ABSTRACT The objective of this survey was to identify what mycotoxins were present in ingredients used in diets offered to beef cattle in feedlots and their concentrations. The survey covered 30 Brazilian feedlots located in the five major beef-producing states. Samples of total mixed ration (TMR) and ingredients were collected and analyzed for mycotoxin using ultra-performance liquid chromatography coupled to tandem mass spectrometry. Mycotoxin concentrations were further interpreted according to known species-specific sensitivities and normalized according to the principles of toxic equivalent factors (risk equivalent quantities - REQ) expressed in µg kg−1 of aflatoxin B1-equivalent. Forty percent of the visited feedlots had apparent fungi in TMR. However, only one feedlot (3%) used a mycotoxin adsorbent. On the other hand, diets with high contamination presented no apparent fungi. One hundred percent of TMR was contaminated. All samples presented at least one mycotoxin contamination, with 65.5% considered low contamination, 27.6% medium contamination, and 6.90% high contamination. The toxins identified in TMR were fumonisins (most frequently), trichothecenes A, trichothecenes B, fusaric acid, aflatoxins, and ergot (mean concentration values: 2,330, 104.3, 79.5, 105, 10.5, and 5.5 µg kg−1, respectively). According to the contamination of TMR samples per region, Mato Grosso do Sul state presented the highest contaminations. Peanut meal was the most contaminated ingredient. One hundred percent of TMR in Brazilian feedlot is contaminated. Fumonisins were the mycotoxin most frequent and at highest concentrations in TMR samples. Moreover, mycotoxin concentrations have a distinct pattern among ingredients, TMR, and feedlots (local).

This study was conducted to develop equations to predict chemical composition of head, limbs, hide and blood in cattle. A database containing 335 animals from 10 trials, with 221 Nellore, 38 Nellore-Simmental and 76 Nellore-Angus (96 steers, 118 heifers and 121 bulls) animals was used. Models were constructed to estimate water, ether extract (EE), crude protein (CP), ash and macrominerals (calcium, phosphorus, magnesium, sodium and potassium) in the non-carcass parts of cattle. A stepwise procedure was conducted to determine the most significant variables within each model. Subsequently, a random coefficient model was used to construct the equation using studies as random effect, and sex and breed as fixed effects. The visceral fat was the most important variable in the prediction models developed, affecting EE and water in head and limbs; head CP; and hide and blood water. Carcass dressing affected head EE and water and water in the limbs. Carcass weight had significant influence on head CP and hide EE; it was also affected by hide percentage in empty body weight (EBW). The percentage of OV in EBW influenced hide water. Lastly, EBW had influence only on hide sodium. Sex affected the EE of head and limbs. No breed effect was observed on any of the equations obtained. The estimation of the composition of head, limbs, hind and blood is possible and recommended, once they do not have great relevance to the estimation of EBW composition.

The objective of this study was to determine the nutritional requirements of energy and protein and estimate the efficiencies of metabolizable energy utilization for fat and protein deposition, as well as for maintenance (k m) and growth (k g). An experiment of comparative slaughter was carried out with thirty-seven 14-month-old (±1 month) Nellore bulls with 259±24.9 kg. Animals were divided as follows: five to reference, four to maintenance level and twenty-eight bulls feeding ad libitum. Bulls were also grouped in 4 different feedlot periods (42, 84, 126 and 168 days) for slaughter. The diet was composed of corn silage and concentrate, at a 55:45 ratio. After the slaughter, the left half carcasses were totally dissected for determination of body composition. The energy requirements for maintenance were obtained by exponentially relating the heat production and the metabolizable energy intake, while the energy requirements for gain (NEg) were obtained according to empty body weight (EBW) and EBW gain (EBG). The net protein requirements for gain (NPg) were estimated according to EBG and retained energy (RE). The net (NEm) and metabolizable (MEm) energy requirements for maintenance were 76.5 and 113.84 kcal/EBW0.75/day, respectively. The k m was 0.67. The equations for NEg and NPg were: NEg (Mcal/day) = 0.0555 × EBW0.75 × EBG1.095 and NPg (g/day) = 263.37 × EBG - 23.21 × RE. The k g was 0.33. The efficiencies to deposition of energy as protein and fat were 0.18 and 0.71, respectively. The model obtained for the percentage of retained energy as protein (%REp) was %REp = 2.4221 × (RE/EBG)-1.6472. The net and metabolizable energy requirements for maintenance of Nellore bulls were 76.5 and 113.84 kcal/EBW0.75/day. The energy and protein requirements for gain could be obtained by the respective equations: NEg (Mcal/day) = 0.0555 × EBW0.75 × EBG1.095 and NPg (g/day) = 263.37 × EBG - 23.21 × RE.

