RESUMEN
The objectives of the current study were to evaluate the efficacy and field safety of GnRH HCl administered at 3 doses in fixed-time artificial insemination (FTAI) programs (Ovsynch) in dairy cows. A common protocol was conducted at 6 commercial dairies. Between 188 and 195 cows were enrolled at each site (total enrolled = 1,142). Cows had body condition scores ≥ 2 and ≤ 4, were between 32 to 140 d in milk, and were clinically healthy. Within pen and enrollment day (enrollment cohort), cows were assigned randomly in blocks of 4 to each of 4 treatments: (1) 25mg of PGF2α on d 7 with FTAI 72 ± 2 h later (control); (2) 100 µg of GnRH on d 0, d 7 a dose of 25mg of PGF2α, and the second administration of 100 µg of GnRH (T100) administered either at 48 ± 2 h (d 9) after PGF2α with FTAI 24 ± 2 h later or 56 ± 2 h (d 9) after PGF2α and FTAI 17 ± 2 h later; (3) same as T100 with both injections of 150 µg of GnRH (T150); and (4) same as T100 with both injections of 200 µg of GnRH (T200). Three sites selected the first option and 3 sites selected the second option for the timing of the second injection of all doses of GnRH. Cows were observed daily for signs of estrus and adverse clinical signs. Cows not returning to estrus had pregnancy diagnosis between 42 and 65 d following FTAI. Pregnancies per FTAI (P/FTAI) were analyzed as a binary variable (1 = pregnant, 0 = not pregnant) using a generalized linear mixed model with a binomial error distribution and a logit link function. The statistical model included fixed effects for treatment, random effects of site, site by treatment, enrollment cohort within site, and residual. Parity (first vs. second or greater) was included as a covariate. For demonstration of effectiveness, α=0.05 and a 2-tailed test were used. Fifty-two cows were removed from the study because of either deviation from the protocol, injury, illness, culling, or death. Among the remaining 1,090 cows, 33.9% were primiparous and 66.1% were multiparous. Back-transformed least squares means for P/FTAI were 17.1, 27.3, 29.1, and 32.2% for control, T100, T150 and T200, respectively. The P/FTAI for each GnRH dose differed from that of the control. No differences were detected in P/FTAI between GnRH doses. No treatment-related adverse events were observed. Mastitis was the most frequently observed adverse clinical sign, followed by lameness and pneumonia. This study documents the efficacy and safety of doses of 100 to 200 µg of GnRH as the HCl salt when used in Ovsynch programs.
Asunto(s)
Bovinos/fisiología , Dinoprost/administración & dosificación , Hormona Liberadora de Gonadotropina/administración & dosificación , Inseminación Artificial/veterinaria , Animales , Estro , Sincronización del Estro , Femenino , Lactancia , Leche/metabolismo , Paridad , Embarazo , Distribución Aleatoria , Factores de TiempoRESUMEN
The objectives of this study were to evaluate efficacy of a 2-dose regimen of ceftiofur crystalline free acid sterile suspension (CCFA-SS) for treatment of acute metritis in lactating dairy cows under field conditions and to provide additional safety and injection site tolerance data for injections at the base of the ear. Cows at 15 dairies with rectal temperature ≥ 39.5°C and fetid uterine discharge ≤ 10 d postcalving were randomly assigned by blocks of 2, based on order of entry and without regard to parity, to treatment with saline (1.5 mL/45.5 kg of body weight, n=509) or CCFA-SS (6.6 mg of ceftiofur equivalents/kg of body weight, n=514). Treatments were administered by subcutaneous injection in the posterior aspect of the ear where it attaches to the head; the first dose was administered on study d 0 and the second dose was administered in the contra lateral ear on study d 3. Rectal temperatures were recorded on study d 1 to 4 and 5 or 6 and cows were clinically evaluated daily from study d 1 to 13. Cows that exhibited increased adverse clinical signs of poor health or complications associated with metritis were categorized as a treatment failure and administered escape therapy. Each cow received a veterinary physical examination on study d 5 or 6 to determine if she should be removed from the study and on study d 14 to determine clinical cure or failure to cure. Clinical cure was defined as rectal temperature <39.5°C and non-fetid and purulent or mucopurulent discharge on study d 14 and no escape therapy administered. The injection procedure was scored after each injection (study d 0 and 3) and injection sites and ear carriage were scored on study d 5 or 6, 14, and 57±3. Of the 1,023 cows enrolled, 7 were completely censored due to protocol deviations and 34 were removed for protocol deviations or medical conditions not related to metritis. Clinical cure rate was higher for CCFA-SS than for saline (74.3 vs. 55.3%) and rectal temperatures for each of study d 1 to 5 or 6 were lower for CCFA-SS than saline. Injection procedure indices showed that CCFA-SS could be practically and safely administered using commercial dairy facilities. Although injection site scores were higher for CCFA-SS than saline at study d 5 or 6 and 14, ≥98.6% of ears were normal on d 57±3. Thus, a 2-dose treatment with CCFA-SS given 72h apart increased metritis clinical cure rate and was well tolerated in dairy cows.
