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A região Sul se diferencia das demais por ter maior produtividade de leite. A heterogeneidade da produção, a diversidade edafoclimática e ambiental, e as distintas realidades socioeconômicas contribuem para diferenciar as regiões político-administrativas. Objetivou-se espacializar os fatores produtivos e os fatores ambientais e socioeconômicos que melhor discriminam a produção de leite de vaca nos estados do Sul do Brasil. Análises multivariadas foram realizadas para discriminar tanto as variáveis em estudo quanto as mesorregiões e municípios destes estados. As mesorregiões Oeste Catarinense e Noroeste Rio-grandense apresentaram os melhores índices de produção, mas foram discriminadas em baixo nível (35,76%). A formação de cluster por municípios mostrou que Casca, Marau e Santo Cristo da mesorregião Noroeste Rio-grandense e Concórdia, Coronel Freitas, Palmitos e São Lourenço do Oeste da mesorregião Oeste Catarinense apresentaram melhores índices produtivos. Os clusters municipais foram discriminados em alto nível pelos fatores produtivos (98,24%) e pelos fatores ambientais e socioeconômicos (72.75%). As variáveis produtivas foram as mais importantes na discriminação dos clusters municipais. As especificidades e peculiaridades específicas a cada região foram evidenciadas por meio da heterogeneidade dos fatores produtivos, ambientais e socioeconômicos. Portanto, faz-se necessário conceber e implementar inovações tecnológicas específicas à cada região para maximizar a eficiência produtiva e minimizar os efeitos ambientais adversos em rebanhos leiteiros.

The objective of this study was to identify types of production system and their main indicators on bioeconomic efficiency, using qualitative and quantitative methods to evaluate beef cattle farms in the western region of the state of Rio Grande do Sul. A survey was carried out with 43 farmers operating in the western region of that state. All farms operated with complete cycle production systems in areas larger or equal to 900 ha. A qualitative questionnaire with binary answers and a quantitative questionnaire with numerical answers were applied. Technology and Management drivers were used for the calculation of the efficiency index of farmers obtained by both questionnaires. Farmers were divided into three clusters: low-efficiency level (LEL), intermediate-efficiency level (IEM), or high-efficiency level (HEL), as a result of the comparison of the scores obtained for the analyzed parameters. Subfactors resulting from each comparison (LEL × IEL; LEL × HEL, and IEL × HEL) were different as a function of the comparison and of the methods applied. Low-efficiency level farmers need to improve essential production processes, such as technology and management, as well as health management practices together with the financial management of the production system. Intermediate-efficiency level farmers need to improve their routine animal management, pasture management, and calculation of financial indicators to become highly efficient. The quantitative method allowed to identify underestimation (39.3%) or overestimation (24.2%) when farmers were are classified in clusters. Different methods may be used, but those based on quantitative information have stronger discrimination power to identify different types of farmers.

This study was intended to estimate the genetic associations between growth traits and visual scores with possible changes in mature weight (MW) in 397,900 Nellore animals. A bi-character analysis was performed to estimate the (co)variances and genetic parameters for MW, which comprises the following traits: conformation, finishing precocity, musculature at weaning (WC, WP, and WM) and yearling (YC, YP, and YM), birth weight (BW), weight from birth to weaning (WG), weight from weaning to yearling (YG), and final index (FIND). The observed mean MW was 417.6±56.2 kg, and the direct genetic effect mean estimated heritability ( h 2 a 1) of MW was 0.45. Overall, the BW was 31.0±3.7 kg, and the estimated h² was 0.34. The heritability estimate of the maternal additive genetic component ( h 2 m 2) of BW was 0.07. We calculated the mean WG to be 144.1±26.3 and estimated the h 2 a 2 as 0.18 and h 2 m 2 as 0.07. The value for h 2 a YG (0.17) and YW (0.26) were also estimated. The heritability of the weaning WC (0.17), WP (0.19), and WM (0.17) and yearling YC (0.25), YP (0.27), and YM (0.25) were estimated using visual scores. The h 2 m values for weaning WC, WP, and WM (0.06) with visual scores were estimated. The genetic correlations between body weight (BoW) at YC and WC (0.62) were considered moderately high and positive. In addition, YP (0.18), YM (0.15), WP (0.13), and WM (0.14) were considered moderately low compared with MW. The genetic correlation between BW and FIND (0.38) was considered positive and moderate. The heritability estimation indicates that growth traits, visual scores, and weight of adult cows could be changed by selection. Cows that presented the highest h 2 a values for live weight responded rapidly to selection based on growth characteristics, visual scores, and FIND and might result in increased final MW.

This study assessed the risks of different management practices to increase pregnancy rate in beef cow-calf systems, aiming at assisting decision-making. The perception of 18 experts on animal sciences regarding the risks of 32 nutritional, breeding, and general management practices applied to increase pregnancy rate were evaluated through questionnaires. The experts were selected by a non-probability sampling of researchers on veterinary and animal sciences. In addition, five farmers and eight technical consultants were also selected. The questionnaire was applied during a face-to-face meeting. The risk of each practice was assessed according to four factors, namely, cost, technical knowledge, operational complexity, and flexibility, and an equation was developed to calculate this risk. The applied method allowed to determine the risk of each practice, obtaining results similar to those previously perceived by the experts. Operational complexity and cost had greater influence on the estimated risks compared with the other factors. Moreover, the increase of one unit in operational complexity and cost increased the perceived risk and the estimated risk scores in 0.43 and 0.28 points, respectively. Overall, the application of general management practices presented lower risk score compared with nutritional and breeding practices, which were not different from which other. Equations to estimate the risks of farm managers should routinely apply management practices to increase the efficiency of cow-calf production systems.

This study evaluated the chemical and fermentation quality of corn and sorghum silage enriched with whole-plant soybeans. Whole soybean proportions of 75%, 50% and 25% were used for ensiling corn or sorghum. The increasing inclusion levels of whole-plant soybeans resulted in a linear increase in the dietary protein content of corn and sorghum silage and in an increase in acid detergent fiber of corn silage, while a decrease was observed in the energy content of corn silage and in neutral detergent fiber content of sorghum silage. The in vitro dry matter and organic matter digestibility did not differ between soybean inclusion levels in corn or sorghum silage. The addition of whole-plant soybeans increased the pH and N-NH3 concentration of corn and sorghum silage, but maintained the pH at acceptable levels when the inclusion level of whole soybeans was 50%. With respect to chemical composition, whole soybeans can be added to corn and sorghum silage at a proportion of up to 50%, with improvements of the final product.

