RESUMO
The Vietnamese pot-bellied pig is a breed with high investigation potential. However, at the reproductive level, its testicular characteristics are still unknown, as well as the different stages of its development. Therefore, the objective of this work is to describe the postnatal testicular development of Vietnamese pot-bellied pigs. In this study, we used pigs grouped into the neonatal stage, animals at zero weeks; prepubertal stage, animals at three and eight weeks; pubertal stage, animals at twelve and sixteen weeks; and postpubertal stage animals at twenty, twenty-four, twenty-eight and thirty-two weeks of age. The neonatal stage is characterized by gonocytes at different migration phases. In the prepubertal stage, gonocytes were differentiated into spermatogonia at 3 weeks of age, and the first spermatocytes were observed at 7 weeks of age. Puberty was determined to start at 12 weeks because seminiferous tubules are found with complete spermatogenesis and the highest peaks in positive cell counting of androgen receptors (AR) and proliferating cell nuclear antigen (PCNA) factor that later decreased and further stabilized in the following weeks. In the postpubertal stage, an increase in seminiferous tubule areas was observed. The number of apoptotic cells ranged from low to null at all ages. Testosterone (T) and gonadotropin levels had two important peaks at 3 and 24 weeks. The seminiferous epithelium cycle was found to have 11 stages according to acrosome development. These characteristics of Vietnamese pot-bellied pig testes, which are different from rat testes and more similar to human testicles, make them a viable model to study human male reproductive biology. The postnatal testicular development of pot-bellied pigs is different from the postnatal testicular development of other breeds. Therefore, due to this difference in size and easy manipulation, the Vietnamese pig is an alternative for investigation compared to other pig breeds.
Assuntos
Escroto/crescimento & desenvolvimento , Epitélio Seminífero/crescimento & desenvolvimento , Espermatogônias/crescimento & desenvolvimento , Testículo/crescimento & desenvolvimento , Animais , Animais Recém-Nascidos , Proliferação de Células , Humanos , Masculino , Modelos Animais , Antígeno Nuclear de Célula em Proliferação/metabolismo , Receptores Androgênicos , Túbulos Seminíferos/crescimento & desenvolvimento , Espermatogênese/fisiologia , Suínos , Fatores de TempoRESUMO
Scrotal circumference (SC) is considered a useful tool for predicting age at puberty and is performed to improve the reproductive performance in beef cattle industry. We aimed to fit several nonlinear mixed models for SC measurements of five different breeds to better predict testicular growth. Data of SC (cm), body weight (BW; kg), and age (A; days), farm location, sire and dam, and birth dates of 169,094 beef bulls were collected from five breeds: Nelore (N) (n = 110,814); Angus (AA) (n = 6541); Brangus (BA) (n = 42,910); Polled Hereford and Hereford (HH) (n = 4640); and Braford (BH) (n = 7480). Data comprise a total of 8640 sires and 115,172 dams and grouped in 2908 contemporary groups (CG). The full model development for SC was defined as: SC = CG + A + A*A + BW + BW*BW + Æ. Bulls from HH (34.1 ± 3.2) and AA (33.5 ± 3.0) had the highest value of SC, followed by BH (32.2 ± 3.7), BA (30.6 ± 4.1), and N (26.9 ± 3.6). There was a curvilinear effect of BW on the SC measurements of HH and AA bulls, reaching the maximum point around 600 kg, whether both breeds presented a similar testicular growth pattern. In British breeds, inflection points of average daily SC growth of 0.039 and 0.042 cm/kg were obtained from 700 kg HH and 600 kg AA bulls, respectively. Scrotal circumference values of 0.042 and 0.046 cm/kg reaching the maximum growth point at 450 kg BW were obtained for BH and BA bulls, respectively. We also observed SC values of 0.044 and 0.048 cm/d reaching the maximum growth point at 550 d of age for BH and BA bulls, respectively. Thus, estimate testicular size at maturity should be measured between 500 and 600 kg BW in British genotypes and between 550 and 600 d in Bos indicus and crossbreeds animals. Therefore, SC adjustment can be used by breed-specific criteria associated with BW and/or age to determine testis growth as a selection criterion in beef cattle breeding programs.