Asunto(s)
Antibacterianos/administración & dosificación , Enfermedades de los Bovinos/tratamiento farmacológico , Enfermedades de los Bovinos/microbiología , Cefalosporinas/administración & dosificación , Endometritis/veterinaria , Animales , Temperatura Corporal , Bovinos , Endometritis/tratamiento farmacológico , Endometritis/microbiología , Femenino , Inyecciones Subcutáneas/veterinaria , LactanciaRESUMEN
A synthetic gonadotropin-releasing hormone (GnRH) agonist (fertirelin acetate, FA) was administered to beef cattle within 12 h after onset of estrus (Day = 0) to study effects on subsequent endocrine responses and fertility. In Study 1, 16 crossbred beef heifers were injected with either 100 mug FA (n = 8) or saline (n = 8) at 6 or 12 h (n = 7; n = 9) after onset of estrus. Concentrations of luteinizing hormone (LH) over time were affected (P<0.01) by the interaction of treatment and interval from onset of estrus to treatment. Heifers treated with FA at 6 h after onset of estrus exhibited the greatest increase in LH after treatment. There was no effect of treatment, interval from onset of estrus to treatment or treatment by interval interaction on duration of the estrous cycle, on concentrations of progesterone from Days 1 through 14 posttreatment, or on concentrations of progesterone prior to subsequent estrus (Day -10 through 0, posttreatment estrus). In summary, FA administered to beef cattle within 12 h after onset of estrus effectively increased peripheral plasma concentration of LH, but this increase had no effect on subsequent luteal function as measured by duration of the estrous cycle or concentrations of plasma progesterone. In Study 2, 86 parous beef cows were bred artificially to one of two bulls following natural or prostaglandin F(2)alpha induced estrus. Cows received either no treatment or 50 or 100 mug FA at the time of AI. There was no effect of treatment, breed, parity, technician, service sire or interactions on conception rate (mean = 76.7%). Although not significant, the numerical pattern of conception rate among experimental groups (control = 71.4%, 50 mug FA = 76.7%, 100 mug FA = 82.1%) supports further investigation of this GnRH agonist with larger numbers of cattle.
RESUMEN
This study was conducted to describe the changes in serum LH and FSH concentrations in Holstein heifers following intramuscular (i.m.) injection of various dosages of fertirelin acetate and other commercially available GnRH products at their labeled dosages. The design was an incomplete Latin-square which gave nine replicates of each treatment. Treatments administered on Days 8 to 16 of the estrous cycle consisted of saline; 25, 50, 100 or 200 microg fertirelin acetate; 100, 250 or 500 microg gonadorelin; and 10 or 20 microg buserelin. Blood samples were collected via jugular catheters from 1 h before to 8 h after each injection. Log (Base 2) area under the LH and FSH curves (log AUC) were used to evaluate response to fertirelin acetate dosages and to determine difference (LSD: 0.05) and bioequivalence (alpha = 0.05) between the various dosages of GnRH products tested. Significant quadratic dose response relationships were detected for the LH and FSH log AUC data. Plots of the LH log AUC but not the FSH log AUC data suggested that a response plateau was being approached at the higher dosages of fertirelin acetate. Bioequivalence (alpha = 0.05) was based on the assumption that two means are equivalent if they differ by no more than 20% of the reference log AUC mean. Using these criteria fertirelin acetate is 2.5 to 10 times more potent than gonadorelin, whereas buserelin is approximately 10 to 20 times more potent than fertirelin acetate in the bovine for LH and FSH release.
