ABSTRACT This study was intended to evaluate body size structure and growth parameters of crossbred heifers fed at four nutritional levels to achieve puberty earlier. Animals were classified depending on their level of crossing between Nelore and Hereford and subjected to four nutritional levels (kg day−1) as follows: 0.5 (light; n = 32), 0.75 (medium; n = 32), 1.00 (high; n = 29), and 1.25 (very high; n = 27). Heifers at puberty and at weaning were individually classified for growth parameters. The fat thickness and longissimus muscle area throughout the experimental period were determined by ultrasonography. The height, heart girth, frame, and weight:height ratio were variables used to evaluate body traits. Univariate analysis of variance using the GLIM MIXED procedure os SPSS was performed and the significance level was set at 0.05. Age and body weight at puberty were 388±1.9 days and 331.4±1.3 kg, respectively. Body condition score demonstrated an interaction between nutritional level and crossbred degree. Heifers with the highest degree of Nelore had higher fat thickness and lower weight:height ratio compared with other racial groups at puberty. Pearson correlation coefficient showed a negative association for body condition score (−0.34) and fat thickness (−0.58) compared with age at puberty. The increased fat thickness at younger ages at puberty was observed in all racial groups. The increased weight:height ratio at younger ages at puberty was observed in all racial groups. We observed higher values for a frame in animals at the higher level of supplementation. There is a greater correlation between live weight gain and phenotypic traits during weaning to achieve puberty at an earlier age in crossbred heifers.

ABSTRACT The objective of this study was to evaluate the effects of mineral and protein-energy (MPES), exogenous fibrolytic enzyme supplements (ES), combination of MPES + ES, and straw without supplement (WS) on digestibility, fermentation kinetic parameters, cumulative gas production, methane, CO2 production, and volatile fatty acid concentration of rice straw of low and high nutritional value, estimated by in vitro techniques. The experimental design was randomized and factorial 2 × 4: two straws (low and high nutritional value) incubated with four supplements (MPES, ES, MPES + ES, and WS) and their interactions. Four experimental periods were used, totaling four replications per treatment over time. Data were analyzed by PROC MIXED of SAS. The in vitro dry matter and organic matter digestibilities of the rice straw with high nutritional value was improved by MPES, while the combination of MPES + ES supplements inhibited the digestibility of this straw. Dietary carbohydrate and nitrogen increased through MPES and MPES + ES supplements resulted in an increase in NH3-N concentration and a decrease in CO2 production due to the microbial mass formation. However, this increase was not enough to improve organic matter degradability parameters, cummulative gas production, gas production kinetics, and acetate:propionate ratio and reduce methane emissions. The straw with high nutritional value showed greater content of nitrogen fraction a, effective degradability, cummulative gas production, and methane and CO2 productions comparing with low-nutritional value straw. The use of MPES and MPES + ES supplements can be used as strategy to mitigate CO2 in ruminant production systems that use rice straw.

ABSTRACT The objectives of this study were to evaluate the effects of cultivation and hay making factors on chemical composition, protein fractionation, and digestibility in rice straw, as well as to identify the chemical fractions that contribute to the variation in its nutritional value for ruminants. Statistical procedures were performed in a model that included rice crop cycle, sowing season, baling season, soil classification, fertilizer application, and productivity (kg/ha) as fixed effects and the hay bale as random effect. Chemical composition, protein fractionation, and digestibility data were subjected to multivariate analyses including factor, cluster, and discriminant. Considering the cultivation and haymaking factors, development cycle, baling season, and grain production explained the most variation in the rice straw nutritional value. Straws derived from early maturing cultivars showed the lowest levels of neutral detergent fiber, acid detergent fiber, acid detergent insoluble nitrogen, and C nitrogen fraction in comparison with straw originating from mid cycle cultivars. Rice straw from more productive cultivars had lower levels of lignin and C fraction as well as higher levels of crude protein and B3 fraction compared with straws from less productive cultivars. However, the main variation in the nutritional value between the samples of rice straw was related to the baling season. The bailing seasons were grouped in two clusters. Straws with better nutritional value were those with lower levels of cell wall fractions, from more productive crops, with early development cycle and baled until March. Rice crop cycle, baling season, and grain production effects explain the variation in the nutritional value of rice straws. Straws with better nutritional value have lower levels of fractions related to secondary cell wall and lignification.

