RESUMEN
Based upon observations across a series of experiments that pregnancy rate to timed-AI was positively related to length of proestrus, the traditional 7-day CO-Synch + CIDR program was modified to allow an increased interval from PGF/CIDR removal to GnRH/timed-AI; resulting in the 5-day CO-Synch + CIDR program. This modification has been demonstrated to increase timed-AI pregnancy rates relative to the traditional approach. The impact of this modification on preovulatory estradiol concentrations, as a result of extending the period of gonadotropic stimulus provided to the follicle, initiation of proestrus at a time when ovulatory follicles are highly estrogenic and/or through reduction in the incidence of ovulation of very young follicles, are potential mechanisms for increased estradiol concentrations and enhanced fertility. Conversely, for females in these estrous control programs in which follicular growth is adequately controlled, differences in age of the ovulatory follicle may not be a significant contributor to variation in timed-AI pregnancy rate.
Asunto(s)
Femenino , Animales , Bovinos , Bovinos/fisiología , Hormona Liberadora de Gonadotropina , Inseminación Artificial/métodos , Inseminación Artificial/veterinariaRESUMEN
Based upon observations across a series of experiments that pregnancy rate to timed-AI was positively related to length of proestrus, the traditional 7-day CO-Synch + CIDR program was modified to allow an increased interval from PGF/CIDR removal to GnRH/timed-AI; resulting in the 5-day CO-Synch + CIDR program. This modification has been demonstrated to increase timed-AI pregnancy rates relative to the traditional approach. The impact of this modification on preovulatory estradiol concentrations, as a result of extending the period of gonadotropic stimulus provided to the follicle, initiation of proestrus at a time when ovulatory follicles are highly estrogenic and/or through reduction in the incidence of ovulation of very young follicles, are potential mechanisms for increased estradiol concentrations and enhanced fertility. Conversely, for females in these estrous control programs in which follicular growth is adequately controlled, differences in age of the ovulatory follicle may not be a significant contributor to variation in timed-AI pregnancy rate.(AU)
Asunto(s)
Animales , Femenino , Bovinos , Inseminación Artificial/métodos , Inseminación Artificial/veterinaria , Bovinos/fisiología , Hormona Liberadora de GonadotropinaRESUMEN
Prepubertal Bos indicus heifers (n = 774) were submitted to an E2/P4-based timed artificial insemination (TAI) protocol at three different intervals after induction of their pubertal ovulation by insertion of an intravaginal progesterone (P4) device for 12 days. Heifers were randomly assigned to start the TAI protocol at 10 (group 10; n = 253), 12 (group 12; n = 265), or 14 (group 14; n = 256) days after the P4 device was removed. The TAI protocol consisted of the following: insertion of intravaginal device containing P4 (Controlled internal drug release [CIDR]; previously used twice for 9 days each) + estradiol benzoate (2 mg) on Day 0, CIDR withdrawal + estradiol cypionate (0.5 mg) and PGF2α (12.5 mg) on Day 9, and TAI on Day 11. A subgroup of heifers (n = 472) was evaluated by ultrasound on Days 9 and 11 to evaluate the ovaries and to determine P4 concentrations on Day 9. On Day 9, more (P < 0.05) CLs were present, and follicular diameter was smaller (P < 0.05) for group 10 than for groups 12 and 14 (38.4%, 29.3%, and 23.3% with CL and 9.4 ± 0.1, 9.9 ± 0.1, and 9.8 ± 0.1 mm diameter, respectively), but P4 concentrations did not differ (P > 0.1) between treatments (2.4 ± 0.06 ng/mL). Follicular diameter at TAI (11.08 ± 0.09 mm) and ovulation rate (88.4%) did not differ between treatments (P > 0.1). However, conception and pregnancy rates for all heifers were greater (P < 0.05) in group 12 (50.4% and 45.5%, respectively) than in group 10 (38.2% and 33.7%, respectively), with group 14 intermediate to other treatments (45.6% and 40.6%, respectively). The final pregnancy rate did not differ between treatments (80.9%). In conclusion, a 12-day interval from the end of the puberty induction protocol to the start of the TAI protocol resulted in greater conception and pregnancy rates in prepubertal Nellore heifers.