RESUMEN
Day 13 to 24 bovine conceptuses convert C-19 and C-21 neutral steroids to 5 beta-reduced steroids with great efficiency. Pregnancy steroids have been reported to be immunomodulatory in several species. This study examined the possibility that 5 beta-reduced products of bovine conceptus steroid metabolism, precursors, related steroids, progesterone or cortisol might affect bovine T-cell blastogenesis. The steroids tested were 5 alpha-androstan-17 beta-ol-3-one, androstene-3, 17-dione, 5 beta-pregnane-3,20-dione and 5 beta-pregnane-3 alpha,20 alpha-diol. The ability of each steroid, over a dose range of 10(-2) to 10(4) nM, to affect phytohemagglutinin (PHA)-induced or concanavalin A (Con A)-induced bovine T cell blastogenesis, or the mixed lymphocyte reaction (MLR) was evaluated. Five lactating Holstein cows served as lymphocyte donors for mitogen studies and two, that exhibited strong MLR, were donors for the MLR evaluation. Of the seven steroids tested none affected blastogenesis in a dose-related manner except for cortisol, which suppressed Con A-induced lymphocyte transformation as well as the MLR. Cortisol did not affect PHA-induced blastogenesis. Thus, of the pregnancy steroids tested at the concentrations noted, none had significant immunomodulatory effects.
Asunto(s)
Activación de Linfocitos/efectos de los fármacos , Esteroides/farmacología , Linfocitos T/inmunología , Androstenodiona/farmacología , Animales , Bovinos , Dihidrotestosterona/farmacología , Femenino , Hidrocortisona/farmacología , Prueba de Cultivo Mixto de Linfocitos , Pregnanodiol/farmacología , Pregnanodionas/farmacología , Progesterona/farmacología , Linfocitos T/efectos de los fármacosRESUMEN
One hundred and two nonparous females, 18 to 24 mo old, and 55 parous or multiparous beef females, 3 to 12 yr old, were mated naturally (d 0) and slaughtered on d 2 to 5, 6 to 8 or 14 to 16 of gestation. Each reproductive tract was flushed with phosphate-buffered saline, and the flushings were searched for an oocyte or embryo. Parous females had a higher (P less than .05) fertilization rate than nonparous females. In nonparous females, reproductive failure was attributed equally to fertilization failure and embryonic mortality, which had occurred or was occurring by d 8 of gestation. In parous females, reproductive failure was attributed entirely to embryonic death. About 67% of this embryonic mortality had occurred or was occurring by d 8 of gestation; the other 33% occurred between d 8 and 16 of gestation. These findings show that in both nonparous and parous beef females, a large portion of the reproductive failure occurs by d 8 of gestation and would not have any noticeable influence on length of the estrous cycle.