Assuntos
Bovinos/anatomia & histologia , Escroto/anatomia & histologia , Animais , Peso Corporal , Bovinos/crescimento & desenvolvimento , Masculino , Dinâmica não Linear , Escroto/crescimento & desenvolvimento , Maturidade SexualRESUMO
Morada Nova breed sheep are without wool, tropicalized, small-sized animals, known for their high-quality meat and skin. Their body development naturally depends on the genetic potential and adequate nutritional support, which suggests that the offer of high-energy density diets positively influences their productive indicators. Thus, the present study investigated the effect of a high-energy diet for the Morada Nova lambs on body development and testicular function, considering their histomorphometric characteristics and seminal quality. Forty-two males (19.2 weeks, 20.7 ± 3.5 kg) were equally divided into two groups and fed with 2.05 Mcal (G7, n = 21) or 2.37 Mcal (G24, n = 21) of metabolizable energy/day, equivalent to 7% and 24% above the minimum for growing lambs. The animals were confined for 23 weeks (W0 to W23). Weight and body score differed significantly from the W1 (P < 0.05). From the W5, thoracic perimeter, body length, wither height, and rump attributes were higher in G24 (P < 0.05). The scrotal circumference and testicular volume were higher in G24 from the W3 (P < 0.05). Although testosterone levels were not affected (P = 0.05), the highest energy intake increased the diameter of the seminiferous tubules and the development of the epididymal epithelium (P < 0.05). This positively influenced the seminal quality and reduced the minor defects (21.87% vs. 17.13%) and the total spermatic defects (26.34% vs. 21.78%, P < 0.05). Thus, it is possible to employ higher levels of dietary energy for Morada Nova young males to express higher productive efficiency and earlier reproductive attributes of interest.
Assuntos
Dieta/veterinária , Ingestão de Energia , Ovinos/crescimento & desenvolvimento , Ração Animal/análise , Fenômenos Fisiológicos da Nutrição Animal , Animais , Peso Corporal , Metabolismo Energético , Masculino , Reprodução , Escroto/crescimento & desenvolvimento , Testículo/crescimento & desenvolvimentoRESUMO
The aim of this study was to estimate genetic parameters for scrotal circumference at 365 (SC365) and 450 (SC450) days of age, age at first calving (AFC), ribeye area (REA), backfat (BF) thickness, and rump fat (RF) thickness, in order to provide information on potential traits for Nelore cattle breeding program. Genetic parameters were estimated using the Average Information Restricted Maximum Likelihood method in single- and multitrait analyses. Four different animal models were tested for SC365, SC450, REA, BF, and RF in single-trait analyses. For SC365 and SC450, the maternal genetic effect was statistically significant (P < 0.01) and was included for multitrait analyses. The direct heritability estimates for SC365, SC450, AFC, REA, BF, and RF were equal to 0.31, 0.38, 0.24, 0.32, 0.16, and 0.19, respectively. Maternal heritability for SC365 and SC450 was equal to 0.06 and 0.08, respectively. The highest genetic correlations were found among the scrotal circumferences. Testing for the inclusion of maternal effects in genetic parameters estimation for scrotal circumference should be evaluated in the Nelore breeding program, mostly for correctly ranking the animal's estimated breeding values. Similar heritability estimates were observed for scrotal circumference, as well as favorable genetic correlations of this trait with AFC and carcass traits. Thus, scrotal circumference measured at 365 days of age could be a target trait for consideration in the Nelore selection index in order to improve most of the traits herein analyzed.
Assuntos
Composição Corporal/fisiologia , Bovinos/fisiologia , Reprodução/fisiologia , Envelhecimento , Animais , Composição Corporal/genética , Cruzamento , Bovinos/genética , Feminino , Masculino , Modelos Genéticos , Reprodução/genética , Escroto/crescimento & desenvolvimentoRESUMO
O objetivo do estudo foi avaliar perímetro escrotal e características seminais de touros da raça Senepol, de acordo com a idade e as correlações entre elas. Foram avaliados 397 touros na raça Senepol, com idade entre 12 e 30 meses, puros de origem, do estado de Minas Gerais. O método de coleta foi massagem das ampolas e eletroejaculação. Foram avaliados motilidade e vigor do sêmen e os defeitos espermáticos. Os dados foram analisados pelo teste de Kruskal-Wallis e pelo método de Spearman. Os testículos apresentaram um crescimento linear com a idade. Houve maior diferença na motilidade espermática em animais com 18 e 20 meses de idade e o vigor espermático apresentou maior diferença em animais com 20 meses. Houve correlação significativa entre todas as características analisadas. O perímetro escrotal em touros Senepol apresentou crescimento linear dos 12 aos 30 meses e mesmo os animais mais jovens, com menor perímetro escrotal, já apresentaram boa qualidade de sêmen, o que mostra a precocidade reprodutiva dos machos dessa raça. Conclui-se que o perímetro escrotal em touros Senepol apresenta crescimento linear dos 12 aos 30 meses e mesmo os animais mais jovens, já apresentam boa qualidade de sêmen, indicando uma precocidade reprodutiva dos machos dessa raça.(AU)
