The percentages of samples containing residues were 82, 73, 64, 82 and 27 per cent for bile, urine, liver, kidney and muscle, respectively.  相似文献   

5.
Two trials were conducted to study the effect of zeranol implants on growth and sexual development of bull calves. Trial 1 compared the effects of implanting with 72 mg of zeranol at 48 d of age (branding), at 215 d of age, or at both times with nonimplanted control bulls. Implanting at branding resulted in decreased scrotal circumference, testicle weight and proportion of bulls that could produce an ejaculate at 14 mo of age (P less than .01). Implanting at 215 d of age had no effect on any of these traits. Growth rate was not increased by implanting at either time but was decreased (P less than .02) in animals implanted at both times when compared with control bulls. In trial 2, both bulls and steers were implanted with zeranol and compared with nonimplanted control bulls and steers. Thirty-six-milligram implants were given at 21, 103, 260 and 343 d of age. Scrotal circumference, testicle weight and serum testosterone concentrations decreased (P less than .01) and the occurrence of penis abnormalities increased (P less than .01) in implanted bulls compared with control bulls. By the time of slaughter, however, testosterone concentrations were equal in control and implanted bulls; and the difference in scrotal circumference was diminishing. This is interpreted as evidence that as the bulls get older, they can overcome the effect of the implants. Carcass weights were heavier in implanted steers than in control steers but were lighter in implanted bulls than in control bulls (P less than .02). Carcasses of implanted bulls had higher quality scores and more marbling than control bulls, but carcasses of implanted steers had lower quality scores and less marbling than control steers (both interactions, P less than .01). Implanting bulls with zeranol at an early age resulted in restricted sexual development but not in total sterility. Repeated zeranol implants throughout the growing and finishing phase enhanced carcass quality in bulls slaughtered at 14 to 16 mo of age.  相似文献   

6.
A radioimmunoassay (RIA) method for hexoestrol using an antiserum against hexoestrol-carboxypropyl ether-BSA and H3-hexoestrol was used to measure the concentrations of residues of hexoestrol in 0.1 ml biological fluids and 1 g edible tissues of implanted cattle and sheep. A preliminary ether extraction of biological fluids was necessary before RIA. The ether extract from tissues was further purified by solvent partition and silica gel column chromatography before RIA. Conjugates of hexoestrol were measured after enzymatic hydrolysis to free hexoestrol. In untreated animals residues were either not detected or very low in all tissues except urine from sheep. The method has a lower limit of detection of approximately 0–10 pg/ml for biological fluids in cattle and 20–100 pg/g for tissues in both sheep and cattle but the lower limit of detection in sheep urine was 70–294 pg/ml urine. In two heifers implanted with 60 mg hexoestrol and slaughtered 2 and 7 days after implantation, residues of hexoestrol were detected in all tissues except muscle with highest concentrations between 2 - 17 ng/g in urine, bile and kidney. The concentration of residues in steers which had been implanted with 45 mg or 60 mg hexoestrol and slaughtered at 90 days after implantation were 0, < 50, 46–96 and 200 pg/ml or g of plasma, muscle, liver and urine, respectively. The concentrations of hexoestrol in sheep implanted with 15 ml hexoestrol and slaughtered after 60 days were 70, 0, 964, 3100 and 4074 pg/g or ml of muscle, fat, liver, kidney and urine, respectively. No hexoestrol was found in control untreated cattle and sheep. It was concluded that some residues of hexoestrol were present in the excretory fluids and tissues of cattle and sheep which had been implanted with hexoestrol at the recommended dose and slaughtered after the recommended withdrawal periods. However, the concentrations of hexoestrol in muscle and fat were extremely low or not detectable. The method could be used for the routine screening of animals for treatment with hexoestrol.  相似文献   

