The objectives were to determine the effect of progesterone supplementation on fertility responses in lactating dairy cows without corpora lutea (CL) at initiation of the timed artificial insemination (AI) program. Holstein cows from 5 commercial dairy farms were subjected to the Ovsynch-56 protocol (d -10 GnRH, d -3 PGF2α, d -0.7 GnRH, d 0 AI). Ovaries were scanned by ultrasonography on d -10. Within farm, cows without CL were blocked by pen and assigned randomly to remain as nonsupplemented controls (CON; n = 652) or to receive 2 controlled internal drug-release (CIDR) inserts containing 1.38 g of progesterone each from d -10 to -3 (2CIDR; n = 642). Cows with CL were randomly selected within pen and used as positive controls as cows in diestrus at the initiation of the Ovsynch protocol (DIEST; n = 640). Signs of estrus were detected beginning on d -9 based on removal of tail chalk, and cows in estrus received AI on the same day. Blood samples from subsets of cows on d -10, -9, -7, -5, -3, and 0 (n = 109) and on d 6, 13, and 19 (n = 156) were analyzed for progesterone concentrations. Pregnancy was diagnosed on d 32 and 60 after AI. The average progesterone concentration during the timed AI program was lowest for CON, intermediate for 2CIDR, and highest for DIEST (0.92, 2.77, and 4.93 ng/mL, respectively). The proportions of cows that ovulated in response to the first GnRH (63.6, 61.1, and 47.2%, respectively) and that had a new CL on d -3 at PGF2α injection (72.4, 67.9, and 47.4%, respectively) were greater for CON and 2CIDR compared with DIEST, respectively. The diameter of the ovulatory follicle and the proportion of cows that ovulated in response to the second GnRH did not differ among treatments. A greater proportion of CON and 2CIDR cows were detected in estrus at AI compared with DIEST cows (35.8, 39.6, and 30.6%, respectively). Pregnancy per AI was less for CON compared with 2CIDR and DIEST on d 32 (31.3, 42.2, and 38.4%, respectively) and d 60 after AI (28.9, 37.2, and 33.9%, respectively), indicating that progesterone supplementation reestablished fertility in cows lacking a CL similar to that of cows in diestrus at the initiation of the timed AI program. Treatment did not affect pregnancy loss between d 32 and 60 of gestation. Pregnancy from a subset of cows with plasma progesterone concentrations indicated that a minimum concentration of 2.0 ng/mL was needed to optimize fertility. A single ultrasound examination effectively identified a low-fertility cohort of cows based on the absence of CL at the first GnRH injection of the Ovsynch protocol. Supplementation with 2 CIDR inserts increased progesterone in plasma by an additional 1.85 ng/mL compared with CON, resulting in concentrations of 2.77 ng/mL during development of the ovulatory follicle, which restored fertility in dairy cows lacking CL to a level similar to that of cows in diestrus.

No abstract

High milk production, heat, physiological status and management impair reproduction in Holstein cows. The use of in vivo-produced embryos has been reported as an alternative to enhance pregnancy outcome in the tropics; however there are several limitations for its production, especially from variations in superovulatory responses. The in vitro production of embryos would avoid such variations, but few studies have been reported. This study aims to verify the effects of variables related to recipients under a program of routine in vitro embryo transfer on a commercial dairy farm in southeastern Brazil. It was hypothesized that pregnancy rates after transfer of ovum pick up or OPU-derived embryos (ET) to lactating Holstein recipients may be influenced by recipient GnRH-treatment at ET, parity, milk production and body condition score. Recipients (267) were allocated to one of three i.m. treatments given at ET: Control (92) -2.5 ml saline; Buserelin (86) -10 μg Buserelin acetate; Deslorelin (89) -750 μg Deslorelin acetate. Ultrasound images and blood samples were taken at ET and seven days later. The first pregnancy diagnosis was performed between 30-40 days and the second between 60-80 days post ET. Data were analyzed by GENMOD (SAS ® ). The proportion of pregnant cows was greater (P<0.05) in Buserelin-treated recipients (38.3%) at the first pregnancy diagnosis than Controls (24.1%), but similar to Deslorelin and control cows at the second diagnosis (13.0, 20.9 and 14.6% in Control, Buserelin and Deslorelin, respectively). In conclusion, Buserelin improved pregnancy rate only transitorily, under the present conditions. Index terms: Bovine; GnRH agonists; progesterone. RESUMOAlta produção leiteira, calor, estado fisiológico e manejo prejudicam a reprodução em vacas Holandesas nos trópicos. A utilização de embriões produzidos in vivo é uma alternativa para melhorar taxas de gestação; no entanto, existem limitações, especialmente pelas variações nas respostas superovulatórias. A produção in vitro de embriões evitaria tais variações, mas poucos estudos estão relatados. O objetivo é verificar os efeitos de variáveis relacionadas às receptoras sob um programa de transferência de embriões (TE) in vitro em fazenda comercial no sudeste do Brasil. Hipotetiza-se que taxas de gestação, após TE de embriões derivados de OPU em receptoras Hosltein em lactação, são influenciadas pelo GnRH aplicado no momento da TE, paridade, produção de leite e escore de condição corporal. As receptoras (267) foram alocadas para um de três tratamentos aplicados no momento da TE: Controle (92) -Salina 2,5 ml; Buserelina (86) -10 µg de buserelina; Deslorelina (89) -750 µg de deslorelina. Ultrassonografia e amostras de sangue realizadas no momento da TE e sete dias depois. O primeiro diagnóstico de gestação foi realizado entre 30-40 dias e o segundo entre 60-80 dias pós-TE. Dados foram analisados pelo GENMOD (SAS ® ). A proporção de vacas prenhes foi superior (P<0,05) nas receptoras tratadas com Buserelina (38,1%) comparadas com Controle (24...