The objective of this study was evaluate scrotal perimeter and seminal characteteristics of Senepol bulls acording to age and correlations between them. 397 Senepol bulls were avaliable, with ages between 12 and 30 months, pure breed, in the state of Minas Gerais. The collect method were massage of ampoules and electro-ejaculation. Motility and vigor of semen and sperm defects were avaliable. Data were analyzed by the Kruskal-Wallis test and the Spearman method. The tests had a linear growth with age. The biggest difference of motility were in animals with 18 and 20 months of age and the biggest difference of vigor were in animals with 20 months. There was a significant correlation between all analyzed characteristics. Concludes that the scrotal perimeter in Senepol bulls have a linear growth from 12 to 30 months and even the youngest animals, it is a already a good semen quality, indicating a reproductive precocity in males of this breed.(AU)
Assuntos
Animais , Bovinos , Escroto/anatomia & histologia , Escroto/crescimento & desenvolvimento , Testículo/crescimento & desenvolvimento , Análise do Sêmen , Fatores Etários , Medicina ReprodutivaRESUMO
O objetivo do estudo foi avaliar perímetro escrotal e características seminais de touros da raça Senepol, de acordo com a idade e as correlações entre elas. Foram avaliados 397 touros na raça Senepol, com idade entre 12 e 30 meses, puros de origem, do estado de Minas Gerais. O método de coleta foi massagem das ampolas e eletroejaculação. Foram avaliados motilidade e vigor do sêmen e os defeitos espermáticos. Os dados foram analisados pelo teste de Kruskal-Wallis e pelo método de Spearman. Os testículos apresentaram um crescimento linear com a idade. Houve maior diferença na motilidade espermática em animais com 18 e 20 meses de idade e o vigor espermático apresentou maior diferença em animais com 20 meses. Houve correlação significativa entre todas as características analisadas. O perímetro escrotal em touros Senepol apresentou crescimento linear dos 12 aos 30 meses e mesmo os animais mais jovens, com menor perímetro escrotal, já apresentaram boa qualidade de sêmen, o que mostra a precocidade reprodutiva dos machos dessa raça. Conclui-se que o perímetro escrotal em touros Senepol apresenta crescimento linear dos 12 aos 30 meses e mesmo os animais mais jovens, já apresentam boa qualidade de sêmen, indicando uma precocidade reprodutiva dos machos dessa raça.
The objective of this study was evaluate scrotal perimeter and seminal characteteristics of Senepol bulls acording to age and correlations between them. 397 Senepol bulls were avaliable, with ages between 12 and 30 months, pure breed, in the state of Minas Gerais. The collect method were massage of ampoules and electro-ejaculation. Motility and vigor of semen and sperm defects were avaliable. Data were analyzed by the Kruskal-Wallis test and the Spearman method. The tests had a linear growth with age. The biggest difference of motility were in animals with 18 and 20 months of age and the biggest difference of vigor were in animals with 20 months. There was a significant correlation between all analyzed characteristics. Concludes that the scrotal perimeter in Senepol bulls have a linear growth from 12 to 30 months and even the youngest animals, it is a already a good semen quality, indicating a reproductive precocity in males of this breed.
Assuntos
Animais , Bovinos , Análise do Sêmen , Escroto/anatomia & histologia , Escroto/crescimento & desenvolvimento , Fatores Etários , Testículo/crescimento & desenvolvimento , Medicina ReprodutivaRESUMO
BACKGROUND: Central testing is used to select young bulls which are likely to contribute to increased net income of the commercial beef cattle herd. We present genetic parameters for growth and reproductive traits on performance-tested young bulls and commercial animals that are raised on pasture and in feedlots. METHODS: Records on young bulls and heifers in performance tests or commercial herds were used. Genetic parameters for growth and reproductive traits were estimated. Correlated responses for commercial animals when selection was applied on performance-tested young bulls were computed. RESULTS: The 90% highest posterior density (HPD90) intervals for heritabilities of final weight (FW), average daily gain (ADG) and scrotal circumference (SC) ranged from 0.41 to 0.49, 0.23 to 0.30 and 0.47 to 0.57, respectively, for performance-tested young bulls on pasture, from 0.45 to 0.60, 0.20 to 0.32 and 0.56 to 0.70, respectively, for performance-tested young bulls in feedlots, from 0.29 to 0.33, 0.14 to 0.18 and 0.35 to 0.45, respectively, for commercial animals on pasture, and from 0.24 to 0.44, 0.13 to 0.24 and 0.35 to 0.57 respectively, for commercial animals in feedlots. The HPD90 intervals for genetic correlations of FW, ADG and SC in performance-tested young bulls on pasture (feedlots) with FW, ADG and SC in commercial animals on pasture (feedlots) ranged from 0.86 to 0.96 (0.83 to 0.94), 0.78 to 0.90 (0.40 to 0.79) and from 0.92 to 0.97 (0.50 to 0.83), respectively. Age at first calving was genetically related to ADG (HPD90 interval = -0.48 to -0.06) and SC (HPD90 interval = -0.41 to -0.05) for performance-tested young bulls on pasture, however it was not related to ADG (HPD90 interval = -0.29 to 0.10) and SC (HPD90 interval = -0.35 to 0.13) for performance-tested young bulls in feedlots. CONCLUSIONS: Heritabilities for growth and SC are higher for performance-tested young bulls than for commercial animals. Evaluating and selecting for increased growth and SC on performance-tested young bulls is efficient to improve growth, SC and age at first calving in commercial animals. Evaluating and selecting performance-tested young bulls is more efficient for young bulls on pasture than in feedlots.