Asunto(s)
Blastocisto , Bovinos/fisiología , Fertilidad , Fertilización , Paridad , Animales , Femenino , EmbarazoRESUMEN
Beef (n = 783) and dairy (n = 209) heifers at 14 locations were used to evaluate the efficacy of feeding melengestrol acetate (MGA; .5 mg/d) for 7 d followed by an i.m. injection of 25 mg prostaglandin F2 alpha (PGF) on the last day of MGA feeding (MGA + PGF) to synchronize estrus. Untreated heifers (C) and heifers injected once i.m. with PGF served as contemporary controls. Heifers were observed for estrual behavior for a minimum of 38 d starting on the 2nd d of MGA feeding. Heifers in estrus from d 1 through d 60 after PGF injection were artificially inseminated (AI) or bred to bulls (d 30 to 60 post PGF only). During the 7-d MGA feeding period fewer (P less than .01) MGA + PGF (1.5%) than C (20.6%) or PGF (18.1%) heifers were observed in estrus. Percent of heifers in estrus d 1 to 6 post PGF was different among groups (P less than .05; 30.5, 52.8, 72.3 for C, PGF and MGA + PGF, respectively). More (P less than .01) MGA-fed (92%) than non-MGA-fed (C and PGF combined) heifers (85.4%) were observed in estrus during d 1 to 24. Conception rate (CR) during d 1 to d 6 was not different (P = .19) between C (58.9%) and MGA + PGF (51.2%) heifers; CR was lower (P = .01) for MGA + PGF than for PGF (68.3%) heifers.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Bovinos/fisiología , Dinoprost/farmacología , Sincronización del Estro/efectos de los fármacos , Acetato de Melengestrol/farmacología , Pregnadienos/farmacología , Análisis de Varianza , Animales , Interacciones Farmacológicas , Estro/efectos de los fármacos , Femenino , Fertilización , Distribución AleatoriaRESUMEN
Beef cows and heifers (n = 263) at three locations that were exhibiting estrous cycle either were fed .5 mg/d melengestrol acetate (MGA) for 7 d and administered prostaglandin F2 alpha (25 mg, i.m.) on the last day of MGA feeding or were untreated. State of the estrous cycle at the beginning of the experiment was determined based on estrous detection and (or) progesterone concentrations in pretreatment blood samples. Estrous was checked twice daily for 30 d posttreatment. Animals were artificially inseminated approximately 12 h after detection of estrus. A synchronized estrus (less than 7 d posttreatment) was detected in 72% of the treated animals. More animals in the treated group became pregnant during the first 7 d of breeding, but their conception rate was lower than that of animals in the control group (P less than .05). Conception rate (36%) was reduced among treated animals when MGA feeding began late (d 14 to 20) in the estrous cycle. Conversely, the conception rate (66%) of treated animals fed MGA beginning earlier in the cycle was not different from that of control animals (73%; treatment x stage of cycle; P less than .05).
Asunto(s)
Bovinos/fisiología , Sincronización del Estro/efectos de los fármacos , Acetato de Melengestrol/farmacología , Pregnadienos/farmacología , Preñez/efectos de los fármacos , Prostaglandinas F/farmacología , Animales , Dinoprost , Femenino , EmbarazoRESUMEN
Plasma progesterone (P4) profile and estrous detection were used during three experiments to evaluate the effects of exogenous progestogens on the life span of gonadotropin releasing hormone (GnRH)-induced corpora lutea (CL) in postpartum (pp) beef cows. Experiment 1 utilized primiparous fall-calving cows (n = 28, trial 1); and spring-calving cows (n = 29, trial 2). On d 18 to 27 pp (d 0) all cows received intravaginal devices containing either P4 or no P4 (NP) for 5 d. On d 5 the devices were removed and calves were either removed (CR) or were present (CP) with half of the cows within steroid group. At 50 h after device removal, 500 micrograms of GnRH was given (iv) to all cows, and weaned calves were reunited with their dams. The induced CL had a normal life span (greater than 16 d) in 17 and 86% (trial 1) and 8 and 79% (trial 2) of NP and P4 cows, respectively. Calf removal did not affect (P greater than .10) the life span of the CL. In Exp. 2, spring-calving multiparous cows (d 18 to 24 pp; d 0) received either no P4 (NP; n = 19), P4 for 6 d via intravaginal devices (P4H; n = 19) or a single im injection of 300 mg P4 (P4 IM; n = 18). At 48 h after device removal or at 8 d after the injection of P4, half of the cows within steroid group received either 500 micrograms GnRH or saline. Corpora lutea