RESUMO

In an attempt to develop accessible methods for the precocious individual selection based on phenotypic attributes related to reproductive superiority, this study evaluated the effects of follicular wave stages (emergence and dominance) and the repeatability coefficients of potential fertility predictors (vulvar morphometry, uterine biometry, echogenicity and echotexture, ovarian biometry, and antral follicle count - AFC) in two breeds of purebred prepubertal heifers. Nellore (n = 30) and Caracu (n = 28) heifers were submitted to a sequence of 11 evaluations conducted every 48 h (D0 - random day of the antral follicular wave until D20) to study potential fertility indicators under natural conditions. The data obtained were compared according to breed and follicular wave stage. Statistical analysis included the fixed effects of breed, evaluation day, and their statistical interaction and was performed using MIXED, GENMOD, GLM, and CORR procedures of the SAS program. Breed was found to influence rima height, ovarian area, and AFC, which were greater in Nellore heifers (P < 0.02). The follicular wave stage also influenced most of the potential predictors, highlighting AFC which was higher in the presence of a dominant follicle in both breeds (P < 0.0001). The repeatability coefficients for vulvar width (0.76 and 0.66), ovarian area (0.70 and 0.62), and AFC (0.76 and 0.74) were considered to be high in Nellore and Caracu heifers, respectively. Only ovarian biometry was able to predict AFC (Pearson correlation coefficient ≥ 0.66; P < 0.0001) in prepubertal heifers. The results indicate that most of the phenotypic reproductive parameters analyzed can be characterized throughout prepuberty using a single measure since they are intrinsic attributes of the individual.

Assuntos

RESUMO

O objetivo do presente experimento foi avaliar efeito do estresse e da dificuldade de inseminação (DifIA) sobre a taxa de concepção (TC) de vacas (n=93) e novilhas (n= 72) Nelore submetidas à IATF. No D9, anotou-se nota de temperamento (NTe) e tempo da saída do brete (TSB) de todos os animais e coletou-se sangue das novilhas. No dia da IATF (D11), anotou-se NTe, TSB, DifIA e tempo de IA. A TC foi 36% para vacas e 46% para novilhas (P>0,05). Não foi observado efeito de Nte sobre TC (P>0,05). Porém, houve tendência para maior (P<0,10) TC nos animais que não apresentaram dificuldade de inseminação (DifIA1; TP=42%) em comparação aos animais com moderada ou alta dificuldade (DifIA2+DifIA3; TP=27%). Foi observado menor (P<0,05) tempo de IA para animais DifIA1 (17:31±06:02s) que animais DifIA2-3 (30:10±15:45s). Novilhas com maiores (P<0,05) níveis de cortisol apresentaram maior NTe (P<0,05). Entretanto, TC (59%) das novilhas menos reativas (cortisol=4,12±1,12ng/mL; NTe=3,2±0,6) não diferiu da TC (41%; P>0,05) das mais agitadas (cortisol=7,76±1,33ng/mL; NTe=3,82±0,79). Concluiu-se que avaliações de temperamento se relacionaram com nível de estresse, embora esses parâmetros não tenham afetado a TC deste trabalho. A maior dificuldade e/ou tempo necessário para se completar a IA demonstrou ser um potencial fator para a redução da fertilidade na IATF.(AU)

