Objectives were to determine: 1) whether estradiol benzoate (EB) provides a superior alternative to GnRH for synchronizing emergence, growth and maturation of a new follicular wave for fixed timed AI (TAI) in Bos indicus-influenced cattle using CIDR-based protocols, 2) the effect of 48 h calf removal at CIDR removal on the rate of maturational synchrony of the dominant follicle and 3) the effect of varying the magnitude of peak plasma progesterone (P4) concentrations following CIDR insertion on the suppression of FSH and LH secretion in a CIDR-based protocol using EB. In experiment 1, sixty-four Braford (F-1) females were stratified by BCS, parity and days postpartum and assigned randomly to one of four groups in a 2 x 2 factorial arrangement of treatments: 1) Select-Synch + CIDR, 2) Select-Synch + CIDR with 48 h calf removal, 3) E-Synch + CIDR or 4) E-Synch + CIDR with 48 h calf removal. A greater number of cattle in the EB treated group exhibited NFWE compared to the GnRH group, 29 vs 17 cows for EB and GnRH respectively, (P<0.0006). Intervals to NFWE were also greater in EB treated cattle than in GnRH treated cattle, 4.2 vs 2.7 d for EB and GnRH treated cattle respectively, (P<0.0001). Proportions of GnRH- and EB-treated cows ovulating after CIDR removal did not differ. Post-CIDR suckling status did not affect ovulation frequency or interval to ovulation. In experiment 2, eight pubertal (F-1) heifers were used in a Latin Square design with four treatment levels of P4: 1) EB only, 2) EB and new CIDR, 3) EB and new autoclaved CIDR, 4) EB, new autoclaved CIDR and P4 injection at CIDR insertion. Treatments 2 through 4 increased (P < 0.01) mean plasma P4 concentrations compared to treatment 1, with treatment 4 creating the greatest increase in P4 with the longest duration. Suppression of plasma FSH was greatest in group 4 (P<0.08), with mean 60 h concentrations less than in all other groups. Mean concentrations of LH were lesser in group 4 than groups 1 and 2. Frequencies of occurrence of NFWE and ovulation and intervals to NFWE did not differ among treatments. Results indicate that the use of EB and CIDR to synchronize Brahman x Hereford females may provide better synchronization for TAI compared to GnRH and CIDR based protocols.

Objectives were to determine: 1) whether estradiol benzoate (EB) provides a superior alternative to GnRH for synchronizing emergence, growth and maturation of a new follicular wave for fixed timed AI (TAI) in Bos indicus-influenced cattle using CIDR-based protocols, 2) the effect of 48 h calf removal at CIDR removal on the rate of maturational synchrony of the dominant follicle and 3) the effect of varying the magnitude of peak plasma progesterone (P4) concentrations following CIDR insertion on the suppression of FSH and LH secretion in a CIDR-based protocol using EB. In experiment 1, sixty-four Braford (F-1) females were stratified by BCS, parity and days postpartum and assigned randomly to one of four groups in a 2 x 2 factorial arrangement of treatments: 1) Select-Synch + CIDR, 2) Select-Synch + CIDR with 48 h calf removal, 3) E-Synch + CIDR or 4) E-Synch + CIDR with 48 h calf removal. A greater number of cattle in the EB treated group exhibited NFWE compared to the GnRH group, 29 vs 17 cows for EB and GnRH respectively, (P<0.0006). Intervals to NFWE were also greater in EB treated cattle than in GnRH treated cattle, 4.2 vs 2.7 d for EB and GnRH treated cattle respectively, (P<0.0001). Proportions of GnRH- and EB-treated cows ovulating after CIDR removal did not differ. Post-CIDR suckling status did not affect ovulation frequency or interval to ovulation. In experiment 2, eight pubertal (F-1) heifers were used in a Latin Square design with four treatment levels of P4: 1) EB only, 2) EB and new CIDR, 3) EB and new autoclaved CIDR, 4) EB, new autoclaved CIDR and P4 injection at CIDR insertion. Treatments 2 through 4 increased (P < 0.01) mean plasma P4 concentrations compared to treatment 1, with treatment 4 creating the greatest increase in P4 with the longest duration. Suppression of plasma FSH was greatest in group 4 (P<0.08), with mean 60 h concentrations less than in all other groups. Mean concentrations of LH were lesser in group 4 than groups 1 and 2. Frequencies of occurrence of NFWE and ovulation and intervals to NFWE did not differ among treatments. Results indicate that the use of EB and CIDR to synchronize Brahman x Hereford females may provide better synchronization for TAI compared to GnRH and CIDR based protocols.