The objective of this study was to evaluate, using meta-analysis, the main factors related to post-weaning body weight and weight gain that affect pregnancy rate of heifers bred at 18 months of age. Data of 1398 beef heifers from six experiments were analyzed as a set. Information related to methodology and results of each experiment were codified in Microsoft Excel spreadsheets. The independent variables analyzed were: body weight at seven months of age (BW7M), daily weight gain from seven to 12 months (DWG7-12), body weight at 12 months of age (BW12M), daily weight gain from 12 to 15 months (DWG12-15), body weight at 15 months of age (BW15M), daily weight gain from 15 to 18 months (DWG15-18), daily weight gain from 7 to 18 months (DWG7-18) and body weight at 18 months of age (BW18M). The response variable was pregnancy rate (PR). Body weight at 18 months of age and DWG7-18 showed high correlation with PR and between each other. The other variables presented low correlation with PR. Body weight at first breeding and daily weight gain from seven to 18 months are the most important variables affecting the pregnancy rate of heifers bred at 18 months of age in the autumn. Weaning weight and weight gain during intermediate steps of the post-weaning period are not good predictors of pregnancy rate. Higher pregnancy rates can be obtained provided enough post-weaning weight gain and minimum body weight at first breeding are achieved, irrespective of when weight is gained.

Um experimento foi conduzido utilizando-se a técnica semiautomática de produção cumulativa de gás in vitro com o objetivo de avaliar a combinação da suplementação energética com a proteica em dietas à base de um volumoso de baixa qualidade, feno de capim-tifton (Cynodon dactylon L.), com 7,69% de proteína bruta, 70,34% de fibra em detergente neutro e 57,98% de digestibilidade in vitro da matéria orgânica. Foram avaliadas duas fontes de proteína degradável no rúmen (ureia ou proteína isolada de soja); quatro níveis de grão de milho moído (0, 20, 40 e 60%) e quatro níveis suplementares de proteína degradável no rúmen (0; 2,8; 5,6 e 8,4%) em delineamento completamente casualizado em um fatorial 2 × 4 × 4. A digestibilidade in vitro da matéria orgânica aumentou linearmente em resposta à inclusão de milho com inclinação maior utilizando proteína isolada de soja. O fator de partição foi superior com proteína isolada de soja e foi detectado aumento linear em resposta ao aumento da proteína degradável com 20% de milho. A produção máxima de gás da fração de rápida (A) e de lenta (D) degradação aumentou linearmente em resposta à inclusão de milho, com proteína isolada de soja, e quadraticamente com ureia. A taxa de degradação de A aumentou com a inclusão de até 20% de milho e a taxa de degradação de D foi maior com ureia. O lag-time de A aumentou linearmente em resposta a inclusão de milho e no lag-time de D foi observada diminuição com até 20% de milho sem alterações em níveis superiores. A suplementação com até 60% de milho moído foi benéfica para a digestibilidade de dietas com volumoso de baixa qualidade. A associação entre energia e proteína foi benéfica em alguns parâmetros estudados. A ureia gerou melhores respostas em níveis moderados de grão de milho moído.

It was conducted an experiment using the semi-automatic in vitro cumulative gas production with the objective of evaluating the combination of energy and protein supplementations in diets based on low quality roughage, Tifton hay (Cynodon dactylon L.), with 7.69% of crude protein; 70.34% of neutral detergent fiber and 57.98% of organic matter in vitro digestibility. It was evaluated two sources of rumen degradable protein (urea or isolated soybean protein); four levels of ground corn grain (0, 20, 40 and 60%) and four supplementary levels of rumen degradable protein (0; 2.8; 5.6 and 8.4%) in complete random design in a 2 × 4 × 4 factorial arrangement. The organic matter in vitro digestibility increased linearly in response to grain corn inclusion with a greater slope by using isolated soybean protein. The partitioning factor was higher with isolated soybean protein and it was detected a linear increase in response to increasing rumen degradable protein with 20% of grain corn. The maximum gas production of the fraction of fast (A) and slow (D) degradation increased linearly in response to the grain corn inclusion, with isolated soybean protein, and it quadratically increased with urea. The A degradation rate was increased with inclusion of up to 20% of grain corn and the degradation rate of D was higher with urea. The A lag-time increased linearly with the inclusion of grain corn and in the D lag-time it was observed a decrease with up to 20% of grain corn unchanged at high levels. The supplementation with up to 60% of grain corn was beneficial to digestibility of diets with low quality roughage. The association between energy and protein supplementation was positive in some studied parameters. Urea gave better responses at moderate levels of ground grain corn.