-The objective of this study was to investigate whether the use of rbST and eCG prior to ultrasound-guided follicular aspiration (OPU) improves oocyte yield and quality in Tabapuã and Holstein heifers. The study was conducted in two phases, 20 days apart, in a change-over design. The dominant follicle was ablated two days (D-2) before two treatments: stimulation (6 Holstein and 8 Tabapuã), 500 mg of rbST (Boostin ® ) on D0 and 500 IU of eCG (Folligon) on D2; and control (6 Holstein and 8 Tabapuã), in which heifers received injections of the excipient. Heifers were aspirated on D4. Oocytes were subjected to a well established commercial in vitro embryo production protocol (Vitrogen ® ) and embryos were evaluated seven days after fertilization. There was an effect from the interaction of treatment and breed, so that hormonal stimulation increased antral follicle count (2-8 mm) in Tabapuã (29.9±2.6 to 41.4±2.6), but not in Holstein heifers (14.4±2.6 to 15.5±2.6). Tabapuã heifers had higher mean antral follicle count than Holsteins (35.6±1.8 vs. 15.0±2.1). The number of viable oocytes was not increased by stimulation in Tabapuã (from 4.7±1.0 to 5.2±1.1 in control and simulation, respectively) or in Holstein heifers (1.3±1.9 to 2.0±1.6 in control and simulation, respectively). There was no difference in the percentage of heifers with more than five viable oocytes in the group treated (33 vs 27%). The number of blastocysts was not affected by treatment (1.75 vs. 1.00 in hormonal stimulation and control, respectively). The increase in antral follicle count in the stimulated Tabapuã heifers did not reflect upon oocyte yield. The differential breed response to the hormonal treatment underscores the need for additional tests, especially for the Holstein breed, in order to enhance OPU efficiency.

Ovum pick (OPU) up is a technique upon which in vitro embryo production (IVP) depends. It permits donor cow maternal ancestry to be assessed by mtDNA analysis. Repetitive ablation of follicles is thought to interfere with the donor cow endocrine profile and influence embryo yield. The objective was to evaluate the effects of mtDNA and OPU order on IVP fertility traits. Gyr donors (85) were submitted to 363 OPU sessions (5 OPU sessions/donor). Donor mtDNA was extracted from leukocytes and sorted by the presence of the HindIII restriction site within the amplified region, indicative of Bos taurus taurus mtDNA (Paneto et al. 2008 Genet. Mol. Res. 7, 592). All animals in the donor pedigree were classified, and the population was divided into two groups according to their maternal genetic grouping: Bos taurus indicus and Bos taurus taurus. For statistical analyses, data from 5 OPU sessions per each donor were submitted to the mixed model procedure of SAS® (SAS Institute Inc., Cary, NC, USA), using the lowest Akaike value to determine the best covariance structure between repeated OPU session results. The model included the effect of OPU session order (1–5) and mtDNA-based maternal grouping (Bos taurus v. Bos indicus) as independent variables. Total and viable oocytes, as well as blastocyst yield per OPU session, were the dependent variables studied. The means of total and viable oocytes and blastocysts produced per donor per OPU were compared by the Tukey test, at 5% significance. The combined OPU sessions resulted in 6084 oocytes, 2537 embryos, which produced 1105 pregnancies. Mean numbers (n = 42 donors/OPU session) of total and viable oocytes between OPU sessions 1 (31.9 ± 4.6 and 19.2 ± 2.9), 2 (35.3 ± 3.5 and 21.2 ± 2.2), 3 (28.9 ± 3.7 and 19.3 ± 2.4), 4 (25.0 ± 5.2 and 18.9 ± 33), and 5 (20.5 ± 6.3 and 13.8 ± 4.0) did not differ. Mean blastocyst production after IVP between OPU sessions 1 (6.5 ± 1.4), 2 (5.15 ± 1.04), 3 (5.5 ± 1.1), 4 (5.8 ± 1.6), and 5 (5.2 ± 1.9) was similar. Mean viable oocyte number was greater (P < 0.0001) for B. t. taurus (21.7 ± 1.4, n = 192 OPU sessions) compared with B. t. indicus (16.1 ± 0.9, n = 138 OPU sessions) maternal genetic groupings. However, in vitro blastocyst yields were similar (P = 0.23) between maternal genetic groupings (7.3 ± 1.6 and 6.2 ± 1.4 for B. taurus and B. indicus, respectively). In conclusion, repeated OPU sessions did not reduce oocyte and embryo yields as expected. Maternal B. taurus genetic origin was associated with higher oocyte quality, although it was not translated into higher embryo yields after in vitro culture. Results warrant further research, which may result in additional selection criteria for OPU Gyr donors considering their maternal genetic background.