Orientador: José Luiz Moraes Vasconcelos / Resumo: Os objetivos foram avaliar o efeito da remoção de bezerros (RB) no desenvolvimento folicular e na indução de ciclicidade e a eficácia do MGA precedendo protocolos de IATF, que utilizam GnRH ou BE, nas taxas de concepção a IATF e gestação. Foram utilizadas 163 vacas paridas em anestro da raça Nelore com 80 ± 29 dias pós-parto e ECC de 3,0 ± 0,29, divididas em 4 grupos: G1: (n=40, controle); G2: (n=42, RB): RB (60 h) 11 dias antes da estação de monta (EM); G3: (n=43, MGA + GnRH): MGA (MGA PREMIX®, 0,5 mg/dia, v.o.) por 10 dias, seguido por RB (60 h), após este período receberam GnRH (CYSTORELIN®, 50 mcg, i.m). Após 6,5 dias, PGF2α (LUTALYSE®, 25 mg, i.m.) que foi seguida por outra RB (54h). Após a RB, todos os animais receberam GnRH e foram inseminados; G4: (n=38, MGA + BE): MGA por 10 dias, seguido por RB (60h), após este período receberam BE (Estrogin , 1,0 mg, i.m.). Após 7 dias, PGF2α que foi seguida por outra RB (54h). Após 24 horas da PGF2α, os animais receberam BE e foram inseminados 30 horas depois. Após a IATF, nos 4 grupos, foi realizado observação de cio e IA (30 d) e por monta natural por mais 32 dias. A ciclicidade, o efeito do MGA e RB no desenvolvimento folicular, as taxas de sincronização, concepção e gestação foram determinados por exames ultra-sonográficos. A variável dias para ficar gestante foi analisada pela curva de sobrevivência, enquanto que as variáveis binomiais e contínuas foram analisadas por regressão logística e pelo GLM do SAS, respectivamente. Foram incluídos no modelo efeito de tratamento, ordem, sexo da cria e suas interações e ECC como co-variável. O MGA foi fornecido, ao G3 e G4, diariamente e os animais ingeriram, em média, 0,99 mg/dia de MGA. O MGA aumentou (P<0,05) o diâmetro do maior folículo (11,2 ± 0,28 vs. 10,3 ± 0,29 mm, respectivamente), que também foi maior (P<0,05) na associação MGA + RB... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objectives of this trial were to evaluate the effects of calf removal (CR) on follicular development and its ability to induce cyclicity and the effects of melengestrol acetate (MGA) preceding TAI protocols, with GnRH or EB on conception and pregnancy rates. Suckled anestrous Nellore cows (n=163) with 80 ± 29 days postpartum and BCS of 3.0 ± 0.29 were assigned into one of four groups: G1: (n=40, control); G2: (n=42, CR): calf removal (60 h) 11 days before the breeding season (BS). G3: (n=43, MGA + GnRH): MGA (MGA PREMIX®, 0.5 mg/day, v.o.) per 10 days, followed by CR (60 h), and GnRH (CYSTORELIN®, 50 mcg, i.m) after CR. Cows received by PGF2α (LUTALYSE®, 25 mg, i.m.) 6.5 days later, and another CR (54h) followed by GnRH and TAI; G4: (n=38, MGA + EB): MGA per 10 days, followed by CR (60h) and injection of EB (Estrogin , 1.0 mg, i.m.) after CR. Cows received PGF2α 7 days later and 24 hours after that, all animals received another EB and were TAI 30 hours later. Calf removal was performed between PGF2α and EB (54 h). After TAI, in all groups, was performed heat detection and AI (30 d) and natural service per more 32 days. Cyclicity status, effect of MGA supplementation and CR on follicular development, synchronization, conception and pregnancy rates were determined by ultrasound. The variable days to pregnancy was analyzed by survival analyses and the binomial and continuous variables were analyzed by logistic regression and GLM of SAS, respectively. The effects of treatment, parity, calf gender and interactions were included in the model, BCS was included as covariable. The MGA was offered to G3 and 4 daily (mixed into the mineral) and the average consumption was 0.99 mg/day. MGA supplementation increased (P<0.05) follicular diameter (11.2 ± 0.28 vs. 10.3 ± 0.29 mm, respectively) Follicular diameter was also increased (P<0.05) when MGA was associated with CR (11.3 ± 0.26 mm)... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:27:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2005Bitstream added on 2014-06-13T18:31:49Z : No. of bitstreams: 1 perez_gc_me_botfmvz.pdf: 244671 bytes, checksum: d92a00f6fbf47e3db20740d4e0a01437 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Os objetivos foram avaliar o efeito da remoção de bezerros (RB) no desenvolvimento folicular e na indução de ciclicidade e a eficácia do MGA precedendo protocolos de IATF, que utilizam GnRH ou BE, nas taxas de concepção a IATF e gestação. Foram utilizadas 163 vacas paridas em anestro da raça Nelore com 80 ± 29 dias pós-parto e ECC de 3,0 ± 0,29, divididas em 4 grupos: G1: (n=40, controle); G2: (n=42, RB): RB (60 h) 11 dias antes da estação de monta (EM); G3: (n=43, MGA + GnRH): MGA (MGA PREMIX®, 0,5 mg/dia, v.o.) por 10 dias, seguido por RB (60 h), após este período receberam GnRH (CYSTORELIN®, 50 mcg, i.m). Após 6,5 dias, PGF2α (LUTALYSE®, 25 mg, i.m.) que foi seguida por outra RB (54h). Após a RB, todos os animais receberam GnRH e foram inseminados; G4: (n=38, MGA + BE): MGA por 10 dias, seguido por RB (60h), após este período receberam BE (Estrogin , 1,0 mg, i.m.). Após 7 dias, PGF2α que foi seguida por outra RB (54h). Após 24 horas da PGF2α, os animais receberam BE e foram inseminados 30 