Genetic correlation estimates between calving ease in primiparous cows and economically important traits in Nellore cattle.

This study aimed to estimate (co)variance components and genetic parameters for calving ease (CE) and their genetic correlations with growth, reproductive, carcass, and feed efficiency traits in Nellore cattle. Phenotypes for CE are scored in two categories: normal calving and assisted calving. The traits considered were probability of precocious calving, age at first calving, stayability, adjusted scrotal circumference at 365 days of age, accumulated cow productivity, age at puberty of males, gestation length, birth weight, adjusted weights at 210 and 450 days of age, adult cow weight, frame score, hip height, rib eye area, subcutaneous backfat thickness, rump fat thickness, intramuscular fat percentage, residual feed intake and dry matter intake. The estimation of genetic parameters was performed using a two-trait threshold-linear animal model, except for CE, stayability, and probability of precocious calving, which were evaluated through a two-trait threshold animal model. The direct (0.27) and maternal (0.19) heritability estimates for CE in heifers primiparous Nellore indicated that selecting for this trait is feasible. The selection to improve the female sexual precocity should consider CE during the selection and mating decisions to reduce calving problems. Genetic correlation estimates between CE and BW suggest that selecting low birth weight to reduce calving problems is not an appropriate strategy to improve calving ease in heifers Nellore. Therefore, adopting a multi-trait selection model with CE and BW in the Nellore breed would reduce calving difficulties, particularly in sexually precocious heifers, without impairing the growth, reproductive, feed efficiency conversion, and carcass indicator traits.

Selection for feed efficiency does not change the selection for growth and carcass traits in Nellore cattle.

The objectives were to conduct a genetic evaluation of residual feed intake (RFI) and residual feed intake adjusted for fat (RFIFat) and to analyse the effect of selection for these traits on growth, carcass and reproductive traits. Data from 945 Nellore bulls in seven feed efficiency tests in a feedlot were analysed. Genetic evaluation was performed using an animal model in which the feed efficiency test and age of the animal at the beginning of the test were considered as a systematic effect. Direct additive genetic and residual effects were considered as random effects. Correlations and genetic gains were estimated by two-trait analysis between feed efficiency measures (RFI and RFIFat) and other traits. Feed conversion showed low heritability (0.06), but dry matter intake (DMI), average daily gain, RFI, RFIFat, metabolic body weight and scrotal circumference measured at 450 days of age (SC450) showed moderate to high heritability (0.49, 0.28, 0.33, 0.36, 0.38 and 0.80, respectively). Similarly, ribeye area, backfat thickness, rump cap fat thickness, marbling score and subcutaneous fat thickness also had high heritability values (0.46, 0.37, 0.57, 0.51 and 0.47, respectively). Genetic correlations between RFI and SC450 were null, and between RFIFat and SC450 were strongly positive. Genetic and phenotypic correlations of RFI and RFIFat with carcass traits were not different from zero, as correlated responses for carcass traits were also not different from zero. The Nellore selection for feed efficiency by RFI or RFIFat allows the recognition of feed efficient animals, with DMI reduction and without significant changes in growth and carcass traits. However, because of the observed results between RFIFat and SC450, selection of animals should be analysed with caution and a preselection for reproductive traits is necessary to avoid reproductive impairments in the herd.

Morfologia de potros da raça Brasileiro de Hipismo / Morphology of Brasileiro de Hipismo foals

Objetivou-se avaliar a morfologia de potros da raça Brasileiro de Hipismo, utilizando análise de imagens digitais e medidas de perímetros corporais para estimativa de índices corporais dos animais. As mensurações lineares e angulares foram obtidas utilizando imagens digitais dos potros com câmera acionada pelo aplicativo Simi Reality Motion Systems®. As medidas foram baseadas em pontos anatômicos realçados com 19 marcadores reflexivos. A análise estatística descritiva dos resultados foi realizada utilizando o programa SAS. Os potros estavam em crescimento, com aumento das medidas lineares de altura na cernelha e na garupa, comprimento do corpo, distância escápulo-metacarpofalângica e nos comprimentos do pescoço, da perna e do antebraço. Os ângulos úmero-radial, metacarpo-falângico, fêmoro-tibial, tíbio-metatarsico aumentaram com a idade, enquanto que os ângulos da cabeça, do pescoço, coxo-femoral, metatarso-falângico, escápulo-solo e coxo-solo foram variáveis entre os momentos de avaliação. Os potros foram classificados em mediolíneos e hipermétricos pelos índices Corporal e Dáctilo-torácico, respectivamente. A avaliação do crescimento dos potros foi possível através da imagem digital.