had a normal life span in 0, 11, and 80% of NP, P4 IM and P4H cows, respectively, that received GnRH and in 22% of P4-saline cows. In Exp. 3, fall-calving multiparous and primiparous cows (d 25 to 31 pp) received either no progestogen (NP; n = 20), P4 via intravaginal devices for 5 d (P4H; n = 21) or melengestrol acetate (MGA; .5 mg.head-1.d-1 for 5 d orally, n = 15). At 48 d after device removal or at 72 h after the last MGA feeding, all cows received 500 micrograms GnRH. Progesterone post-GnRH injection was increased (greater than 1 ng/ml) at d 7 in 64, 100 and 100%, and remained elevated at d 14 in 11, 46 and 100% of NP, MGA and P4H cows, respectively. For all experiments plasma P4 was increased (range 2 to 5 ng/ml) when the devices containing P4 were in place, then decreased (less than 1 ng/ml) by 48 to 50 h after device removal.(ABSTRACT TRUNCATED AT 400 WORDS)
Asunto(s)
Bovinos/fisiología , Cuerpo Lúteo/efectos de los fármacos , Gonadotropinas Hipofisarias/fisiología , Hormonas Liberadoras de Hormona Hipofisaria/farmacología , Periodo Posparto/fisiología , Progesterona/farmacología , Animales , Femenino , Periodo Posparto/sangre , Embarazo , Progesterona/sangreRESUMEN
Corpora lutea were collected from 18 beef heifers on day 4 or 12 of the estrous cycle, 1 hour after prostaglandin (PG) F2 alpha or saline (control) treatment. Five heifers also were treated with PGF2 alpha on day 4, but their corpora lutea were not collected until day 12. The relative percentage of cytoplasm occupied by granules decreased only in large luteal cells (LLC) in heifers given PGF2 alpha on day 12, compared with the percentage in controls. Small luteal cells (SLC) were not as affected. The luteal concentration of progesterone was similarly decreased only in heifers given PGF2 alpha on day 12. Treatment of heifers with PGF2 alpha on day 4 had no marked effect on progesterone values or on the relative percentage of cytoplasm occupied by granules in LLC or SLC. Seemingly, LLC were more responsive to PGF2 alpha than were SLC, and PGF2 alpha treatment of beef heifers at day 4 did not markedly impair luteal function.
Asunto(s)
Bovinos/fisiología , Cuerpo Lúteo/efectos de los fármacos , Estro/efectos de los fármacos , Células Lúteas/efectos de los fármacos , Prostaglandinas F/farmacología , Animales , Dinoprost , Femenino , Células Lúteas/análisis , Células Lúteas/ultraestructura , Luteólisis/efectos de los fármacos , Microscopía Electrónica , Progesterona/análisis , Progesterona/sangre , Distribución AleatoriaAsunto(s)
Luteólisis , Ovario/irrigación sanguínea , Ovinos/fisiología , Útero/irrigación sanguínea , Animales , Colesterol/metabolismo , Implantes de Medicamentos , Estradiol/metabolismo , Estro , Femenino , Metiltirosinas/metabolismo , Microesferas , Tamaño de los Órganos , Embarazo , Progesterona/sangre , Radioinmunoensayo , Flujo Sanguíneo Regional , Elastómeros de Silicona , Radioisótopos de Estroncio , Útero/fisiologíaAsunto(s)
Bovinos/fisiología , Fertilidad/efectos de los fármacos , Prostaglandinas/administración & dosificación , Animales , Cuerpo Lúteo/anatomía & histología , Estro , Femenino , Inyecciones Intramusculares , Inyecciones Subcutáneas , Inseminación Artificial , Palpación , Embarazo , Prostaglandinas/farmacologíaRESUMEN
The objective of this study was to determine if fertirelin acetate and buserelin, two GnRH agonists, improve conception rate when administered at the time of first or second AI in lactating dairy cows. The study consisted of a common protocol conducted at 10 commercial dairy farms. Approximately 150 cows within each dairy were assigned randomly in replicates to receive intramuscularly either no injection or injection of 25, 50, 75, or 100 micrograms fertirelin acetate or 10 micrograms buserelin immediately after AI. Cows were subjected to the reproductive management practices normal for each location. Cows at each location were palpated for pregnancy status at 35 to 60 d postinjection. No improvement in conception rate was detected in response to either agonist (control = 48%, fertirelin acetate = 41.5%, buserelin = 39.7%). Conception rate was unaffected by either days postpartum at injection or overall fertility of the individual herds. These observations do not support the routine use of doses of 25 to 100 micrograms fertirelin acetate or 10 micrograms buserelin at the time of first or second AI as a means to improve conception rate in lactating dairy cows.
