The objective of this work was to evaluate the effects of protein and/or starch supplementation on the nutritional performance of cattle grazing on low-quality tropical forage. Five crossbred steers (Holstein × Gyr) with an average body weight (BW) of 397 kg that were fitted with ruminal and abomasal cannulae were used. The animals were kept in individual signal-grass (Bracharia decumbens) paddocks. Five treatments were evaluated: 1 - control (without supplementation); 2 - supplementation with 1 g of crude protein (CP) per kg of BW; 3 - supplementation with 2.5 g of starch per kg of BW; 4 - supplementation with CP and starch as described for treatments 2 and 3; and 5 - supplementation as described for treatment 4 but replacing the corn starch with a mixture of corn starch and nitrogenous compounds, thereby resulting in an energy supplement of 150 g CP/kg of dry matter. The experiment was performed according to a 5 × 5 Latin square design in a 2 × 2 + 1 factorial arrangement. The forage intake was not affected by any of the factors evaluated in this study. The production of microbial nitrogen in the rumen was not affected by nitrogen or starch supplementation. The apparent nitrogen balance was only increased when both starch and nitrogen were supplied. Supplementation with both starch and nitrogenous compounds for cattle grazing on low-quality tropical forage is characterized by an interactive metabolic effect that increases nitrogen accretion by the animals.

The objective of this study was to evaluate the effect of different levels of multiple supplement supply on the nutritional characteristics and productive performance of pregnant cows grazing on Brachiaria decumbens Stapf. during the dry season. The experimental area was composed of four 3.0 ha paddocks with availability of potentially digestible dry matter of 2,582 kg/ha. Twenty-eight crossbred pregnant cows with predominance of Zebu breed at body weight of 446±12 kg were utilized in a completely randomized experimental design. Treatments consisted of mineral supplement (control treatment) and supply of multiple supplement at 0.5, 1.0 and 1.5 kg/animal/day with 300 g crude protein (CP)/kg of dry matter (DM). There was quadratic effect of multiple supplementation levels on daily weight gain and a linear increase for final body condition score. The intakes of DM, organic matter (OM) and total digestible nutrients presented no effect with levels of multiple supplement. The coefficients of apparent digestibility of DM and OM had cubic effect with multiple supplementation levels. There was no effect of levels of multiple supplementation on the microbial nitrogen flow and efficiency, but the microbial nitrogen flow in relation to nitrogen intake showed decreasing linear profile. The supply of 1.0 kg of multiple supplement optimizes the performance of grazing cows during the dry season.

The objectives of this experiment were to estimate the endogenous excretion of purine derivatives (PD), the intake and digestibility of nutrients, the urinary excretion of PD from the intake of total digestible nutrients (TDN) and digestible organic matter (DOM) in Nellore heifers. Eight heifers, 267±17 kg body weight (BW), were assigned to two 4 × 4 latin squares. The planned treatments were four dry matter intake (DMI) levels: 10, 14, 18 and 22 g/kg BW. The diet contained 70% corn silage and 30% concentrate. The endogenous losses were obtained by regression between excretion of PD (mmol/BW0.75) and DMI (g/BW0.75). When PD excretion (mmol/d) was related to the intake of DOM and TDN (kg/d), the following equations were obtained: ŶPD= 32.98 + 21.94*DOM and ŶPD= 32.47 + 20.40*TDN, respectively. The excretion of PD (mmol/d) was a function of DMI (kg/d): ŶPD = 0.605 + 0.014 x (r² = 0.46), and 0.60 mmol/BW0.75 was the endogenous fraction of PD. The endogenous losses of PD and nitrogen compounds obtained when the animals were fasted for 5 d, with free access to water, were 0.332 mmol/BW0.75 and 0.384 gN/BW0.75, respectively. The net protein requirement for maintenance was estimated at 2.4 g/BW0.75. Creatinine excretion is not affected by feed restriction.

