scholarly journals Considerations for reproductive management of bos indicus-influenced beef heifers

2017 ◽  
Author(s):  
◽  
James William Cameron Locke
Keyword(s):  
United States ◽  
Bos Taurus ◽  
Bos Indicus ◽  
Fixed Time ◽  
The United States ◽  
Pregnancy Rates ◽  
Breeding Period ◽  
Beef Heifers ◽  
Reproductive Management ◽  
Natural Service

The Bos indicus species of beef cattle presents a number of unique reproductive challenges, especially with regard to those that influence reproductive efficiency including timely attainment of puberty, response to certain pharmaceutical drugs used to control estrus and ovulation, and response to physiological stressors. Cattle of this biological type comprise a substantial percentage of the beef cattle population in southern regions of the United States because of their ability to withstand high ambient temperatures and relative humidity. Additionally, Bos indicus cattle are regarded to exhibit increased parasite and disease resistance, resulting in improved production in subtropical climates as compared to Bos taurus cattle in those same regions. Research utilizing composite breeds of Bos taurus and Bos indicus beef heifers has been limited in the United States, and adoption of reproductive technologies such as artificial insemination and estrus synchronization has been sluggish compared to Bos taurus cattle in other regions of the country. To help answer a number of questions about this biological type, an experiment was designed to evaluate reproductive performance of Bos indicus-influenced heifers (n = 1,456). Weights and reproductive tract scores (RTS; Scale 1-5) were obtained for heifers prior to assignment of one of five treatments: Non-synchronized + natural service (NS); melengestrol acetate + natural service (MGA + NS; 0.5 mg x animal-1 x d-1); 14-d controlled internal drug release + natural service (CIDR + NS; 1.38g progesterone); 14-d MGA-PG + fixed-time AI (FTAI); and 14-d CIDR-PG + FTAI. Heifers in the three NS treatments were exposed to fertile bulls for 65 d, beginning 10 d after progestin removal for CIDR + NS and MGA + NS groups. Heifers in FTAI treatments were administered PGF2[alpha] (PG; 25 mg, IM) 16 or 19 d following CIDR or MGA removal. Fixed-time AI was performed 66 and 72h after PG for CIDR-PG and MGA-PG treatments, respectively. Gonadotropin-releasing hormone (GnRH; 100[mu]g, i.m.) was administered at FTAI. Estrus detection aids were applied at PG for heifers in FTAI treatments and evaluated at AI. Heifers in FTAI treatments were exposed to fertile bulls 12 d following FTAI. Blood samples were collected and ovarian ultrasounds performed at PG administration and FTAI to compare serum concentrations of estradiol and progesterone and to evaluate follicular dynamics among a subset of heifers assigned to FTAI treatments. Pregnancy status was determined at the end of a 65-d breeding period. Data were analyzed using PROC FREQ and GLIMMIX procedures of SAS. Mean concentrations of estradiol at AI differed between MGA- versus CIDR-treated heifers (P = 0.04; 8.2 versus 6.6 pg/ml), however estrous response after PG (52% versus 53%) and pregnancy rates after FTAI (40%) did not differ between MGA- and CIDR-PG treatments, respectively. Across all treatments, pregnancy rates were compared on 21, 30 and 60 d of the breeding period based on pubertal status (prepubertal RTS = 1 and 2; peripubertal RTS = 3; pubertal RTS = 4 and 5). Pregnancy rates differed at each time point based on pretreatment pubertal status (P [less than or equal to] 0.02) and weight (P [less than or equal to] 0.05). No differences were apparent with regard to progestin type at any time point, although higher pregnancy rates (P [less than or equal to] 0.004) were observed among NS treatments than FTAI followed by NS exposure at Days 30 and 60. This experiment is the largest comprehensive field trial conducted in the United States and reported in the literature involving Bos indicus-influenced beef heifers utilizing estrus synchronization prior to natural service or FTAI. This study reinforced results from previous studies, however raises a number of questions yet to be answered for heifers of this biological type. These data should be used as a basis for improvements in reproductive management of Bos indicus-influenced beef heifers prior to their first breeding season, and creates a number of possibilities for future research trials that build upon results reported in this thesis. Selection, management, and post-weaning to pre-breeding development of Bos indicus-influenced replacement beef heifers should involve the cooperative efforts of beef producers, veterinarians, and research scientists to further investigate methods to improve reproductive efficiency and genetic merit of these herds.