Asunto(s)
Bovinos/fisiología , Inseminación Artificial/veterinaria , Maduración Sexual/efectos de los fármacos , Animales , Dinoprost/administración & dosificación , Dinoprost/farmacología , Estradiol/administración & dosificación , Estradiol/análogos & derivados , Estradiol/farmacología , Femenino , Fármacos para la Fertilidad/administración & dosificación , Fármacos para la Fertilidad/farmacología , Inseminación Artificial/métodos , Folículo Ovárico/efectos de los fármacos , Folículo Ovárico/fisiología , Ovulación/efectos de los fármacos , Ovulación/fisiología , Embarazo , Índice de Embarazo , Progesterona/administración & dosificación , Progesterona/farmacología , Resultado del TratamientoRESUMEN
Two experiments were designed to evaluate the effects of treatments with low versus high serum progesterone (P4) concentrations on factors associated with pregnancy success in postpubertal Nellore heifers submitted to either conventional or fixed timed artificial insemination (FTAI). Heifers were synchronized with a new controlled internal drug release device (CIDR; 1.9 g of P4 [CIDR1]) or a CIDR previously used for 18 days (CIDR3) plus 2 mg of estradiol (E2) benzoate on Day 0 and 12.5 mg of prostaglandin F2α on Day 7. In experiment 1 (n = 723), CIDR were removed on Day 7 or 9 and heifers were inseminated after estrus detection. In experiment 2 (n = 1083), CIDR were all removed on Day 9 and FTAI was performed either 48 hours later in heifers that received E2 cypionate (ECP) on Day 9 (0.5 mg; E48) or 54 or 72 hours later in conjunction with administration of GnRH (100 µg; G54 or G72). Synchronization with CIDR1 resulted in greater serum P4 concentrations and smaller follicle diameters on Days 7 and 9 in both experiments. In experiment 1, treatment with CIDR for 9 days decreased the interval from CIDR removal to estrus (Day 7, 3.76 ± 0.08 days vs. Day 9, 2.90 ± 0.07; P < 0.01) and improved conception (Day 7, 57.1% vs. Day 9, 65.8%; P = 0.05) and pregnancy rates (Day 7, 37.6% vs. Day 9, 45.3%; P = 0.04). In experiment 2, treatment with ECP improved (P < 0.01) the proportion of heifers in estrus (E48, 40.9%(a); G54, 17.1%(c); and G72, 32.0%(b)), but the pregnancy rate was not affected (P = 0.64) by treatments (E48, 38.8%; G54, 35.5%; G72, 37.5%). Synchronization with CIDR3 increased follicle diameter at FTAI (CIDR1, 11.07 ± 0.10 vs. CIDR3, 11.61 ± 0.10 mm; P < 0.01), ovulation rate (CIDR1, 82.8% vs. CIDR3, 88.0%; P < 0.01) and did not affect conception (CIDR1, 42.2 vs. CIDR3, 45.1%; P = 0.38) or pregnancy rates (CIDR1, 34.7 vs. CIDR3, 39.4%; P = 0.11). In conclusion, length of treatment with P4 affected the fertility of heifers bred based on estrus detection. When the heifers were submitted to FTAI protocol, follicle diameter at FTAI (≤10.7 mm, 23.6%; 10.8-15.7 mm, 51.5%; ≥15.8 mm, 30.0%; P < 0.01) was the main factor that affected conception and pregnancy rates.
