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PubMed1995

Chemicals for evaluating the sensitivity and specificity of reduced/transgenic rodent cancer bioassay protocols.

The standard two-species/two-gender lifetime carcinogenicity bioassay protocol is not practical when assessing the possible carcinogenicity of a large number of chemicals. This has led to consideration of reduced cancer bioassay protocols (e.g., male rat/female mouse), or to the use of genetically altered rodents that succumb to chemically induced cancer in a fraction of their lifespans. Two uncertainties accompany these endeavours. First, that use of reduced protocols may lead to the non-detection of some weak or tissue-specific carcinogens. Second, that genetically altered rodents may be so sensitive to chemical disturbance of homoeostasis that their carcinogen specificity may be low. Such uncertainties lead to the requirement that the modified test protocols should be validated using appropriate carcinogens and non-carcinogens. Given that several such studies may take place over the coming years it seems appropriate that a common pool of chemicals should be agreed upon for this purpose. To this end a selection of human carcinogens, and rodent carcinogens/non-carcinogens defined by the US National Toxicology Program (NTP), have been collected together. Six categories of chemicals are listed: (1) representative human carcinogens; (2) representative trans-species genotoxic carcinogens; (3) all two-species non-carcinogens reported to be negative in the Salmonella mutation assay and lacking structural alerts to electrophilicity; (4) representative single-species/presumed non-genotoxic carcinogens; (5) all two-species non-carcinogens that are mutagens in the Salmonella mutation assay and which are structurally alerting; (6) all chemicals possessing equivocal evidence of carcinogenicity and which are both structurally alerting and mutagenic to Salmonella. Chemicals in the first four groups provide robust calibrants for determining the sensitivity and specificity of reduced/accelerated rodent carcinogenicity bioassay protocols. Chemicals in the last two groups may be of value when studying the interface between the sensitivity and the specificity of modified rodent carcinogenicity bioassay protocols.

Animals↗

PubMedDate not supplied

Comparison of single-, double- or triple-exposure protocols for the rodent bone marrow/peripheral blood micronucleus assay using 4-aminobiphenyl and treosulphan.

Two human carcinogens, 4-aminobiphenyl (4AB) and treosulphan (Treo), were tested in male B6C3F1 mice for the induction of micronuclei in bone marrow and peripheral blood cells by 1-, 2- and 3-exposure protocols. Both compounds tested positive. The magnitude of response with respect to the incidence of micronucleated polychromatic erythrocytes by 2- and 3-exposure protocols was considerably higher than by the single-exposure protocol. The peripheral blood results for Treo were as typically seen with a 24-h delay when compared to the bone marrow. The peripheral blood results for 4AB, however, differed from those expected. The incidence of MN-PCE in peripheral blood of animals exposed to 4AB was significantly greater than seen in the bone marrow in 2- and 3-exposure protocols. There was also an increase in the % PCE at the 60 mg/kg dose level as a function of time. Based on these studies, it is concluded that a step-wise scoring scheme may be the best protocol for rodent micronucleus assay, involving a 3-exposure protocol with single sampling of bone marrow (24 h after the last treatment) and two samplings of peripheral blood (24 h and 48 h after the first treatment). This approach is cost-effective, it limits the number of animals required and provides maximum sensitivity.

Aminobiphenyl Compounds↗

PubMed1995

Clinical implementation of an objective computer-aided protocol for intervention in intra-treatment correction using electronic portal imaging.

In order to test the feasibility of a protocol for intra-fractional adjustment of the patient position, during radiation therapy treatment in the pelvic region, a two-fold study is carried out. The protocol involves an objective quantitative measurement of the error in positioning starting from the comparison of a portal image with a reference image. The first part of the study applies the protocol to determine the efficacy of adjustment using subjective determination of the positioning errors by a clinician by measuring the residual errors after adjustment. A group of 13 patients was followed extensively throughout their treatment, analyzing 240 fields. In the second part the measurement itself determines the extent of readjustment of the position. Throughout the procedure elapsed time is measured to determine the extra time involved in using this procedure. For this part a group of 21 patients was followed yielding statistics on 218 fields. Using this computer aided protocol it is shown that systematic as well as random errors can be reduced to standard deviations of the order of 1 mm. The price to pay however is additional treatment time up to 58% of the treatment time without the protocol. Time analysis shows that the largest part of the added time is spent on the readjustment of the patients' position adding a mean of 37% of time to the treatment of one field. This is despite the fact that the readjustment was performed using a remote couch controller. Finally a statistical analysis shows that it is possible to select patients benefiting from the use of such a protocol after a limited number of fractions.