Asunto(s)
Buserelina/farmacología , Bovinos/fisiología , Fertilización/efectos de los fármacos , Hormona Liberadora de Gonadotropina/análogos & derivados , Inseminación Artificial/veterinaria , Análisis de Varianza , Animales , Sesgo , Relación Dosis-Respuesta a Droga , Femenino , Hormona Liberadora de Gonadotropina/farmacología , Hormonas/farmacología , Lactancia , Embarazo , Distribución AleatoriaRESUMEN
Prostaglandin F2alpha caused rapid regression of the corpus luteum and initiated normal transitory hormonal patterns that culiminated in ovulation. PGF2alpha was effective in heat stressed heifers and a thermal stress of 32 C caused no major hormonal alterations from the time of CL regression to ovulation. A luteolytic dose of PGF2alpha tham salt (33.5 mg) given intramuscularly caused no major alterations in blood pressure, heart rate, and uterine or aortic blood temperatures. However, the same dose given as an intravenous jugular infusion over a 2 min period caused major alterations in circulatory homeostasis and body temperature. Treatment of all cattle twice with PGF2alpha tham salt (33.5 mg), 12 days apart, increased the number of responsive heifers at the second PGF2alpha injection. Synchronization of ovulation after the second injection is apparently precise enough to allow for a single timed insemination. Blood injection of estradiol benzoate and GnRH after PGF2alpha treatment will synchronize occurrence of estrus and the preovulatory surge of LH, respectively. However, GnRH treatment at 48 h lowers the frequency of PGF2alpha induced heats and this may be due to alterations in plasma progestins and estradiol.
Asunto(s)
Bovinos/fisiología , Prostaglandinas F/farmacología , Reproducción/efectos de los fármacos , Animales , Sangre , Presión Sanguínea/efectos de los fármacos , Temperatura Corporal , Ambiente Controlado , Estradiol/sangre , Estradiol/farmacología , Estro/efectos de los fármacos , Femenino , Hormona Liberadora de Gonadotropina/farmacología , Frecuencia Cardíaca/efectos de los fármacos , Calor , Inseminación , Hormona Luteinizante/sangre , Ovulación/efectos de los fármacos , Embarazo , Progestinas/sangre , Estrés Fisiológico , Factores de Tiempo , Útero/efectos de los fármacos , Útero/fisiologíaRESUMEN
Total ovarian blood flow of cows (sum of flows through the ovarian artery and uterine branch of the ovarian artery), measured by electromagnetic flow probes, followed a consistent cyclic pattern, being highest from Day 10 of the oestrous cycle (oestrus = Day 0) until 4 days before the subsequent oestrus. During this period of high ovarian blood flow, blood of uterine origin flowed to the ovary through the uterine branch of the ovarian artery and was found to comprise 20-40% of the ovarian blood flow. Between Days -4 and -3, ovarian blood flow dropped (P less than 0.01) from 3.2 +/- 0.5 to 1.0 +/- 0.4 ml/min, coincident with a reversal of flow through this anastomosis. Uterine arterial blood flow was highest (P less than 0.05) from 1 day before oestrous to the day of oestrus when compared to the remaining days of the oestrous cycle. Throughout the oestrous cycle, ovarian blood flow was positively correlated with systemic concentrations of progesterone (r = 0.55, P less than 0.01) and negatively correlated with systemic concentrations of oestradiol-17 beta (r = -0.42, P less than 0.01). In contrast, uterine arterial blood flow was negatively correlated with systemic progesterone (r = -0.25, P less than 0.05) and positively correlated with systemic oestradiol (r = 0.45, P less than 0.05). These data provide direct evidence in the cow that a portion of the blood flowing to the ovary containing a fully functional corpus luteum is contributed by the ipsilateral uterine artery.