7.
This study was conducted to assess the impact of implanting intact beef males with protein anabolic agents at varying intervals throughout life. Ninety-six intact males were assigned to three implant treatments: 1) not implanted, 2) implanted at 9 wk of age, weaning and at 56-d intervals thereafter with a 36-mg zeranol implant or 3) estradiol implant at 9 wk of age and 68 d post-weaning. During the 118-d, post-weaning growing period, eight animals per treatment (one replication) were castrated. After a 114-d finishing period, cattle were slaughtered (average age of 13 to 14 mo). Feedlot performance, carcass and palatability data were obtained. Average daily gains and feed efficiency did not differ (P greater than .05) between zeranol and estradiol-implanted intact males. Regardless of implant treatment, steers had lighter carcass weights (P less than .05) and higher (P less than .01) quality grades than intact males. Implanting either intact males or steers with zeranol or estradiol resulted in higher (P less than .05) numerical yield grades. Quality grades were higher in zeranol-implanted cattle than the non-implanted or estradiol-implanted cattle. Intact males implanted with zeranol were similar in carcass fatness to zeranol-implanted steers. No differences (P greater than .05) in tenderness or connective tissue were detected. Implanting intact males early and throughout life with zeranol made them similar to steers in fatness, while estradiol implantation had few effects on carcass and palatability traits of intact males or steers.  相似文献   

8.
Nine experiments on the effect upon bodyweight change of subcutaneous ear implantation of 36 mg zeranol in 605 Bos indicus crossbred cattle were conducted. Bullocks aged 3 to 4 years, steers aged 18 months and entire heifers aged 18 to 30 months were used over the period January to August, 1980. They were grazed on 6 commercial farms in tropical northern Australia. Seven of the experiments examined the results of single implantation after the initial 60 to 97 days. Growth rates of untreated cattle in the January to May period ranged from 0.43 kg/day over 97 days in heifers to 1.07 kg/day in bullocks. Bodyweight gains attributed to zeranol ranged from 1.8 kg (4.3% increase) over 97 days in heifers (NS) to 22.3 kg (28.9% increase) over 90 days in 18 month-old steers (P < 0.01). The significant bodyweight responses to zeranol treatment in all 5 experiments involving older 3-to 4-year-old bullocks have not been previously reported. Hot dressed weights of the zeranol-treated bullocks were significantly heavier than the untreated controls and dressing percentages were similar. Increases in bodyweight attributable to implantation with zeranol yielded 50 to 54% saleable carcase weight. Single-, repeat-, and non-implanted treatments were compared over 186 days from January to August. Both zeranol treatments significantly out-performed the controls (P < 0.05), and the repeat-implanted bullocks gained 9.2 kg more than the single-implanted bullocks (P<0.10) in spite of bodyweight tosses recorded in the 3 treatments over the final 105 days. In 2 experiments bullocks implanted once in January/February were weighed in August to monitor compensatory bodyweight changes after April/May. The cattle retained 72.4% and 92.6% of the original bodyweight advantage attributed to zeranol treatment, depending upon whether they lost or gained in bodyweight respectively during the April/May to August period. The commercial relevance of these results is discussed and suggestions are made for further work.  相似文献   

9.
Three trials involving 513 exotic crossbred steers were conducted to determine the effect of zeranol implanting in the suckling and growing phases on subsequent feedlot performance and carcass characteristics. Treatments were 1) unimplanted control, 0000; 2) implanted twice in the finishing phase, 00II; 3) implanted in the growing phase and twice in the finishing phase, 0III; 4) implanted in the suckling phase and twice in the finishing phase, I0II; 5) implanted in the suckling and growing phases with a single implant in the finishing phase, III0; and 6) implanted in the suckling and growing phases and twice in the finishing phase, IIII. Implanting in the suckling period did not significantly affect preweaning gain. Implanting in the growing period produced a treatment x trial interaction (P less than .05), but zeranol increased gains by an average of 8.4% over the three trials. Growing period gain was not influenced by implanting during suckling. Implanting twice during the finishing period increased gain (P less than .05) over unimplanted and III0 steers. Finishing gain was not influenced by previous suckling and(or) growing implant treatment. Lifetime ADG of steers was increased (P less than .05) by all implant treatments compared with unimplanted controls. Zeranol tended (P = .14) to improve feed conversion in the finishing phase. All implant treatments increased hot carcass weight (P less than .05), and all but III0 reduced fat deposition, as indicated by lower quality grade (P less than .05). Other carcass characteristics were not significantly affected by treatment. These trials demonstrated that implanting in the suckling and(or) growing phases of production did not reduce performance in the finishing phase.  相似文献   