Feasibility Studies↗

PubMed1986

Type 1 error and power of the linear trend test in proportions under the National Toxicology Program's modified pathology protocol.

This paper investigates the relationship between the probability of detecting a statistically significant linear trend in the proportion of animals observed to have tumors for the modified pathology protocol currently being employed by The National Toxicology Program. We considered over 300 possible dose-response relationships and tested at 5% and 1% significance levels. The results indicate that a small loss in the probability of detecting a statistically significant result will occur when the modified protocol is used instead of the previous pathology protocol. This loss varies as a function of the design of the study in terms of dose and animal allocation and as a function of the steepness of the dose-response relationship. The absolute difference between the probability of a statistically significant result for the original pathology protocol and that for the modified pathology protocol never exceeded 0.03. This difference was always less than 8% of the probability of a statistically significant result for the original pathology protocol.

Animals↗

PubMed2005

Back muscle strength and fatigue in healthy and chronic low back pain subjects: a comparative study of 3 assessment protocols.

OBJECTIVE: To compare the sensitivity of 3 different back test protocols in measuring differences in strength and fatigue between subjects with and without chronic low back pain (CLBP). DESIGN: Descriptive study using a repeated-measures design. SETTING: A research laboratory within a rehabilitation center. PARTICIPANTS: Eighteen healthy subjects and 13 subjects with CLBP were assessed in a single session to compare the 3 protocols. The protocols were an upright position test (UPP), a semicrouched lifting test (LIF), and the Sorensen fatigue test. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Moments of force and surface electromyography were recorded bilaterally from 4 homologous back muscles while the subjects performed static trunk extension efforts for each protocol. Fatigue was quantified by the slopes of the linear regression of electromyography time-series. RESULTS: The back muscle fatigue and strength scores did not differ significantly for the 2 subject groups for any of the 3 protocols. The electromyography fatigue indices revealed that the Sorensen fatigue test and UPP produced more fatigue in the back muscles than the LIF. CONCLUSIONS: It was impossible to specify which protocol is more sensitive to low back status because no between-group difference was observed for any of the 3 tests.

Adult↗

PubMed2006

Inter-rater reliability of the Illinois Structured Decision Support Protocol.

OBJECTIVE: The purpose of this study was to determine the level of inter-rater reliability of the Illinois Structured Decision Support Protocol by examining the level of Child Protective Services (CPS) caseworkers' agreement regarding state interventions. The Protocol was designed to guide CPS workers to consistent decisions related to the level of state intervention in child maltreatment cases. METHOD: Forty-one workers recruited from three CPS field offices in Illinois participated in this study by assessing three cases using the Illinois Structured Decision Support Protocol. The three cases were developed based on actual cases investigated by the agency. The kappa statistic was used to calculate the level of workers' agreement. RESULTS: The result showed a weak reliability (kappa=.29). Further analysis showed that workers identified a wide range of risk factors and differing levels of intervention for each identified risk factor even among the workers who made the same final decisions. CONCLUSIONS: Decision support protocols are developed to provide systematic structures for workers' decision-making. However, this study suggested that workers demonstrated a low level of agreement on such a protocol. Several suggestions for developing more reliable computerized protocols include: more specified inquiries with criteria to assess the range of risk for a factor, consideration of interactions among risk factors, assessment of family strengths, and having the final decision made by a computerized program.

Case Management↗

PubMed2005

A patient-tailored N-acetylcysteine protocol for acute acetaminophen intoxication.