The objective of this study was to evaluate intake, digestibility and nitrogen (N) compounds use efficiency in F1 Holstein × Zebu grazing cows. Eighteen crossbred cows (six Holstein × Gir, six Holstein × Guzerat, and six Holstein × Nellore) were used in the experiment, constituting three experimental treatments in simple random samples, under the same feeding conditions. At the estimation of individual intake at grazing, titanium dioxide was used for estimating fecal excretion and indigestible neutral detergent fiber, in order to determine pasture intake. There was effect of the lactation period on nutrient intake, except for the intakes of dry matter (DM), organic matter (OM) and total digestible nutrients (TDN) in % of body weight (BW), as well as those of non-fibrous carbohydrates (NFC), in kg. The digestibility coefficients of crude protein (CP), neutral detergent fiber corrected for ash and protein (NDFap) and the contents of TDN varied in function of the lactation period, whereas the coefficients of digestibility of DM, ether extract (EE) and OM did not present such effect. The total milk production projected at 305 days of lactation for Holstein × Gir cows was superior in relation to Holstein × Guzerat and Holstein × Nellore cows. The excretion of urea into urine and of urea N into the milk and the plasma presented quadratic behavior in function of the lactation period. The utilization of the genetic group from Holstein × Zebu grazing cows does not cause alterations in intake, nutrient digestibility or nitrogen use efficiency; however, there is variation in function of the lactation period. Holstein × Gir cows presented greater accumulated production during lactation and persistence, followed by Holstein × Guzerat and Holstein × Nellore cows.

The objective of this study was to estimate the urinary creatinine excretion by the shrunk body weight (SBW). In experiment I, 32 Nellore bulls with initial body weight of 259±24.9 kg and 14±1 months-old were used. The group was divided in four animals to maintenance and twenty eight animals feeding ad libitum and separated in four groups; each group was slaughtered at different times of feedlot (42, 84, 126 and 168 days). The diet was composed of corn silage and concentrate (55:45). Before the slaughters, the total urinary collection was realized during three days. A database of creatinine excretion was collected from other five studies that had been conducted with Nellore cattle. In all the studies, the total urinary collection was realized during at least three days. At the end of each collection, the animals were weighted. Urinary creatinine excretion (UCE) was related with the shrunk body weight and it can be estimated by the equation: UCE (g/day) = 0.0345 × SBW0.9491.

