J. C. F. Moraes

The role of angiotensin II in the early stages of bovine ovulation

There is evidence that the renin-angiotensin system plays an important role in ovulation in cattle. Using an in vivo model, we investigated the role of angiotensin (Ang) II in bovine ovulation by injecting Ang II receptor antagonists into ovulatory follicles. Animals (n = 102) were pre-synchronized and, when the follicles reached 12 mm, they were given the respective treatment and the cows received GnRH agonist (i.m.) to induce ovulation. The ovulation rate was significantly lower when 100 mu M saralasin (Ang II receptor antagonist) was intrafollicularly injected (14.3%) in comparison with saline solution (83.3%). Based on these results, a second experiment was carried out to determine the timing of Ang IIs critical role in ovulation. Saralasin inhibited ovulation only when applied at 0 and 6 h (16.7 and 42.9% ovulation rate in the 0- and 6-h groups respectively), but not at 12 h (100%) following GnRH agonist treatment. To investigate the subtypes of Ang II receptors implicated in the LH-induced ovulation, losartan (LO; AT(1)-Ang II receptor antagonist), PD123 319 (AT(2)-Ang II receptor antagonist), LO+PD123 319, or saline were intrafollicularly injected when the cows were challenged with GnRH agonist. Ovulation was inhibited by PD123 319 and LO+PD123 319 (50.0 and 33.3% on ovulation rate respectively), but not by LO or saline solution (100% ovulation in both groups). From these results, we suggest that Ang II plays a pivotal role in the early mechanism of bovine ovulation via the AT(2) receptor subtype.

Follicular development and steroid concentrations in cows with different levels of fertility raised under nutritional stress

The aim of the present study was to characterize ovarian follicular development and steroid concentrations during postpartum and the estrous cycle of Brangus Ibagé cows (3/8 Nelore + 5/8 Aberdeen Angus) with different levels of fertility. Cows were classified as having high or low fertility according to the calving interval (CI). The average CI of the herd from which cows used in this study were selected was 404.6+/-5.44 and 711.2+/-20.89 days for the high and low fertility groups, respectively. Four cows of high fertility and five cows of low fertility had calves removed between 70 and 100 days after parturition. Ovarian activity was monitored daily by ultrasound for 16 days after calf removal. Days to emergency of the first follicular wave after calf removal, number of follicles with diameter >9 mm, growth rate of largest follicle, maximum diameter of largest follicle, length (days) and number of follicular waves were recorded. During this period, blood was collected daily for measurements of serum progesterone (P(4)) and estradiol (E(2)) concentrations. In another experiment, ovarian activity and P(4) and E(2) concentrations were examined during estrous cycle in five cows of high fertility and four cows of low fertility. Ovarian activity and steroid concentrations were assessed from the day prior to estrus to the 15th day of the estrous cycle (estrus = day 0). In postpartum cows of high fertility, the total number of follicles >5mm and the maximum diameter of the largest follicle were higher than in cows of low fertility (P < 0.05). Concentrations of P(4) and E(2) did not differ between groups in the postpartum cows. However, E(2) increased 5 days after calf removal (around 90 days of postpartum) in the high fertility group, followed by an increase in P(4) with average values indicating ovulation around 100 days postpartum. In cycling cows, the profile of follicular development was similar between cows of high and low fertility. There was no difference between groups for number of follicles >5mm, but the day effect was significant (P < 0.01). Plasma concentrations of P(4) and E(2) were similar in both groups. These data suggest that cows, from a population raised in the same environment have different fertility as a consequence of individual physiological characteristics.