This research aimed to evaluate the morphology of Brasileiro de Hipismo foals using digital image analysis and girth measurements to estimate body indexes of animals. The linear and angular measurements were obtained by digital images of the foals with camera triggered by Simi Reality Motion Systems®. The measures were based on anatomical landmarks highlighted with 19 reflective markers. A descriptive statistical analysis of the results was performed using the SAS program. The foals were growing, with increased linear measurements of height at withers and croup, body length, distance from shoulder-fetlock and neck length, leg length and forearm length. The angles humerus-radial, metacarpal-falangeano, femoro-tibial, tibio-metatarsal increased with age, whiles the angles of the head, neck, coxofemoral, metatarsal-falangeano, shoulder-floor and coxae-floor were variable among the periods. The foals were classified as medium shape and hypermetric by Corporal Index, Dactilo-thoracic Index, respectively. Assessment of growth of the foals was possible through a digital image.

Estudo genético-quantitativo de medidas lineares de eqüinos da raça Mangalarga Marchador -I. Estimativas dos fatores de ambiente e parâmetros genéticos / Genetic-quantitative study of body measurements of Mangalarga Marchador horse bred in Brazil -I. Estimates of genetic and environmental effects

Embora o interesse em pesquisas sobre morfologia em algumas espécies tenha sido menor do que aquele proporcionado aos estudos sobre a produtividade, as características em eqüinos são importantes por estarem intrinsecamente relacionadas à sua funcionalidade de aptidão. Desta forma, os objetivos do presente estudo foram os de estimar herdabilidades e correlações fenotípicas e genéticas entre doze medidas corporais provenientes dos Livros de Registro Genealógicos da Associação Brasileira dos Criadores do Cavalo Mangalarga Marchador, entre 1967 e 1992, por ocasião do Registro Genealógico de 29.076 animais. As estimativas foram efetuadas pelo método dos quadrados mínimos, através do programa Harvey (1990). Os efeitos fixos de ano, idade à avaliação e sexo foram significativos para a maioria das medidas estudadas. Estimativas de herdabilidade apresentam valores de moderados (0,40 para o perímetro torácico) a altos (0,80 para o comprimento do dorso), com um valor médio para as doze medidas corporais de 0,56, evidenciando a importância do componente genético aditivo nas características morfológicas dos animais Mangalarga Marchador. As correlações genéticas entre as características variaram de -0,09 (perímetro da canela-comprimento do dorso) a 0,96 (altura na cernelha - altura na garupa). Sessenta e três das 66 correlações possíveis (95,5%) apresentaram sinal positivo e destas, 40 (60,6%) apresentaram valor igual ou superior a 0,30. Este achado demonstra o sinergismo existente entre a maioria das características estudadas.

The objective of this study was to estimate heritabilities, genetic and phenotypic correlation of twelve body measurements of the Brazilian horse bred Mangalarga Marchador. Records from 29,076 animais, measured between 1967 and 1992, were analyzed by Least-Square and Maximum Likelihood Computer Program (Harvey, 1990). The fixed effect of year, age, and sex of foal were signifcant for most of the characteristics. Heritability estimates varied between 0.40 (thoracic diameter) to 0.80 (back length), with a medium value of 0.56, characterizing the importance of the genetic component of body measurements in horses. Genetic correlations varied between -0.09 (cannon diameter-back length) and 0.96 (withers height). Sixty-three of the 66 possible correlations (95.5%) were positive; 40 (60.6%) were superior to 0.30. lt was evident that selection for one (or combination) of traits would have effect on almost all other morphological traits.

Fatores de meio e herança como causas de variaçäo do intervalo entre partos na raça Santa Gertrudis / Genetic and enviromental factors as sources of variation of calving interval in a Santa Gertrudis herd

Avaliaram-se fatores ambientais e genéticos associados á variaçäo no intervalo entre partos de um rebanho Santa Gertrudis. Os dados, referentes a partos ocorridos na propriedade localizada no município de Itaí, SP, desde o ano de 1975 até 1983, foram analisados pelo método dos quadrados mínimos para dados com freqüência desiguais nas subclasses. A média de 546 intervalos entre partos de 157 vacas, filhas de 27 touros, foi de 16,5 ñ 0,3 meses, com coeficiente de variaçäo igual a 22,5%. Foram estatisticamente significativos os efeitos do ano do parto (P < 0,01) e do sexo da cria (P < 0,05). A média dos intervalos entre partos diminuiu com o passar dos anos. Os intervalos subsequentes às pariçöes de machos foram em média, 23,0 dias mais longos que aqueles subseqüentes às pariçöes de fêmeas. Os efeitos de origem e idade da vaca e do mês do parto näo foram significativos (P > 0,05). A repetibilidade da característica, estimada pela correlaçäo intraclasse entre intervalos da mesma vaca foi de 0,19 ñ 0,05, e a herdabilidade, estimada pela correlaçäo intraclasse entre meio-irmäs paternas, foi de 0,10 ñ 0,10