This study aimed to determine the protein requirements for females of Nellore, F1 Nellore × Angus and F1 Nellore × Simmental fed on two concentrate levels (30 and 50%). Sixty heifers from three genetic groups with 18 months of age were used: 20 Nellore, 20 Nellore × Angus and 20 Nellore × Simmental. Twelve heifers of the reference group (four of each genetic group) were slaughtered at the beginning of the experiment. Another 12 heifers (four of each genetic group) were fed on the level of maintenance and 36 heifers (12 animals of each genetic group) were kept in power system ad libitum with 30% (six of each group) or 50% (six of each group) dietary dry matter in concentrate. Heifers were randomly assigned to six treatments in a 3 × 2 factorial arrangement (three genetic groups and two diets) with six replicates per treatment. Nine more heifers (three from each genetic group) were used to estimate the apparent digestibility coefficients of food in a parallel experiment. A model was fitted according to the protein retained as function of the gain of empty body weight (EBW) and retained energy (RE) to calculate the protein net requirements. To estimate the metabolizable protein requirements for maintenance the consumption of metabolizable protein was contrasted with EBW. The joint use of the equation net protein gain (NPG) = 197.40 × EBWg - 11.14 × RE is recommended to predict the protein net requirements for weight gain. Protein and metabolizable protein net requirements for maintenance are 1.07 and 3.88 g/EBW0.75/day, respectively. The use efficiency of metabolizable protein for gain of all genetic groups is 37.04%.

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.

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%.

Avaliaram-se o consumo, digestibilidade aparente total, desempenho e comportamento alimentar de bovinos alimentados com dietas constituídas de silagem de milho, cana-de-açúcar triturada e fornecida in natura ou triturada e fornecida após 72 horas de armazenamento, cana-de-açúcar ensilada sem ou com 1% de cal e concentrado fixado em 1% do peso corporal. Utilizaram-se 35 bovinos, distribuídos em delineamento com blocos casualizados, com 5 tratamentos e 6 repetições. Os animais foram alojados em baias coletivas com cochos individualizados por portões eletrônicos. Os animais alimentados com dieta contendo silagem de milho apresentaram maior consumo de todos os nutrientes e digestibilidade total da matéria seca, matéria orgânica, fibra em detergente neutro e teor de nutrientes digestíveis totais, assim como maior ganho de peso e espessura de gordura subcutânea. Os animais alimentados com dietas de cana-de-açúcar in natura apresentaram maior consumo dos nutrientes assim como melhor digestibilidade da matéria seca, extrato etéreo e teor de NDT e desempenho superior em relação aos alimentados com dietas de cana-de-açúcar ensilada. Os animais alimentados com dietas de silagem de cana-de-açúcar com cal apresentaram maior digestibilidade da matéria orgânica, CNF e teor de NDT, no entanto, não diferiram quanto ao desempenho produtivo em relação ao uso da silagem de cana-de-açúcar sem cal. Com ou sem armazenamento da cana-de-açúcar, o consumo e desempenho dos animais não alteraram. Concluiu-se que animais alimentados com dietas contendo silagem de milho apresentam desempenhos superiores aos que recebem dietas à base de cana-de-açúcar, sendo os alimentados com dietas de cana-de-açúcar ofertada in natura superiores aos alimentados com dietas de silagem de cana-de-açúcar.

It was evaluated intake, total apparent digestibility, performance and feeding behavior of bovine fed diets constituted of corn silage, crushed sugar cane given fresh or crushed and given 72 hours after storage, ensilaged sugar cane with or without 1% of calcium oxide and concentrate at the proportion of 1% of the body weight. It was used 35 bovines, distributed in a random block design, with 5 treatments and 6 repetitions. The animals were housed in collective stalls with troughs individualized by electronic gates. The animals fed diet with corn silage presented greater intake of all nutrients and greater total digestibility of dry matter, organic matter, neutral detergent fiber and total digestible nutrients, as well as greater weight gain and subcutaneous fat thickness. Animals fed diet with fresh sugar cane presented greater nutrient intake as well as better dry matter digestibility, ether extract and TDN content and a superior performance in relation to animals fed ensilaged sugar cane diets. Animals fed silage of sugar cane with calcium oxide presented greater digestibility of organic matter, NFC and content of TDN but they did not differ on performance in relation to the use of silage of sugar cane without calcium oxide. Intake and performance of animals did not change with or without storage of sugar cane. It was concluded that animals fed diets with corn silage present performances superior to the ones which are fed sugar cane based diets, and animals fed fresh sugar diet are superior to the animals fed diets with sugar cane silage.