Foi avaliada a utilização de cinco níveis de casca proteinada de soja (0, 4, 8, 12 e 16%) em substituição ao farelo de soja em dietas para ovinos em confinamento. Foram avaliados o desempenho, o consumo, a digestibilidade dos nutrientes e os balanços energético e nitrogenado em função da dieta. Vinte cordeiros da raça Texel, com peso vivo médio inicial de 28 kg, foram distribuídos em delineamento inteiramente casualizado com cinco tratamentos e quatro repetições. A dieta foi composta de 30% de volumoso e 70% de concentrado. O farelo de soja dos concentrados foi gradativamente substituído pela casca proteinada de soja (CPS). O consumo de nutrientes, a conversão alimentar e o ganho de peso não foram influenciados pelo aumento do nível de inclusão da CPS na dieta. Os níveis de CPS também não influenciaram as digestibilidades da MS, MO, N (PB), FDN e EB e os balanços energético e nitrogenado.

The aim was to evaluate the use of five levels of soybean protein hulls (0, 4, 8, 12 and 16%) in place of soybean meal in diets for sheep in confinement. We evaluated the performance, intake, nutrient digestibility and, energy and nitrogen balance in terms of diet. Twenty Texel lambs with an average weight of 28 kg were distributed in a completely randomized design with four replications. The diet consisted of 30% roughage and 70% concentrate. The soybean meal in the concentrates was gradually replaced by soybean protein hulls (SPH). Nutrient intake, feed-to-gain ratio and weight gain were not affected by increasing the inclusion level of SPH en the diet. SPH levels also did not influence the digestibility of DM, OM, N (CP), NDF and GE and the energy and nitrogen balance.

Avaliou-se o efeito da subépoca de parição sobre a taxa de prenhez de 7.726 vacas de corte multíparas Hereford mantidas em campo natural no Sul do Brasil, entre os anos de 1994 e 2007. As subépocas foram divididas em intervalos de 20 dias: de 12 a 31 de agosto; de 1 a 20 de setembro; 21 de setembro a 10 de outubro; 11 a 31 de outubro; e 1 a 20 de novembro. Foram analisados os partos ocorridos na subépoca de parição e a taxa de prenhez (PR) pelo qui-quadrado. As médias gerais de cada subépoca foram 92.7% (12 a 31 de agosto), 90.6% (1 a 20 de setembro), 82.1% (21 de setembro a 10 de outubro), 77.7% (11 a 31 de outubro) e 70.6% (1 a 20 de novembro), respectivamente. Houve efeito significativo da subépoca de partos sobre a taxa de prenhez. As vacas que pariram nas primeiras subépocas apresentaram maiores taxas de prenhez em relação às que pariram a partir da quarta subépoca de parição. No entanto, essa diferença não se manteve nos anos de 1999 e 2007, uma vez que as taxas de prenhez não diferiram estatisticamente nas cinco subépocas. Nos anos de 1998 e 2004, as taxas de prenhez foram menores e os efeitos da subépoca de parição sobre a taxa de prenhez foram de maior magnitude, possivelmente em decorrência de variações climáticas. De modo geral, as taxas de prenhez diminuem com o avanço da data de parto dentro do ano, sobretudo nos anos de eventos climáticos desfavoráveis ao crescimento do pasto.