Assuntos
Criação de Animais Domésticos/métodos , Cruzamento/métodos , Bovinos/fisiologia , Animais , Peso Corporal , Bovinos/genética , Bovinos/crescimento & desenvolvimento , Feminino , Variação Genética , Genótipo , Masculino , Fenótipo , Reprodução , Escroto/crescimento & desenvolvimento , Escroto/fisiologiaRESUMO
The aim of this study was to evaluate the effect of genotype × environment interaction (G×E) on age at first calving (AFC), scrotal circumference (SC), and yearling weight (YW) and to estimate genetic correlations between these traits in Nellore cattle using reaction norms in multitrait random regression models. In this study, 28,871, 41,386, and 89,152 records of Nellore cattle for AFC, SC, and YW, respectively, were used. The data were obtained from farms located in the north, northeast, midwest, and southeast regions of Brazil that participate in the DeltaGen Breeding Program. Environmental levels were defined as a function of contemporary groups, that is, animals born in the same herd and year, from the same management group (from birth to yearling), and of the same sex. Postweaning weight gain was used as a criterion to evaluate the environmental conditions for all traits. For reaction norm analyses, residual variances were modeled with homogeneous and heterogeneous classes. The model for SC and YW included the fixed effects of contemporary group and age of the animal as a covariate as well as random direct additive genetic and residual effects. The same model, excluding the covariate age of the animal, was used for AFC. The heritability estimates were low to high for AFC (0.09 to 0.50), high for SC (0.51 to 0.67), and moderate to high for YW (0.33 to 0.71). The genetic correlations (within each trait) along the environmental levels varied from -0.27 to 1.0 for AFC, from 0.73 to 1.0 for SC, and from 0.26 to 1.0 for YW. The genetic correlations between different traits in different environments varied from -0.14 to -0.60 between AFC and SC, from -0.05 to -0.32 between AFC and YW, and from -0.05 to 0.72 between YW and SC. The genetic correlations have had different magnitudes for AFC, SC, and YW, which could indicate the presence of G×E. The present results should support researchers and farmers in defining selection criteria to improve growth traits and sexual precocity. Our results suggest that animals for breeding have to be selected in the same environment and management conditions as their progeny will be reared.