10.
Three groups of beef steer calves were implanted in 1983 with 36 mg of zeranol at 2 months or 4.5 months age or at both these ages, and their growth rates were compared with an untreated group. At approximately 8 months age in December the 3 implanted groups were heavier than the control group by 14.6 kg (P less than 0.05), 23.4 kg and 22.1 kg (P less than 0.01). At peak animal weights recorded in March the differences were 18.7 kg (P less than 0.05), 31.3 kg and 31.0 kg (P less than 0.01). In June 1984, following loss of weight by the steers, differences between the implanted groups and the control groups had declined to 7.7 kg (P greater than 0.05), 19.4 kg (P less than 0.01) and 21.1 kg (P less than 0.001), differences similar to those recorded approximately 3 months after implantation. It is concluded that higher weight gains resulted from implanting suckling calves at 4.5 months of age, than by implanting calves at 2 months of age, and that implanting suckling calves twice is unlikely to be any better than implanting them once at 3 to 6 months age. Part of the maximal response can be lost if steers subsequently lose weight.  相似文献   

11.
A 2 X 2 factorially arranged trial was conducted to compare effects of implant (zeranol) and frame size on weight and compositional gain, and plasma hormone concentrations. Angus, Charolais X Hereford and Hereford X Angus yearling steers (34 steers averaging 270 kg body weight) were randomly assigned to treatments of small (SF) vs large frame (LF) and implant (I) vs no implant (NI). Steers were implanted at 0 and 97 d and individually fed an 81% whole shelled corn and 11.5% corn silage-based diet (dry basis) for a 175-d period. Shrunk weights and body measurements for frame size determination were taken initially and at approximately 28-d intervals; blood was collected via venipuncture at 14-d intervals for analyses of insulin (IN), triiodothyronine (T3), thyroxine (T4) and glucose concentrations. Steers were also counted in a whole body counter for measurement of 40K content and prediction of whole body protein and fat. The I steers showed an improvement (P less than .05) in daily gain regardless of frame size for the total trial. The I LF steers required 18% more dry matter to attain higher daily gain for 97 to 175 d; I steers were more efficient (P less than .05) at converting dry matter to gain during 0 to 97 d and 0 to 175 d. Daily fat deposition was increased (P less than .05) in I steers, while protein deposition was not affected by I. Plasma IN concentrations were numerically elevated (P less than .10) in I steers regardless of frame size, during the initial 97 d. Implant did not influence (P greater than .10) plasma T3, T4 and glucose concentrations regardless of frame size. Steers responded differently to zeranol implant over time regarding plasma T4 concentrations (P less than .003). Steers differing in frame size responded similarly in rate of gain, in feed conversion and in patterns of plasma insulin concentrations to zeranol implants.  相似文献   

12.
The ability of zeranol and trenbolone acetate (trenbolone) to alter testis function, weight gain and carcass traits of young bulls was studied. In Exp. 1, the effects of age at initial zeranol implantation was determined. After a 235-d experimental period, sequential implantation (56-d intervals) beginning at 100 or 150 d of age had reduced testis growth (P less than .01), sperm production (P less than .01) and serum testosterone concentration in response to gonadotropin releasing hormone (GnRH; P less than .01). The 200-d age group was partially suppressed, while the 250-d age group was not affected. Body weights were similar to controls in all groups. In Exp. 2, bulls previously implanted with zeranol at 175 and 231 d of age received single implants of zeranol, trenbolone or trenbolone plus zeranol at approximately 300 d of age. At slaughter (135 d later), body weight and carcass characteristics in all treatments were similar to controls. However, trenbolone reduced sperm production (P less than .05), zeranol reduced sperm production and testes weight (P less than .05), but trenbolone plus zeranol was similar to controls. Mean testosterone response to GnRH was suppressed in all implant groups on d 65 (P less than .01), but only in trenbolone or trenbolone plus zeranol groups on d 112 (P less than .05). Results indicate that zeranol suppresses spermatogenesis and testosterone production if implanted before approximately 200 d of age. Reduction of endogenous testosterone without alteration of weight gain or carcass characteristics may be of benefit if behavioral or masculinity traits of bulls are altered. Also, it appears that no benefit is derived from implanting bulls with both trenbolone and zeranol.  相似文献   