BACKGROUND: Hepatotoxicity as a result of acetaminophen(APAP) intoxication has become an important problem, but early intervention with N-acetylcysteine (NAC) is effective in preventing hepatic injury. Two NAC regimens are currently approved for acute APAP intoxication: NAC administered orally every 4 hours for 72 hours, and NAC administered intravenously for 20 hours within 8 to 10 hours after ingestion of a potentially hepatotoxic amount of APAP. However, clinical observations suggest that a variable treatment duration may be more appropriate than use of these predetermined, fixed-duration protocols. OBJECTIVES: This study investigated the tolerability and efficacy of a patient-tailored NAC protocol for acute APAP intoxication by comparing the incidence of hepatotoxicity in patients receiving this protocol and in historical controls receiving 1 of 2 fixed-duration protocols: oral NAC for 72 hours and intravenous NAC for 20 hours within 8 to 10 hours after ingestion of a potentially hepatotoxic amount of APAP. METHODS: This was a retrospective case series study that included all patients admitted through the emergency department (ED) of the National Taiwan University Hospital with a diagnosis of APAP intoxication between October 1997 and October 2002. According to the patient-tailored protocol, which had been used in the ED since 1997, patients with a serum APAP concentration above the limit for possible risk based on a modified Rumack-Matthew nomogram received oral treatment with NAC 140 mg/kg, followed by maintenance doses of 70 mg/kg every 4 hours. NAC treatment was discontinued when the APAP concentration was <10 mg/L and serum aspartate aminotransferase (AST) was <40 IU/L. For the purposes of assessing clinical outcomes, patients were divided into 3 groups based on duration of treatment: the short-course group (</=36 hours), the intermediate-course group (37-72 hours), and the long-course group (>/=73 hours). The primary outcome measure was development of hepatotoxicity, defined as a serum AST or alanine aminotransferase concentration >1000 IU/L. RESULTS: Twenty-seven patients were included in the study, 17 in the short-course group, 4 in the intermediate-course group, and 6 in the long-course group. The mean (SD) durations of NAC treatment in the respective groups were 22.1 (5.5) hours, 45.0 (8.2) hours, and 97.3 (33.2) hours. All 6 patients (22%) in the long-course group had hepatotoxicity (peak AST range, 1083-9770 IU/L); their treatment duration ranged from 80 to 164 hours. No patients in the short- or intermediate-course group had evidence of hepatotoxicity. One woman in the long-course group in whom initiation of NAC treatment was delayed by 28 hours died of fulminant hepatic failure. The overall incidence of hepatotoxicity was similar to that in the historical controls. CONCLUSIONS: In this retrospective case series inpatients who received patient-tailored NAC therapy for acute APAP intoxication, the incidence of hepatotoxicity was low and comparable to that in historical controls who received treatment with 1 of 2 fixed-duration regimens. Use of this protocol may have the potential to shorten hospital stays without increasing the risk to patients. However, the sample size was small, and the findings require confirmation in prospective clinical trials.

Acetaminophen↗

PubMed2004

A novel protocol of ovulation induction with delayed gonadotropin-releasing hormone antagonist administration combined with high-dose recombinant follicle-stimulating hormone and clomiphene citrate for poor responders and women over 35 years.

OBJECTIVE: To evaluate the efficacy of a novel protocol of ovulation induction for poor responders. DESIGN: Prospective, controlled, clinical study. SETTING: Research institute's reproductive unit. PATIENT(S): One hundred forty-five infertile women, aged 27-39 years, candidates for assisted reproductive techniques (ART). INTERVENTION(S): Before undergoing ART, 85 patients received clomiphene citrate, high-dose recombinant human FSH, and a delayed, multidose GnRH antagonist, whereas 60 patients underwent a standard long protocol. MAIN OUTCOME MEASURE(S): Estradiol levels (pg/mL), cancellation rate, oocyte retrieval, embryo score, and fertilization and pregnancy rates. RESULT(S): Patients undergoing the study protocol obtained lower cancellation rates (4.7% vs. 34%) and higher E(2) levels (945.88 +/- 173.2 pg/mL vs. 169.55 +/- 45.07 pg/mL), oocyte retrieval (5.56 +/- 1.13 vs. 3.36 +/- 1.3), and pregnancy (22.2% vs. 15.3%) and implantation rates (13.5% vs. 7.6%) compared with those receiving the long protocol. Age negatively correlated with ovarian response in the latter, whereas the ovarian outcome results were comparable in younger (<35 yrs) and older (>35 yrs) women treated with the study protocol. CONCLUSION(S): The proposed protocol of ovulation induction can be usefully administered in poor responders as well as in aged woman, probably because the delayed administration of GnRH antagonist prevents its adverse effects on ovarian paracrine activity and on oocyte maturation.