Assuntos
Peso Corporal/fisiologia , Cruzamento/métodos , Bovinos/genética , Meio Ambiente , Genótipo , Modelos Genéticos , Escroto/crescimento & desenvolvimento , Fatores Etários , Animais , Peso Corporal/genética , Brasil , Cruzamento/normas , Bovinos/crescimento & desenvolvimento , Feminino , Masculino , Análise de RegressãoRESUMO
Foram analisadas mensurações de perímetro escrotal (PE) obtidas aos 365 (PE365, n = 8.564), 455 (PE455, n = 7.463) e 550 (PE550, n = 4.447) dias de idade, com o objetivo de estimar parâmetros genéticos e verificar a adequação do ajuste do modelo de análise de PE para os efeitos de peso ou ganho de peso (GP). Os parâmetros foram estimados pelo método da máxima verossimilhança restrita, com o aplicativo MTDFREML, sob modelo animal e com a inclusão de 54.987 animais na matriz de parentesco. A inclusão no modelo dos efeitos de peso e do GP não influenciou os valores de estimativa de herdabilidade (h2) nas três idades. As h2 variaram de 0,50 a 0,59, dependendo do modelo, sem diferenças importantes entre as três idades estudadas. Os resultados indicaram a possibilidade de ganho genético no PE por meio da seleção direta para esta característica. A melhor idade para seleção do PE seria aos 365 dias.(AU)
The aims of this study were to estimate genetic parameters for scrotal circumference (SC) at 365 (SC365, n = 8,564), 455 (SC455, n = 7,463) and 550 (SC550, n = 4,447) days of age using different models and to verify the effect of adjustments for body weight and for weight gain (WG) on parameter estimates. Parameters were estimated using the REML methodology (MTDFREML), with an animal model and considering the relationship among 54,987 animals. The adjustment for weight and WG did not influence heritability (h2) estimates for SC at any age. No important difference among h2 estimates for SC in the three ages was observed. The h2 estimates ranged from .50 to .59 depending on the model. Results suggested that selection for SC would be effective. The best age for SC selection would be at 365 days.(AU)
Assuntos
Bovinos , Bovinos/anatomia & histologia , Escroto/crescimento & desenvolvimento , Biometria , Melhoramento Genético , Aumento de PesoRESUMO
Foram analisadas mensurações de perímetro escrotal (PE) obtidas aos 365 (PE365, n = 8.564), 455 (PE455, n = 7.463) e 550 (PE550, n = 4.447) dias de idade, com o objetivo de estimar parâmetros genéticos e verificar a adequação do ajuste do modelo de análise de PE para os efeitos de peso ou ganho de peso (GP). Os parâmetros foram estimados pelo método da máxima verossimilhança restrita, com o aplicativo MTDFREML, sob modelo animal e com a inclusão de 54.987 animais na matriz de parentesco. A inclusão no modelo dos efeitos de peso e do GP não influenciou os valores de estimativa de herdabilidade (h2) nas três idades. As h2 variaram de 0,50 a 0,59, dependendo do modelo, sem diferenças importantes entre as três idades estudadas. Os resultados indicaram a possibilidade de ganho genético no PE por meio da seleção direta para esta característica. A melhor idade para seleção do PE seria aos 365 dias...
The aims of this study were to estimate genetic parameters for scrotal circumference (SC) at 365 (SC365, n = 8,564), 455 (SC455, n = 7,463) and 550 (SC550, n = 4,447) days of age using different models and to verify the effect of adjustments for body weight and for weight gain (WG) on parameter estimates. Parameters were estimated using the REML methodology (MTDFREML), with an animal model and considering the relationship among 54,987 animals. The adjustment for weight and WG did not influence heritability (h2) estimates for SC at any age. No important difference among h2 estimates for SC in the three ages was observed. The h2 estimates ranged from .50 to .59 depending on the model. Results suggested that selection for SC would be effective. The best age for SC selection would be at 365 days...
Assuntos
Bovinos , Biometria , Bovinos/anatomia & histologia , Escroto/crescimento & desenvolvimento , Melhoramento Genético , Aumento de PesoRESUMO
Data from 69,525 animals were used to compare two types of analyses, one of them having the weaning management group (WEMANG) included as an effect in the contemporary group (F_WEMANG) and the other considering the weaning management group as a random effect, not related to the mathematical model (R_WEMANG) for post-weaning traits. The components of (co)variance were estimated for pre-weaning traits (birth weight and weaning weight) and for post-weaning traits [scrotal circumference (SC), weight gain from weaning to 18 months of age (WG) and muscle score (MUSC)] in Nellore cattle, based on a complete animal model. Heritability of SC, WG and MUSC for the F_WEMANG model was equal to 0.46 ± 0.02, 0.38 ± 0.03 and 0.26 ± 0.01, and for the R_WEMANG model it was 0.45 ± 0.02, 0.31 ± 0.03 and 0.25 ± 0.01, respectively. Genetic correlations between all the studied traits varied between 0.07 ± 0.01 and 0.77 ± 0.03 in F_WEMANG and between 0.02 ± 0.01 and 0.76 ± 0.04 in R_WEMANG. The R_ WEMANG model allowed a decrease in the number of contemporary groups as well as an increase in the number of observations per group without significant alterations in heritability coefficients, for the post-weaning traits. Consequently, the analysis became more robust and avoided having contemporary groups with low variability.