Foi avaliada a viabilidade econômica de três sistemas de produção por meio da mensuração dos custos de produção e da análise dos indicadores financeiros. Os três sistemas (S1, S2 e S3), situados na fronteira oeste do Rio Grande do Sul, foram avaliados no período de outubro de 2010 a outubro de 2011. A pastagem estabelecida no S1 foi de azevém (Lolium multiflorum Lam) e trevo branco (Trifolium repens Lam); no S2, trevo branco, trevo vermelho (Trifolium pratense Lam), cornichão (Lotus corniculatus Lam), azevém e aveia preta (Avena strigosa Schreb); e no S3, azevém, cornichão, trevo branco e trevo vermelho. Os animais foram pesados na entrada e na saída das pastagens. A coleta de dados para mensuração do custo foi realizada mensalmente utilizando-se planilhas apropriadas. As produtividades foram de 369, 772 e 637kg/ha para os sistemas S1, S2 e S3, respectivamente. O S2 apresentou o maior custo total (R$ 2.101,59/ha), enquanto o menor foi obtido pelo S1 (R$ 1.626,93/ha). Na análise do custo operacional médio dos três sistemas, os itens que apresentaram maiores valores foram a implantação de pastagem, a energia elétrica, a manutenção da pastagem e a depreciação. Quanto às margens, os sistemas S1, S2 e S3 apresentaram, respectivamente, R$ 33,46, 1.162,55 e 701,01/ha para margem bruta; R$ -63,51, 955,40 e 541,05/ha para margem operacional; e R$ -583,18, 291,61 e -28,99/ha para lucro total. A rentabilidade foi de -0,47, 4,37 e 3,01% e a lucratividade foi de -5,94, 39,92 e 27,38% para o S1, S2 e S3, respectivamente. A irrigação de pastagens para terminação de bovinos é viável economicamente, no entanto a sua adoção deve sempre visar a altas produtividades zootécnicas devido ao seu elevado custo de produção. The economic viability of three systems of production was evaluated through the measurement of costs and analysis of financial indicators. The three systems (S1, S2 and S3), located on the Western Border of Rio Grande do Sul, were evaluated from October 2010 to October 2011. The pasture established is S1 was ryegrass (Lolium multiflorum Lam) and white clover (Trifolium repens Lam), in S2, white clover, red clover (Trifolium pratense Lam), Bird’s-foot trefoil (Lotus corniculatus Lam), ryegrass and oats (Avena strigosa Schreb), and in S3, ryegrass, birdsfoot trefoil, white clover and red clover. The animals were weighed before and after the pastures. Data collection was conducted monthly, using spreadsheets suitable for the measurement of production cost. Productivities were 369, 772 and 637 kg/ha for systems S1, S2 and S3, respectively. S2 had the highest total cost (R$ 2101.59/ha), while the lower was obtained by S1 (R$ 1626.93/ha). In the analysis of the average operating costs, items that showed the highest values were the establishment of pasture, electricity, maintenance of pasture and depreciation. As for margins, the systems S1, S2, and S3 were, respectively, R$ 33.46, 1162.55 and 701.01/ha for gross margin; R$ -63.51, 955.40 and 541.05 ha-1 for operating margin; and R$ -583.18, -28.99 and 291.61 ha-1 for total profit. The return was -0.47, 4.37 and 3.01% and profitability was -5.94, 39.92 and 27.38% for the S1, S2 and S3 respectively. The positive result found in the financial evaluation of the three systems studied indicates the economic viability of irrigated pasture in finishing cattle. Irrigation of pasture for finishing cattle is economically feasible, however, its application should always aim high yields husbandry due to their high cost of production.

The objective of this study was to determine the main causes of failure in bull breeding using a soundness evaluation in Rio Grande do Sul State/Brazil. We evaluated 19,836 bulls from 15 different breeds with ages ranging from two to eight years. The failures of bulls in each step were analyzed by logistic regression. The binary logistic regression was applied because the response variable had only two responses: Success (1) and Failure (0). Older bulls are more likely to be rejected than are younger bulls, regardless of their genetic group. Depending on the step of the assessment, one or another group is rejected. All steps of bull breeding soundness evaluation (BBSE) are important, with special attention to the failures of the behavioral evaluation (libido and physical ability). A BBSE performed before the breeding season reduces the risk of sub-fertile bulls in the herd.

This study aimed at estimating the heritability of age at first calving and of performance traits included in the selection index and the genetic correlations between age at first calving and these performance traits. Data were extracted from the Conexão Delta G database and only data from herds in which heifers were bred younger than 24 months of age were used, resulting in a file with 331,310 evaluated animals. The following traits were included in the analyses: age at first calving, birth to weaning gain, post-weaning weight gain, visual scores of conformation, precocity, and muscling evaluated at weaning and in yearling heifers. Covariance components were obtained by bi-character analyses between traits. An alternative age at first calving was also taken into account, in which all heifers were used, including those that were mated and did not calve. Covariance components and estimates of the effects included in the model were obtained using the software program DMU. Heritability estimates were 0.11 and 0.13 for age at first calving and alternative age at first calving, 0.38 for birth to weaning gain, and 0.13 for post-weaning weight gain. Visual score estimates ranged between 0.16 and 0.18 at weaning and 0.19 and 0.29 in yearlings. Genetic correlation estimates of the traits were low, but in the desirable direction. Selection for birth to weaning gain and visual scores does not have a negative effect on age at first calving or alternative age at first calving.

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.

The objective of this study was to investigate the effects of genetic group and calf sex on selling prices in auctions in the state of Santa Catarina (SC), Brazil. We evaluated 33,143 animals, representing 3,587 lots in 47 auctions from 2009 to 2014. The calves were classified according to genetic groups: British breed or crossbreed (BX); Continental breed or crossbreed (CX); Zebu breed or crossbreed (ZC); British and Continental crossbreed (BC); and Bos taurus and Bos indicus crossbreed (TI). The lots were composed of male and female calves. The years presenting low and high changes in the price of calves were similar to the variation in the price of beef cattle and, in 2014, the calf price reached its highest value (R$5.36). Male calves were sold at prices higher than female calves (average 7.8%), but this difference was driven by year of analysis, in which the closest approach occurred during periods of reduction in the price of live cattle in SC (2012 and 2013). Calves of genetic groups ZX and TI received, on average, lower prices (R$4.49 and R$4.64, respectively) compared with the other groups. In 2013, males from the BX group had greater variation in price compared with CX (3.9%) and BC (5.7%). On the other hand, female heifers from the BX group received higher average prices in 2011 compared with the CX, BC, IT, and ZX groups (8.1, 8.5, 14.7, and 16.5%, respectively). Recently, female British heifers have had a greater appreciation in auctions held in SC, possibly for their reproductive performance potential of beef cows. Thus, sex and different genetic groups are factors that impact the selling price of calves in the SC region.

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.

