Genetic analysis of growth traits and scrotal circumference in Brangus cattle

O objetivo deste trabalho foi estimar os parâmetros genéticos e a tendência genética de características de crescimento e perímetro escrotal em animais da raça Brangus. Dados de 6.340 animais, criados em cinco propriedades nas regiões Sul, Sudeste e Centro‑Oeste do Brasil, foram utilizados para avaliação de: perímetro escrotal (PE) ao sobreano e pesos ao nascer (PN), à desmama (P205), ao ano (P365) e ao sobreano (P550). Os componentes de covariância foram estimados por inferência bayesiana, sob modelo animal, com efeitos fixos de grupos de contemporâneos e de classe de idade da vaca ao parto, e efeitos aleatórios genético aditivo direto e residual. Os efeitos aleatórios genético materno e de ambiente permanente materno foram incluídos somente para PN e P205. O efeito linear da covariável idade do animal na mensuração foi considerado para todas as características analisadas, exceto PN. As médias observadas foram 33,6, 184,6, 235,9, 344,9 e 33,8 cm para PN, P205, P365, P550 e PE, respectivamente, e as tendências genéticas foram de ‑0,001, 0,107, 0,177, 0,217 kg por ano e 0,001 cm por ano. As estimativas das herdabilidades direta e materna variaram de 0,16 (PN) a 0,61 (PE) e de 0,08 (PN) a 0,09 (P205), indicativas de que as características avaliadas são passíveis de seleção para o melhoramento genético da raça Brangus.The objective of this work was to estimate the genetic parameters and genetic trends for growth traits and scrotal circumference of Brangus cattle. Data on 6,340 animals, raised in five farms in the South, Southern, and Midwestern regions of Brazil, were used for the evaluation of: yearling scrotal circumference (SC) and the weights at birth (PN), weaning (P205), yearling (P365), and post‑yearling (P550). The covariance components were estimated by Bayesian inference using the animal model with fixed effects of contemporary groups and cow age class at calving, and direct additive genetic and residual random effects. The maternal genetic and maternal permanent environmental random effects were included only in PN and P205. The linear effect of the covariable animal age at measurement was considered for all evaluated traits, except for PN. The averages observed were 33.6, 184.6, 235.9, 344.9 kg, and 33.8 cm for PN, P205, P365, P550, and SC, respectively, and the genetic trends were ‑0.001, 0.107, 0.177, 0.217 kg per year, and 0.001 cm per year. Estimates for direct and maternal heritabilities ranged from 0.16 (PN) to 0.61 (SC), and from 0.08 (PN) to 0.09 (P205), respectively, indicating that the evaluated traits are liable to selection for Brangus genetic breeding

Análise genética da espessura do couro, do crescimento pós desmama e das resistências ao carrapato e à babesiose em bovinos de corte

Recent studies about mechanisms of resistance to the tick are rare in cattle, justifying the need for further research. The hide of the animals is one of the tick habitats and some hide features can provide favorable conditions for the establishment and development larval. The aim of this study was to estimate genetic parameters for the skin thickness (ST) and post weaning weight gain (PWG550) of Nellore cattle, and to verify the relationship among skin thickness, tick resistance and parasitaemia level by Babesia bovis in heifers, Caracu and Nellore, that it were artificially infested with ticks. The database of the Nellore Qualitas breeding program was used to estimate the heritability of the ST and PWG550 traits and to verify the genetic association among these traits. Genetics parameters were estimated by bayesian analysis with a multivariate model. Another project phase was developed with 20 Nellore heifers and 20 Caracu heifers, belonging to the Instituto de Zootecnia, in order to allow the study the association of the resistance to tick with parasitaemia level by B. bovis and skin thickness. Heifers were submitted to three (3) ticks' artificial infestations, with 14 days interval. ST was measured in the mid-side area of animals with a double caliper. Engorged females counts were performed in the range of 19th and 23th days after infestation. Blood samples were collected on the 1st, 7th, 21th, 35th and 49th day of the experiment. Blood samples were used to evaluate the parasitaemia level by B. bovis, by quantitative PCR (qPCR) method. Statistical analysis were performed using the MIXED procedure of SAS. Estimates heritability (h²) of the ST and PWG550 traits were 0.12 and 0.29, respectively. Correlation coefficient among the EC and GPD550 traits was 0.17. Nellore showed lower amount of ticks in artificial infestations, however, both groups were efficient to control the B. bovis parasitaemia. The skin thickness group effect was ...Estudos recentes sobre mecanismos de resistência dos bovinos aos carrapatos são raros, justificando a necessidade de novos estudos. O couro dos animais é um dos habitats do carrapato, e algumas características do mesmo podem propiciar condições mais ou menos favoráveis para a fixação e desenvolvimento das larvas. O objetivo do trabalho foi estimar parâmetros genéticos para as características espessura do couro (EC) e ganho de peso pós desmama (GPD550) em bovinos Nelore, e verificar as associações de espessura do couro, resistência aos carrapatos e nível de parasitemia por Babesia bovis em fêmeas, Caracu e Nelore, infestadas artificialmente. O banco de dados do programa de melhoramento genético Nelore Qualitas foi utilizado para estimação da herdabilidade das características EC e GPD550 assim como na verificação da associação genética. Os parâmetros genéticos foram estimados por análise bayesiana com uso de modelo multivariado. Outra etapa do projeto foi conduzida com uso de 20 novilhas Nelore e 20 novilhas Caracu, provenientes do Centro de Pesquisa em Pecuária de Corte do Instituto de Zootecnia de forma a possibilitar a verificação da associação da resistência ao carrapato com nível de parasitemia por B. bovis e espessura do couro. As novilhas foram submetidas a três (3) infestações artificiais de carrapatos, em intervalos de 14 dias. A EC foi medida na região posterior à escápula dos animais com uso de paquímetro. Foram realizadas contagens de fêmeas ingurgitadas no intervalo entre o 19º e 23º dia após a infestação e colheitas de sangue no 1o, 7o, 21o, 35o e 49o dia do experimento. As amostras de sangue foram utilizadas para avaliar o nível de parasitemia por B. bovis por meio de reações de PCR quantitativo (qPCR). Análises estatísticas foram executadas com o procedimento MIXED do programa SAS. As estimativas de herdabilidade (h²) das características EC e GPD550 foram ..