Adult↗

PubMed2005

Ovarian response and follicular development for single-dose and multiple-dose protocols for gonadotropin-releasing hormone antagonist administration.

OBJECTIVE: To determine the efficiency of a single-dose and a multiple-dose protocol for GnRH antagonist administration. DESIGN: Randomized clinical trial. SETTING: University hospital, tertiary medical center. PATIENT(S): Sixty-one patients undergoing controlled ovarian stimulation (COS) and IVF/ICSI. INTERVENTION(S): COS with either a multiple-dose (MD) or a single-dose (SD) protocol for GnRH antagonist (cetrorelix) administration, or with a long protocol (LP) for GnRH agonist (buserelin) administration, followed by oocyte retrieval, IVF/ICSI, and embryo transfer. MAIN OUTCOME MEASURE(S): Follicular development and serum levels of E2 and LH. RESULT(S): The SD protocol for cetrorelix was associated with a more reduced level of follicular development, lower levels of serum estradiol on the day of HCG administration, and a more reduced number of zygotes than the LP for buserelin. The pregnancy and implantation rates did not differ significantly for the three study groups. CONCLUSION(S): The MD and SD GnRH antagonist protocols were effective for preventing LH surge and appear to elicit an equivalent pregnancy rate to that corresponding to a LP GnRH agonist. In terms of follicular development, the SD protocol requires further modification, including flexible scheduling or possibly a small reduction of the dosage of the administered cetrorelix.

Adult↗

PubMed2005

An enhanced protocol to reduce error in electromagnetic tracking of first metatarsophalangeal joint motions.

BACKGROUND: Error associated with markers or sensors surface-mounted onto skin reduces the validity of kinematic models. Extensor tendon excursion at the first metatarsophalangeal joint (MTPJ) has been noted previously to be especially problematic. An enhanced skin mounting protocol is described and validated. METHODS: A Fastrak system was used to obtain kinematic data concurrently from two pairs of sensors mounted on either side of the first MTPJ of nine freshly frozen cadaveric feet. One sensor pair was mounted directly into the medulla of each of the first metatarsal and proximal phalanx of the hallux, with the second pair attached to the skin over the same segments, using each of two mounting protocols. A standard mounting protocol was compared to a new enhanced protocol that secured the sensor on the hallux with a stabilizing cuff. RESULTS: The addition of a stabilizing cuff on the hallux sensor reduced root mean square error in first MTPJalpha rotations by 1.45 degrees during passive rotation and 1.61 degrees during active rotation compared with the standard protocol (P = 0.008 and 0.028, respectively). The cuff protocol improved CMC reliability coefficients for alpha rotations from 0.918 to 0.973 for passive MTPJ motion, and from 0.922 to 0.973 for active motion. CONCLUSION: Securing the hallux mounted sensor with a stabilizing cuff reduced error by more than one-third without reducing first MTPJ total range of motion.

Biomechanical Phenomena↗

PubMed2006

Effects of changing protocol, grade, and direction on the preferred gait transition speed during human locomotion.

Although the preferred transition speed (PTS) reported by various researchers is relatively consistent, the amount of observed hysteresis (difference between the walk-run and the run-walk transition speed) varies considerably. Variations in reported hysteresis appear to be related to the protocol used to determine the transition speeds. This investigation compared the PTS, and the amount of hysteresis observed between the incremental and continuous protocols at various inclination conditions. The PTS was significantly greater in the continuous than the incremental protocol within both the 10% and 15% inclination conditions. The amount of hysteresis, however, did not vary significantly between protocols nor between inclination conditions. In the incremental protocol, the amount of hysteresis appears to be related to the size of the speed increment used. In the continuous protocol, the amount of hysteresis could be related to the rate of treadmill acceleration.

Acceleration↗

PubMed2005

Retrospective analysis of prostate cancer patients with implanted gold markers using off-line and adaptive therapy protocols.