It was evaluated in this work the effect of calving sub-season on the pregnancy rate of 7,726 multiparous Hereford beef cows grazing on natural pastures in southern Brazil, from 1994 to 2007. Calving sub-season periods were divided in 20-day intervals from August 12th to 31st; from September 1st to 20th; from September 21st to October 10th; from October 11th to 31st; from November 1st to 20th. Calving in each sub-season and pregnancy rate (PR) were analyzed by the Chi-square test. Overall means of each sub-season were 92.7% (from August 12th to 31st), 90.6% (from September 1st to 20th), 82.1% (from September 21st to October 10th), 77.7% (from October 11th to 31st), and 70.6% (from November 1st to 20th). Calving sub-season significantly influenced pregnancy rate. Cows which calved in the initial sub-season showed higher pregnancy rates than cows which calved from the fourth calving sub-season. However this difference did not occur in 1999 and in 2007 since calving rates did not statistically differ among the five sub-seasons. In 1998 and 2004, calving rates were lower and the effects of calving sub-season on pregnancy rates were higher, possibly due to climate variations. In general, pregnancy rate decreases as calving occurs later in the year, particularly in years when the weather adversely affects pasture growth.

Um modelo de simulação bioeconômico foi desenvolvido em um sistema de produção tradicional em pecuária de cria (SPT) para a aplicação da metodologia dos centros de custos com o objetivo de avaliar sua sensibilidade mediante a introdução de tecnologias de desmame precoce em vacas primíparas (SDP), campo melhorado para vacas primíparas e metade do lote das vacas secundíparas (SCM) e suplementação protéica para novilhas de reposição (SSP) destinadas a aumentar a taxa de prenhez neste sistema (SPT). As informações do desempenho biológico foram obtidas por meio de revisão bibliográfica sobre os indicadores de produção e os dados econômicos e de custos foram obtidos a partir de valores de mercado. As entradas do modelo foram: estrutura do rebanho; custos de produção; e tecnologias de produção. As saídas do modelo foram: custo operacional (CO); custo de desembolso (CD); custo de produção por centro (CPC); custo unitário por bezerro (CUB); custo por quilo desmamado (C/kg); custo anual por vaca (CAV); ponto de equilíbrio financeiro (PEF), margem operacional (MO), taxa de prenhez (TP), taxa de desmame (TD), produtividade/vaca (Pr), número de bezerros desmamados (NBD), ponto de equilíbrio em bezerros (PEB) e produção total em quilos (PT). A utilização da metodologia dos centros de custos se mostrou sensível ao identificar variações nos indicadores técnicos e econômicos e nos custos de cada centro produtivo. A introdução do SDP, SCM e SSP melhorou os indicadores técnicos e a margem operacional e, ao mesmo tempo, apresentou relação direta com as variações nos centros de custo, comprovando a sensibilidade da metodologia de custeio em relação ao impacto no SPT.

A bioeconomical simulation model was developed in a traditional cow-calf production system (TPS) for the application of cost center methodology with the objective of evaluating its sensibility by the introduction of early weaning technologies in primiparous cows (EWS), improved pasture for primiparous cows and half lot of secundiparous cows (IPS) and protein supplementation for replacement heifers (PSS). All technologies were used to increase the pregnancy rate in this system (TPS). Data on biological performance was obtained from a bibliographic review on production indicators and cost and economic values were obtained from market. The inputs of the model were: herd structure, production costs and production technology. The outputs of the model were: operational cost (OC); expenditure cost (EC); production costs per center (PCC); unitary cost per calf (UCC); cost per weaned kilo (WC/kg); annual cost per cow (ACC); financial break-even (FBE), operational margin (OM), pregnancy rate (PT), calf crop (CC), productivity/cow (P/C), number of weaned calves (NWC), calves break-even (CBE) and total production in kilos (TP/kg). The use of the cost center methodology was sensitive in identifying variations in the technical economic indicators and in the costs of each productive center. The introduction of EWS, IPS and PSS showed in the increase of technical indicators and in the operational margin, presented a straight relation with the changing in the cost centers, proving the sensibility of the costs methodology in relation to the impact in TPS.