O trabalho foi realizado para caracterizar a gordura intramuscular dos cortes contrafilé, picanha e costela de seis marcas comerciais (A, B, C, D, E e F) de carne bovina comercializadas no município de Porto Alegre, Rio Grande do Sul. As amostras foram coletadas em uma rede de hipermercados. As marcas A e B foram associadas a animais de raças britânicas, as marcas C e D de animais de raças européias produzidos em sistema convencional e orgânico, respectivamente, e provenientes do Uruguai e as marcas E e F de animais sem raça definida e sistema de alimentação não identificado, obtidas em um frigorífico regional e em uma rede de hipermercados, respectivamente. As amostras foram desossadas, moídas, embaladas a vácuo e armazenadas em temperatura de resfriamento até o momento das análises. Em cada amostra foram realizadas a extração dos lipídios e a identificação dos ácidos graxos. O delineamento experimental foi inteiramente casualizado, com arranjo fatorial 6 × 3 e os dados analisados pelo procedimento GLM do aplicativo computacional SAS. Não houve interação significativa entre cortes e marcas para o perfil lipídico dos cortes comerciais. O percentual lipídico foi de 0,95; 3,01 e 0,97% nos cortes contrafilé, costela e picanha, respectivamente. A costela apresentou maior percentual de ácidos graxos (AG) saturados e maior estimativa da D9 desaturase a partir do C16:0 e C18:0. O maior percentual de C18:2 cis-9, trans 11, ácido linoleico conjugado, CLA, n-6 e n-3 foi encontrado na picanha. A marca F apresentou maior grau de saturação e a marca D, maior valor de ácidos graxos poliinsaturados, relação poliinsaturados/saturados e trans18 e menor valor de ácidos graxos saturados. Houve interação significativa entre corte e marca para o conteúdo de CLA, sendo o maior conteúdo encontrado no contrafilé da marca F. As características da gordura intramuscular da carne bovina dependem do corte e da marca comercial.The objective of this work was to characterize the intramuscular fat of short loin, ramp loin and rib and six commercial brands (A, B, C, D, E and F) of beef commercialized in Porto Alegre, Rio Grande do Sul. Samples were collected from a supermarket chain. The brands A and B were associated with British animals breeds, the brands C and D were from European animals breeds produced in conventional and organic system, respectively, from Uruguay, while the brands E and F were derived from non specific breed and unidentified feeding system, obtained in a slaughterhouse and a regional chain of supermarkets, respectively. The samples were deboned, ground, vacuum packed and stored in cooling temperature until the moment of analysis. In each sample were extracted lipids and fatty acids were identified. The experimental design was a completely randomized, with a 6 × 3 factorial arrangement and analyzed by the GLM procedure of SAS computing application. Regarding lipid profile no significant interaction were found among cuts and brands of commercial cuts. The lipid percentage was 0.95; 3.01 and 0.97% in short loin, ribs and ramp loin cuts. Rib presented the greatest percentage of saturated fatty acids (FA) and the greatest estimate of D9 desaturase from C16:0 and C18:0. The highest percentage of C18:2 cis-9, trans 11, conjugated linoleic acid, CLA, n-6 and n-3 was found in ramp loin. Brand F showed a higher degree of saturation, while the brand D showed higher polyunsaturated fatty acids, polyunsaturated/saturated ratio and trans18 and the lowest saturated fatty acids. There was a significant interaction between cuts and brands for the content of CLA, with the highest content found in the short loin of brand F. The characteristics of intramuscular beef fat depending on the cuts and the commercial brands.

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 cascaproteinada 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 osbalanços 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.

Foram avaliados o desempenho e as características de carcaça de 36 novilhos Brahman (Bh), Brangus (Bg) e Hereford adaptado (He), terminados em pastejo com suplementação (PSu) ou em confinamento (Conf). Os animais foram abatidos quando apresentavam espessura de gordura maior do que 4mm. Na dieta do Conf, a relação volumoso:concentrado foi de 60:40 (com base na matéria seca), continha 13% de proteína bruta (PB) e 62% de nutrientes digestíveis totais (NDT). O capim-mombaça continha, em média, 7% de PB e 54% de NDT, e o suplemento 24% de PB e 76% de NDT. Foi observada diferença (P

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.

It was evaluated statistical models with different assumptions to define the one that best describes the presence of genotype × environment interaction on adjusted post-weaning weight gain (PWG345) of Hereford cattle, through the study of reactions norms to the environment, obtained by random regression using a Bayesian approach. Four reaction norms hierarchical models (RNHM) were used through the INTERGEN program. The RNHM K uses the solutions of contemporary groups previously estimated by the standard animal model (AM) and considers them as environmental level for predicting the reaction norms and the RNHM S, which jointly estimate these two sets of unknowns. For both models, two versions were considered, one with a homogeneous (hm) and another with a heterogeneous (ht) residual variance. Based on the deviance information criterion and Bayes factor, RNHMs hm showed the best fit to the data, and by the deviance based on conditional predictive ordinate, the best fit was the RNHM Kht, whereas, by all the three criteria used, the worst fit was obtained by using the standard animal model. Heritabilities estimated on RNHM were increasing in the environmental gradients for PWG345, at -60 kg, 0 and +60 kg. The genetic correlation estimated between the level and slope of reaction norms was high, from 0.97 to 0.99, characterizing a scale effect on genotype × environment interaction. The reaction norms hierarchical models are efficient to describe the changes in variance components due to the environment and to describe the presence of genotype × environment interaction on PWG345 trait of Hereford cattle.Avaliaram-se modelos estatísticos com diferentes pressuposições para definir o que melhor descreva a presença de interação genótipo × ambiente no ganho de peso pós-desmama ajustado (GPD345) de bovinos Hereford, mediante o estudo de normas de reação ao ambiente, obtidas por regressão aleatória, usando uma abordagem bayesiana. Quatro modelos hierárquicos de normas de reação (MHNR) foram empregados por meio do programa INTERGEN. O MHNR K utiliza as soluções de grupos contemporâneos estimadas previamente pelo modelo animal padrão (MA) e as considera como nível ambiental para predizer as normas de reação e o MHNR S, que estima simultaneamente esses dois conjuntos de incógnitas. Para ambos os modelos, foram consideradas duas versões, uma com variância residual homogênea (hm) e outra heterogênea (ht). Pelo critério de informação da deviance e fator de Bayes, o MHRN Shm apresentou melhor ajuste aos dados e, pela deviance baseada na ordenada preditiva condicional, o melhor ajuste foi do MHNR Kht, enquanto, pelos três critérios, o pior ajuste foi obtido pelo modelo animal padrão. As herdabilidades estimadas nos MHNR foram crescentes nos gradientes ambientais em GPD345 de -60; 0 e +60 kg. As correlações genéticas estimadas entre o nível e inclinação das normas de reação foram de alta magnitude, entre 0,97 e 0,99, caracterizando efeito de escala em interação genótipo × ambiente. Os modelos hierárquicos de normas de reação são eficientes para descrever as alterações nos componentes de variância decorrentes do ambiente e para descrever a presença de interação genótipo × ambiente na característica GPD345 em bovinos Hereford.