PURPOSE: To determine the efficacy of applying adaptive and off-line setup correction models to bony anatomy and gold fiducial markers implanted in the prostate, relative to daily alignment to skin tattoos and daily on-line corrections of the implanted gold markers. METHODS AND MATERIALS: Ten prostate cancer patients with implanted gold fiducial markers were treated using a daily on-line setup correction protocol. The patients' positions were aligned to skin tattoos and two orthogonal diagnostic digital radiographs were obtained before treatment each day. These radiographs were compared with digitally reconstructed radiographs to obtain the translational setup errors of the bony anatomy and gold markers. The adaptive, no-action-level and shrinking-action-level off-line protocols were retrospectively applied to the bony anatomy to determine the change in the setup errors of the gold markers. The protocols were also applied to the gold markers directly to determine the residual setup errors. RESULTS: The percentage of remaining fractions that the gold markers fell within the adaptive margins constructed with 1.5sigma' (estimated random variation) after 5, 10, and 15 measurement fractions was 74%, 88%, and 93% for the prone patients and 55%, 77%, and 93% for the supine patients, respectively. Using 2sigma', the percentage after 5, 10, and 15 measurements was 85%, 95%, and 97% for the prone patients and 68%, 87%, and 99% for the supine patients, respectively. The average initial three-dimensional (3D) setup error of the gold markers was 0.92 cm for the prone patients and 0.70 cm for the supine patients. Application of the no-action-level protocol to bony anatomy with N(m) = 3 days resulted in significant benefit to 4 of 10 patients, but 3 were significantly worse. The residual average 3D setup error of the gold markers was 1.14 cm and 0.51 cm for the prone and supine patients, respectively. When applied directly to the gold markers with N(m) = 3 days, 5 patients benefited and 3 were significantly worse. The residual 3D error of the gold markers was 1.14 cm and 0.76 cm for the prone and supine patients, respectively. Application of the shrinking-action-level protocol to bony anatomy with an initial action level of 1.0 cm and N(max) = 5 days decreased the residual systematic offset of the gold markers in 2 of 10 patients. The residual average 3D setup error of the gold markers was 1.2 cm and 1.0 cm for the prone and supine patients, respectively. When applied directly to the gold markers with N(max) = 5 days, the residual systematic offset of the gold markers decreased in 6 of 10 patients (0.84 cm and 0.67 cm for the prone and supine patients, respectively). In general, between 3 and 5 of the 10 patients showed significant decreases in setup errors with the application of these off-line protocols, and the remaining patients showed no significant improvement or showed significantly larger setup errors, as determined by the residual error of the gold markers. CONCLUSION: Changes in a prostate cancer patient's systematic and random setup characteristics during the course of therapy often violate the gaussian assumptions of adaptive and off-line correction models. Thus, off-line setup correction procedures, especially those directed at prostate localization using markers, will result in limited benefit to a minority of patients. The relative benefit of on-line localization is still potentially significant if the intrafraction motion is relatively small.

Gold↗

PubMed2006

An ethanol protocol to prevent alcohol withdrawal syndrome.

BACKGROUND: Alcohol withdrawal syndrome (AWS) occurs in dependent patients during the initial period of sudden onset abstinence. It is usually manifested by mild symptoms such as disorientation, agitation, and tachycardia, but, if untreated, can lead to severe confusion, seizures, and even cardiovascular collapse. Prevention of AWS has been shown to improve morbidity and mortality and shorten hospital and ICU stays. We examined the efficacy of ethanol as a method of prophylaxis. STUDY DESIGN: Our patient population was divided into two groups. Group 1 consisted of surgical patients receiving alcohol prophylaxis for AWS between January 2001 and July 2004 (n=124), as identified by retrospective chart review. We then developed a protocol for the initiation, dosage, and weaning of intravenous ethanol in patients at risk for AWS, based on blood alcohol levels and clinical assessment of withdrawal symptoms and signs. Group 2 consisted of all patients treated prospectively with this protocol during the subsequent year (n=76). Patients who did not fit inclusion criteria for the protocol were excluded from analysis, resulting in 92 and 68 patients in group 1 and group 2, respectively. We compared initiation criteria, efficacy, dosage, route, duration, and referral pattern to the substance abuse clinic before and after initiation of the protocol. RESULTS: Our initial use of intravenous ethanol was very variable in dosage, duration, and indication. The protocol decreased the duration of treatment between the two groups from 7 days to a mean of 3 days. The failure rate dropped from 20% to 7%. Referral to the substance abuse clinic rose from 7.6% to 20%. The only complication was asymptomatic hyponatremia in one patient. CONCLUSIONS: Intravenous ethanol is a viable option for AWS prophylaxis when administered in a systematic protocol.