The objective was to evaluate the influence of stress and difficulty of insemination (DifIA) on conception rate (CR) of Nellore cows (n= 93) and heifers (n= 72) in Timed-AI. On D9, temperament (NTe) and time for chute exit (TSB) were recorded for all animals, and blood samples were colected from heifers. On the day of Timed-AI (D11), NTe, TSB, DifIA and time for AI were recorded. For cows, CR was 36% and for heifers 46% (P> 0.05). No effect (P> 0.05) of NTe was observed on CR. However, a tendency (P< 0,10) for higher CR was observed in animals with no difficulty for insemination (DifIA1; CR=42%) compared to animals that presented moderate or high difficulty (DifIA2+DifIA3, CR=27%). Time required for AI was lower (P< 0.05) in animals DifIA1 (17:31±06:02sec) than in animals DifIA2-3 (30:10±15:45sec). Heifers with greater (P< 0.05) cortisol levels presented higher Nte (P< 0.05). However, CR (59%) of less reactive heifers (cortisol=4,12±1,12ng/mL; NTe=3,2±0,6) did not differ from CR (41%; P> 0.05) of stressed animals (cortisol=7,76±1,33ng/mL; NTe=3,82±0,79). It was concluded that assessments of temperament were related to stress level, although these parameters did not affect the CR of this study. However, the higher difficulty and/or time to complete AI showed to be a potential factor for reducing fertility after timed-AI.(AU)

Assuntos

RESUMO

O objetivo do presente experimento foi avaliar efeito do estresse e da dificuldade de inseminação (DifIA) sobre a taxa de concepção (TC) de vacas (n=93) e novilhas (n= 72) Nelore submetidas à IATF. No D9, anotou-se nota de temperamento (NTe) e tempo da saída do brete (TSB) de todos os animais e coletou-se sangue das novilhas. No dia da IATF (D11), anotou-se NTe, TSB, DifIA e tempo de IA. A TC foi 36% para vacas e 46% para novilhas (P>0,05). Não foi observado efeito de Nte sobre TC (P>0,05). Porém, houve tendência para maior (P<0,10) TC nos animais que não apresentaram dificuldade de inseminação (DifIA1; TP=42%) em comparação aos animais com moderada ou alta dificuldade (DifIA2+DifIA3; TP=27%). Foi observado menor (P<0,05) tempo de IA para animais DifIA1 (17:31±06:02s) que animais DifIA2-3 (30:10±15:45s). Novilhas com maiores (P<0,05) níveis de cortisol apresentaram maior NTe (P<0,05). Entretanto, TC (59%) das novilhas menos reativas (cortisol=4,12±1,12ng/mL; NTe=3,2±0,6) não diferiu da TC (41%; P>0,05) das mais agitadas (cortisol=7,76±1,33ng/mL; NTe=3,82±0,79). Concluiu-se que avaliações de temperamento se relacionaram com nível de estresse, embora esses parâmetros não tenham afetado a TC deste trabalho. A maior dificuldade e/ou tempo necessário para se completar a IA demonstrou ser um potencial fator para a redução da fertilidade na IATF.(AU)

The objective was to evaluate the influence of stress and difficulty of insemination (DifIA) on conception rate (CR) of Nellore cows (n= 93) and heifers (n= 72) in Timed-AI. On D9, temperament (NTe) and time for chute exit (TSB) were recorded for all animals, and blood samples were colected from heifers. On the day of Timed-AI (D11), NTe, TSB, DifIA and time for AI were recorded. For cows, CR was 36% and for heifers 46% (P> 0.05). No effect (P> 0.05) of NTe was observed on CR. However, a tendency (P< 0,10) for higher CR was observed in animals with no difficulty for insemination (DifIA1; CR=42%) compared to animals that presented moderate or high difficulty (DifIA2+DifIA3, CR=27%). Time required for AI was lower (P< 0.05) in animals DifIA1 (17:31±06:02sec) than in animals DifIA2-3 (30:10±15:45sec). Heifers with greater (P< 0.05) cortisol levels presented higher Nte (P< 0.05). However, CR (59%) of less reactive heifers (cortisol=4,12±1,12ng/mL; NTe=3,2±0,6) did not differ from CR (41%; P> 0.05) of stressed animals (cortisol=7,76±1,33ng/mL; NTe=3,82±0,79). It was concluded that assessments of temperament were related to stress level, although these parameters did not affect the CR of this study. However, the higher difficulty and/or time to complete AI showed to be a potential factor for reducing fertility after timed-AI.(AU)