13.
Twenty crossbred yearling steers (421 kg) were used to evaluate the effects of implanting with trenbolone acetate (TBA; 120 mg), estradiol-17β (E(2); 25.7 mg), and a combination (120 mg of TBA and 24 mg of E(2)) on adipogenic and myogenic mRNA concentrations. Animals were blocked by BW and within each block were assigned to 1 of 4 treatments. Animals were housed and fed in individual pens with 5 animals per treatment. All animals were weighed weekly, and muscle biopsy samples were taken from the LM of each steer on d 0 (before implantation), 7, 14, and 28. Total RNA was isolated from each sample and real-time quantitative PCR was used to measure the quantity of C/EBPβ, PPARγ, stearoyl CoA desaturase (SCD), myogenin, and 3 isoforms of bovine myosin heavy chain (MHC) mRNA. Total BW gain from the 28-d period was adjusted to d 0 by use of covariant analysis, and steers in the implant groups tended (P = 0.09) to have increased BW gain compared with nonimplanted control steers. Analysis of the gene expression of MHC showed that neither implant nor day (P > 0.20) had a significant effect on the expression of type I or IIX MHC mRNA There was also no treatment effect (P > 0.20) on MHC-IIA and myogenin, but increasing days on feed increased (P = 0.05) the expression of MHC-IIA mRNA. Relative mRNA abundance of C/EBPβ, PPARγ, and SCD increased (P < 0.05) during days of feed but PPARγ decreased (P < 0.05) with the treatment of combined TBA/E(2) implant. Results of this study indicate that implanting with TBA, E(2), or both increased BW gain and decreased adipogenic gene expression of finishing steers without significantly affecting the concentration of type I, IIA, or IIX MHC mRNA. Increasing days on feed increased both MHC-IIA and adipogenic gene expression in bovine skeletal muscle biopsy samples. We conclude that administration of steroidal implants had no effect on the proportion of the 3 MHC mRNA isoforms but decreased C/EBPβ, PPARγ, and SCD mRNA in bovine skeletal muscle.  相似文献   

14.
Seven Angus and six Brangus steers averaging 225 and 245 kg, respectively, were assigned randomly to zeranol (36 mg) implant (I) and no implant (NI) treatments. Steers had ad libitum access to a corn silage diet plus .68 kg of a soybean meal-based supplement fed daily. Steers were bled via jugular catheters on d 0, 28, 56, and 84 at 15-min intervals for 4 h before and 4 h after feeding. Concentrations of growth hormone (GH), insulin (INS), triiodothyronine (T3), thyroxine (T4), and glucose were determined. Whole-body protein and fat contents were monitored. A breed x I interaction (for d 56 to 84 and d 0 to 84) was observed for ADG (P less than .05 and P less than .07, respectively), feed conversion (P less than .05 and P less than .07, respectively), and protein deposition (for d 0 to 29 and d 0 to 84; P less than .07 and P less than .05, respectively). These interactions were attributed to a greater response to I by Angus than by Brangus steers. A feeding x period interaction (P less than .10) was observed for mean GH concentration, and INS, T4, and T3 concentrations were higher (P less than .05) during the 4-h postfeeding period than during the 4-h prefeeding period. The implant increased (P less than .08) mean GH concentration but did not alter the frequency, duration, or amplitude of plasma GH peaks. Steers that were implanted had lower (P less than .05) plasma T3. Brangus steers had lower (P less than .05) plasma glucose, T3, and T4 concentrations than Angus steers. Results indicate that growth factors beyond those measured are responsible for the anabolic response to zeranol.  相似文献   

