This trial was conducted to evaluate some beef quality attributes of Nellore, F1 Simmental × Nellore and F1 Angus × Nellore steers finished on feedlot. The effects of feeding regime and genetic group on shear force, thawing losses, cooking (leak + evaporation) losses, total losses and muscle fiber type, as well as carcass pH and temperature during 24 h of chilling were evaluated. There was a genetic group effect on shear force, where the beef from F1 Simmental × Nellore and F1 Angus × Nellore animals had lower values than Nellore animals. Beef of the animals fed the diets with 1% and 2% of body weight on concentrated lost more liquid than the meat of the animals fed at maintenance during thawing and when considering total losses. During cooking there was a difference among the feeding regimes for drip losses which were greater on the animals fed the diet of 1% of body weight on concentrate, followed by the 2% diet and, finally, by the animals fed at maintenance. The muscle of the Nellore steers had larger proportion of intermediate fibers and lower proportion of oxidative fibers than the crossbred animals. The proportion of glycolytic fibers was not influenced by genetic group. The Nellore animals had larger proportion of fibers of fast contraction and smaller proportion of fibers of slow contraction when compared with the crossbred animals. Feeding regime did not influence the proportion of muscular fibers or shear force. Nellore cattle produce tougher beef than crossbred Simmental × Nellore or Angus × Nellore, although all of them have the potential to produce an acceptable beef when slaughtered at young age. Feed restriction up to 90 days is not enough to cause modification on muscle fiber frequencies, then not affecting beef quality.

Sixty 18-month-old steers (20 Nellore, 20 F1 Simmental × Nellore and 20 F1 Angus × Nellore with average body weight of 265.6±6.4 kg; 325.3±4.7 kg and 324.6±6.0 kg, respectively) were used. The effects of feeding regime and genetic group on physical carcass composition, empty body composition, composition of the gain, as well as the pattern of tissue deposition were evaluated in this trial. The interaction between genetic group and feeding regime was not significant for any variable evaluated. Animals fed at the maintenance level produced carcass with larger proportions of bones and muscle than the animals fed ad libitum and Nellore animals had larger muscle portion and smaller adipose tissue portion on the carcass than the crossbred animals. Nellore animals and those fed at maintenance had smaller amount of total fat in the carcass than the crossbred animals and those fed ad libitum, respectively. Fat was deposited more pronouncedly in the intermuscular depot, followed by the visceral depot. The rate of deposition of the carcass tissues was smaller in the Nellore animals and in the animals fed the diet with concentrate allowance equivalent to 1% body weight (except for subcutaneous fat tissue), when compared with the crossbred animals and those fed the diet with 2% BW on concentrate, respectively. The rate of fat deposition on the visceral depot was larger in the F1 Angus × Nellore animals and on those fed the 2% of BW of concentrate diet when compared with F1 Simmental × Nellore animals and those fed the diet with the lowest concentrate allowance (1% BW).

This trial was conducted to evaluate the quantitative carcass traits of Nellore, F1 Simmental × Nellore and F1 Angus × Nellore steers fed at maintenance level or ad libitum with 1% and 2% of the body weight in concentrate. The animals were allotted to the treatments in a completely randomized experimental design, in a 3 × 3 factorial arrangement. The animals fed the ad libitum diet with more concentrate had greater cold carcass weight, cold carcass yield and longissimus muscle area/100 kg of cold carcass weight when compared with animals fed the diet with low concentrate allowance. There was no difference between the ad libitum diets for all of the carcass cuts yields, except for top sirloin. Crossbred animals had cold carcass yield larger than the Nellore animals. F1 Angus × Nellore animals had greater rib fat thickness and smaller longissimus muscle area/100 kg than the F1 Simmental × Nellore cattle. The yield of commercial carcass cuts was not influenced by genetic group, except for the shoulder clod yield, which was smaller in crossbred animals compared with Nellore animals. The longissimus muscle area, rib fat thickness and rump fat, taken by ultrasound were influenced by the body weight of the animals. Crossbred animals fed diets with higher concentrate level produce carcasses most suitable for the requirements of the market.