Assuntos

RESUMO

Brucellosis remains as a major infectious disease of domestic animals and is considered a re-emerging zoonosis in several countries. B. abortus infections in bulls are related to reproductive tract infections, although infected animals show transient serological titers or nonreactor status. Thus, diagnosis of bovine brucellosis based exclusively on serological tests probably underestimates B. abortus infections in bulls. In this scenario, three hundred thirty-five serum samples from reproductively mature bovine bulls were subjected simultaneously to standard serodiagnosis using the rose Bengal test (RBT), 2-mercaptoethanol (2-ME), complement fixation (CFT), and fluorescence polarization assay (FPA). Furthermore, conventional semen plasma agglutination (SPA) and modified 2-ME, FC and, FPA were carried out in all bulls replaing serum by seminal plasma. Semen from all bulls was also analyzed for sperm viability, microbiological culture in Farrell media, and polymerase chain reaction (PCR). Only eight (2.38%) semen samples were considered improper for reproduction services (necrospermia and azoospermia), although none of these animals was positive in any of the diagnosis methods used. Five bulls (1.49%) were simultaneously positive in conventional RBT, 2-ME, SPA, modified 2-ME, microbiological culture in Farrell media, and in PCR for B. abortus strain 19. Two (1.67%) bulls were positive in PCR for B. abortus field strains and negative in all other tests, although semen was considered viable to reproduction service. The identification of B. abortus B19 strain in serum and semen of bulls occurred probably due to improper vaccination of males or infection by B19 strain shedding by vaccinated females that could to contaminated environment of farms. In addition, detection of B. abortus field strains only using PCR in bulls without sperm viability abnormalities indicate the need for including molecular methods to improve diagnosis of the disease in bovine bulls.

Assuntos

RESUMO

Cryopreservation causes damage to spermatozoa, and methods minimizing this damage are therefore needed. Although much discussed, seminal plasma removal has become an alternative to improve sperm quality and viability after freezing and has been applied to different species in attempt to obtain good results. The objective of this study was to evaluate semen quality in buffaloes submitted to two methods for seminal plasma removal (filtration and centrifugation). Semen samples were collected from seven Murrah buffalo bulls (Bubalus bubalis) once a week for 8 weeks. Each ejaculate was divided into three groups: control (presence of seminal plasma), centrifugation and filtration. Sperm kinetics was evaluated with the computer-assisted sperm analysis (CASA) system. Plasmalemma and acrosomal membrane integrity, mitochondrial membrane potential and reactive oxygen species (ROS) were measured by flow cytometry, and lipid peroxidation was evaluated by the thiobarbituric acid reactive substances (TBARS) assay. Seminal plasma removal did not improve sperm kinetics compared to the control group. Centrifugation increased the number of cells with damaged acrosomal membranes (0.77 ± 0.05) and filtration caused greater plasmalemma and acrosomal membrane damage (22.18 ± 1.07). No difference in the mitochondrial membrane potential was observed between groups. In contrast, ROS production was higher in the centrifugation group compared to the control and filtration groups, although no differences in TBARS formation were detected. In conclusion, seminal plasma removal did not improve the quality of thawed buffalo semen compared to control in terms of sperm kinetics, membrane integrity, mitochondrial membrane potential or lipid peroxidation.