39 EFFECT OF TIME OF FIXED-TIME AI ON PREGNANCY RATES IN ZEBU CROSS-BRED BEEF HEIFERS TREATED WITH PROGESTERONE RELEASING DEVICES AND ESTRADIOL CYPIONATE

2010 ◽  
Vol 22 (1) ◽  
pp. 177 ◽  
Author(s):  
M. Ramos ◽  
L. Cutaia ◽  
P. Chesta ◽  
G. A. Bó
Keyword(s):  
Bos Taurus ◽  
Body Condition Score ◽  
Bos Indicus ◽  
Fixed Time ◽  
Estradiol Benzoate ◽  
Pregnancy Rates ◽  
Beef Heifers ◽  
Treatment Groups ◽  
Condition Score ◽  
To Receive

Two experiments were designed to evaluate the effect of the timing of fixed-time AI (FTAI) in relation to the removal of an intravaginal progesterone-releasing device (1 g of progesterone, DIB, Syntex SA, Buenos Aires, Argentina) on pregnancy rates in Bos indicus × Bos taurus cross-bred heifers. In experiment 1, 285 Bonsmara × zebu cross-bred heifers, between 18 and 24 months of age and with a body condition score (BCS) between 3.0 and 3.5 (1-5 scale) were used. On the day of initiation of treatment (Day 0), the heifers’ ovaries were palpated (92% of them had a CL) and they received a new DIB plus 2 mg of estradiol benzoate (EB; Syntex SA) and 250 μg of cloprostenol (Ciclase DL, Syntex SA). On Day 8, DIB devices were removed and all heifers received 250 μg of Ciclase plus 0.5 mg of estradiol cypionate (ECP; Cipiosyn, Syntex SA). At that time the heifers were randomly divided to receive FTAI between 48 to 49 h, 53 to 54 h, or 58 to 59 h after DIB removal. The heifers underwent FTAI with semen from 4 bulls by 2 inseminators. In experiment 2, 260 heifers from the same group as those used in experiment 1 (87% with a CL) were treated exactly as those in experiment 1, except that previously used DIB was inserted on Day 0. Pregnancy diagnosis was performed 30 days post-fixed-time AI by ultrasonography. The data were analyzed by logistic regression, taking into account the effect of time of FTAI, semen, and inseminator on pregnancy rates. In experiment 1, pregnancy rates were lower (P = 0.04) in the heifers undergoing FTAI between 48 and 49 h after DIB removal (46/95, 48.4%) than those undergoing FTAI 53 to 54 h (61/99, 61.6%) or 58 to 60 h (57/91, 62.6%) after DIB removal. However, no differences in pregnancy rates were found (P = 0.72) in experiment 2 between the 3 treatment groups, with 39/91 (42.9%) for the 48 to 49 h group, 45/89 (50.6%) for the 53 to 54 h group, and 35/89 (43.8%) for the 58 to 59 h group. There was no effect of the semen or inseminator (P > 0.2) in either experiment. We conclude that when Bos indicus × Bos taurus beef heifers are synchronized with new DIB devices and ECP, higher pregnancy rates are obtained in heifers undergoing FTAI late (between 53 to 60 h after DIB removal) than in those undergoing FTAI early (48 to 49 h after DIB removal). However, time of insemination does not apparently affect pregnancy rates when Bos indicus × Bos taurus beef heifers are synchronized with previously used DIB devices and ECP.

scholarly journals Cattle adapted to tropical and subtropical environments: genetic and reproductive considerations

2020 ◽  
Vol 98 (2) ◽  
Author(s):  
Reinaldo F Cooke ◽  
Rodolfo C Cardoso ◽  
Ronaldo L A Cerri ◽  
G Cliff Lamb ◽  
Ky G Pohler ◽  
...  
Keyword(s):  
United States ◽  
Bos Indicus ◽  
Reproductive Function ◽  
Fixed Time ◽  
The United States ◽  
Beef Industry ◽  
Tropical Regions ◽  
Reproductive Management ◽  
Adaptation Response ◽  
Equine Chorionic Gonadotropin