Geographical distribution of sheep breeds in Brazil and their relationship with climatic and environmental factors as risk classification for conservation

BackgroundThe aim of this study was to evaluate the distribution of sheep breeds in Brazil, correlate their occurrence with environmental factors and determine their risk for extinction.MethodsThe localization of all flocks of purebred sheep (commerical and naturalised, hair and wool) in Brazil was spatialized in ARCGIS along with climatic (Thermal Humidity Index, precipitation, solar radiation, relative humidity) and physical environmental controls (altitude, pasture type). Data were analysed using analysis of variance, logisitic regression and cluster analyses. Distance matrices were constructed using longitude/latitude and those from environmental controls and these were correlated using Mantel test.ResultsSanta Ines and Dorper were the most popular breeds with a countrywide distribution. Over 80% of most breeds occurred within 500 km of their midpoint which has implications for their conservation and vulnerability as those breeds with few flocks and restricted geographical distribution are at higher risk. This was especially evident for the naturalised breeds. Spatial distribution of breeds was highly correlated with environmental controls and two distinct clusters were found. Spatial distribution of breeds was highly correlated with environmental controls. Naturalised sheep breeds in Brazil tend to be more localized than commercial breeds which may mean they are at greater risk. Hair and wool sheep tend to occur in specific environments.ConclusionsFlocks in the center west and northeast tend to further away from the midpoint for the breed, making germplasm exchange, and therefore avoidance of inbreeding and their conservation, more difficult.

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.

Diversity of microsatellites linked to the FSHbeta gene, their usefulness for individual identification and association with reproductive performance

A diversidade genetica de tres microssatelites (ILSTS027, MBO22, BM4325) mapeados no cromossomo bovino 15 e ligados ao gene do hormonio foliculo estimulante, cadeia b (FSHb) foi investigada em femeas de um rebanho bovino Brangus Ibage. Alem de estimar a variabilidade genetica do rebanho, avaliou-se a eficiencia destes marcadores para a identificacao individual e controle de paternidade. Verificaram-se tambem possiveis associacoes entre os marcadores e o desempenho reprodutivo. Seis alelos foram detectados em BM4325 e ILSTS027 e 12 foram observados em MB022, os mais frequentes sendo, BM4325*101, BM4325*103, ILSTS027*169 e MB022*229. O conteudo de informacao polimorfica variou entre 0,58 a 0,88 enquanto a heterozigosidade esperada oscilou entre 65% e 89%, sendo o valor medio de 77%. Embora apenas tres marcadores tenham sido investigados, os valores combinados indicam alto poder de exclusao de um falso progenitor (94%) e de identificacao individual (3,8 x 10-4). As analises de associacao baseadas nos parâmetros estatisticos [MB022 (n=104, CI=545,3±127,0, WFC=349,9±53,4), BM4325(n=106, CI=542,2±124,9, WFC=350,5±54,4) e ILSTS027(n=105, CI=543,4±124,5, WFC=350,1±54,5)] nao indicaram associacao positiva entre os microssatelites e o peso da vaca ao parto. O intervalo entre partos tambem nao parece ser influenciado pelos marcadores ILSTS027 ou MB022. No entanto, portadores de pelo menos um alelo BM4325*101 apresentaram intervalo entre partos 54 dias mais curto que os demais animais (p=0,04; n=106). Este marcador pode ser util para selecao assistida por marcadores, permitindo a melhoria do desempenho reprodutivo, pelo menos no rebanho Brangus Ibage.

Eficiência produtiva e reprodutiva em vacas leiteiras

The present study was conducted to evaluate the effects of post partum disorders on productive and reproductive performance of Holstein cows, from a dairy experimental station, during 24 years. Productive and reproductive data were collected from 350 cows. Analyses of variance was conducted to evaluate the effects of occurrence of post partum disorders (abortion, stillbirth, dystocia, retained placenta) and mastitis on calving interval (IEP), calving to conception interval (IPC), calving to first estrus interval (IPPC), number of estrus before conception (NC) and milk production (PL). The mean age at first estrus was 29.4 months and the mean age at first calving was 37.1 months. Mean IEP was 14.6 months, mean IPPC was 97.04 days and median IPC was 150.71 days. Median interestrus interval was 24 days, suggesting problems in a estrus detection. A significant effect of occurrence of abortion (P<0.05) was observed on IEP. Calving intervals were 258 days longer in the cows that aborted than in the ones that did not abort. The occurrence of stillbirth (P<0.01) and dystocia (P<0.05) significantly increased IEP in 82.4 days and 136.1 days, respectively. The IPPC was not affected by any of the diseases considered. Milk production was affected by dystocia (P<0.05). Cows that had dystocia produced 380.5kg less milk than normal calving cows. We concluded that preventive procedures to control herd health, criterious clinical diagnosis of post partum disorders and development of data bases with precise recordings for regular analysis of the productive and reproductive parameters may lead to a more economic dairy production.