The objective of this study was to evaluate the in situ and in vitro degradation kinetics and to predict the digestible neutral detergent fiber (dNDF) from the incubation times; in situ and in vitro degradation kinetic parameters; and equations fitted for agricultural and agro-industrial byproducts. Byproducts from pineapple, cocoa, palm kernel, corn gluten meal, common bean, sunflower, guava, cassava bark, cassava stems, cassava foliage, papaya, mango, passion fruit and turnips were evaluated. There were differences between the byproducts as for the potentially neutral detergent fiber (NDF) fraction and the in situ NDF degradation rate in the final volume of the gases generated by fibrous carbohydrates (FC), for the lag time and for the in vitro fractional degradation rate of the FC. There was equivalence between the dNDF values predicted in situ and those observed in vivo; however, there was low precision of estimates. The degradability in the in vitro incubation times of 30 and 48 hours presented equivalence with the values observed, but also did not present precision in the estimates. The equations fitted without lignin were not precise and accurate to estimate the dNDF of agricultural and agro-industrial byproducts. The equation with lignin and with the digestion rate obtained by the in vitro method presented more precise estimates. Byproducts from common bean, cassava bark and papaya presented greater NDF availability, whereas those of guava had the lowest NDF availability. The digestible NDF fraction was best predicted with the in situ incubation time of 72 hours. The equation fitted utilizing in vitro or in situ digestion rates enables the prediction of the NDF availability of agricultural and agroindustrial byproducts.

Objetivou-se avaliar a taxa de deposição de tecidos corporais de novilhas Nelore e suas cruzas com Angus e Simental. Foram utilizadas 57 novilhas de três grupos genéticos, das quais 19 eram do grupo Nelore, 19 Angus e 19 Simental, destas 12 (4 de cada grupo genético) foram abatidas no início do experimento (grupo referência) para estimativa da composição da carcaça dos demais animais. Outras 36 novilhas (12 animais de cada grupo genético) foram distribuídas em seis tratamentos, em esquema fatorial 3x2, de modo a constituir três grupos genéticos (Nelore, Angus e Simental) e dois níveis de oferta de concentrado (30 e 50% da matéria seca da ração em concentrado), com seis repetições por tratamento. As nove novilhas restantes foram utilizadas em um experimento paralelo (quadrado latino) para determinação da digestibilidade das rações experimentais. Ao final do experimento, todos os animais foram abatidos e a composição corporal determinada. O percentual de gordura subcutânea foi maior para as novilhas Angus. Os constituintes químicos do peso de corpo vazio e do ganho de peso de corpo vazio não sofreram efeito dos grupos genéticos. Constatou-se que o cruzamento entre fêmeas Nelore com animais Angus, bem como o nível de concentrado melhoram o padrão de deposição dos tecidos corporais.

The objective of this work was to evaluate deposition pattems of body tissues of Nellore and crossbreed with Angus and Simmental heifers. Fifty seven heifers (19 Nellore, 19 Angus and 19 Simmental) were used, being 12 heifers (four in each genetic group) slaughtered before the beginning of the experiment as the baseline group. Thirty six (twelve in each genetic group) were ad libitun fed with 30 (six in each group) and 50% (six in each group) of dry matter diet in concentrate. The animals were in a completely randomized design, 3x2 factorial (tree genetic group and two diet), with six replicates per treatment. Nine remaining animals were used for a digestibility trial. At the end of the experiment all these animals were slaughtered and its corporal composition determined. The percentage of subcutaneous fat was greater for Angus heifers. Chemical constituents of empty body weight and empty body gain there did not suffer effects of genetic group. The crossing between Nellore and Angus, as well as the level of concentrate improve carcass characteristics and pattern of deposition of body tissues.