Abstract Efforts to understand biological functions and develop management schemes specific to Bos indicus-influenced cattle raised in tropical and subtropical environments are critical to meet the increasing global demand for protein. In the United States, B. indicus breeds are mostly used to generate B. indicus × B. taurus crosses with increased thermal and parasite tolerance, while retaining some productive characteristics of B. taurus cattle. Although crossbreeding represents a proven strategy to improve cattle adaptation almost immediately, research has also attempted to identify B. taurus genetics that can withstand subtropical and tropical climates. Reduced milk production and delayed reproductive maturation appear to be related with tropical adaptation of B. taurus breeds, as a means to conserve energy under stressful conditions and limited nutrition. Moreover, longevity may be the ultimate adaptation response to unfavorable environments, and retention of bulls and heifers from proven cows is the recommended strategy to improve longevity in B. indicus-influenced herds. Besides selection for longevity, other aspects should be considered when planning reproductive management in tropical and subtropical regions. Bos indicus and B. taurus breeds have multiple differences pertaining to reproductive function, including age at puberty, ovarian dynamics, and pregnancy development. Nutritional strategies such as the stair-step regimen, and use of exogenous progesterone (P4) inserts are options to hasten puberty attainment of late-maturing B. indicus-influenced heifers. Yet, limited pharmacological alternatives are available for reproductive management of B. indicus-influenced females in the United States, which rely on GnRH-based protocols not specifically designed to the reproductive function of B. indicus breeds. In contrast, hormonal protocols based on exogenous P4, estradiol esters, and equine chorionic gonadotropin are available for use in B. indicus females in South America. These include protocols tailored to prepubertal heifers, anestrous cows, and cycling nulliparous or parous females, which often yield pregnancy rates of 50% to fixed-time artificial insemination. The global dairy industry also faces similar challenges in increasing demand and production as the beef industry. Selection of cows capable of sustaining optimal milk yield, reproductive success, and health status in hot and humid conditions is essential for optimal dairy production in subtropical and tropical regions.

scholarly journals 34 Reproductive management of beef females in tropical and sub-tropical environments

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 37-37
Author(s):  
Nicola Oosthuizen ◽  
Pedro Levy Piza Fontes ◽  
G Cliff Lamb
Keyword(s):  
Assisted Reproductive Technologies ◽  
Bos Taurus ◽  
Management Strategies ◽  
Bos Indicus ◽  
The United States ◽  
Reproductive Technologies ◽  
Pregnancy Rates ◽  
Embryo Production ◽  
Reproductive Management

Abstract Bos indicus and Bos taurus cattle diverged from an evolutionary standpoint more than 110,000 years ago. Since then, Bos indicus cattle have undergone genetic adaptations beyond the commonly discussed increased thermo-tolerance and parasite resistance. Several physiological differences exist between Bos indicus and Bos taurus cattle, and it is important to consider these differences when establishing reproductive management strategies. It has been well described that Bos indicus cattle have a delayed onset of puberty and longer periods of postpartum anestrus, yet through the utilization of estrus synchronization protocols these challenges can be attenuated. However, when Bos indicus females are exposed to these protocols, they are known to have smaller dominant follicles, lower expression of estrus, and decreased pregnancy rates to artificial insemination (AI) when compared to Bos taurus females. These factors can be overcome through the utilization of estradiol and progesterone based synchronization protocols, which improve follicular dynamics and yield acceptable pregnancy rates to assisted reproductive technologies in cattle adapted to tropical or subtropical conditions. However, the use of estrogens for synchronization purposes is not permitted in the United States, and cattle producers need to rely on GnRH-based protocols. Another key difference between subspecies, is that Bos indicus females have greater antral follicle counts than Bos taurus females, which proves beneficial for in vitro embryo production. Therefore, an opportunity exists to explore the greater productivity of donors in embryo production in order to improve genetics in herds that utilize these breeds.