horas depois. Após a IATF, nos 4 grupos, foi realizado observação de cio e IA (30 d) e por monta natural por mais 32 dias. A ciclicidade, o efeito do MGA e RB no desenvolvimento folicular, as taxas de sincronização, concepção e gestação foram determinados por exames ultra-sonográficos. A variável dias para ficar gestante foi analisada pela curva de sobrevivência, enquanto que as variáveis binomiais e contínuas foram analisadas por regressão logística e pelo GLM do SAS, respectivamente. Foram incluídos no modelo efeito de tratamento, ordem, sexo da cria e suas interações e ECC como co-variável. O MGA foi fornecido, ao G3 e G4, diariamente e os animais ingeriram, em média, 0,99 mg/dia de MGA. O MGA aumentou (P<0,05) o diâmetro do maior folículo (11,2 ± 0,28 vs. 10,3 ± 0,29 mm, respectivamente), que também foi maior (P<0,05) na associação MGA + RB... / The objectives of this trial were to evaluate the effects of calf removal (CR) on follicular development and its ability to induce cyclicity and the effects of melengestrol acetate (MGA) preceding TAI protocols, with GnRH or EB on conception and pregnancy rates. Suckled anestrous Nellore cows (n=163) with 80 ± 29 days postpartum and BCS of 3.0 ± 0.29 were assigned into one of four groups: G1: (n=40, control); G2: (n=42, CR): calf removal (60 h) 11 days before the breeding season (BS). G3: (n=43, MGA + GnRH): MGA (MGA PREMIX®, 0.5 mg/day, v.o.) per 10 days, followed by CR (60 h), and GnRH (CYSTORELIN®, 50 mcg, i.m) after CR. Cows received by PGF2α (LUTALYSE®, 25 mg, i.m.) 6.5 days later, and another CR (54h) followed by GnRH and TAI; G4: (n=38, MGA + EB): MGA per 10 days, followed by CR (60h) and injection of EB (Estrogin , 1.0 mg, i.m.) after CR. Cows received PGF2α 7 days later and 24 hours after that, all animals received another EB and were TAI 30 hours later. Calf removal was performed between PGF2α and EB (54 h). After TAI, in all groups, was performed heat detection and AI (30 d) and natural service per more 32 days. Cyclicity status, effect of MGA supplementation and CR on follicular development, synchronization, conception and pregnancy rates were determined by ultrasound. The variable days to pregnancy was analyzed by survival analyses and the binomial and continuous variables were analyzed by logistic regression and GLM of SAS, respectively. The effects of treatment, parity, calf gender and interactions were included in the model, BCS was included as covariable. The MGA was offered to G3 and 4 daily (mixed into the mineral) and the average consumption was 0.99 mg/day. MGA supplementation increased (P<0.05) follicular diameter (11.2 ± 0.28 vs. 10.3 ± 0.29 mm, respectively) Follicular diameter was also increased (P<0.05) when MGA was associated with CR (11.3 ± 0.26 mm)... (Complete abstract click electronic access below)

The objectives of the present research were to study the factors that influence postpartum reproductive characteristics of suckling beef cows in extensive production systems in Mozambique and to develop new management strategies to improve their reproductive efficiency. The effects and interactions between post-partum BW, BCS, age and parity number on plasma concentrations of estradiol, progesterone, creatinine, urea and cortisol around oestrus and the related conception rates of Bos indicus cows in extensive production system were analysed as well as the minimum BCS at the beginning of breeding to maximise the subsequent conception rates. Thirty-five days prior to the breeding season cows were synchronised using Crestar. During the second oestrus after synchronisation, 18 blood samples were collected per animal for hormonal analysis, from 24 hr before oestrus to 24 hr after oestrus. The hormonal pattern of estradiol and progesterone around oestrus were similar to that observed in Bos taurus cows under intensive conditions. Conception rates of cows in the experimental group were 90.5%. Better results on estradiol pattern and conception rates were related to a BCS of ≥ 2.5 and it was thus concluded that the post-partum management of extensive Bos inducus cows should aim to achieve at least a BCS of 2.5 at the beginning of the breeding season. Twelve-hour and 48-hr calf removal were conducted separately to evaluate their effects on conception rates of Bos indicus beef cows in extensive production systems and to quantify the related effects on calf-weaning weights. The 12-hr calf removal was performed from 45 days post-partum to the beginning of the breeding season, and the 48-hr calf removal was performed preceding the onset of the breeding season. It was concluded that 12-hr calf separation at night enhance the energy balance (3%), increases the conception rates (80%) and improves the calf-weaning weights, whereas 48-hr calf removal increases conception rates (76%) and does not affect calf weaning weights. Both calf removal management strategies concentrate conceptions in the early part of the breeding season and stress the importance of the effect of BCS and estradiol on conception rates in Bos indicus beef cows in extensive production systems. / Thesis (PhD)--University of Pretoria, 2012. / Animal and Wildlife Sciences / unrestricted