Comportamento ingestivo de bovinos Nelore e Bonsmara durante teste de eficiência alimentar

O artigo não apresenta resumo em português

Comportamento ingestivo de bovinos Nelore e Bonsmara durante teste de eficiência alimentar

O artigo não apresenta resumo em português

Ingestive behavior of Nellore and Bonsmara cattle during the feed efficiency test

Several studies have reported relationship between eating behavior and performance in feedlot cattle. The evaluation of behavior traits demands high degree of work and trained manpower, therefore, in recent years has been used an automated feed intake measurement system (GrowSafe System ®), that identify and record individual feeding patterns. The aim of this study was to evaluate the relationship between feeding behavior traits and average daily gain in Nellore calves undergoing feed efficiency test. Date from 85 Nelore males was recorded during the feed efficiency test performed in 2012, at Centro APTA Bovinos de Corte, Instituto de Zootecnia, São Paulo State. Were analyzed the behavioral traits: time at feeder (TF), head down duration (HD), representing the time when the animal is actually eating, frequency of visits (FV) and feed rate (FR) calculated as the amount of dry matter (DM) consumed by time at feeder (g.min-1). The ADG was calculated by linear regression of individual weights on days in test. ADG classes were obtained considering the average ADG and standard deviation (SD) being: high ADG (>mean + 1.0 SD), medium ADG (± 1.0 SD from the mean) and low ADG (<mean - 1.0 SD). Data were analyzed using the PROC MIXED procedure (SAS 9.3). The model included animal and residue as random effects and the fixed effects of ADG class (1, 2 and 3) and age at the middle of test as a covariate. Low gain animals remained 21.8% less time of head down than medium or high gain animals (P<0.05). Were observed significant effects of ADG class on FR (P<0.01), high ADG animals consumed more feed per time (g.min-1) than the low and medium ADG animals. No diferences were observed (P>0.05) among ADG classes for FV, indicating that these traits are not related to each other. These results shows that the ADG is related to the agility in eat food and not to the time spent in the bunk or to the number of visits in a range of 24 hours

Ingestive behavior of Nellore and Bonsmara cattle during the feed efficiency test

This study was conducted to describe the ingestive behavior in Nellore and Bonsmara cattle during the feed efficiency test. The test was performed at the Centro APTA Bovinos de Corte – Instituto de Zootecnia, Sertãozinho, São Paulo State. Twenty-three Nellore and 19 Bonsmara calves, aging 276 ± 19.2 and 278 ± 29.2 days and weighing 246 ± 26.7 and 273 ± 30.7 kg, on average, at the beginning of the test, respectively, were used. Animals were randomly located in individual pens, during four periods of 28 days, being the first period a pre-test adjustment period. Calves were fed twice a day, with the same diet. Daily the amount of food offered was adjusted in order to maintain 5 to 10% of refusals. Dry matter intake (DMI) was calculated by the difference between food offered and refusals. Animals were weighed each seven days. Average daily gain (ADG) was obtained by linear regression of weights in days in test. Feed conversion was obtained by the DMI:ADG ratio. Ingestive behavior was measured three times, every 28 days, excluding de pre-test period. Observations lasted 24 hours, with records at intervals of five minutes. The behavioral traits analyzed were: bunk attendance duration (BAD), rumination time (RT) and idle time (IT) expressed in minutes per day. Data were analyzed using the PROC MIXED procedure (SAS 9.3). The model included the fixed effects of period, breed and weight nested in breed. The weight nested in breed effect was significant for all traits analyzed (P<0.05). The breed effect was significant for BAD, RT, IT, e ADG (P<0.05). Nellore calves had higher means for ADG, BAD and RT and lower mean for IT (P<0.05) than Bonsmara calves. There were significant differences among periods for traits ADG, BAD and IT (P<0.05), showing that the animals had greater weight gain at the beginning of the feed efficiency test because they had spent more time feeding and consequently less time in idle. Thus, it is evident that there are differences in ingestive behavior of Nellore and Bonsmara and among periods of test, showing that the animals spend more time feeding at the beginning. This fact is the probable reason for higher weight gain at this stage

Comportamento ingestivo de bovinos Nelore e Bonsmara durante teste de eficiência alimentar

O artigo não apresenta resumo em português

Comportamento ingestivo de bovinos Nelore e Bonsmara durante teste de eficiência alimentar

O artigo não apresenta resumo em português