Adult↗

PubMed2005

Effectiveness of protocols for preventing occupational exposure to blood and body fluids in Dutch hospitals.

Compliance of different healthcare workers (HCWs) (nurses, physicians, laboratory technicians and cleaners) with protocols to prevent exposure to blood and body fluids (BBF) was studied. Questionnaires were used to assess perception of risks, familiarity with protocols, motivation and actual behaviour. Performance of the protocols in practice was also tested. The practical test provided more reliable results than the questionnaire. HCWs overestimated their knowledge and skills, and compliance was influenced by risk perception. HCWs encountered problems with comprehension, acceptability and applicability of protocols, especially for post-exposure precautions. Protocols are not tailored to the differences in knowledge, risk perception and practical needs of different professional groups, probably because HCWs have rarely been involved in writing them and they are governed more by legal considerations than applicability. Most HCWs experienced a lack of organizational support to aid compliance. To improve compliance, we recommend information and training on risk management and individual responsibilities regarding the safety of coworkers and patients, participation of HCWs in protocol development, and support of management to avoid reversion to previous habitual behaviour.

Accidents, Occupational↗

PubMed2006

Comparison of incremental and accelerating protocols of the rotarod test for the assessment of motor deficits in the 6-OHDA model.

The rotarod test, in which animals must balance on a rotating drum, is widely used to assess motor deficit in neurodegenerative disease models in rodents. Performance is measured by the duration that an animal stays on the rod as a function of drum speed. Two different protocols are widely used, incremental fixed speeds or an accelerating protocol, but there is little information on their equivalence or the relative power, reliability and sensitivity of the two protocols. The present study was undertaken to compare the incremental fixed-speed and accelerating rotarod protocols on two different lesions of the ascending forebrain dopamine pathways. Three groups of rats were used, controls, rats with 6-OHDA lesions of nigrostriatal bundle, and rats with terminal 6-OHDA lesions within the striatum. Rats were tested at different time points after the lesion. We report that whereas the incremental protocol is more sensitive to detect the presence of a lesion, the accelerating protocol provides a more discriminative test to correlate motor deficits against lesion size.

Acceleration↗

PubMed2005

Randomized prospective trial of early steroid withdrawal compared with low-dose steroids in renal transplant recipients using serial protocol biopsies to assess efficacy and safety.

BACKGROUND: Corticosteroid therapy after renal transplantation is associated with many adverse effects. Newer immunosuppressive agents may allow for safe and effective reductions in dose or early steroid withdrawal. METHODS: In this prospective, single-center clinical trial, 60 patients were randomized into 2 groups: control patients (n = 28), who received low doses of prednisone throughout, and study patients (n = 32), who were withdrawn from steroids 7 days posttransplant. Patients received a limited course of rabbit antilymphocyte globulin (rALG) induction therapy, tacrolimus (TAC), and mycophenolate mofetil (MMF). Patients were followed for clinical outcomes and renal function. Protocol biopsies were performed at 1, 6, and 12 months. RESULTS: Clinical rejections occurred in 11% of controls and 13% of study patients. Renal function was well maintained and equivalent in both groups. In all, 111 protocol biopsies were performed without complications. Subclinical rejection was noted in only 2 protocol biopsies, and borderline changes were seen in 12 biopsies, all of which were distributed equally between both groups. Unsuspected acute TAC toxicity was seen in 8 biopsies. Protocol biopsies led to changes in therapy in 10% of patients. In both groups, serial protocol biopsies demonstrated increased allograft fibrosis over time, which was significant at 1 year in the steroid withdrawal group. CONCLUSION: The immunosuppressive combination of rALG, TAC, and MMF prevents subclinical rejection and the need for high doses of steroids after transplantation. However, continual low-dose steroid therapy may aid in preventing chronic allograft fibrosis. Protocol biopsies help define the short-term and long-term risks of steroid withdrawal therapy.

Adult↗

PubMed2004

Estrus synchronization in beef heifers with progestin-based protocols. I. Differences in response based on pubertal status at the initiation of treatment.