207 INFLUENCE OF THE INTERVAL BETWEEN THAWING TO TRANSFER ON PREGNANCY RATES OF FROZEN - THAWED DIRECT-TRANSFER EMBRYOS

2007 ◽  
Vol 19 (1) ◽  
pp. 220
Author(s):  
G. A. Bo ◽  
L. C. Peres ◽  
D. Pincinato ◽  
M. de la Rey ◽  
R. Tribulo
Keyword(s):  
Bos Taurus ◽  
Body Condition Score ◽  
Bos Indicus ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Direct Transfer ◽  
Condition Score ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

An experiment was designed to evaluate the effect of the interval between thawing to deposition of the embryo into the uterine horn on pregnancy rates of in vivo-produced frozen–thawed embryos in 1.5 M ethylene glycol (direct transfer). Data were collected from 1122 embryo transfers performed in the same farm (Estancia El Mangrullo, Lavalle, Santiago del Estero, Argentina) during the spring and summer of 2004/05 and 2005/06 (6 replicates, ambient temperature between 20 and 40�C). Recipients used in all replicates were non-lactating, cycling, multiparous Bos taurus � Bos indicus crossbred cows with body condition score between 3 and 4 (1 to 5 scale) that were synchronized using fixed-time embryo transfer protocols. Briefly, the synchronization treatments consisted of the insertion of a Crestar ear implant (Intervet, Sao Paulo, Brazil) or a progesterone-releasing device (DIB; Syntex SA, Buenos Aires, Argentina), plus 2 mg of estradiol benzoate (EB; Syntex) intramuscularly (IM) on Day 0, and 400 IU of eCG (Folligon 5000; Intervet, or Novormon 5000; Syntex) IM plus 150 �g d-cloprostenol IM (Preloban; Intervet, or Ciclase; Syntex) on Day 5. Progestin devices were removed on Day 8 and all cows received 1 mg of EB IM on Day 9. All cows were examined by ultrasonography on Day 16 and those with a luteal area >76 mm2 (by calculating the area of the CL minus the area of the cavity) received, on Day 17, frozen–thawed embryos by nonsurgical transfer. All embryos were Grade 1, and all were frozen in 1.5 M ethylene glycol at the Embryo Plus Laboratory (Brits, South Africa). After being stored in liquid nitrogen, the embryos were plunged directly (no air thawing) in a 30�C water bath for 30 s, and then transferred to the recipient cows by either one of two technicians. Based on the interval between thawing and transfer, the transfers were classified as being in one of 3 groups: Group 1: <3 min; Group 2: 3 to 6 min; and Group 3: 6 to 16 min. The main reason for delayed transfers beyond 6 min was the replacement of one recipient for another because of difficulty in threading the cervix (1% of the total transfers) or a recipient falling down into the chute or with very bad disposition and behavior. Pregnancy was determined by ultrasonography 28 to 35 days after fixed-time embryo transfer, and data were analyzed by logistic regression. There were no effects of replicate, technician, CL area, recipient body condition score, embryo stage, and time from thawing to transfer on pregnancy rates. Pregnancy rates in the 3 thawing to transfer intervals were: Group 1: 215/385, 55.8%; Group 2: 372/655, 56.8%; Group 3: 42/82, 51.2%; P > 0.6. These results may be interpreted to suggest that there is no significant effect of time from thawing to transfer (up to 16 min) in direct transfer embryos using Bos taurus � Bos indicus recipients transferred at a fixed time.

scholarly journals 180EFFECT OF TIME OF ECG TREATMENT ON PREGNANCY RATES IN BOS INDICUS×BOS TAURUS RECIPIENTS SYNCHRONIZED WITH PROGESTERONE VAGINAL DEVICES AND TRANSFERRED WITHOUT ESTRUS DETECTION

2004 ◽  
Vol 16 (2) ◽  
pp. 212
Author(s):  
L.F. Nasser ◽  
E.L. Reis ◽  
A.M. Oliveira ◽  
G.A. Bo ◽  
P.S. Baruselli
Keyword(s):  
Bos Taurus ◽  
Bos Indicus ◽  
Fixed Time ◽  
Estradiol Benzoate ◽  
Pregnancy Rates ◽  
Bovine Embryo ◽  
Treatment Groups ◽  
Estrus Detection ◽  
Treatment Interaction