O objetivo neste trabalho foi evidenciar a importância do custo de produção na pecuária de cria, descrevendo uma metodologia padronizada que consiga mensurar o custo de produção de bezerros de corte e, simultaneamente, validar o método em um sistema de produção. Dentro deste contexto, neste trabalho discute-se, inicialmente, a relevância da implantação da metodologia dos centros de custos como suporte à tomada de decisão, devido à necessidade de uma análise segmentada dos processos em sistemas de produção pecuários especializados na cria. As etapas para implantação deste método são descritas. Um sistema de produção, característico da Região Sul do Brasil, foi definido a partir de indicadores técnicos relatados em revisões bibliográficas. Foi simulada a aplicação desta metodologia no sistema em questão, no qual se visualizaram os custos de produção dos diferentes centros produtivos: touros, vacas de cria, recria das novilhas e desmame dos bezerros, possibilitando compreender o impacto de determinados processos e/ou tecnologias no sistema. Conseqüentemente, calcular o custo de produção de bezerros de corte a partir da utilização da metodologia dos centros de custos, mostrou-se factível de utilização em sistemas de produção baseados em pecuária de cria.

The production cost in cow-calf was designed by a standard methodology that can be able to measure the production cost of calves and, simultaneously to validate the method in a production system. Within this context, the present paper discusses, initially, the relevance of the implementation of methodology in cost centers as a support decision-making, due to the need for a segmented analysis of the processes, specialized in cow-calf production systems. The stages for implementation of this method are described. A production system, typical of the Southern of Brazil, was defined from technical indicators reported in reviews. It was simulated the application of this methodology of the subjected system, where it was viewed the production costs of the different productive centers: bulls, cows, rearing of heifers and weaning of calves, enabling to understand the impact that determinates process and/or technologies bring on to the system. Consequently, to calculate the production cost of calves from the methodology based on the cost centers was feasible to be used in production systems based on cow-calf.

Este trabalho teve por objetivo avaliar o desempenho de novilhos de corte em pastagem nativa (PN), suplementados com níveis de farelo de arroz integral (FAI) de 0; 0,5; 1,0 e 1,5% do peso vivo dos animais, num delineamento inteiramente casualizado em parcelas subdivididas, durante 126 dias. Na parcela principal, foram alocados os níveis de suplemento e, nas subparcelas, os períodos de tempo (6 períodos de 21 dias). A suplementação foi oferecida de forma individual, duas vezes por dia, às 7h e às 15h:30min. O método de pastejo empregado foi o contínuo com lotação fixa e carga variável. As médias encontradas para proteína bruta foram de 6,8 e 14,9%, e para os coeficientes de digestibilidade "in vitro" da matéria orgânica, foram de 59,54 e 71,47% na PN e no FAI, respectivamente (dados expressos na matéria seca). Os ganhos médios diários dos animais foram de 0,35; 0,55; 0,53; e 0,63kg animal-1 dia-1 para os níveis de inclusão de farelo de arroz de 0; 0,5; 1,0 e 1,5% do peso vivo dos animais, diferindo entre animais suplementados e não-suplementados. Os resultados de rendimento e peso de carcaça fria dos animais não diferiram entre os tratamentos. A suplementação com FAI nos níveis entre 0,5 a 1,5% proporcionou incremento no ganho médio diário de aproximadamente 60%, quando comparado com os animais que não receberam suplemento.

This study was aimed at investigating steers performance on native pasture supplemented with levels of full fat rice bran: 0; 0.5; 1.0 and 1.5% of body weight of the animals, in a completely randomized design, with a split plot arrangement, during 126 days. In main plots were allocated the levels of supplement and in a split plot, the periods of time (6 periods of 21 days each). The supplementation was individual, offered twice a day, at 7am and 3.3pm. The system of pasture was continuous grazing with fix stocking density and variable stocking rate. The average percent of crude protein were 6.8% and 14.9% and the in vitro digestibility coefficients were 59.54% and 71.47% in native pasture and rice bran, respectively (in the dry matter). The live weight gains of the animals were 0.35; 0.55; 0.53 and 0.63kg d-1 with the rice bran daily inclusion of 0.0; 0.5; 1.0 and 1.5% of the animals live weigh differing only when it was considered the use or not use of the supplement. The carcass yield and weigh do not differ among the treatments. The supplementation with full fat rice bran in the levels between 0.5% and 1.5% of live weight proportioned an increase on the live weigh gain of approximately 60% when compared with the animals that did not receive supplement.