The objectives of this research were to analyse data on the international market of frozen boneless beef and to classify its participants into groups according to their trade relationships, identifying the main factors that influence the preference of a country to beef from a determined supplier country. International beef trade is composed of two markets: in one of them, the relationships between supplier and client depend on the lowest price, and Brazil is found in favorable conditions; and the other, the relationships are preferably based on the sanitary quality of the herd and traceability systems recognized by the purchaser, to which Brazilian participation is low.Os objetivos nesta pesquisa foram analisar os dados referentes ao mercado internacional de carne bovina congelada desossada e classificar seus participantes em grupos de acordo com suas relações comerciais elencando os principais fatores que influenciam a preferência de um país pela carne bovina de determinado país fornecedor. O comércio internacional de carne bovina é composto de dois mercados: num deles as relações entre fornecedor e cliente dependem do menor preço e Brasil encontra-se em condições favoráveis; e no outro as relações se dão preferencialmente em razão da qualidade sanitária do rebanho e de sistemas de rastreabilidade reconhecidos pelo comprador, cuja participação do Brasil é pequena.

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.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.

Avaliaram-se as características sensoriais da carne de novilhos não-castrados ou castrados terminados em confinamento e abatidos aos 16 (superjovens) ou 26 (jovens) meses de idade. A dieta com relação volumoso:concentrado de 50:50 continha 11,8% de proteína bruta e 2,83 Mcal de energia digestível/kg de matéria seca. A maior amplitude do pH final da carne foi observada nos novilhos jovens e a menor, nos superjovens. A carne dos animais não-castrados, independentemente da idade de abate, foi mais escura, mais grosseira e com menor grau de marmorização em comparação à dos castrados. A carne dos animais castrados teve maior perda de líquidos durante o processo de descongelamento em relação à dos não-castrados (8,55 vs 4,99%). Ocorreu interação entre categoria e sexo do animal para perda de líquido durante a cocção, palatabilidade e suculência. Novilhos jovens não-castrados apresentaram maior quebra à cocção, carne menos palatável e menos suculenta em relação aos jovens castrados e aos superjovens castrados e não-castrados. A redução da idade de abate de 26 para 16 meses de idade, independentemente da condição sexual, melhora a maciez da carne avaliada pelo painel de degustadores.It was evaluated in this work the sensorial characteristics of the meat of non-castrate or castrated males feedlot finished and slaughtered at 16 (young steers) or 26 (steers) months old. The diet with 50 roughage: 50concentrate contained 11.8% of crude protein and 2.83 Mcal of digestible energy/kg of dry matter. The highest amplitude of the final pH of the meat was noted on the steers, and the lowest on the young steers. The meat of the non-castrate males, regardless to the age at slaughter, was darker, coarser and showed lower marbling degree than the meat of the castrated animals. Thawing loss was higher for the meat of the castrated animals(8.55 vs 4.99%). There was interaction among categories and sex for cooking loss, palatability and juiciness. Meat of the older non-castrate males showed higher cooking loss, it was less palatable and less juicy regarded to the meat of the older castrated and the younger castrated or non-castrate males. Reduction of slaughtering age from 26 to 16 months old, regardless to sexual condition, improves meat tenderness evaluated by taste panel.

Um modelo de simulação foi desenvolvido e validado com o objetivo de conhecer e predizer o desempenho produtivo de bovinos machos castrados com diferentes pesos e idades iniciais mantidos sobre pastagens cultivadas Panicum sp. e Brachiaria sp. em regiões tropicais e subtropicais. O modelo incluiu relações diretas entre os dois componentes principais (animal e forragem) e relações indiretas entre outros dois componentes (clima e solo). O componente animal incluiu: consumo de matéria seca de forragem, consumo de suplemento, carga animal, peso e idade inicial dos animais, biótipo (peso adulto e peso ao nascimento) e exigências de energia para mantença e produção animal (ganho de peso). O componente forragem incluiu: crescimento, senescência, digestibilidade e disponibilidade. Os resultados obtidos com o modelo foram comparados a dados experimentais obtidos da literatura em condições semelhantes e indicaram baixo (35%) erro percentual de estimação. O modelo possibilita avaliar determinadas estratégias nutricionais e, desta forma, auxilia em decisões que dependem do ganho de peso dos animais e das condições da pastagem no decorrer do tempo.A simulation model was developed and validated with the objective of evaluating and predicting the productive performance of steers with different weights and initial ages kept on Panicum sp. or Brachiaria sp. cultivated pastures in tropical and subtropical regions. The model established the direct relationships between two main components (animal and fodder plant) and two indirect components (climate and soil). The animal component included: intake of forage dry matter, supplement intake, stocking rate, initial weight and age of the animals, biotype (adult weight and weight at birth), energy requirement for maintenance and production (live weight gain). The forage components included: growth, senescence, digestibility and availability. The results obtained with the model were compared to those obtained in the literature under similar conditions in Brazil and a low percentage of estimated error was found (35%). The model is an adequate tool to evaluate certain nutritional strategies and thus to assist in decisions that depend on the weight gain of the animals and pasture conditions over time.

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.

Analisou-se o perfil de consumidores de carne bovina e determinou-se o consumo de carne com certificação visando obter dados sobre a importância e o valor da certificação da carne na hora da compra. Avaliou-se ainda o conhecimento do consumidor de carne bovina quanto à certificação da carne e quanto esse consumidor paga por este processo. A pesquisa foi realizada em uma rede de supermercados, mediante a aplicação de questionários dirigidos às pessoas próximas aos balcões com carne, independentemente da espécie animal. Os consumidores exigem alimentos com qualidade e certificados confiáveis que demonstrem e garantam a qualidade dos alimentos, porém, estão dispostos a pagar somente um pouco a mais pela certificação, em comparação ao valor atual de mercado, provavelmente pelo fato de sua renda mensal não permitir maior valorização desse atributo.The profile of beef meat consumers was analyzed, as well as the consumption of certificated meat, with the objective of obtaining data on the importance the of certification value at the purchasing occasion. The aim of this study was to evaluate the beef meat consumers awareness regarding the meat certification and how much they are willing to pay for this process. The data survey was carried out in only one supermarket chain from the city of Porto Alegre - RS, Brazil, which authorized the research interviewing people through questionnaires, close to refrigerator counters of any meat species. It was observed that consumers are demanding for food with quality attributes, with trustful certifications that testify these quality attributes. However, the data obtained from interviews with consumers showed that they are willing to pay only little more for certification than the current price, probably due to the fact that their average monthly income ranges from one to six minimum wages.