Assuntos

RESUMO

The aim of the present study was to evaluate whether repeated ovum pick-up (OPU) procedures may affect the efficiency of OPU programs for in vitro embryo production (IVEP) in Bos indicus (Nelore) donors. In addition, the repeatability (r) efficiency of IVEP was also assessed. Data available were from 432 OPU-IVEP sessions that were performed at random stages of the estrous cycle in 36 cycling, nonlactating Nelore donors. Semen from three Nelore bulls was used for the IVF. Donors were submitted to 12 consecutive OPU procedures, with an interval of approximately 30 days between sessions. Data were analyzed as repeated measures using the GLIMMIX procedure of SAS 9.3. Cows yielding ≥15 COCs were defined as "high" COCs and cows with less than 15 COCs were defined as "low" COCs donors. The number of COCs retrieved decreased over time in donors classified with high COCs and remained fairly steady in cows with low COCs at the beginning of the program (Psession*COC retrieved groups = 0.02). Moreover, the number of COCs retrieved (P < 0.0001), and number of blastocysts produced per OPU (P = 0.001) was greater for the high COCs donors compared with the low COCs category, and these results were consistent across OPU sessions. Interestingly, there was no effect of COCs category on the rate of blastocyst development (P = 0.83). In addition, number of blastocysts produced were not affected by repeated OPU (P = 0.37) and interactions between time and COC category (P = 0.72). Similarly, blastocyst rate was not affected by repeated OPU (P = 0.21) and interactions between time and COC category (P = 0.58). Despite of COC category of the donor cows, repeatability was high for the number of COCs retrieved (r = 0.81), number of blastocysts produced per OPU (r = 0.79), and blastocyst rate (0.69). In conclusion, overall numbers of COCs decreased over time in donors classified as having high COCs. However, cumulative amounts of produced blastocysts were greater in donors with high COCs. More importantly, high repeatability was observed in terms of IVEP efficiency. Therefore, IVEP programs can be significantly improved with more aggressive selection toward donors with greater numbers of COCs.

Assuntos

RESUMO

The aim of the present study was to evaluate small follicle number, oocyte yield, and in vitro embryo production (IVEP) in Zebu beef cows treated long term with a GnRH agonist to suppress ovarian follicular growth. Nelore (Bos indicus) cows (n = 20) showing regular estrous cycles were randomly assigned to one of two groups: control (n = 10, placebo ear implant without a GnRH agonist); GnRH agonist (n = 10, GnRH agonist ear implant containing 9.4-mg deslorelin). All cows underwent an ovum pick-up (OPU) session 14 days (Day 14) before the start of treatments (Day 0) followed by seven OPU-IVEP procedures at 30-day intervals (Days 0, 30, 60, 90, 120, 150, and 180). Semen from a single batch of a previously tested bull was used for all the IVEP. Cows treated with agonist reported a decrease over time in the proportion of animals with a (CL; P ≤ 0.05) and large follicles (>10 mm, P ≤ 0.05). These cows had a lesser number of medium + large follicles (>5 mm; 1.74 ± 0.5 vs. 4.13 ± 0.5; P ≤ 0.05), greater number of small follicles (2-5 mm; 44.3 ± 2.8 vs. 30.8 ± 1.8; P ≤ 0.05), greater yield of cumulus-oocyte complexes (COCs; 21.0 ± 2.3 vs. 15.6 ± 1.9; P ≤ 0.05), greater proportion of COCs cultured (79.2 vs. 73.9%; P ≤ 0.05), COCs cleaved (10.6 ± 1.5 vs. 6.8 ± 1.1, P ≤ 0.05), and cleaved rate (52.8 vs. 44.3%; P ≤ 0.05) compared with control cows. The number (3.4 ± 0.7 vs. 3.0 ± 0.6; P > 0.05) and proportion (16.5 vs. 19.1%; P > 0.05) of blastocysts produced were similar between agonist and control cows, respectively. The study has shown that Zebu beef cows treated long term with a GnRH agonist had follicular growth restricted to small follicles. This did not compromise the ability of oocytes to undergo IVF and embryonic development.