Assuntos
Peso Corporal/genética , Bovinos/genética , Desmame , Aumento de Peso/genética , Algoritmos , Animais , Cruzamento/métodos , Bovinos/anatomia & histologia , Bovinos/crescimento & desenvolvimento , Feminino , Masculino , Modelos Genéticos , Desenvolvimento Muscular/genética , Músculos/anatomia & histologia , Tamanho do Órgão/genética , Característica Quantitativa Herdável , Escroto/anatomia & histologia , Escroto/crescimento & desenvolvimento , Seleção GenéticaRESUMO
This study was conducted to examine the relationship among average annual productivity of the cow (PRODAM), yearling weight (YW), postweaning BW gain (PWG), scrotal circumference (SC), and stayability in the herd for at least 6 yr (STAY) of Nelore and composite beef cattle. Measurements were taken on animals born between 1980 and 2010 on 70 farms located in 7 Brazilian states. Estimates of heritability and genetic and environmental correlations were obtained by Bayesian approach with 5-trait animal models. Genetic trends were estimated by regressing means of estimated breeding values by year of birth. The heritability estimates were between 0.14 and 0.47. Estimates of genetic correlation among female traits (PRODAM and STAY) and growth traits ranged from -0.02 to 0.30. Estimates of genetic correlations ranged from 0.23 to 0.94 among growth traits indicating that selection for these traits could be successful in tropical breeding programs. Genetic correlations among all traits were favorable and simultaneous selection for growth, productivity, and stayability is therefore possible. Genetic correlation between PRODAM and STAY was 0.99 and 0.85 for Nelore and composite cattle, respectively. Therefore, PRODAM and STAY might be influenced by many of the same genes. The inclusion of PRODAM instead of STAY as a selection criterion seems to be more advantageous for tropical breeding programs because the generation interval required to obtain accurate estimates of genetic merit for PRODAM is shorter. Average annual genetic changes were greater in Nelore than in composite cattle. This was not unexpected because the breeding program of composite cattle included a large number of farms, different production environments, and genetic level of the herds and breeds. Thus, the selection process has become more difficult in this population.
Assuntos
Bovinos/fisiologia , Característica Quantitativa Herdável , Seleção Genética , Animais , Peso Corporal , Brasil , Cruzamento , Bovinos/genética , Bovinos/crescimento & desenvolvimento , Feminino , Masculino , Modelos Genéticos , Escroto/anatomia & histologia , Escroto/crescimento & desenvolvimento , Especificidade da Espécie , Aumento de PesoRESUMO
The objective of the present study was to determine the presence of genotype by environment interaction (G × E) and to characterize the phenotypic plasticity of birth weight (BW), weaning weight (WW), postweaning weight gain (PWG) and yearling scrotal circumference (SC) in composite beef cattle using the reaction norms model with unknown covariate. The animals were born between 1995 and 2008 on 33 farms located throughout all Brazilian biomes between latitude -7° and -31°, longitude -40° and -63°. The contemporary group was chosen as the environmental descriptor, that is, the environmental covariate of the reaction norms. In general, higher estimates of direct heritability were observed in extreme favorable environments. The mean of direct heritability across the environmental gradient ranged from 0.05 to 0.51, 0.09 to 0.43, 0.01 to 0.43 and from 0.12 to 0.26 for BW, WW, PWG and SC, respectively. The variation in direct heritability observed indicates a different response to selection according to the environment in which the animals of the population are evaluated. The correlation between the level and slope of the reaction norm for BW and PWG was high, indicating that animals with higher average breeding values responded better to improvement in environmental conditions, a fact characterizing a scale of G × E. Low correlation between the intercept and slope was obtained for WW and SC, implying re-ranking of animals in different environments. Genetic variation exists in the sensitivity of animals to the environment, a fact that permits the selection of more plastic or robust genotypes in the population studied. Thus, the G × E is an important factor that should be considered in the genetic evaluation of the present population of composite beef cattle.
Assuntos
Peso ao Nascer , Bovinos/crescimento & desenvolvimento , Bovinos/genética , Interação Gene-Ambiente , Escroto/crescimento & desenvolvimento , Aumento de Peso , Criação de Animais Domésticos , Animais , Brasil , Cruzamento , Feminino , Masculino , Modelos Genéticos , DesmameRESUMO
The aim of the present study was to estimate genetic parameters for flight speed and its association with growth traits in Nellore beef cattle. The flight speed (FS) of 7,402 yearling animals was measured, using a device composed of a pair of photoelectric cells. Time interval data (s) were converted to speed (m/s) and faster animals were regarded as more reactive. The growth traits analyzed were weaning weight (WW), ADG from weaning to yearling age, and yearling scrotal circumference (SC). The (co)variance components were estimated using REML in a multitrait analysis applying an animal model. The model included random direct additive genetic and residual effects, fixed effects of contemporary groups, age of dam (classes), and age of animal as covariable. For WW, the model also included maternal genetic and permanent environmental random effects. The direct heritability estimate for FS was 0.26 ± 0.05 and direct heritability estimates for WW, SC, and ADG were 0.30 ± 0.01, 0.48 ± 0.02, and 0.19 ± 0.01, respectively. Estimates of the genetic correlation between FS and the growth traits were -0.12 ± 0.07 (WW), -0.13 ± 0.08 (ADG), and -0.11 ± 0.07 (SC). Although the values were low, these correlations showed that animals with better temperaments (slower FS) tended to present better performance. It is possible to infer that longterm selection for weight and scrotal circumference can promote a positive genetic response in the temperament of animals. Nevertheless, to obtain faster genetic progress in temperament, it would be necessary to perform direct selection for such trait. Flight speed is an easily measured indicator of temperament and can be included as a selection criterion in breeding programs for Nellore cattle.