Avaliou-se o processo de comercialização de 1.757 lotes de bezerros, totalizando 28.495 animais, incluindo a ordem e o tempo de permanência em pista, as estratégias de divulgação aos compradores e uniformização dos lotes, o preço final (R$/kg de PV) e o número de lances. O modelo proposto foi eficiente em cenários desfavoráveis à atividade de cria. Em períodos de grande oferta de bezerros e preços baixos, todas as variáveis estudadas podem influenciar o preço final por quilograma de peso vivo, o que indica que alguns aspectos fora do controle do produtor, mas bem próximo dele, podem influenciar o valor recebido, portanto, são importantes no acompanhamento do processo de comercialização dos animais.The commercialization process of 1.757 lots of calves was evaluated, totaling 28.495 animals, including the order and time of permanence in track, the divulgation strategies to the buyers and uniformity of the lots, as well as the final price (R$/kg WL) and number of biddings. The model proposed was efficient in showing unfavorable scenarios for the breeding activity, and in periods of great offer of calves and low prices, the studied variables can influence the final price per kilogram of live weight. This indicates that some aspects out of the control of breeders but very close to them can influence the final value; therefore, are of extreme importance in the follow-up of the commercialization process of animals.

Foram avaliados os componentes não-integrantes da carcaça de novilhos terminados em confinamento e abatidos aos 16 (superjovem) ou 26 (jovem) meses de idade. A dieta foi formulada com 50% de volumoso e 50% de concentrado e continha 11,8% de proteína bruta e 2,83 Mcal de energia digestível por kg de matéria seca. Animais superjovens apresentaram maior rendimento de corpo vazio (92,39 versus 89,76% para os jovens), como resultado de seu menor conteúdo gastrintestinal (35,23 versus 53,46 kg para os jovens). Animais não-castrados apresentaram maior peso de cabeça (13,84 versus 12,35 kg), patas (11,12 versus 8,96 kg) e couro (46,44 versus 37,71 kg) em comparação aos castrados, o que está relacionado ao seu maior peso corporal (541,26 versus 445,47 kg). Observou-se influência da interação categoria x condição sexual sobre o peso absoluto dos órgãos vitais (coração, fígado e pulmões) e dos componentes do trato gastrintestinal. O peso total de órgãos vitais e do trato gastrintestinal foi maior nos animais não-castrados, mas deixou de ser significativo quando ajustado para peso de corpo vazio (PCV) e de abate (PA). Animais superjovens apresentaram maior peso absoluto das gorduras interna (25,91 versus 20,13 kg) e de toalete (13,96 versus 10,98 kg). A castração dos animais resultou em maior participação de gordura interna calculada em relação ao peso de corpo vazio e ao peso de abate.The non-carcass components of castrated and non-castrated cattle (sex condition) finished in feedlot and slaughtered at 16 (super young) or 26 (young) months of age (animal category) were evaluated. The diet was formulated to contain 11.8% of CP and 2.83 Mcal/kg DM of DE with 50:50 forage to concentrate ratio (%MS). Super young animals showed higher of empty body dressing percentage (92.39 versus 89.76%), as a result of their lower gastrointestinal content (35.23 versus 53.46 kg) as compared to the young animals. Non-castrate animals showed higher head weight (13.84 versus 12.35 kg), feet (11.12 versus 8.96 kg) and rawhide (46.44 versus 37.71 kg) as compared to castrate animals, which are related to their higher body weight (541.26 versus 445.47 kg). There was influence of animal category x sex condition interaction on absolute weight of vital organs (heart, liver and lungs) and the gastrointestinal tract components (GIT). The total weight of vital organs and GIT was higher in non-castrate animals, but not significant when adjusted for empty body weight and slaughter weight. Super young animals showed higher absolute internal fat weight (25.91 versus 20.13 kg) and hot fat trim (13.96 versus 10.98 kg). The castration of animals resulted in higher participation of internal fat calculated on empty body weight and slaughter weight.

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 foi realizado com o objetivo de caracterizar os efeitos dos aspectos dependentes da genética de bezerros comercializados no estado do Rio Grande do Sul e verificar sua influência no preço de venda. Foram coletados em 13 feiras municipais de bezerros de corte no estado dados referentes ao grupo genético predominante, ao tamanho e à musculatura dos animais de 739 lotes, correspondendo a 11.986 cabeças. Foram avaliados o preço obtido por kg de peso vivo, a porcentagem de liquidez e a valorização do bezerro durante a comercialização. A freqüência de bezerros sem predominância genética ainda é grande nas feiras do estado, no entanto, esses animais têm menor preferência do comprador, pois têm menor liquidez em relação ao outros grupos ofertados. Os bezerros do grupo genético sintético (Braford, Brangus ou Canchim) são comercializados com maiores preços por kg de peso vivo e são mais valorizados. Para características de tamanho e desenvolvimento muscular, os bezerros grandes e fortes tiveram maior liquidez em comparação aos de estrutura média ou pequena, portanto, têm maior preço e valorização por kg de peso vivo.This work aimed at to characterize the effects of the dependent aspects of the genetics of the calves marketed in the state of Rio Grande do Sul, as form of verifying the influence of these in the sale price. They were collected at 13 municipal auction of calves in the State, referring data to the predominant genetic group, size and musculature of the animals of 739 lots of animals corresponding to 11,986 heads. They were evaluate for the price obtained by kg of live weight, liquidity percentage and the valorization of the calf during the commercialization. The calves without genetic predominance still demonstrate great frequency in the auction of RS. However, these animals have less buyer's preference because they show small liquidity in relation to the other affered groups. The calves of the synthetic genetic group (Braford, Brangus or Canchim) obtained larger prices for kg of live weight and larger valorization. For size characteristics and muscular development, the big and strong calves had larger liquidity in relation to animals of medium or small structure, obtaining larger price and valorization for kg of live weight.

The complexity of the consumers' behavior has taken the food industry to a new level of dynamism. Therefore, understanding the factors that influence this behavior is decisive for the differentiation of products to niche markets and even to adjust the supply according to consumers' expectancy. This article proposes a conceptual model to identify the factors influencing beef consumption in Brazil. The methodological approach was characterized by a systematic review through a synthesis of research related directly to this topic. Therefore, 76 papers published during the 2000-2014 period, including official documents (statistics), full research papers, abstracts, proceedings, and reports, were selected. Four main factors were related to influences in consumer behavior and/or directly in beef consumption: sociocultural, economic, health/food, and environmental. Among these dimensions, there was an emphasis on recent publications related to health/food and the environment. The compilation and analysis of these papers enabled the conception of the proposed model and suggests the consideration of four main dimensions in beef consumption.