15.
This experiment compared the growth response of untreated steer calves with those given a long acting oestradiol-silicone rubber implant or implants of zeranol or oestradiol-progesterone pellets either singly, or repeated after 79 days. The experiment extended through the 6 weeks prior to weaning at 8 months of age, 5 weeks of grazing oat stubble and a 16-week finishing phase on a feedlot. The oestradiol-silicone rubber implant was the only product to significantly increase weight gains compared to controls (0.69 vs 0.52 kg/head/day, 18.2% advantage) in the pre-weaning phase. All anabolic agents produced higher weight gains ranging from increases of 0.16 to 0.19 kg/head/day (18.2-21.6%) above controls in the first 60 days of the feedlot phase. Responses did not differ significantly among the products and were the same whether or not steers had been previously implanted. Lower planes of nutrition in the late suckling and post-weaning periods were accompanied by smaller and non-significant responses to both the short acting anabolics, zeranol and oestrogen-progesterone, compared to the increased weight gains of steers given oestradiol-silicone rubber implants. Implanting with oestradiol in a silicone rubber matrix resulted in similar increases in weight gain both before and during the feedlot phase. This may have been due to the implant maintaining a continuously high level of circulating anabolic agent for the 190 days of the experiment.  相似文献   

16.
A trial was carried out using 490, 12- to 15-month-old steers which were at pasture from April to November and then housed and fed grass silage and concentrates until sold live or slaughtered. Animals were allocated at random to one of the following treatments: (i) Control; (ii) implanted with 45 mg oestradiol -17 beta in silastic rubber in April; (iii) implanted with oestradiol in April and with 300 mg trenbolone acetate in April, August and November; (iv) implanted with 36 mg zeranol in April, August and November and (v) implanted with zeranol and trenbolone acetate in April, August and November. Daily liveweight gains were 0.69, 0.75, 0.78, 0.83 and 0.86 (+/- 0.02) kg, and carcase weights were 300, 306, 311, 316 and 321 (+/- 3.4) kg, for treatments (i) to (v), respectively. All implanted animals had significantly higher daily gains than control animals and an additive response was obtained where trenbolone acetate was used with oestradiol or zeranol. Pooled results for animals treated with oestradiol plus zeranol, with or without trenbolone acetate, show that the overall response for zeranol treated animals was higher than from the animals treated with oestradiol. Daily gains after the first, second and third implant period show a reduced response from the oestradiol implant for the final 63 days of the trial. This may have been caused by loss of some oestradiol implants from animals early in the trial.  相似文献   

17.
A single oral dose of oxytetracycline hydrochloride (50 mg/kg) produced detectable residues in the following tissues; adrenal, bile, fat, heart, kidney (cortex), kidney (medulla), liver, lung, lymph node (mesenteric), muscle, serum, spleen, thyroid and urine. The highest residue levels were observed in the urine (441 μg/mL) at three hours after administration and they were still present at 48 hours. Maximum serum levels were observed at two hours after administration. Bile samples were positive for inhibitors in all animals sampled. Drug residues were not detected in spleen, thyroid, lymph node, adrenals and heart at 48 hours.

Drug levels in important edible tissues were expressed as a percentage of drug levels in two tissues with high drug concentrations — urine and kidney cortex. The percentages were highly variable when compared with urine and much less variable when compared to kidney cortex.

Kidney cortex appears to be an excellent tissue for drug residue monitoring.