It has been shown recently that treatments with progesterone (P4)-releasing devices combined with estradiol benzoate (EB) plus P4 on Day 0, eCG and PGF on Day 5 and a second application of EB one day after device removal (Day 9) can be used successfully to transfer bovine embryos at a self-appointed time, without the necessity of estrus detection. Although the treatment solved one of the major problems in recipient management, estrus detection, it requires handling the recipients at least five times for treatments and embryo transfer. An experiment was designed to evaluate whether reducing one day of handling, by the administration of eCG and PGF at the time of removal of the P4 device (Day 8), results in comparable pregnancy rates than giving eCG on Day 5. A secondary objective was to determine the effect of injectable P4 at the time of device insertion plus EB treatment. Crossbred Bos taurus×Bos indicus beef heifers (n=301) were randomly assigned to 4 treatment groups in a 2 by 2 factorial design. All Heifers received a P4 device (DIB, Syntex, Argentina) plus 2mg EB i.m. (Syntex) at unknown stages of the estrous cycle (Day 0), with or without 50mg of P4 given i.m. at the same time. Heifers were further subdivided to receive PGF (0.150mg d-cloprostenol, Prolise, Tecnopec, Sao Paulo, Brazil) and 400IU of eCG (Novormon, Syntex) i.m. on Days 5 or 8. In all heifers, DIB devices were removed on Day 8 and 1 mg EB was administered i.m. on Day 9. Day 10 was arbitrarily considered as the day of estrus. On Day 17, heifers were bled for plasma P4 concentrations and examined by ultrasonography to determine the number of CL and their diameter. Heifers that had >1 CL or a single CL with diameter ≥18mm received an in vitro-produced (IVP) embryo by nonsurgical transfer performed by the same veterinarian. Pregnancy rates were determined by ultrasonography 30 days later. The effects of Day of eCG administration (Day 5 or Day 8), P4 of treatment (E2 or E2+P4) and the day-by-P4 treatment interaction on the numbers of CL and plasma P4 were analyzed by ANOVA, and the proportion of recipients selected and pregnant were analyzed using non-parametric tests (NPAR1WAY, SAS). There was no significant effect of P4 treatment or the P4-by-day of eCG interaction in any of the parameters evaluated. However, there was a significant effect of day of eCG administration on plasma P4 concentrations (Day 5=2.4±0.3 v. Day 8=1.7±0.2; P=0.03) and the number of CL (Day 5=1.4±0.1 v. Day 8=1.1±0.0; P=0.02) on Day 17. Furthermore, the proportion of recipients pregnant/treated tended (P=0.1) to be higher in heifers in the Day 5 Group (71/151, 47.0%) than in those in the Day 8 Group (61/150, 40.7%). Although delaying the eCG and PGF administration from Day 5 to Day 8 saves one trip through the chute for treatments, it resulted in lower plasma P4 concentrations and tended to decrease pregnancy rates in bovine embryo recipients synchronized with DIB devices and EB and transferred at a fixed time. Furthermore, the administration of injectable P4 at the time of DIB insertion did not affect pregnancy rates.

170 Embryonic loss and pregnancy rate in response to resynchronisation using oestradiol benzoate or injectable progesterone at 14 days after timed AI in Bos taurus×Bos indicus beef heifers

2020 ◽  
Vol 32 (2) ◽  
pp. 212
Author(s):  
C. C. Vieira ◽  
V. Buss ◽  
A. M. Oliveira ◽  
M. E. R. Costa ◽  
B. G. Freitas ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Bos Taurus ◽  
Bos Indicus ◽  
Pregnancy Rates ◽  
Beef Heifers ◽  
Graduate Studies ◽  
Oestradiol Benzoate ◽  
Embryonic Loss ◽  
Long Acting ◽  
Intravaginal Device