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.

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.

RESUMO - O objetivo deste estudo foi avaliar o efeito da substituição do milho pelo bagaço de mandioca no concentrado sobre a digestibilidade aparente, o consumo de nutrientes digestíveis, o ganho de peso diário médio (GPDM) e a conversão alimentar (CA) em bovinos em crescimento. Dezesseis novilhos mestiços machos inteiros foram distribuídos em delineamento em blocos casualizados completos em dois períodos. Quatro tipos de concentrados foram testados, em associação com o fornecimento a vontade de feno de aveia/azevém (Avena strigosa, L.; Lolium multiflorum, L.) e suplementação média de concentrado de 0,83% PV. Os concentrados fornecidos aos animais diferenciaram-se pelo nível de substituição do milho por bagaço de mandioca: T1, 0; T2, 33; T3, 66 e T4, 99. Não houve efeito dos níveis de substituição do milho pelo bagaço de mandioca sobre os coeficientes de digestibilidade aparente das frações nutritivas estudadas. O consumo de fibra em detergente ácido digestível (FDAD) aumentou linearmente com a substituição do milho por bagaço de mandioca. Não houve efeito dos tratamentos sobre o consumo de matéria seca digestível (MSD), matéria orgânica digestível (MOD), fibra em detergente neutro digestível (FDND), energia digestível (ED) e energia metabolizável (EM), que foram, respectivamente, para T1, T2, T3 e T4, 53,51; 54,50; 53,63; e 53,69 (g MSD/ kg0,75·dia), 51,77; 52,37; 51,27; e 51,23 (g MOD/ kg0,75·dia) e 30,13; 30,93; 30,46; e 30,88 (g FDND/ kg0,75·dia), 224,13; 228,51; 224,77; e 225,33 (kcal ED/ kg0,75·dia), 183,75; 187,56; 184,38; e 184,43 (kcal EM/ kg0,75·dia). Os resultados obtidos para GPDM foram 1,10; 0,95; 1,12; e 0,75 kg/animal·dia, e para CA 4,61; 6,17; 4,58; e 7,98, respectivamente, para T1, T2, T3 e T4. Os valores de GPDM e CA, para o nível de substituição de 99% do milho por bagaço de mandioca no concentrado, foram inferiores aos obtidos para os níveis de 0 e 66%, porém semelhantes aos do nível de 33% de substituição do milho pelo bagaço de mandioca no concentrado.ABSTRACT - The objective of this study was to evaluate the effect of the substitution of corn by cassava bagasse in concentrate on apparent digestibility, digestible nutrient intakes, average daily gain (ADG) and feed:gain ratio (F:G) in growing cattle. Sixteen cossbred bulls, were allotted to a completely randomized block design and in two periods. Four types of concentrade were tested, in association with an ad libitum allowance of oat/ryegrass hay (Avena strigosa, L.; Lolium multiflorum, L.) and an average concentrate suplemetation of .83% LW. The concentrates fed to the animals were different by the substitution level of corn by cassava bagasse: T1 0,0; T2, 33,0; T3, 66,0; e T4, 99,0. There was no effect of the substitution of corn by cassava bagasse on the apparent digestibility coefficients of the studied nutritive fractions. The digestible acid detergent fiber intake (DADF) linearly increased with the substitution of corn by cassava bagasse. There was no effect of the treatments on the intakes of digestible dry matter (DDM), digestible organic matter (DOM), digestible neutral detergent fiber (NDF), digestible energy (DE) and metabolizable energy (ME), which were, respectively, for T1, T2, T3 and T4, 53.51; 54.50; 53.63 and 53.69 (g DDM kg0.75·day), 51.77; 52.37; 51.27 and 51.23 (g DOM/ kg0.75·day, 30.13; 30.93; 30.46 and 30.88 (g DNDF/ kg(.7)5·day), 224.13; 228.51; 224.77 and 225.33 (kcal DE/ kg.75·day), 183,75; 287,56; 184,38 and 184,43 (kcal ME/ kg.75·day). The results obtained for ADG were 1.10; 0.95; 1.12 and 0.75 kg/animal·day, and for F:G 4.61; 6.17, 4.58 and 7.98, respectively for T1, T2, T3 and T4. The values of ADG and F:G, for the substitution of 99% of corn by cassava bagasse in concentrate, were lower than those obtained by the levels of 0 and 66%, however, they were similar to the 33% of substitution level of corn by cassava bagasse in the concentrate.

The objective of this study was to measure and classify the international beef trade. For this, data related to the international chilled boneless beef (CBB) trade, the major and most important market, were analyzed. Producing countries were classified into groups according to their trade relations, and the main factors that influenced one country to prefer to import CBB from a specific exporting country were analyzed. The results revealed four markets related to client demands with regard to the sanitation and traceability of beef products. Furthermore, extrinsic characteristics of the product are discussed, such as a productive system that aims to minimize environmental impacts and to value animal welfare and respect for social demands. The markets that pay highest prices require sanitary quality of suppliers, demanding traceable and process-certified products. Brazil does not access these markets because it does not meet these requirements. To change this scenario it is necessary to eradicate FMD across the Brazilian territory, acquiring a status of a zone with minimal BSE risk, aligning the intrinsic value of the CBB with expectations of consumers and implementing a traceability program that is both feasible and acceptable for clients.

The objective of this study was to evaluate performance and biometrics of lambs fed different sources of forage. Twenty-four six-month-old Santa Inês female lambs were randomly allocated to four experimental diets and housed in individual stalls. They weighed on average 26.35±0.20 kg. The diets were coast cross hay (HAY), cassava hay (CAS), dehydrated by-product of pea crop (PEA) and saccharin (SAC). The diets were formulated with the same amount of protein and energy with fixed levels of forage (60%) and concentrate (40%). Adaptation to the diet took 7 days, with 45 days on experiment. Weights and biometric measurements were obtained every fortnight and feed intake three times a week. Rights half-carcasses were weighed and sectioned into retail cuts, rib, loin, shoulder, belly, neck and leg, which were weighed individually. Weight gain in lambs was significantly different between diets, with those fed saccharin gaining more. Overall, treatments did not significantly affect biometric measurements. There was a significant difference for feed intake and live weight at the end of the experiment. Animals fed PEA and SAC showed the best results. Average positive correlations were found between biometric measurements and live weight. Treatment PEA had heavier hot (14.36 kg) and cold (14.01 kg) carcass weights than the other groups. Hot carcass kill-out was higher for animals fed PEA as well as ham weight, belly, neck and heart girth. The weight of the abdominal viscera (%) for lambs fed CAS was greater than those fed SAC and PEA. The weights of the thoracic viscera as well as the liver, for lambs fed PEA were higher. The by-product of pea yielded best results, followed by saccharin, and can replace traditional forage sources in the region, providing similar results in terms of cuts and body components. These could be an alternative for feeding sheep in the dry season. The substitution of forages using by-product of pea and saccharin led to improved productivity over the coast-cross hay available in the Federal District - Brazil.