  相似文献   

18.
OBJECTIVE: To measure the reduction in fecal nematode egg counts and productivity impact of treatment of yearling steers with doramectin at entry into the feedlot, compared with control steers treated only with fenthion. ANIMALS: 6,096 crossbred yearling steers with a mean (+/- SD) body weight of 377.0 (+/- 37) kg. PROCEDURE: Steers were implanted with zeranol and alternately separated to fill each of 24 pens. Groups of steers within 12 matched pairs of pens were randomly allocated to treatment with doramectin or no treatment with doramectin for internal nematodes. Fecal samples were collected from approximately every twentieth steer from each pen at day 0 and at reimplant (approx day 60). Each steer was weighed on day 0 and at reimplant and then mean body weights of steers per pen were determined at 120 to 140 days after trial initiation. RESULTS: Treatment steers had a significantly lower fecal egg count at reimplant than control steers. Treatment steers had a significantly greater mean daily gain during the study, significantly greater feed consumption, significantly lower feed-to-gain ratio, and significantly better quality carcass grades at slaughter. CONCLUSIONS AND CLINICAL RELEVANCE: Under the conditions of our trial, there was a significant fecal egg count reduction response to doramectin treatment, which resulted in significantly improved productivity. Results of economic analysis of return on investment indicated that even with low egg counts in heavy body weight cattle, nematode egg count reduction with doramectin significantly improved returns.  相似文献   

19.
The metabolic fate of the anabolic agents, diethylstilbestrol, hexestrol, trenbolone acetate, zeranol and the endogenous steroids are discussed under the headings absorption, distribution and excretion. There is an optimum concentration of anabolic agent in the systemic circulation that results in a maximum increase in growth rate of farm animals. This optimum blood concentration should be maintained over a long period. However, there is rapid metabolism and excretion of anabolic agents with short half-lives in blood, and metabolic clearance rate equals entry rate. The rate of absorption of the agent, which is determined by formulation and site of administration, is most important and is best achieved by the use of slow release implants. The pattern of exponential absorption from compressed pellets of single anabolic agents is not ideal, and a more constant payout of drug, in particular estradiol-17 beta, is best achieved in combined preparations of agents or from silicone rubber implants impregnated with the agent. The high metabolic clearance rate and rapid excretion of anabolic substances influences the distribution of residues. Outside the site of administration, less than 1% of the administered dose is present in the animal. The lowest concentrations of residues are found in muscle and fat, higher concentrations are present in liver and kidney and the highest concentrations are in the bile, urine and feces.  相似文献   

20.
Twelve Charolais-crossbred steers (256 kg) received one of three treatments: nonimplanted controls (C), implanted initially and at 84 days with 36 mg zeranol (Ralgro, R) and implanted initially and at 84 days with 200 mg of progesterone and 20 mg of estradiol benzoate (Synovex-S,S). All steers were fed a corn-based diet (calculated metabolizable energy 2.89 Mcal/kg dry matter) ad libitum. In a parallel comparative slaughter trial, rates of empty body protein accretion were increased 14% in R and 24% in S steers (P less than .01). R and S steers in the present study had heavier pituitary weights (P less than .001), more pituitary growth hormone content (P less than .04) and more pituitary weight/unit live weight (P less than .05) than did C steers. Cattle implanted with R or S exhibited an increased growth hormone (GH) secretory response to a pituitary challenge with thyrotropin releasing hormone (TRH). Plasma insulin profiles were not significantly altered, but tended to be greater for steers given implants. Overall 9-hr GH secretory profiles were not affected by implantation. Plasma urea N at 94 days post-implantation was decreased (P less than .01) by implantation. Plasma glucose was increased (P less than .04) at both 94 and 199 days in R and S vs C steers. Overall mean and total (integrated area) plasma GH, as well as secretory profile components (baseline mean, amplitude of secretory spikes) were negatively correlated with body weight and size on days 94 and 199. Overall mean, baseline and integrated area of plasma insulin on days 94 and 199 were positively related to body weight and size. Thus positive protein anabolic growth responses from implantation (parallel comparative slaughter trial) were coupled with increased pituitary GH content and little change in circulating plasma GH concentrations between implanted and control steers. This may suggest that changes in tissue sensitivity, an increased plasma clearance rate of GH and/or a direct effect on target tissues may be involved in the improved growth performance of cattle implanted with R or S.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号