Foi desenvolvido um experimento para identificar os efeitos que influenciam a taxa de prenhez de 117 vacas de corte Nelore x Hereford aos 2 e 20 anos de idade e com diferentes frações gênicas de Nelore (25,0; 37,5; 50,0 e 100,0%), paridas no período de 11/08/03 a 23/12/03 e acasaladas, por monta natural, entre 10/12/03 e 12/03/04. Foram avaliados os efeitos dos fatores data juliana de parto (DJ), peso ao nascer (PN), sexo do bezerro (S) do parto anterior, ordem de parto (OP), altura de garupa (H), peso ao início do acasalamento (PI), escore de condição corporal ao início do acasalamento (ECCI), ganho diário médio de peso durante o acasalamento (GDA), fração gênica de Nelore (FGN) e peso ao desmame ajustado (PAJ205) do parto anterior sobre a probabilidade de prenhez e de concepção. Os dados foram submetidos à análise de regressão logística, por meio do procedimento LOGISTIC do pacote computacional SAS, para identificar os efeitos de cada variável. A média da taxa de prenhez foi de 43,2%. A probabilidade de prenhez e as chances de concepção foram explicadas pelas variações de DJ, PI, ECCI e GDA. A mudança na chance de prenhez para cada acréscimo na variável regressora foi estimada com base na estatística da razão entre chances (odds ratio), determinada por OR = exp(b k), considerando que chance é a razão entre a probabilidade de o evento ocorrer e a de não ocorrer. Não foram observados efeitos significativos de PN, S, OP, H, FGN e PAJ205. Portanto, para aumentar as taxas de prenhez de vacas de corte, são necessárias melhorias no escore de condição corporal (ECC) no início do acasalamento e no ganho de peso (GP) durante a estação de monta, ambos decorrentes de adequada nutrição pré e pós-parto.

This experiment was conducted to evaluate factors affecting pregnancy rate of 117 crossbred Nelore x Hereford beef cows with age varying from 2 to 20 years, different gene proportion from Nellore breed (25.0, 37.5, 50.0, and 100.0%), calved between 08/11/03 and 12/23/03 and bred by natural service, between 12/10/03 and 03/12/04. The effects of July calving date (JCD), birth weight (BW) and calf sex (S) from previous calving, parity order (PO), hip height (H), weight (WM) and body condition score at the beginning of the mating season (BCS), daily gain during the mating season (DGM), gene proportion from Nellore (GPN) and calf 205-d weight (WW205) from previous calving were all investigated on the probabilities of pregnancy and conception. Data were analyzed by Logistic Regression using SAS to identify the effects of each variable. The average pregnancy rate was 43.2%. The probability of pregnancy and conception were affected by changes on JCD, WM, BCS and DGM. The pregnancy odd changing to each increase on the variable were based on the odds ratio estimative by OR = exp (b k), considering that odd is ratio between the probability of the event occur and not occur. No significant effects of BW, S, PO, H, GFN and WW205 were observed. Pregnancy rate in beef cows can be increased by improving body condition score at the beginning of breeding season and weight gain during the breeding season. Both can be achieved by pre and postpartum nutritional management.