Asunto(s)
Bovinos/fisiología , Estro , Ovario/irrigación sanguínea , Preñez , Útero/irrigación sanguínea , Animales , Bovinos/anatomía & histología , Estradiol/sangre , Femenino , Embarazo , Progesterona/sangre , Flujo Sanguíneo RegionalRESUMEN
Blood flow to each uterine horn of cows during the oestrous cycle and early pregnancy was determined daily by use of electromagnetic blood flow probes placed around both middle uterine arteries. The pattern of blood flow to uteri of pregnant and non-pregnant cows was similar until Day 14 after mating or oestrus. Between Days 14 and 18 of pregnancy blood flow to the uterine horn containing the conceptus increased (P less than 0.01) 2- to 3-fold, whereas blood flow to the non-gravid uterine horn in these cows remained constant. No corresponding increase in blood flow to the uterine horn ipsilateral to the ovary bearing the CL was observed in non-pregnant cows during this 4-day period. By Day 19 of pregnancy, blood flow to the gravid uterine horn had returned to a level similar to that observed on Day 13. Blood flow to both uterine horns of pregnant cows remained constant from Days 19 to 25 and then increased to the gravid horn (P less than 0.01) markedly until Day 30 whereas blood flow to the non-gravid horn remained low. Uterine blood flow during the oestrous cycle of non-pregnant cows was positively correlated (P less than 0.01) with systemic concentrations of oestradiol and the ratio of oestradiol (pg/ml) to progesterone (ng/ml). There was no association between oestradiol concentrations and blood flow to the gravid uterine horn. These data indicate local control of uterine blood flow by the bovine conceptus which may function to create optimal conditions for the continuation of pregnancy.
Asunto(s)
Bovinos/fisiología , Estro , Feto/fisiología , Preñez , Útero/irrigación sanguínea , Animales , Velocidad del Flujo Sanguíneo/métodos , Velocidad del Flujo Sanguíneo/veterinaria , Bovinos/embriología , Fenómenos Electromagnéticos , Estradiol/sangre , Femenino , Embarazo , Progesterona/sangre , Flujo Sanguíneo RegionalRESUMEN
Vaginal thermal conductance was measured in 12 heifers and 7 cows with a gradient layer heat flow probe. Values rose for 4 to 5 days prior to day of behavioral estrus (day 0), with a peak on days --2 and --1, and then declined from day 0 to +5. Curves for heifers were higher than those for cows although there was no evidence that they were not parallel. Changes during the cycle appear to result from estrogen-induced alterations in blood flow rate in vaginal tissues.
Asunto(s)
Bovinos/fisiología , Estro , Vagina/irrigación sanguínea , Factores de Edad , Animales , Circulación Sanguínea , Velocidad del Flujo Sanguíneo , Estrógenos/fisiología , Femenino , Hiperemia , Embarazo , Conductividad Térmica , Vagina/fisiologíaRESUMEN
Progestins, estradiol, and luteinizing hormone were measured by radioimmunoassay in bovine plasma samples collected from indwelling jugular catheters daily on days minus 6 to minus 4, every 6 h on days minus 3 and minus 2, and every 2 h from day minus 1 to ovulation. Least squares analyses characterized time trends within animals and interrelationships between these hormones. Plasma progestins decreased from 5.7 ng/ml at day minus 6 to .07 ng at the peak of luteinizing hormone. No preovulatory peripheral increase in plasma progestins was detected. Estradiol increased from 2 pg/ml at day minus 4 to 6 pg at minus 12 h and then increased abruptly to 7.4 pg at the peak of luteinizing hormone. This matter increase in estradiol was synchronous with the acute preovulatory surge of luteinizing hormone. Association was positive between estradiol and luteinizing hormone, but negative between progestins and estradiol. Estradiol decreased 50% by 5 h following the peak of luteinizing hormone with a return to base (2 pg) at 14 h. An increase of .1 ng luteinizing hormone/ml plasma per day was linear from day minus 6 to 8 h prior to the luteinizing hormone peak. Luteinizing hormone increased to a peak of 13.5 ng/ml and remained elevated for 10.5 h. These results are consistent with the hypothesis that an increase at proestrus in estradiol rather than progestins triggers the preovulatory surge of luteinizing hormone in the bovine.