O experimento foi conduzido com os objetivos de avaliar a altura do dossel com 95% de interceptação luminosa e quantificar a influência da adubação nitrogenada e da densidade de plantas nas características morfogênicas e estruturais de capim-tanzânia. Quatro doses de nitrogênio, N (0, 80, 160 e 320 kg.ha-1), foram combinadas com três densidades de plantas (9, 25 e 49 plantas.m-2), em um arranjo fatorial 4 × 3, em delineamento inteiramente casualizado com três repetições, para avaliação da produção de biomassa, e duas repetições, para avaliação das características morfogênicas e estruturais. O acúmulo de MS total durante o período experimental foi influenciado pela adubação nitrogenada e pela densidade de plantas. No período das águas, as maiores doses de nitrogênio diminuíram o intervalo de colheitas e, consequentemente, aumentaram o número de colheitas. A altura do dossel de capim-tanzânia com 95% de IL foi positivamente influenciada pela densidade de plantas nos períodos das águas e de transição água-seca e seca. A altura do capim-tanzânia com 95% de IL apresentou variações ao longo das avaliações, de modo que os valores foram maiores (próximos a 70 cm) no período das águas, seguido pelos períodos de transição água-seca e seca.

This experiment was carried out to evaluate canopy height of guinea grass with 95% of photosynthetic active radiation interception and quantify the nitrogen fertilization influence and plants' density on the morphogenesis and structural characteristics of Tanzania grass. Four doses of N (0, 80, 160 e 320 kg.ha-1), were arranged with three plant densities (9, 25 and 49 plants.m-2), according to 4 × 3 completely randomized design, with three repetitions. Total dry matter (DM) accumulation throughout the experimental period was influenced by nitrogen fertilization and plants' density. In the rainy period, the higher nitrogen fertilization decreased the harvesting intervals, and consequently, increased the number of harvests. The rate of leaf appearance and the phyllochron were influenced only under nitrogen fertilization in the transition period of rainy and dry weather. Tanzania grass canopy height under 95% of light interception was positively influenced because of the plant densities in rainy period and transition period between rainy/drought and drought. Tanzania grass height under 95% of light interception presented variations along the evaluations and the values were higher (near 70 cm) in the rainy period, followed by transition period rain/drought and drought.

Objetivou-se estimar as exigências de proteína de animais Nelore, Nelore-Angus e Nelore-Simental, assim como a eficiência de uso da proteína metabolizável para ganho. Foram utilizados 69 animais (23 Nelore, 23 Nelore-Angus e 23 Nelore-Simental): 12 (quatro de cada grupo genético) foram abatidos antes do início do experimento, como grupo-referência, e nove animais foram separados para um ensaio de digestibilidade. Os animais restantes foram divididos em três dietas (ofertas de concentrado na base de 1 ou 2% do peso corporal à vontade e 1% do nível de mantença). Ao final do experimento, todos os animais foram abatidos e a composição corporal e o peso de corpo vazio (PCVZ) determinados. O consumo de proteína metabolizável (CPmet) foi estimado pela proteína microbiana verdadeira digestível média somada à proteína digestível não-degradada no rúmen. As exigências líquidas de proteína para ganho foram estimadas pela proteína retida (PR) em função do ganho de PCVZ (GPCVZ) e da energia retida. As exigências de proteína metabolizável para mantença foram estimadas pelo CPmet em função do GMD e as exigências líquidas para mantença pela PR em função do CPmet. O grupo genético influenciou apenas a relação entre os diferentes ganhos, mas não teve efeito sobre as exigências líquidas de proteína para ganho, que podem ser estimadas por meio do modelo PR = GPCVZ × (238,5 - 16,73 × (ER/GPCVZ)). Não há influência de grupo genético sobre as exigências líquidas e metabolizáveis de proteína para mantença, cujos valores são de 1,72 g/PCVZ0,75 e 3,09 g/PC0,75, respectivamente. Também não há efeito de grupo genético na energia retida em forma de proteína, assim como na eficiência de uso da proteína metabolizável para ganho, que é de 37,5%.