Assuntos

RESUMO

A taxa de prenhez é de extrema importância para a eficiência produtiva de bovinos de corte, e a fertilidade dos touros pode influenciar na taxa de prenhez das matrizes em monta natural. O objetivo deste trabalho foi avaliar a relação entre as características do exame andrológico, especialmente a circunferência escrotal (CE), de touros da raça Nelore (Bos indicus), selecionados para reprodução com base em maior ganho de peso pós-desmama, com a taxa de prenhez de vacas Nelore em estação de monta natural de 90 dias de duração. Foram avaliados registros de 7171 entradas na monta de 1923 vacas submetidas a 216 touros em 368 lotes de estação de monta a campo (touro único), durante os anos de 1995 a 2014, e a CE dos touros. A CE foi pré-ajustada para idade do touro (2,67±0,62 anos) na entrada da estação de monta, em modelo de regressão linear, sendo posteriormente expressa em 3 classes: classe 1: CE < 35 cm; classe 2: 35 ≥ CE < 37 cm; classe 3: CE ≥ 37. Mais da metade das observações de CE ficaram na classe 2, e 74,52% das exposições aos touros resultaram em prenhez, com mínimo de 0% e máximo de 100% de sucesso de prenhez nos 368 lotes de monta. Parte (n=33) dos 216 touros tinham registros de características obtidas em exame andrológico parcial [CE, volume, motilidade, vigor, concentração e morfologia espermática (defeitos maiores e menores)]. Verificou-se que a classe de valores intermediários de CE (classe 2: 35 ≥ CE < 37 cm) foi a de maior risco relativo para sucesso na prenhez. Na amostra dos 33 touros, a taxa de prenhez apresentou correlação moderada e positiva (r = 0,66) somente com a concentração espermática. A fraca relação entre as características do andrológico os touros e taxa de prenhez das vacas pode ser devido ao fato da amostra dos touros avaliados neste tipo de trabalho ser sempre viesada. Ou seja, só são considerados os touros que entraram em monta...(AU)

The pregnancy rate is extremely important for the productive efficiency of beef cattle and bull fertility can influence the pregnancy rate of cows in natural mating. The objective of this study was to evaluate the relationship of andrological traits, especially scrotal circumference (SC), of Nellore bulls (Bos indicus) selected for breeding based on greater postweaning weight gain with the pregnancy rate of naturally mated Nellore cows in a 90-day breeding season. Records of 7,171 entries into the breeding season of 1,923 cows exposed to 216 bulls in 368 mating batches in the field (single bull) from 1995 to 2014, as well as records of SC, were evaluated. Scrotal circumference was pre-adjusted for bull age (2.67±0.62 years) at the start of the breeding season using a linear regression model and was divided into three classes: class 1: SC < 35 cm; class 2: 35 ≥ SC < 37 cm; class 3: SC ≥ 37. More than half the observations of SC were in class 2 and 74.52% of the exposures to bulls resulted in pregnancy, with a minimum rate of successful pregnancy of 0% and a maximum rate of 100% in the 368 mating batches. Thirty-three of the 216 bulls had records of andrological traits [SC, sperm volume, motility, vigor, concentration and morphology (major and minor defects)]. The class of intermediate SC values (class 2: 35 ≥ SC < 37 cm) was associated with a higher relative risk of pregnancy success. In the sample of the 33 bulls, pregnancy rate showed a moderate positive correlation (r = 0.66) only with sperm concentration. The weak association between andrological traits of bulls and pregnancy rate might be due to the fact that the sample of bulls evaluated in this type of study will be always biased. In other words, only bulls that enter the breeding season are considered, which correspond to a small percentage of all males born. Consequently, the variation observed in these bulls does...(AU)