Asunto(s)
Bovinos/fisiología , Estradiol/sangre , Hormona Luteinizante/sangre , Ovulación , Progestinas/sangre , Animales , Cateterismo , Estro , Femenino , Venas Yugulares , Detección de la Ovulación , Embarazo , Factores de TiempoRESUMEN
Milk from pregnant cows contains concentrations of progesterone (P4) considered safe for human consumption. The objective of this study was to determine if concentrations of P4 in milk during administration of an intravaginal progesterone insert (CIDR insert) are less than concentrations of P4 in milk associated with pregnancy. Results have implications for human use of milk from cows receiving CIDR inserts. Holstein cows (N = 64; > 40 and < 150 d after calving) were administered 25 mg of PGF2alpha i.m. (study d 0) and 20 cows detected in estrus from 2 to 4 d later were assigned randomly to either control (N = 10; no further treatment) or CIDR insert (N = 10; 1.38 g of P4) inserted on study d 17 (14 +/- 1 d after estrus) and removed 7 d later. Composite milk samples were collected contemporaneously from each of the 20 estrous cycling cows and from 10 pregnant cows (> or = 60 and < or = 220 d of gestation) twice daily from study d 17 to 27. Concentrations of P4 in defatted milk samples were quantified using a validated radioimmunoassay. Mean logs of areas under the curve of concentrations of P4 from the afternoon on study d 17 through the afternoon on study d 27 were 3.05 ng day/ml for control, 3.33 ng day/ml for CIDR insert, and 3.81 ng day/ml for pregnant cows. Therefore, increased P4 due to pregnancy was 0.76 ng day/ml (3.81-3.05), whereas the increase in P4 due to CIDR insert was only 0.28 ng day/ml (3.33-3.05). Applying a 95% confidence interval to 0.28 ng day/ml provided an upper value of 0.70 ng day/ml, lower than the increase due to pregnancy. Because milk from pregnant cows is considered safe for human consumption, it follows that milk from cows administered CIDR inserts should also be considered safe, based on concentrations of P4.
Asunto(s)
Bovinos/metabolismo , Leche/química , Progesterona/administración & dosificación , Progesterona/análisis , Administración Intravaginal , Animales , Dinoprost/administración & dosificación , Ciclo Estral , Femenino , Cinética , Embarazo , Seguridad , Factores de TiempoRESUMEN
An intravaginal progesterone insert (CIDR insert; 1.38 g of progesterone) was evaluated for synchronization of returns to estrus (SR), conception rate (CR), and pregnancy rate (PR) in dairy cows previously artificially inseminated (AI). Healthy, nonpregnant, lactating Holstein cows, > or = 40 and < or = 150 d postpartum at eight commercial farms were used. Cows detected in estrus and receiving AI 2, 3, or 4 d after one injection of PGF2alpha (25 mg) were assigned as either controls (n = 945), or to receive a CIDR insert (n = 948) for 7 d (14 to 21 +/- 1 d after AI). Cows were observed for returns to estrus from 18 to 26 +/- 1 d after initial AI (resynchrony period) and were reinseminated if in estrus. Vaginal mucus on CIDR inserts (97.3% retention) at removal was scored: 1 = no mucus; 2 = clear; 3 = cloudy; 4 = yellow; and 5 = red or brown. Percentage of cows in estrus (SR) during the 3 d after CIDR insert removal was contrasted to the highest 3-d cumulative percentage in estrus for controls. Cows conceiving to initial AI were omitted in calculations of SR, CR, and PR during resynchrony. Mucous scores of 3 or 4 (mild irritation) were observed in 65% of cows and a score of 5 (more severe irritation) was observed in 2%; otherwise, health was unaffected. The PR to initial AI was lower for cows subsequently receiving CIDR inserts than for controls (32.7 vs. 36.7%). The CIDR insert increased SR (34.1 vs. 19.3% in 3 d) and overall estrus detection (43% in 4 d vs. 36% in 9 d) compared with controls. For the 9-d resynchrony period, CR and PR for CIDR-treated (26.7, 12.2%) and control (30.9, 11.1%) cows did not differ significantly. The CIDR inserts improved synchrony of returns to estrus, slightly reduced PR to initial AI, but did not affect CR or PR to AI during the resynchrony period.