The objective was to estimate the protein requirements of Nellore, Nellore × Angus and Nellore × Simmental cattle, as well as efficiency of metabolizable protein for gain. Sixty-nine animals (23 Nellore, 23 Nellore × Angus and 23 Nellore × Simmental) were used, with 12 animals (four of each genetic group) slaughtered before the beginning of the experiment as the baseline group, and nine split for the performance of digestibility trial. The remaining animals were divided in three diets (concentrate offer of 1 or 2% of body weight and maintenance). At the end of the experiment, all animals were slaughtered and their corporal composition and empty body weight (EBW) were determined. The metabolizable protein intake (MPI) was estimated by the mean digestible microbial protein summed to digestibile rumen undegradable protein. The net protein requirements were estimated as retained protein by the retained energy (RE) and empty body gain (EBG). The requirements of metabolizable protein for maintenance were estimated as the MPI as function of average daily gain, and the net requirements for maintenance as retained protein (RP) as a function of MPI. The genetic group influenced only the ratio among gains. There were no effects of genetic group on net protein requirements for gain, and the model RP = EBW × (238.5 - 16.73 × (RE/EBG)) is recommended to estimate them. Genetic group did not affect net or metabolizable protein requirement for maintenance, and the values obtained were 1.72 g/EBW0.75 and 3.09 g/BW0.75, respectively. Also, there were no genetic group effects on retained energy as protein, nor in metabolizable protein efficiency for gain, which is 37.5%.

Objetivou-se comparar o consumo, o desempenho, a eficiência alimentar e as características de carcaça de bovinos de três grupos genéticos (GG) alimentados com dois níveis de concentrado. Foram utilizados 48 bovinos castrados, sendo 16 Nelore (NE), 16 Nelore-Angus (NA) e 16 Nelore-Simental (NS). Doze animais (quatro de cada GG) foram abatidos como referência e para os 36 animais remanescentes, a mistura de concentrado da ração foi oferecida em 1 e 2% com base no peso corporal, perfazendo um fatorial 3 × 2, em delineamento inteiramente casualizado, com seis repetições. O valor de significância foi definido em 0,05. As dietas isoproteicas foram compostas de silagem de milho e concentrado. O experimento foi composto de três períodos de 28 dias cada e todos animais abatidos ao final. O consumo de matéria seca (CMS) e demais nutrientes, exceto fibra em detergente neutro, foi maior nas dietas com alto nível de concentrado. O consumo de matéria seca dos animais mestiços foi maior que dos nelores, porém os Nelore-Angus apresentaram consumo maior quando comparado ao dos Nelore-Simental. Não foram observadas diferenças no desempenho dos animais entre os níveis de concentrado. Igualmente, os ganhos de carcaça e de corpo vazio foram maiores quando 2% de concentrado do peso corporal foi oferecido. O desempenho dos animais mestiços foi superior ao dos nelores, embora diferenças não tenham sido identificadas entre os mestiços. Não foram encontradas diferenças no índice bionutricional dos animais entre os dois níveis de concentrado, em eficiência alimentar para carcaça e ganho de peso do corpo vazio. Animais que consomem mistura de concentrado no nível de 2% do peso corporal apresentam maior consumo e desempenho se comparados àqueles que recebem o nível 1%, porém não ocorre diferença na eficiência alimentar. Nelore-Simental é mais eficiente que Nelore-Angus, mas ambos os grupos genéticos de mestiços são mais eficientes que o Nelore.