Assuntos
Peso Corporal , Bovinos/fisiologia , Locomoção , Característica Quantitativa Herdável , Escroto/crescimento & desenvolvimento , Animais , Cruzamento , Bovinos/anatomia & histologia , Bovinos/genética , Bovinos/crescimento & desenvolvimento , Feminino , Masculino , Modelos Genéticos , Tamanho do Órgão , Fenótipo , Temperamento , DesmameRESUMO
Se conoce con el nombre de escroto agudo el cuadro clínico caracterizado por la aparición de dolor agudo acompañado de tumefacción y signos inflamatorios a nivel escrotal y generalmente resulta ser una consulta de emergencia.
Assuntos
Humanos , Escroto/cirurgia , Escroto/crescimento & desenvolvimento , Escroto/fisiologia , Genitália , Genitália Masculina , EscrotoRESUMO
In eutherian mammals, sex differentiation is initiated by expression of the testis-determining gene on the Y chromosome. Subsequent phenotypic development of the reproductive tract and genitalia depends on the production of hormones by the differentiated testis. In marsupials the mechanisms of phenotypic development may vary from this pattern, as differentiation of the scrotal primordia has been shown to occur before that of the gonad. Thus, the development of the scrotum in the marsupial has been regarded as an androgen-independent process. We have sought to clarify the ontogeny of scrotal development and the appearance of androgen receptor immunoreactivity by examining Monodelphis domesticaembryos/pups from 1 day prior to birth until 2 days after birth. We have also used immunocytochemistry to determine the expression of the key steroidogenic enzyme 3beta-hydroxysteroid dehydrogenase as an indicator of when the developing gonad may be capable of synthesizing androgens. Expression of this enzyme was first detected in the gonads and adrenals of both sexes 1 day prior to birth and before the appearance of scrotal bulges. Androgen receptor immunoreactivity was detected in the scrotal anlagen of male opossum pups as early as 1 day following birth. This finding is significantly earlier than previous reports and coincides with the appearance 1 day after birth of distinct scrotal bulges. Androgen receptor immunoreactivity was also observed in the genital tubercles of male pups, but not female pups, 2 days after birth. These results suggest that androgens may play an important role in the development of the male genitalia at a much earlier stage than that indicated by previously published work and that scrotal development in this species may not be androgen-independent.
Assuntos
Androgênios/fisiologia , Gambás/embriologia , Gambás/crescimento & desenvolvimento , Organogênese/fisiologia , Escroto/embriologia , Escroto/crescimento & desenvolvimento , Diferenciação Sexual/fisiologia , 3-Hidroxiesteroide Desidrogenases/metabolismo , Animais , Animais Recém-Nascidos , Feminino , Técnicas Imunoenzimáticas , Células Intersticiais do Testículo/citologia , Células Intersticiais do Testículo/enzimologia , Masculino , Próstata/citologia , Próstata/metabolismo , Ratos , Receptores Androgênicos/metabolismo , Testículo/embriologia , Testículo/enzimologia , Testículo/crescimento & desenvolvimentoRESUMO
Four functions to characterize scrotal circumference (SC) growth in Nellore bulls were compared to identify which was the most suitable for biological interpretation. Nellore bulls (n = 532), born between September and December of 1992 to 1994 were used in the study. Measurements were made on fixed dates in January, April, July and October of each year. At the time of SC measurements, the ages of the bulls ranged from 200 to 1300 d. The functions used to describe the data were: Brody, SC = A (1 - B exp -kt); Logistic, SC = A/(1 + B exp -kt); Gompertz, SC = A exp(-B exp -kt) and Richards SC = A (1 + B exp -kt)m, where SC is the scrotal circumference at t days of age, A is the estimated SC at maturity, B is the integration constant established by the initial values of SC and t, k is the maturity constant, which equals the ratio between the maximum rate of growth and SC at maturity; m is the inflection point parameter for Richards function, which did not converge. The Brody, Gompertz and Logistic functions fitted the data in a similar fashion, with similar values for the statistics EMS and R2, and they reached convergence with similar computational costs. The Logistic function presented the best pattern of average prediction error, and therefore, it was selected for biological interpretation. For the Logistic function, estimated SC at maturity (A) was 37.95 cm at 72 mo of age. The maturity index (k) was .11 cm, and the inflection point (time of maximum growth) was reached at 13.09 mo of age at an average SC of 18.97 cm.
