Carlos José Hoff de Souza

Multiple factors affecting the efficiency of multiple ovulation and embryo transfer in sheep and goats

This review offers an overview of the basic characteristics of in vivo embryo technologies, their current status, the main findings and the advances gained in recent years, and the outstanding subjects for increasing their efficiency. The use of superovulation and embryo transfer procedures remains affected by a high variability in the ovulatory response to hormonal treatment and by a low and variable number of transferable embryos and offspring obtained. This variability has been classically identified with both extrinsic (source, purity of gonadotrophins and protocol of administration) and intrinsic factors (breed, age, nutrition and reproductive status), which are reviewed in this paper. However, emerging data indicate that the main causes of variability are related to endocrine and ovarian factors, and so the number of studies and procedures addressing a better understanding and control of these factors may be increased in the future. The accomplishment of this objective, the improvement of procedures for embryo conservation and for the selection and management of recipient females, will allow further development and application of this technology.

A new polymorphism in the Growth and Differentiation Factor 9 (GDF9) gene is associated with increased ovulation rate and prolificacy in homozygous sheep

Brazilian Santa Inês (SI) sheep are very well-adapted to the tropical conditions of Brazil and are an important source of animal protein. A high rate of twin births was reported in some SI flocks. Growth and Differentiation Factor 9 (GDF9) and Bone Morphogenetic Protein 15 (BMP15) are the first two genes expressed by the oocyte to be associated with an increased ovulation rate in sheep. All GDF9 and BMP15 variants characterized, until now, present the same phenotype: the heterozygote ewes have an increased ovulation rate and the mutated homozygotes are sterile. In this study, we have found a new allele of GDF9, named FecG(E) (Embrapa), which leads to a substitution of a phenylalanine with a cysteine in a conservative position of the mature peptide. Homozygote ewes presenting the FecG(E) allele have shown an increase in their ovulation rate (82%) and prolificacy (58%). This new phenotype can be very useful in better understanding the genetic control of follicular development; the mechanisms involved in the control of ovulation rate in mammals; and for the improvement of sheep production.

Body condition score to predict the postpartum fertility of crossbred beef cows

A relacao entre as modificacoes no escore de condicao corporal (BCS) e a fertilidade de vacas de corte durante o pos-parto foi examinada em grupos organizados em funcao das datas dos partos. Foram efetuadas quatro avaliacoes com inicio em torno de um mes pos-parto. Na segunda avaliacao, as vacas receberam pessarios impregnados com acetato de medroxi-progesterona e uma injecao de benzoato de estradiol. Na sua remocao, foi efetuada a terceira avaliacao e separacao dos terneiros durante quatro dias. Durante esse periodo foi observado cio duas vezes ao dia, sendo as inseminacoes realizadas 12 horas apos. Depois do retorno dos terneiros as vacas, foram introduzidos touros ate completar 60 dias de estacao reprodutiva. As distribuicoes dos BCS diferiram significativamente entre grupos de paricao e momentos de avaliacao. Os resultados indicaram que apenas vacas com BCS 3 (escala de 1 a 5) em torno do primeiro mes pos-parto podem ser incluidas em programas de inseminacao artificial com possibilidade de ficarem prenhas. Nao foi observada diferenca estatisticamente significativa entre grupos de paricao quanto a taxa de prenhez. A evolucao do BCS durante o pos-parto pode ser empregada para ajustar a estacao reprodutiva a melhor epoca do ano, visando maiores taxas de gestacao.

Effect of the Booroola gene on time of ovulation and ovulatory dynamics

A three-quarter Romney Marsch × one-quarter Merino Booroola flock, composed of 31 (FecB Fec+) and 53 (fec+ Fec+) ewes, was used to investigate the ovulation time and ovulatory dynamics after the onset of spontaneous estrus during the reproductive season and after MAP (medroxy-progesterone acetate) treatment and gonadotrophin injection during seasonal anestrus. These studies involved laparoscopic examination of ovaries at pre-determined times, between 16 and 40 h after onset of estrus (Trial 1); and serial laparoscopies between 48 and 80 h after MAP + 500 IU PMSG injection (Trial 2). In Trial I, the FecB Fec+ ewes had smaller pre-ovulatory follicles than the Fec+ Fec+ ewes (P 0.05). A great variation in the time of ovulation was observed in both trials, ranging over a period of 16 h in Trial 1 and 24 h in Trial 2. ovulation began at 24 h after the onset of estrus, and the mode was observed at 32 h, although 20% of ewes had not ovulated by 40 h. In Trial 2, the first ovulation was observed at 54 h after PMSG injection, and the mode at 72 h. However, at 80 h ovulation had not been observed in about 10% of ewes. Ovulation rate was greater in Booroola gene carriers than in non-carriers in either spontaneous or induced ovulation (P<0.01). This demonstrated that the Fec gene acts on the ovulation rate without changing the aspects of time of ovulation and ovulatory dynamics studied in this experiment.

Momento da ovulação em ovelhas corriedale após cio natural e induzido com progestágeno e eCG

The aim of the present study was to verify the time of ovulation after natural or induced estrus in the Comedale ewe. The ram effect was also evaluated in the presence of induced estrus. Both treatments were examined by laparoscopy every four hours, from 20h to 40h after beginning the natural estrus, and from 48h to 120h after withdrawing the sponges or until ovulation was observed. After natural estrus, 96% from 56 ewes had ovulated, and most of the ovulations (85%) had occurred from 24 to 32h after the onset of heat. The mean time of ovulation in 60 ewes treated with progestagen pessaries (50mg, MAP, 12 days) and eCG injection (500IU at sponge withdrawai) was 65.1 ± 2.2h and 73.8 ± 3.2h respectively for groups with and without the presence of rams. This trait was affected by the ram effect (P < 0.05); however, it was neither influenced by the age of the ewes nor the repeated hormonal treatments. The time of ovulation after natural estrus, due to its small variation, is not likely to affect the results of artificial insemination with frozen semen. On the contrary, the time of ovulation, but not the range of ovulation distribution, was significantly increased in ewes with induced estrus when in the presence of rams. These results probably play a role in the success rate of the artificial insemination with frozen semen.

VIABILIDADE DO EMPREGO DE UMA MINIDOSE DE PROSTAGLANDINA NA SINCRONIZAÇÃO DE CIOS EM OVINOS

RESUMO Sao apresentados resultados de tres experimentos sequenciais que investigaram a viabilidade da reducao da dosagem recomendada de prostaglandina para a sincronizacao de cios em ovinos via injecao na submucosa vulvar. Os resultados indicaram a possibilidade de utilizacao de uma terca parte da dose usual. Em sistemas de sincronizacao de nove dias os melhores resultados foram obtidos com a aplicacao no sexto dia de servico.

BIOLOGIA REPRODUTIVA DA LINHAGEM MERINO BOOROOLA: UM MODELO EXPERIMENTAL PARA ESTUDOS RELATIVOS À OVULAÇÃO DOS OVINOS

The prolific sheep strain Merino Booroola, is presented as an experimental model for ovulation biology studies. The heritage, genotype identification, action of the gene and also some aspects of the reproductive biology are described as a reference for further utilization of this model. The Booroola gene mechanism of action and genic product, will clear some aspects of the ovulation mechanism and can be a tool for ovulation control in mammals.