The objective of this study was to evaluate nutrients and dry matter intake, average daily gain, feed efficiency and digestibility of diets, microbial efficiency, cold carcass yield and basic cuts yields of young Nellore heifers receiving two concentrate levels. Nineteen heifers with initial average weight of 165.6±29.8 kg were used. Three animals were used in a trial to determine the digestibility and microbial efficiency of the two levels of concentrate (225 and 450 g/kgDM) and a treatment with a restricted intake maintenance level. The remaining 16 heifers were confined for 168 days for evaluation of performance and intake, divided into two levels of concentrate. Every 42 days, four animals, two from each concentrate level, were slaughtered to determine carcass characteristics, making a 2 × 4 factorial arrangement. Digestibility and microbial efficiency were not affected by concentrate level or intake level, both for ad libitum and restricted feeding. Heifers fed 450 g/kgDM concentrate diet had greater average daily gain than those fed 225 g/kgDM concentrate. Dry matter intake and feed efficiency did not differ between levels of concentrate. Average daily gain (kg/day), dry matter intake (% body weight/day) and feed efficiency were higher in the first period of feedlot (0-42 days) compared with the other (42 to 168 days). Heifers fed 450 g/kgDM concentrate had greater average daily gain than those fed 225 g/kgDM concentrate.

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.

The objective of this study was to determine the energy nutritional requirements for females of Nellore, Nellore × Angus and Nellore × Simmental fed on two levels of concentrate. Sixty heifers from three genetic groups were used: 20 Nellore, 20 Nellore × Angus and 20 Nellore × Simmental. Twelve belonged to the reference group (four of each genetic group) and were slaughtered at the beginning of the experiment. Another 12 heifers (four of each genetic group) were fed on the maintenance level and 36 heifers (12 animals of each genetic group) were kept in feeding system ad libitum with 30 (six in each group) or 50% (six of each group) dry matter concentrate. Animals 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 were used in a parallel experiment to estimate the apparent digestibility coefficients (three from each genetic group). Net energy requirements were estimated by the equation of retained energy as a function of metabolic empty body weight (EBW0.75) and empty body weight gain (EBWg). Requirements of metabolizable and net energy were estimated for maintenance by the equation of heat production as a function of metabolizable energy intake. Using the combined equation RE (retained energy; Mcal/day) = 0.0703 × EBW.75 × EBWg1.128 to predict net energy requirements for weight gain is recommended. The requirement of metabolizable and net energy for maintenance of all groups is 70.55 and 106.53 kcal/kgEBW0.75/day, respectively. Use efficiencies of metabolizable energy for gain and maintenance are 36.41 and 66.23%, for the three genetic groups respectively.

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%.

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%.

Foram conduzidos dois experimentos com o objetivo de avaliar o efeito da quantidade de suplemento sobre o consumo, a digestibilidade, o ganho de peso e a eficiência de síntese microbiana em bovinos de corte. No experimento 1 foram utilizados quatro novilhos Holandês-Zebu, não-castrados, com peso médio de 250 kg, fistulados no esôfago, rúmen e abomaso. O suplemento foi composto por farelo de algodão, grão de milho triturado, mistura mineral e ureia/sulfato de amônio. As dietas foram: controle (sal) e suplementos oferecidos nos níveis de 0,33; 0,66 e 1% do peso corporal (%PC). Os consumos máximos de matéria seca (MS), fibra em detergente neutro (FDN) e nutrientes digestíveis totais (NDT) foram estimados em 1,09; 0,73 e 1,20% do PC. Aumento linear foi observado para os consumos de matéria orgânica (MO), proteína bruta (PB), extrato etéreo (EE) e carboidratos não-fibrosos (CNF). As digestibilidades totais de MS, MO, PB, EE e FDN aumentaram linearmente com o consumo de suplemento, o que não ocorreu com a eficiência microbiana, que não foi influenciada. No experimento 2 foram utilizados 19 animais, zebuínos, não-castrados com idade e pesos médios iniciais de 18 meses e 320 kg. As dietas foram: mantença, controle e ofertas diárias de 1, 2 e 3 kg do suplemento. Aumento linear foi observado para os consumos de MS, MO, PB, EE, FDN e CNF com o aumento das quantidades de suplemento. Consumos máximos de NDT, teor de NDT da dieta e ganho médio diário (GMD) foram estimados quando 2,88; 2,62 e 2,69 kg de suplemento foram ofertados. A quantidade de suplemento teve efeito quadrático sobre a digestibilidade de todos os nutrientes, mas não afetou a eficiência microbiana. A digestão total máxima de FDN é observada para um consumo aproximado de 1,5 kg de suplemento/dia, o que resulta em resposta ótima do ganho médio diário com taxa de ingestão de 400 g de PB.