Exame andrológico em touros: qualidade dos indicadores da aptidão reprodutiva em distintos grupos raciais

There is a single set of standard for breeding soundness evaluation in bulls for ali breeds and production systems, resulting in economical losses due to high frequencies of culling in bulls of some genotypes. This study presents an analysis on two sets of field data, comparing contemporary groups of bulls from taurine pure-breds and zebu crossbreeds. The results were indicative that more flexible standards could be useful, avoiding injustified culling of bulls. This fact may be justified by the absence of interaction between breed and reproductive condition. It will be importam to continue the studies on procedures and standards for breeding soundness evaluation in bulls, to reduce losses in the production systems due to peculiarities inherent to the genetic groups.

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.

Relationship between clinical and postmortem evaluation in repeat breeder beef cows

The objective of this study was to investigate the causes of the repeat breeder syndrome comparing clinical signs and postmortem findings in beef cows. The identification of factors affecting the reproductive tract can support decisions as to whether treatment of repeat breeder cows is justifiable than culling. Since all animals were submitted to clinical examination before being slaughtered, this study has a differential approach when compared with others, where genital tracts from abattoir were examined. In this study, 130 crossbred cows and heifers that have failed to conceive after three or more services were identified, submitted to a clinical examination and blood collection for karyotyping and sent to an abattoir. postmortem examinations included macroscopic evaluation of the genital tracts, bacteriology and histopathology of the uterus. Uterine alterations were predominant followed by oviduct and ovarian pathologies. Histopathological examination was more sensitive as a diagnostic tool than clinical examination. Repeat breeder cows had a predominance of uterine abnormalities (95%), such as inflammatory (42.9%) and degenerative (59.7%) conditions. Oviduct abnormalities were found in 29.8 % of animals. Furthermore, 1 out 10 karyotyped cows showed aneuploidy. Thus, this study stressed the importance of laboratory exams in the diagnosis of the causes of infertility of repeat breeder cows.

Association between reproductive traits and four microsatellites in Brangus-Ibagé cattle

The aim of the present study was to verify associations between reproductive efficiency and four microsatellite markers located in synteny with genes involved in the regulation of reproductive mechanisms. A sample of 107 females from a Brangus Ibage population (5/8 Aberdeen Angus x 3/8 Nelore) was characterized for ETH225 (D9S1) and MM12E6 (D9S20) microsatellites, mapped on chromosome 9, and HEL5 (D21S15) and AFZ1 (D21S37) on chromosome 21. Associations between the genetic markers and reproductive efficiency were determined by one-way analysis of variance using calving interval (CI), live weight at calving (LWC), live weight at first calving (LW1C) and live weight at second calving (LW2C) as dependent variables. The genotypes were classified according to allele size into homozygous for long alleles, homozygous for short alleles and heterozygous. A longer CI was observed for individuals homozygous for long alleles at the HEL5 locus compared with the others (p = 0.022). For the AFZ1 locus, an inverse correlation between allele size and calving interval was observed (p = 0.022), suggesting that homozygosity for long alleles at this microsatellite could be advantageous. Analysis of the combined effect of favorable genotypes at HEL5 and AFZ1 indicated that animals with unfavorable genotypes (homozygous for long alleles at HEL5 and homozygous for short alleles at AFZ1) presented a significantly longer CI (p = 0.003) when compared to the other genotypes. The ETH225 and MM12E6 systems did not present any association with CI. None of the systems studied showed any significant association with LWC, LW1C or LW2C.