In the present work we aimed to compare intake, performance, feed efficiency and carcass traits of cattle from three genetic groups (GG) fed two concentrate levels in the diet. Forty-eight steers (16 Nellore, 16 Nellore-Red Angus and 16 Nellore-Simmental) were used. Twelve steers were slaughtered at the beginning of experiment as a reference group and for the remaining 36 animals, the concentrate mixture of the ration was offered as 1 and 2% of body weight basis in a 3 × 2 factorial arrangement in a completely randomized design, with six repetitions. The value of significance defined was 0.05. Isoprotein diets were composed of corn silage and concentrate. The trial was comprised of 3 periods of 28 days each and all animals slaughtered at the end. The dry matter and nutrients intake was higher in diets with high concentrate level of steers, except for neutral detergent fiber. The dry matter intake of crossbred steers was higher than that of Nelore, however Nellore-Angus presented greater intake as compared with Nellore-Simmental. No differences were observed for animal performance among concentrate levels. Conversely carcass and empty body weight gain were higher as 2% of body weight concentrate was offered. The crossbreds performance was higher than that of Nelore, although no differences were verified among crossbreds. No differences were found in the bionutritional index between the two concentrate levels, in feed efficiency to both carcass and empty body weight gain. Animals consuming concentrate mixtures at the level of 2% of body weight presents greater intake and performance than those that receive level of 1% of body weight basis, but with no differences in feed efficiency. The Nelore-Simental is more efficient than the Nelore-Angus, but both crossbreds are more efficient than Nelore.

Objetivou-se avaliar correlações entre características estruturais e valor nutritivo do pasto diferido de U. decumbens cv. Basilisk. O experimento foi realizado em esquema de parcelas subdivididas, segundo o delineamento em blocos casualizados, com duas repetições. Os tratamentos foram combinações dos períodos de diferimento da pastagem (73, 103, 131 e 163 dias) com os períodos de pastejo (1, 29, 57 e 85 dias). A massa de lâmina foliar verde correlacionou-se positivamente com os percentuais de proteína bruta (PB), fibra em detergente neutro potencialmente digestível (FDNpoD) e matéria seca potencialmente digestível (MSpoD), mas negativamente com os teores de fibra em detergente neutro (FDN) e FDN indigestível. As correlações para colmo morto foram inversas àquelas obtidas para lâmina verde. Para o perfilho vegetativo, as correlações foram positivas com PB e MSpoD e negativas com FDN e FDNi. Para o perfilho morto, constataram-se correlações positivas com os percentuais de FDN e FDNi da forragem, bem como associação negativa com os teores de PB, FDNpoD e MSpoD. O índice de tombamento correlacionou-se de forma negativa com o número de perfilhos vegetativos e de forma positiva com o número de perfilhos reprodutivos e mortos. O índice de tombamento também se correlacionou positivamente com os teores de FDN e FDNi e de forma negativa com os percentuais de PB e MSpoD. As características estruturais do pasto diferido estão associadas ao seu valor nutritivo. Ações de manejo que reduzam a massa de colmo morto e o número de perfilhos mortos e perfilhos reprodutivos contribuem para melhorar a estrutura e o valor nutritivo do pasto diferido.

The objective of this study was to evaluate correlations between the structural characteristics and nutritional value of different U. decumbens cv. Basilisk pastures. The experiment was carried out in a split-plot design following a randomized block design with two replications. The treatments were combinations among the different pasture periods (73, 103, 131 and 163 days) and the grazing periods (1, 29, 57 and 85 days). The green leaf blade matter (GLB) correlated positively with the percentages of crude protein (CP), potentially digestible neutral detergent fiber (PDNDF) and potentially digestible dry matter (PDDM), but correlated negatively with neutral detergent fiber (NDF) and indigestible neutral detergent fiber (INDF). Dead stem (DS) correlations were inverse to those obtained for green leaf blade. For vegetative tillering (VT), positive correlations were found with CP and PDDM; negative correlations were found for NDF and INDF of the forage. Dead tiller (DT), correlated positively with NDF and INDF of the forage and negative association with the CP, PDNDF and PDDM rates. The falling index (FI) correlated negatively with the number of VT and correlated positively with the number of reproductive tillers (RT) and dead tillers (DT). The falling index also correlated positively with the NDF and INDF rates and negatively with CP and PDDM. The structural characteristics of the different pasture were associated to their nutritive value. Management actions which result in a reduction in the dead stem matter and the numbers of dead tillers and reproductive tillers contribute to improve the structure and nutritional value of the different pasture.