The objective of this study was to analyze the rates of rejection in the different steps of the breeding soundness evaluation of beef bulls in the state of Rio Grande do Sul, Brazil. The breeding soundness of 22,113 young and mature bulls of 14 beef breeds, participating in the Program of Reproductive Evaluation (PARTO) was evaluated in the experiment. Data concerning to the causes of rejection in the four steps of the breeding soundness evaluation (general physical examination, genital tract examination, semen evaluation and sexual behavior assessment) were analyzed by the Chi-square test and univariate regression analysis. According to year, general physical examination, genital tract examination and semen evaluation determined the rejection of 0.9% to 2.5%, 5.1% to 7.7%, 1.8% to 5.3%; and 4.2% to 6.7%, 7.3 to 9.3%, and 2.5% to 5.5% of young and mature bulls, respectively. Mature bulls presented higher chances of rejection than young bulls in the general physical examination in every year evaluated; as to the genital tract examination, their chances of rejection were higher in years I and II, but not in year III. In the semen evaluation, there was no difference between the ages assessed in any of the three years evaluated. Sexual behavior assessment accounted for the rejection of 1.9 to 6.0% of the young bulls and 2.9% to 3.9% of mature bulls, in accordance with the years evaluated; in years I and II, mature bulls presented higher rejection rates than young bulls. These results confirm the importance of performing all steps of the breeding soundness evaluation, including the sexual behavior assessment as a work routine, rather than an additional, optional stage of the evaluation, which should be carried out before the breeding season. The results indicate the relationship between bull age and rejection rate in the breeding soundness evaluation.

An index was developed to estimate the bioeconomic efficiency of production systems, identifying alternative scenarios that could improve their efficiency, and building isoefficiency relations in beef cattle production systems in Rio Grande do Sul. The concept of return on investment was used to develop the indicator. Scenarios regarded as efficient showed values higher than 3. The bioeconomic efficiency index for beef cattle production in the theoretical reference scenario was considered inefficient. At least four modifications in the variables method made it a bioeconomically efficient activity. These circumstances were studied using sensitivity analyses, with theoretical changes in the scenarios by changing variables two by two, while the others were kept constant. In Rio Grande do Sul, alternatives that make the activity efficient were identified by changing productivity, production cost, land price and product price. Isoefficiency relationships were identified in other scenarios. The application of this indicator in other agricultural activities, as well as the design of bioefficiency studies including both environmental and social welfare characteristics are recommended.

This paper aimed to measure the competitiveness of beef cattle in the production systems located at the Northern region of Brazil. In the first quarter of 2010, 29 ranchers were interviewed in different regions of the states of Pará and Rondônia. From a multidisciplinary team, the main indicators that affect the competitiveness within the ranch were defined. They were as follows: technology, management, market relationship and institutional environment. Later on these indicators were divided in ten, ten, four and seven factors, respectively, giving specific values for each one of them in order to determine the competitiveness index using specific equations. The competitiveness index was measured for each production system and, later, the region average was calculated. The competitiveness rate of the indicators and of each of the 31 factors was also calculated, varying from very unfavorable to very favorable. The results were statistically analyzed by item response theory and the correspondent analysis. The competitiveness index of the production systems showed very unfavorable competitiveness rate (4%), unfavorable (31%), neuter (41%) and favorable (24%). The index management s]howed a strong association with the very unfavorable degree of competitiveness, as suggested by correspondent analysis. The main crucial factors identified were: integrated crop-livestock systems, strategic planning, financial indicators measurement, informatics, rancher-packer relationship, technologic innovation access, and rancher’s organization. In this sense strategic actions towards a better competitiveness of the beef cattle sector become essential for the whole beef supply chain.Objetivou-se mensurar a competitividade dos sistemas de produção de bovinos de corte que atuam na Região Norte do Brasil. No primeiro trimestre de 2010 foram entrevistados 29 produtores de bovinos de corte em diferentes regiões dos Estados do Pará e Rondônia. A partir de uma equipe multidisciplinar foram definidos os principais direcionadores que afetam a competitividade “dentro da porteira”: tecnologia, gestão, relações de mercado e ambiente institucional. Posteriormente estes foram desdobrados respectivamente em dez, dez, quatro e sete fatores, e atribuídos pesos específicos para cada um deles a fim de determinar o índice de competitividade por meio de equações específicas. O índice de competitividade foi mensurado para cada sistema de produção e, posteriormente, foi calculada a média regional. Foi calculado também o grau de competitividade dos direcionadores e dos 31 fatores, que variaram de muito desfavorável a muito favorável. Os resultados foram analisados estatisticamente pela teoria de resposta ao item e pela análise de correspondência. O índice de competitividade dos sistemas de produção apresentou grau de competitividade muito desfavorável (4%), desfavorável (31%), neutro (41%) e favorável (24%). O direcionador gestão apresentou uma forte associação com o grau de competitividade muito desfavorável pela análise de correspondência. Os principais fatores críticos identificados foram: integração lavoura-pecuária, planejamento estratégico, cálculo de indicadores financeiros, informatização, relação produtor-frigorífico, acesso a inovações tecnológicas e organização dos produtores. Neste sentido ações estratégicas em prol de uma maior competitividade setorial tornam-se fundamentais para a cadeia produtiva da carne bovina.

A variabilidade da circunferência escrotal e os efeitos de idade e raça,assim como, as relações existentes entre o peso testicular (PT), a circunferência escrotal (CE) e o peso vivo (PV) foram investigados em touros. As raças Devon, Polled Hereford e Red Angus apresentaram valores de CE mais altos que as demais raças avaliadas, tanto inglesas, como continentais, sintéticas e zebuínas. O percentual descartado de touros devido à baixa CE variou de 7,0 a 24,2%. O aumento da CE acompanhou o aumento do PT dos animais, e estes foram altamente relacionados, r2 = 0,90. Os resultados sugerem que, em touros jovens, a CE é a melhor forma de predizer o PT e, portanto, uma ferramenta útil para selecionar touros. The variability of scrotal circumference and the effects of age and breed as well as the relationship between testicular weight (TW), scrotal circumference (SC), and live weight (BW) were investigated in bulls. Devon, Polled Hereford, and Red Angus breeds showed higher SC values than the other British, Continental, Synthetic, and Zebu studied breeds. The percentage of culled bulls because of low SC ranged from 7.01 to 24.25%. The increase of SC was proportional to the increase in TW and they were highly correlated (r2= 0.90). The results suggest that SC in young bulls is the best way to predict TW and, therefore, a useful tool for their selection.