Asunto(s)
Bovinos/fisiología , Inseminación Artificial/veterinaria , Progesterona/sangre , Animales , Constitución Corporal , Dinoprost/uso terapéutico , Estradiol/análogos & derivados , Estradiol/uso terapéutico , Sincronización del Estro/métodos , Femenino , Hormona Liberadora de Gonadotropina/uso terapéutico , Inseminación Artificial/métodos , Embarazo , Índice de Embarazo , Maduración SexualRESUMEN
Four experiments were conducted to evaluate hormonal strategies to induce ovulation in Nellore heifers. In experiment 1, heifers (N = 1039) received a controlled internal drug release (CIDR) of fourth use (CIDR-4) on Day -12 or no CIDR (CIDR-0). The CIDR was removed on Day 0 in the CIDR-4 treatment, and estrus detection and AI were performed from Days 1 to 7. On Day 8, heifers not detected in estrus were evaluated for CL presence and received the same treatment again, followed by estrus detection and AI from Days 21 to 27. All heifers in experiments 2 (N = 896), 3 (N = 839), and 4 (N = 948) received the CIDR-4 treatment on Day -12. In experiment 2, heifers were randomly assigned to a control group (no additional treatment) or to receive equine chorionic gonadotropin (eCG; 200 IU eCG im) on Day 0. In experiment 3, heifers received the same treatments as in experiment 2, or a treatment that included eCG and estradiol cypionate (ECP) (eCG+ECP; 200 IU im eCG plus 0.5 mg ECP im) on Day 0. In experiment 4, heifers received the treatments described in experiment 3 or only ECP (0.5 mg) on Day 0. In experiments 2 and 3, estrus detection and AI was performed from Days 1 to 7 and on Day 8, heifers not detected in estrus were evaluated for CL presence. In experiment 4, heifers were evaluated for presence of a CL between Days 10 and 14. In experiment 1 heifers treated with CIDR-4 had greater estrus detection, ovulation induction, and pregnancy rates than in the CIDR-0 group. In experiment 2, heifers treated with eCG had greater estrus detection, ovulation induction, and pregnancy rates in 7 days than heifers in the control group. In experiment 3, heifers treated with eCG+ECP had greater estrus detection, ovulation induction, and pregnancy rates than the control and eCG treatments. In experiment 4, ovulation induction was greater for heifers treated with eCG and eCG+ECP relative to control, but did not differ from the ECP treatment. In conclusion, the use of a CIDR of fourth use for 12 days and the addition of eCG and/or ECP at CIDR removal efficiently induced ovulation and increased pregnancy rates in prepubertal Nellore heifers.
Asunto(s)
Bovinos , Inducción de la Ovulación/métodos , Preñez , Progesterona/administración & dosificación , Animales , Preparaciones de Acción Retardada/administración & dosificación , Esquema de Medicación , Combinación de Medicamentos , Estradiol/administración & dosificación , Estradiol/análogos & derivados , Femenino , Fármacos para la Fertilidad Femenina/administración & dosificación , Gonadotropinas Equinas/administración & dosificación , Inseminación Artificial/métodos , Inseminación Artificial/veterinaria , Inducción de la Ovulación/veterinaria , Embarazo , Índice de Embarazo , Preñez/efectos de los fármacos , Maduración Sexual/efectos de los fármacos , Maduración Sexual/fisiologíaRESUMEN
The objective was to evaluate the effects of exogenous progesterone (P4) on reproductive performance of prepubertal Bos indicus heifers. Prepubertal Nelore heifers (n = 589; 24.0 +/- 1.13 mo; 298.0 +/- 1.89 kg; body condition score of 3.2 +/- 0.26; mean +/- SEM) were randomly assigned to receive, between experimental Days -12 and 0: no treatments (CIDR0; n = 113); a new intravaginal insert (CIDR) containing 1.9 g of P4 (CIDR1; n = 237); or a similar insert previously used three times, with each use occurring for 9 d (CIDR4; n = 239). An additional treatment group was pubertal heifers given 12.5 mg