Em face das poucas informações disponíveis sobre a composição mineral das pastagens nativas da região dos Campos de Cima da Serra (RS), o presente trabalho de pesquisa objetivou avaliar os teores dos principais macrominerais, em diferentes épocas do ano, e relacionar o perfil mineral destas pastagens com as necessidades nutricionais recomendadas pelo NRC (1996) para bovinos de corte. O projeto foi conduzido em vinte propriedades particulares, em Cambará do Sul, utilizando áreas de campo nativo que estavam sendo normalmente utilizadas em pastoreio por bovinos de corte e/ou ovinos e que não tinham sofrido nenhum tipo de melhoria, reforma ou recuperação (exceto queimada), no mínimo nos últimos 20 anos. Colheram-se, durante oito meses, e dentro de uma mesma área predeterminada em cada propriedade, amostras para determinar as concentrações de Ca, P, Mg, Na e S. Verificou-se efeito do mês de coleta sobre todos os minerais analisados. Foram constatados teores suficientes de Ca e Mg para as categorias de bovinos de corte menos exigentes. Os teores de Mg são deficientes para vacas em gestação e lactação e os teores de Ca são deficientes para terneiros. Por outro lado, os teores de P, Na e S apresentaram-se abaixo das exigências mínimas para as categorias de bovinos de corte avaliadas.

The present study was conducted to determine the mineral status of natural range pastures of Campos de Cima da Serra region, State of Rio Grande do Sul, Brazil, in different months of the year, to compare them to beef cattle requirements (NRC, 1996). The project was led in twenty private farms, in Cambará do Sul county, on grazing areas without improvements (except burning) at the last twenty years. Pasture samples were collected at January, February, March April, May, July, September and December to determine its calcium, phosphorus, magnesium, sodium and sulphur levels. Effect of the season was verified on all analyzed minerals. The Ca and Mg contents on grass samples were higher than the less demanding beef cattle categories requirements. Mg levels were deficient for more demanding animal categories, like gestating and lactating cows. Ca levels were deficient for calves. However, P, Na and S contents were lower than required for beef cattle categories.

O experimento foi desenvolvido com o objetivo de se avaliar duas idades de acasalamento, 18 meses (18M) e 24 meses (24M) em novilhas de corte Hereford, por monta natural, durante 45 dias. As variáveis analisadas foram a taxa de prenhez (TP), a condição corporal no início do acasalamento (CCI), o ganho de peso médio diário durante o período de acasalamento (GDM), a produtividade (P), representada pela quantidade de kg de bezerro desmamado por vaca acasalada, e a eficiência (E), ou seja, a produtividade para cada 100 kg de vaca. O período de acasalamento foi de 05/04/2000 a 20/05/2000 e de 04/11/2000 a 19/12/2000, para os grupos 18M e 24M, respectivamente. Novilhas do grupo 24M demonstraram maiores TP e CCI (86,7% e 3,86) que as do grupo 18M (52,2% e 3,59). O GDM nos períodos de acasalamento não apresentou diferença, sendo 0,728 e 0,724 kg/d, para 18M e 24M, respectivamente. A P e a E das novilhas do grupo 24M foram superiores (135,2 e 38,6 kg) às do grupo 18M (76,2 e 26,6 kg, respectivamente). A redução da idade de acasalamento para os 18 meses requer maiores pesos no início do acasalamento para assegurar maiores índices reprodutivos.

A 45-d experiment was conducted to evaluate two breeding ages of Hereford heifers, 18 (18M) or 24 months (24M), using natural mating. The following parameters were studied: pregnancy rate (PR), body condition score at the beginning of the mating season (BCS), and average daily gain in the mating season (ADG). It was also calculated the productivity (P) = total kg of weaned calf per number of heifers bred and efficiency (E) = productivity per 100 kg of heifers mated. The breeding seasons were from 04/05/2000 to 05/20/2000 (fall) and from 11/04/2000 to 12/19/2000 (spring) for 18M and 24M heifers, respectively. The 24M heifers showed higher PR and BCS than those bred at 18M of age (86.7% vs. 52.2% and 3.86 vs. 3.59, respectively). Conversely, breeding season did not affect the ADG comparing 24M (0.728 kg/d) with 18M (0.724 kg/d) heifers. The 24M heifers had greater P (135.2 vs. 76.2 kg) and better E (38.6 vs. 26.6 kg) than heifers mated at 18M. It can be concluded that decreasing the breeding age from 24M to 18M requires higher body weight at beginning of the mating season in order to improve the reproductive parameters evaluated in the current trial.