The effect of the exposure of pregnant cattle to oestradiol benzoate (EB) or injectable long-acting progesterone (iP4), as well as their use for early resynchronisation of non-pregnant (NP) females within the second week after timed AI (TAI), is yet to be assessed. This study aimed to assess the pregnancy rate and embryonic loss of cross-bred Bos taurus×Bos indicus beef heifers in response to an EB- or iP4-based resynchronisation strategy implemented 14 days after the first TAI. A total of 677 cyclic heifers (Braford and Brangus; 24 months old) were subjected to an EB/P4 synchronisation protocol for the first TAI (Day 0=TAI). On Day 14, all heifers received a new P4 intravaginal device (1g, Sincrogest, Ourofino Saúde Animal) and were randomly assigned to two groups: EB (1mg intramuscularly, Sincrodiol; n=339) or iP4 (75 mg intramuscularly, Sincrogest Injetável; n=338). On Day 22, P4 devices were removed and heifers underwent colour Doppler ultrasonography evaluation. Non-pregnant females were identified by the assessment of structural regression of the corpus luteum, as previously reported by our group. On Day 22, NP heifers received 1mg of oestradiol cipionate (SincroCP), 250µg of sodium cloprostenol (Sincrocio), and 200IU of equine chorionic gonadotrophin (SincroeCG), and they were inseminated on Day 24. On Day 22, the diameter of the preovulatory follicle (POF) was also recorded. Pregnancy was diagnosed via B-mode ultrasonography on Days 35-40 and 54. Statistical analyses were performed using SAS software (ver. 9.2, SAS Institute Inc.). The MIXED procedure was used to evaluate the POF diameter, and the GLIMMIX procedure was used to develop a multivariate model including treatment, breed, age, farm (1-7), and possible interactions of treatment with farm, breed, and age to evaluate the binomial data (pregnancy rates and embryonic loss). In NP heifers, the diameter of the POF on Day 22 did not differ (P>0.05) between the EB (9.77±0.25mm) and iP4 (9.92±0.22 mm) groups. Exposure to EB or iP4 on Day 14 post-TAI did not influence pregnancy rates as assessed on Day 22 (56.3% (191/339) vs. 60.1% (203/338)) and on Days 35-40 (49.6% (168/339) vs. 53.3% (180/338)). In addition, embryonic loss between Days 22 and 35-40 was not different between the EB (12%, 23/191) and iP4 (11.3%, 23/203) groups. On the other hand, pregnancy rates in heifers submitted to the second TAI were greater (P=0.01) in the EB group (45.95%, 68/148) than in the iP4 group (31.85%, 43/135). In conclusion, improved pregnancy rates can be achieved using 1mg of EB associated with a P4 intravaginal device on Day 14 of the resynchronisation protocol without affecting the first TAI pregnancy rates and embryonic loss. However, further investigation is warranted to assess the lower pregnancy rates obtained in response to the association of iP4 and P4 device. This research was supported by FAPESP (2015/10606-9; 2019/15514-6), Graduate Studies Support Program (PAPG-UNIPAMPA), and Ourofino Saúde Animal.

Bovine embryo transfer recipient synchronisation and management in tropical environments

2010 ◽  
Vol 22 (1) ◽  
pp. 67 ◽  
Author(s):  
Pietro S. Baruselli ◽  
Roberta M. Ferreira ◽  
Manoel F. Sá Filho ◽  
Luiz F. T. Nasser ◽  
Carlos A. Rodrigues ◽  
...  
Keyword(s):  
Embryo Transfer ◽  
Bos Taurus ◽  
Bos Indicus ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Bovine Embryo ◽  
Tropical Environments ◽  
Gonadotrophin Releasing Hormone ◽  
Animal Handling ◽  
Repeat Breeder

Numerous studies have shown that it is possible to manipulate follicular and luteal dynamics, thereby eliminating the need for oestrus detection in embryo transfer (ET) programmes. Fixed-time ET (FTET) protocols are based on the use of gonadotrophin-releasing hormone (GnRH) and prostaglandin (PG) F or progesterone/progestogen (P4)-releasing devices and oestradiol. The FTET protocols increases the proportion of recipients transferred, and therefore pregnancy rates, compared with the use of PGF followed by ET 7 days after oestrus. Furthermore, the addition of equine chorionic gonadotrophin (eCG) to the P4 and oestradiol-based FTET protocols results in an even higher proportion of recipients transferred, and thus higher pregnancy rates. The beneficial effect of eCG treatment may be related to increased growth of the dominant follicle and increased plasma P4 concentrations during the subsequent luteal phase. In Bos taurus × Bos indicus recipients, pregnancy rates were positively correlated with the diameter of the corpus luteum (CL) and the number of CL at ET. When repeat-breeder Holstein cows were used as recipients, FTET protocols increased number of recipients transferred and pregnancy rates compared with the traditional PGF-based synchronisation protocols. In conclusion, the use of FTET protocols eliminates the need for the detection of oestrus and results in a greater proportion of recipients transferred and satisfactory pregnancy rates. Thus, FTET optimises the use of recipients, reducing labour and animal handling and facilitating the use of ET.