dinoprost tromethamine im on Day 0 (PGF; n = 346), and used as controls for evaluation of conception rates. On Day 0, transrectal palpation was done for uterine score evaluation (UtS; 1-3 scale), blood samples were taken for serum P4 concentrations, and follicle diameter (FD) was measured. The breeding season started on Day 1 and consisted of AI after detection of estrus between Days 1 and 45, and exposure to bulls between Days 46 and 90. There were effects of treatment (P < 0.05) on serum concentrations of P4 on Day 0 (0.37 +/- 0.16, 2.31 +/- 0.11, and 1.20 +/- 0.11 ng/mL for CIDR0, CIDR1, and CIDR4, respectively; mean +/- SEM), FD on Day 0 (9.45 +/- 0.24, 9.72 +/- 0.17, and 11.42 +/- 0.16 mm), UtS on Day 0 (1.49 +/- 0.06, 1.88 +/- 0.04, and 2.24 +/- 0.04), estrus detection rates at 7 d (19.5, 42.6, and 38.3%) and 45 d (52.2, 72.1, and 75.3%) of the breeding season, and on pregnancy rates at 7 d (5.3, 14.3, and 18.4%), 45 d (27.4, 39.2, and 47.7%) and 90 d (72.6, 83.5, and 83.7%) of the breeding season. Conception rate 7 d after the start of the breeding season was greater (P < 0.05) in heifers from the CIDR4 (46.8%) and PGF (43.8%) groups than in the CIDR0 (27.3%) and CIDR1 (33.7%) groups. In conclusion, exogenous P4 hastened puberty and improved pregnancy rates at the beginning of the breeding season in prepubertal Bos indicus heifers. Furthermore, previously used CIDR inserts were better than new inserts.
Asunto(s)
Bovinos/fisiología , Inducción de la Ovulación/veterinaria , Progesterona/uso terapéutico , Reproducción/efectos de los fármacos , Animales , Tamaño de la Célula , Eficiencia/efectos de los fármacos , Femenino , Folículo Ovárico/citología , Folículo Ovárico/efectos de los fármacos , Ovario/citología , Ovario/diagnóstico por imagen , Ovario/efectos de los fármacos , Ovario/fisiología , Inducción de la Ovulación/métodos , Embarazo , Progesterona/sangre , Progesterona/farmacología , Reproducción/fisiología , Maduración Sexual/efectos de los fármacos , Maduración Sexual/fisiología , UltrasonografíaRESUMEN
Two experiments were performed to test the hypothesis that elevated progesterone concentrations impair pregnancy rate to timed artificial insemination (TAI) in postpuberal Nelore heifers. In Experiment 1, postpuberal Nelore heifers (n=398) received 2mg estradiol benzoate (EB) and either a new progesterone-releasing intravaginal device containing 1.9g of progesterone (CIDR) (first use) or a CIDR previously used for 9 d (second use) or for 18 d (third use) on Day 0, 12.5mg prostaglandin F(2alpha) (PGF(2alpha)) on Day 7, 0.5mg estradiol cypionate (ECP) and CIDR withdrawal on Day 9, and TAI on Day 11. Largest ovarian follicle diameter was determined on Day 11. The third-use CIDR treatment increased largest ovarian follicle diameter and pregnancy rate. Conception to TAI was reduced in heifers with smaller follicles in the first- and second-use CIDR treatments, but not in the third-use CIDR treatment. In Experiment 2, postpuberal Nelore heifers received the synchronization treatment described in Experiment 1 or received 12.5mg PGF(2alpha) on Day 9 rather than Day 7. In addition, 50% of heifers received 300 IU equine chorionic gonadotropin (eCG) on Day 9. Heifers were either TAI (Experiment 2a; n=199) or AI after detection of estrus (Experiment 2b; n=125 of 202). In Experiment 2a, treatment with eCG increased pregnancy rate to TAI in heifers that received PGF(2alpha) on Day 9 but not on Day 7 and in heifers that received a first-use CIDR but not in heifers that received a third-use CIDR. Treatments did not influence reproductive performance in Experiment 2b. In summary, pregnancy rate to TAI in postpuberal Nelore heifers was optimized when lower concentrations of exogenous progesterone were administered, and eCG treatment was beneficial in heifers expected to have greater progesterone concentrations.