Two progestin-based protocols for estrus synchronization in replacement beef heifers were compared on the basis of estrous response, interval to and synchrony of estrus, and pregnancy rate. The objective was to determine, whether addition of GnRH to a melengestrol acetate (MGA)-prostaglandin F2alpha (PGF2alpha) estrus synchronization protocol would improve synchrony of estrus without compromising fertility in yearling beef heifers. Heifers at two locations (Location 1, n = 60 and Location 2, n = 64) were assigned randomly to one of two treatments by breed and pubertal status. Heifers were defined as, pubertal when concentrations of progesterone in serum were elevated (> or = 1 ng/mL) in either one of two samples obtained 10 and 1 day prior to treatment initiation. Prior to MGA administration, 18/60 (30%) and 36/64 (56%) of the heifers at Locations 1 and 2, respectively, were pubertal. Heifers in both treatments were fed MGA (0.5 mg/head/day in 1.8 kg/head/day supplement) for 14 days followed by 25 mg of PGF2alpha i.m. (MGA-PGF2alpha) 19 days after MGA withdrawal (Day 33 of treatment). One-half of the heifers at each location received 100 microg of GnRH i.m. 12 days after MGA withdrawal (Day 26 of treatment; MGA Select). The control group received only MGA-PGF2alpha. Heifers were observed for signs of behavioral estrus continuously during daylight hours for 7 days beginning on the day PGF2alpha was administered. Heifers were inseminated 12 h after observed estrus. There was a treatment by location by pubertal status interaction (P < 0.05) for interval to estrus. Compared to the respective control treatment at each location, prepubertal heifers assigned to the MGA Select protocol at Location 1 had longer intervals to estrus, whereas at Location 2, prepubertal heifers assigned to the MGA-PGF2alpha protocol had longer intervals to estrus. The higher number of pubertal heifers at Location 2 was associated with a reduced variance in the interval to estrus among MGA Select treated heifers. Total estrous response and synchronized conception rates were similar between treatments at both locations. These data suggest that addition of GnRH to the MGA-PGF2alpha protocol may improve synchrony of estrus, however, the degree of synchrony may be influenced by pubertal status of heifers at the time treatments are imposed. Further studies are needed to define production systems in which the MGA Select protocol is warranted for use in beef heifers.

Animals↗

PubMed2005

Effect of presynchronization using prostaglandin F2alpha and a milk-ejection test on pregnancy rate after the timed artificial insemination protocol, Ovsynch.

The objective of this research was to determine if PGF2alpha-induced milk letdown (ML) is an accurate indicator of luteolysis, allowing cows to be synchronized to begin the Ovsynch protocol (GnRH-7d-PGF2alpha-2d-GnRH-24h-AI) at the most beneficial time of the estrous cycle (days 5-9), and determine if this would improve pregnancy rate (PR). Lactating Holstein cows between 55 and 70 days in milk were used to evaluate the ML test and PR after the Ovsynch protocol, when initiated on the basis of the test result (PROSYNCH). PROSYNCH cows (n = 60) had one teat cannulated to test for ML and were treated with 500 microg cloprostenol, PGF2alpha analogue (PG). Cows with ML were started on Ovsynch 10 days later, and those without started 3 days later. Cows in the control group (OVSYNCH, n = 64) were injected with physiological saline and observed for ML. This group was started on Ovsynch 10 days after saline treatment. Milk samples were collected thrice weekly to determine progesterone concentrations. ML indicated luteolysis with a sensitivity of 98% and a specificity of 60%. The positive and negative predictive values were 83 and 92%, respectively. Pregnancy rates were 48% for PROSYNCH and 52% for OVSYNCH (P = 0.72). When data from both groups were combined, PR was greater in cows that started the Ovsynch protocol in stage 2 of the estrous cycle (days 5-9, 67%) than all other stages (stage 1: days 1-4, 35%; stage 3: days 10-16, 45%; stage 4: days 17-21, 42%; P < 0.01). The proportion of animals with ovulation after GnRH#1, luteolysis after PGF2alpha, and ovulation after GnRH#2 were all greater in the PROSYNCH group (77% versus 55%, P < 0.02; 83% versus 66%, P < 0.03; 97% versus 84%, P < 0.03, respectively). Therefore, the ML test indicated luteolysis with sufficient precision to time the initiation of the Ovsynch protocol between days 5 and 9 of the cycle, however, this did not alter PR compared to starting the protocol randomly throughout the cycle. Initiating the Ovsynch protocol between days 5 and 9 of the cycle increased PR, and improved the efficacy of each injection.

Animals↗