20 PREGNANCY RATES IN SUCKLED BEEF COWS SYNCHRONIZED WITH PROGESTERONE INTRAVAGINAL DEVICES AND RECEIVING eCG FOURTEEN DAYS AFTER BREEDING

2010 ◽  
Vol 22 (1) ◽  
pp. 168 ◽  
Author(s):  
L. Cutaia ◽  
M. Ramos ◽  
P. Chesta ◽  
G. A. Bó
Keyword(s):  
Body Condition ◽  
Bos Taurus ◽  
Body Condition Score ◽  
Bos Indicus ◽  
Fixed Time ◽  
Beef Cows ◽  
Estradiol Benzoate ◽  
Pregnancy Rates ◽  
Treatment Groups ◽  
Condition Score

An experiment was designed to test the following hypotheses: (1) the administration of 400IU of eCG (Novormón, Syntex SA, Buenos Aires, Argentina) 14 days after fixed-time artificial insemination (FTAI) increases pregnancy rates in cross-breed Zebu × Bonsmara suckled cows synchronized with progesterone releasing devices (DIB 0.5, 0.5 g of progesterone, Syntex SA); and (2) pregnancy rates in cows treated with estradiol or GnRH, combined with a DIB device, are not different. Primiparous suckled cows (n = 260), between 60 and 120 days postpartum (DPP) and with a body condition score between 2.0 and 2.5 (1 to 5 scale) were used. At the beginning of the experiment (Day 0), all cows were examined by rectal palpation (only 11% had a CL), received a DIB device, and were randomly allocated to 1 of 3 treatment groups. Cows in the E2 group received 2 mg of estradiol benzoate (EB) intramuscularly (i.m.) at DIB insertion and those in the two GnRH groups received 100 μg of gonadorelin (GDR Gonasyn, Syntex SA) at the same time. On Day 7, DIB devices were removed and all cows received 500 μg of cloprostenol (Ciclase DL, Syntex SA) plus 400 IU of eCG (i.m.). Cows in the E2 group received 0.5 mg of estradiol cypionate (ECP, Cipiosyn, Syntex SA) and underwent FTAI administered by one technician, using semen from 1 of 2 bulls between 52 and 56 h later. Cows in the GnRH groups received a dose of 100 μg of gonadorelin (full GnRH group) or 50 μg of gonadorelin (1/2 GnRH group) at the time of the FTAI (52 to 56 h after DIB removal). Fourteen days after FTAI cows in the 3 groups were further subdivided (3 × 2 factorial) to receive or not 400 IU of eCG i.m. Pregnancy was determined 30 days after FTAI using real-time ultrasonography. Data were analyzed by logistic regression, taking into account the effect of the synchronization treatment, eCG or noteCG, 14 days after FTAI and sire used. No differences in pregnancy rates were found (P = 0.16) among treatment groups (E2: 39/87, 43.7%, full GnRH: 38/92, 41.3%, and 1/2 GnRH: 25/81, 30.9%). However, there was a significant (P = 0.02) effect of eCG treatment 14 days after FTAI (eCG: 60/127, 47.2% v. no eCG: 41/133, 30.8%). Furthermore, bull A (77/155, 47.1%) resulted in higher pregnancy rate (P = 0.009) than bull B (28/107, 26.2%), but there were no significant interactions between bull and synchronization treatment or eCG administration 14 days after FTAI (P > 0.1). We conclude that the application of 400 IU of eCG 14 days after FTAI increases pregnancy rates in suckled Bos taurus × Bos indicus primiparous cows with fair to poor body condition score synchronized with progesterone releasing devices. Furthermore, the use of estradiol ester or GnRH at DIB insertion and removal did not affect pregnancy rates.

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