RESUMO - O objetivo deste trabalho foi avaliar o efeito da substituição do milho por bagaço de mandioca, no concentrado das rações, sobre o consumo de matéria seca (MS), matéria orgânica (MO) e proteína bruta (PB) de bovinos em crescimento. Dezesseis bezerros mestiços machos inteiros foram distribuídos em delineamento em blocos casualizados completos, em dois períodos. Quatro tipos de concentrado foram testados em associação com o fornecimento à vontade de feno de aveia/azevém (Avena strigosa, L.; Lolium multiflorum, L.) e suplementação média de concentrado de 0,83% PV. Os concentrados fornecidos aos animais diferenciaram-se pelo nível de substituição do milho por bagaço de mandioca: T1 = 0,0, T2 = 33,0, T3 = 66,0 e T4 = 99,0%. A substituição do milho por bagaço de mandioca no concentrado apresentou relação quadrática com o consumo de MS, MO e PB. O consumo máximo de MS, MO e PB foi, respectivamente, 88,53; 82,34; e 10,61 g/kg0,75. Os níveis de substituição de milho por bagaço de mandioca que geraram os consumos máximos foram 48,74; 44,14; e 43,75%, respectivamente, para MS, MO e PB. Níveis mais altos de substituição do milho por bagaço de mandioca no concentrado reduziram o consumo dos componentes estudados. ABSTRACT - The objective of this study was to evaluate the effect of the substitution of corn by cassava bagasse in the concentrate on dry matter, organic matter and crude protein intake in growing cattle. Sixteen crossbred bulls were allotted to a completely randomized block design, in two periods. Four types of concentrate were tested in association with an ad libitum allowance of oat/ryegrass hay (Avena strigosa, L.; Lolium multiflorum, L.)and an average concentrate supplementation of .83% LW. The concentrates fed to the animals were different of corn by cassava bagasse by the substitution levels of corn: T1 = 0.0, T2 = 33.0, T3 = 66.0, and T.04 = 99%. There was a quadratic relation on DM, OM and CP intake. The maximum DM, OM and CP intake was, respectively, 88.53, 82.34, and 10.61 g/kg.75. The corn by cassava bagasse substitution levels which produced the maximum intakes were: 48.74, 44.14, and 43.75%, respectively, for DM, OM, and CP. Higher corn by cassava bagasse substitution levels in the concentrate reduced the intake of the components studied.

O objetivo deste estudo foi avaliar o efeito da substituição do milho pelo bagaço de mandioca no concentrado sobre a digestibilidade aparente, o consumo de nutrientes digestíveis, o ganho de peso diário médio (GPDM) e a conversão alimentar (CA) em bovinos em crescimento. Dezesseis novilhos mestiços machos inteiros foram distribuídos em delineamento em blocos casualizados completos em dois períodos. Quatro tipos de concentrados foram testados, em associação com o fornecimento a vontade de feno de aveia/ azevém (Avena strigosa, L.; Lolium multiflorum, L.) e suplementação média de concentrado de 0,83% PV. Os concentrados fornecidos aos animais diferenciaram-se pelo nível de substituição do milho por bagaço de mandioca: T1, 0; T2, 33; T3, 66 e T4, 99. Não houve efeito dos níveis de substituição do milho pelo bagaço de mandioca sobre os coeficientes de digestibilidade aparente das frações nutritivas estudadas. O consumo de fibra em detergente ácido digestível (FDAD) aumentou linearmente com a substituição do milho por bagaço de mandioca. Não houve efeito dos tratamentos sobre o consumo de matéria seca digestível (MSD), matéria orgânica digestível (MOD), fibra em detergente neutro digestível (FDND), energia digestível (ED) e energia metabolizável (EM), que foram, respectivamente, para T1, T2, T3 e T4, 53,51; 54,50; 53,63; e 53,69 (g MSD/ kg0,75·dia), 51,77; 52,37; 51,27; e 51,23 (g MOD/ kg0,75·dia) e 30,13; 30,93; 30,46; e 30,88 (g FDND/ kg0,75·dia), 224,13; 228,51; 224,77; e 225,33 (kcal ED/ kg0,75·dia), 183,75; 187,56; 184,38; e 184,43 (kcal EM/ kg0,75·dia). Os resultados obtidos para GPDM foram 1,10; 0,95; 1,12; e 0,75 kg/animal·dia, e para CA 4,61; 6,17; 4,58; e 7,98, respectivamente, para T1, T2, T3 e T4. Os valores de GPDM e CA, para o nível de substituição de 99% do milho por bagaço de mandioca no concentrado, foram inferiores aos obtidos para os níveis de 0 The objective of this study was to evaluate the effect of the substitution of corn by cassava bagasse in concentrate on apparent digestibility, digestible nutrient intakes, average daily gain (ADG) and feed:gain ratio (F:G) in growing cattle. Sixteen cossbred bulls, were allotted to a completely randomized block design and in two periods. Four types of concentrade were tested, in association with an ad libitum allowance of oat/ryegrass hay (Avena strigosa, L.; Lolium multiflorum, L.) and an average concentrate suplemetation of .83% LW. The concentrates fed to the animals were different by the substitution level of corn by cassava bagasse: T1 0,0; T2, 33,0; T3, 66,0; e T4, 99,0. There was no effect of the substitution of corn by cassava bagasse on the apparent digestibility coefficients of the studied nutritive fractions. The digestible acid detergent fiber intake (DADF) linearly increased with the substitution of corn by cassava bagasse. There was no effect of the treatments on the intakes of digestible dry matter (DDM), digestible organic matter (DOM), digestible neutral detergent fiber (NDF), digestible energy (DE) and metabolizable energy (ME), which were, respectively, for T1, T2, T3 and T4, 53.51; 54.50; 53.63 and 53.69 (g DDM kg0.75·day), 51.77; 52.37; 51.27 and 51.23 (g DOM/ kg0.75·day, 30.13; 30.93; 30.46 and 30.88 (g DNDF/ kg.75•day), 224.13; 228.51; 224.77 and 225.33 (kcal DE/ kg.75·day), 183,75; 287,56; 184,38 and 184,43 (kcal ME/ kg.75•day). The results obtained for ADG were 1.10; 0.95; 1.12 and 0.75 kg/animal·day, and for F:G 4.61; 6.17, 4.58 and 7.98, respectively for T1, T2, T3 and T4. The values of ADG and F:G, for the substitution of 99% of corn by cassava bagasse in concentrate, were lower than those obtained by the levels of 0 and 66%, however, they were similar to the 33% of substitution level of corn by cassava bagasse in the concentrate.

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 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.