Assuntos

RESUMO

A taxa de prenhez é de extrema importância para a eficiência produtiva de bovinos de corte, e a fertilidade dos touros pode influenciar na taxa de prenhez das matrizes em monta natural. O objetivo deste trabalho foi avaliar a relação entre as características do exame andrológico, especialmente a circunferência escrotal (CE), de touros da raça Nelore (Bos indicus), selecionados para reprodução com base em maior ganho de peso pós-desmama, com a taxa de prenhez de vacas Nelore em estação de monta natural de 90 dias de duração. Foram avaliados registros de 7171 entradas na monta de 1923 vacas submetidas a 216 touros em 368 lotes de estação de monta a campo (touro único), durante os anos de 1995 a 2014, e a CE dos touros. A CE foi pré-ajustada para idade do touro (2,67±0,62 anos) na entrada da estação de monta, em modelo de regressão linear, sendo posteriormente expressa em 3 classes: classe 1: CE < 35 cm; classe 2: 35 ≥ CE < 37 cm; classe 3: CE ≥ 37. Mais da metade das observações de CE ficaram na classe 2, e 74,52% das exposições aos touros resultaram em prenhez, com mínimo de 0% e máximo de 100% de sucesso de prenhez nos 368 lotes de monta. Parte (n=33) dos 216 touros tinham registros de características obtidas em exame andrológico parcial [CE, volume, motilidade, vigor, concentração e morfologia espermática (defeitos maiores e menores)]. Verificou-se que a classe de valores intermediários de CE (classe 2: 35 ≥ CE < 37 cm) foi a de maior risco relativo para sucesso na prenhez. Na amostra dos 33 touros, a taxa de prenhez apresentou correlação moderada e positiva (r = 0,66) somente com a concentração espermática. A fraca relação entre as características do andrológico os touros e taxa de prenhez das vacas pode ser devido ao fato da amostra dos touros avaliados neste tipo de trabalho ser sempre viesada. Ou seja, só são considerados os touros que entraram em monta...

The pregnancy rate is extremely important for the productive efficiency of beef cattle and bull fertility can influence the pregnancy rate of cows in natural mating. The objective of this study was to evaluate the relationship of andrological traits, especially scrotal circumference (SC), of Nellore bulls (Bos indicus) selected for breeding based on greater postweaning weight gain with the pregnancy rate of naturally mated Nellore cows in a 90-day breeding season. Records of 7,171 entries into the breeding season of 1,923 cows exposed to 216 bulls in 368 mating batches in the field (single bull) from 1995 to 2014, as well as records of SC, were evaluated. Scrotal circumference was pre-adjusted for bull age (2.67±0.62 years) at the start of the breeding season using a linear regression model and was divided into three classes: class 1: SC < 35 cm; class 2: 35 ≥ SC < 37 cm; class 3: SC ≥ 37. More than half the observations of SC were in class 2 and 74.52% of the exposures to bulls resulted in pregnancy, with a minimum rate of successful pregnancy of 0% and a maximum rate of 100% in the 368 mating batches. Thirty-three of the 216 bulls had records of andrological traits [SC, sperm volume, motility, vigor, concentration and morphology (major and minor defects)]. The class of intermediate SC values (class 2: 35 ≥ SC < 37 cm) was associated with a higher relative risk of pregnancy success. In the sample of the 33 bulls, pregnancy rate showed a moderate positive correlation (r = 0.66) only with sperm concentration. The weak association between andrological traits of bulls and pregnancy rate might be due to the fact that the sample of bulls evaluated in this type of study will be always biased. In other words, only bulls that enter the breeding season are considered, which correspond to a small percentage of all males born. Consequently, the variation observed in these bulls does...

Assuntos

RESUMO

The effect of selection for postweaning weight was evaluated within the growth curve parameters for both growth and carcass traits. Records of 2404 Nellore animals from three selection lines were analyzed: two selection lines for high postweaning weight, selection (NeS) and traditional (NeT); and a control line (NeC) in which animals were selected for postweaning weight close to the average. Body weight (BW), hip height (HH), rib eye area (REA), back fat thickness (BFT), and rump fat thickness (RFT) were measured and records collected from animals 8 to 20 (males) and 11 to 26 (females) months of age. The parameters A (asymptotic value) and k (growth rate) were estimated using the nonlinear model procedure of the Statistical Analysis System program, which included fixed effect of line (NeS, NeT, and NeC) in the model, with the objective to evaluate differences in the estimated parameters between lines. Selected animals (NeS and NeT) showed higher growth rates than control line animals (NeC) for all traits. Line effect on curves parameters was significant (P < 0.001) for BW, HH, and REA in males, and for BFT and RFT in females. Selection for postweaning weight was effective in altering growth curves, resulting in animals with higher growth potential.

Assuntos