Em face das poucas informações disponíveis sobre a composição mineral das pastagens nativas da região dos Campos de Cima da Serra (RS), o presente trabalho de pesquisa objetivou avaliar os teores dos principais microminerais, em diferentes épocas do ano, e relacionar o perfil mineral destas pastagens com as necessidades nutricionais recomendadas pelo NRC (1996) para bovinos de corte. O projeto foi conduzido em vinte propriedades particulares, em Cambará do Sul, utilizando áreas de campo nativo que estavam sendo normalmente utilizadas em pastoreio por bovinos de corte e/ou ovinos, e que não tinham sofrido nenhum tipo de melhoria, reforma ou recuperação (exceto queimada), no mínimo nos últimos 20 anos. Colheram-se nas diversas estações, durante um ano, e dentro de uma mesma área predeterminada em cada propriedade, amostras para determinar as concentrações de ferro, manganês, cobre e zinco. Verificou-se efeito do mês de coleta sobre todos os minerais analisados. Constataram-se teores suficientes de Mn e Fe para todas as categorias de bovinos de corte analisadas. Entretanto, algumas amostras apresentaram níveis tóxicos aos animais. Os teores de Cu não são suficientes para todas as categorias de bovinos em alguns meses do ano. Os teores de Zn estiveram abaixo das exigências mínimas para bovinos de corte.

The present study was conducted to determine the mineral status of natural range pastures of the Campos de Cima da Serra region, State of Rio Grande do Sul, Brazil, in different months of the year, to compare them to beef cattle requirements (NRC, 1996). The project was carried out in twenty private farms, in Cambará do Sul county, on grazing areas without improvements (except burning) in the lastest twenty years. Pasture samples were collected in the several seasons during one year to determine its iron, manganese, copper and zinc levels. Effect of the season was verified on all analyzed minerals. The Mn and Fe contents on grass samples were higher than the beef cattle requirements. However, in some samples Fe and Mn levels were higher than the maximum tolerable for cattle. Cu contents were deficient in some months evaluated and Zn contents were lower than the required for cattle.

O objetivo deste trabalho foi avaliar os efeitos da intensidade do ganho de peso no período de recria, dos 13 aos 18 meses de idade, sobre a taxa de prenhez de novilhas de corte acasaladas com o sobreano durante o outono. Os tratamentos foram constituídos de 30 novilhas com peso médio de 208 kg, submetidas a ganho médio de 0,595 kg dia-1 (G600), 41 novilhas com peso médio de 197 kg submetidas a ganho médio de 0,656 kg dia-1 (G700) e 58 novilhas com peso médio de 181 kg submetidas a ganho médio de 0,723 kg dia-1 (G800). Foram avaliados os efeitos dos tratamentos sobre peso, escore de trato reprodutivo e taxa de prenhez. As taxas de prenhez foram 30,0% 47,8% e 50,0% para os grupos G600, G700 e G800, respectivamente, não existindo diferença significativa entre os grupos. Os grupos G700 e G800, submetidos à maior taxa de ganho de peso, apresentaram maiores valores de escore de trato reprodutivo em relação ao G600 no início da estação de monta. Novilhas com escores mais elevados apresentaram tendência a maior taxa de prenhez. A taxa de prenhez esteve associada à intensidade de ganho de peso na recria independentemente das variações de peso no acasalamento.

The objective of this work was to evaluate the effects of growth rate during rearing period, from 13 to 18 months, on pregnancy rate of beef heifers mated at yearling during autumn. Treatments consisted of 30 heifers weighing on average 208 kg submitted to average growth rate of 0.595 kg day-1 (G600), 41 heifers averaging 197 kg with average growth rate of 0.656 kg day-1 (G700) and 58 heifers with 181 kg with average growth rate of 0.723 kg day-1 (G800). Treatment effects were determined on body weight, reproductive tract score and pregnancy rate. Pregnancy rate was 30.0% 47.8% and 50.0%, respectively, for G600, G700 and G800, without significant differences among groups. Treatments G700 and G800, with large growth rates, showed higher values of reproductive tract score than G600 at the start of the mating period. Heifers with higher scores had a tendency to present higher pregnancy rates. Pregnancy rates were related to growth rate during postweaning independently of weight variations at mating.