Assuntos
Bovinos/crescimento & desenvolvimento , Escroto/anatomia & histologia , Escroto/crescimento & desenvolvimento , Envelhecimento , Animais , Bovinos/anatomia & histologia , Modelos Logísticos , Masculino , MatemáticaRESUMO
The objective of the present study was to describe seasonal changes in scrotal circumference (SC), live weight (LW), sperm morphology and plasma levels of testosterone (T) and thyroxine (T4) in young Corriedale rams reared under extensive conditions typical for the southern Latin American region. A total of 31 Corriedale rams, 11 months of age and with a LW of 36 +/- 1.1 kg and (SC) of 23.0 +/- 0.5 cm at the beginning of the experiment (September) were kept on natural pastures. At monthly intervals LW was recorded, animals were clinically examined, and SC was measured. None of the animals were used for breeding. Fifteen animals were randomly selected and bled once a month from January to December and plasma concentrations of T and T4 were determined. In addition, one semen sample was collected by electroejaculation and morphological studies were performed. The mean individual LW increase was 18 kg (50% of the initial LW) during the experiment (p < 0.01). LW decreased in autumn, with the nadir in late autumn. SC reached mean maximum levels in late summer (31.1 +/- 0.4 cm, p < 0.01), then decreased until the beginning of winter (26.3 +/- 0.4 cm, p < 0.01) and remained low until early spring (27.5 +/- 0.5 cm, p > 0.05) to increase again between mid-spring and the end of the experimental period the following summer (30.7 +/- 0.5 cm, p < 0.01). The mean SC in winter was 16% lower than that in late summer. Semen could be collected from the rams throughout the experiment. Frequencies of sperm head, mid-piece and total abnormalities showed monthly variation (p < 0.05), but tail abnormalities were not affected by month. Low abnormalities were found in autumn (9.4% +/- 2.2%). T was high during autumn (p < 0.01). Minimal T4 concentrations were observed during late summer and early autumn (p < 0.01) when T levels were high. Maximum T4 concentrations were registered in late autumn (p < 0.01); when SC was decreasing; in mid-spring (p < 0.01) one month after shearing and in early summer (p < 0.01). The results suggest that Corriedale rams under Uruguayan extensive management systems show a reproductive seasonality that, in general terms, coincides with photoperiodic variations.
Assuntos
Reprodução , Estações do Ano , Ovinos/fisiologia , Criação de Animais Domésticos/métodos , Animais , Peso Corporal , América Latina , Masculino , Escroto/crescimento & desenvolvimento , Escroto/fisiologia , Espermatozoides/citologia , Testosterona/sangue , Tiroxina/sangueRESUMO
Equaçöes pelos modelos mistos adotando modelo animal foram utilizadas para estimar a herdabilidade do perímetro escrotal (PE) e do peso corporal aos 12 e 18 meses de idade e as correlaçöes genéticas entre estas características em animais da raça Nelore. Foram coletados trimestralmente os PE e os pesos de 871 bezerros da raça Nelore, filhos de 45 reprodutores e nascidos nos meses de setembro a dezembro, nos anos de 1991 e 1992. Os pesos aos 12 e aos 18 meses de idade foram obtidos por interpolaçöes e os PE nestas mesmas idades foram tomados, respectivamente, entre 275 e 455 dias de idade e entre 456 e 635 dias de idade. Pesos e PE médios mais ou menos desvios padräo foram 249 mais ou menos 31 kg, 363 mais ou menos 41 kg, 22 mais ou menos 3 cm e 27 mais ou menos 3 cm, respectivamente, aos 12 e 18 meses de idade. Na mesma sequência, estimativas de herdabilidade mais ou menos erros padräo foram 0,32 mais ou menos 0,05, 0,42 mais ou menos 0,06, 0,47 mais ou menos 0,07 e 0,74 mais ou menos 0,06. Correlaçöes genéticas entre PE e pesos foram altas (de 0,46 até 0,52), assim como foram altas as correlaçöes genéticas entre os dois pesos (0,68) e entre os dois PE (0,76). Resultados sugerem que a seleçäo para PE seria mais efetiva quando praticada aos 18 meses de idade, tanto em termos de resposta direta à seleçäo como em termos de resposta correlacionada no peso corporal