Two experiments were conducted aiming to evaluate the effect of amounts of supplement on the intake, digestibility, body weight gain and microbial synthesis efficiency in beef cattle. Four Holstein-Zebu steers fistulated in the esophagus, rumen and abomasum with an average of 250 kg of body weight were used in experiment 1. The supplement was made up cottonseed meal, ground corn grain, mineral mixture and urea/ammonium sulfate. The diets were: control (salt) and supplements levels of 0.33, 0.66 and 1.00% of body weight (BW). Maximum intake of dry matter (DM), neutral detergent fiber (NDF) and total digestible nutrients (TDN) were estimated at 1.09, 0.73 and 1.20% of BW, respectively. It was observed a linear intake increase to organic matter (OM), crude protein (CP), ether extract (EE) and non-fiber carbohydrates (NFC) intake as supplement offer increased. The total digestibility from DM, OM, CP, EE and NDF increased linearly with the intake of supplement but no affected on microbial efficiency. Nineteen Zebu steers aging 18 months and mean body weight of 320 kg were used in experiment 2. The diets were: maintenance, control (salt), and the daily supplement offer of 1, 2 and 3 kg. It was observed linear increase in DM, OM, CP, EE, NDF and NFC intake as supplement offer increased. Maximum intake of TDN, diet TDN content and average daily gain (ADG) were estimated to occur as 2.88, 2.62 and 2.69 kg of supplement offer, respectively. A quadratic effect was observed for total digestibility in all diet components. The microbial efficiency was not influenced by diet supplementation. The neutral detergent fiber digestibility is highest for a intake of approximately 1.5 kg of the supplement/day, which results in the best response to the ADG obtained with the intake of 400 g of CP.

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.

Procurou-se avaliar a precisão de cinco modelos não-lineares em descrever a forma da curva de produção de leite de vacas Nelore e o efeito do consumo voluntário (CV) da vaca e do bezerro sobre a produção de leite (PL). Foram testados os modelos de Sikka, Nelder, Wood, Jenkins & Ferrell, e Jenkins & Ferrell com um parâmetro de ajustamento. Foram utilizadas 12 vacas primíparas com peso corporal médio de 359 kg (± 8) e seus respectivos bezerros. A produção de leite foi estimada pela pesagem do bezerro antes e após a mamada, do nascimento aos 180 dias de idade. As pesagens foram efetuadas duas vezes ao dia, semanalmente, após 6 horas de jejum de líquido e sólidos. Os modelos não-lineares de Sikka, Jenkins & Ferrell, Nelder e Wood não descreveram a curva de lactação apropriada devido ao excesso ou subestimação d o pico da produção de leite. O melhor ajustamento foi encontrado para o modelo de Jenkins & Ferrell com um parâmetro de ajustamento. O efeito do consumo voluntário da vaca e do bezerro, avaliado separadamente, não se correlacionou com a produção de leite. Entretanto, ao avaliar o consumo da vaca e do bezerro conjuntamente, foi encontrada uma correlação positiva e negativa com a produção de leite, respectivamente. A produção de leite está intimamente correlacionada com o consumo da vaca e do bezerro, e a capacidade de ingerir sólidos não lácteos reulta na redução da necessidade de leite da mãe.

This research was carried out to evaluate five non-linear mathematical models to describe lactation curves of Nelore cows and effect of the cow and calf intake on milk yield. In this study we compared the models of Sikka (1950), Nelder (1966), Wood (1967), Jenkins & Ferrell (1984) and Jenkins & Ferrell (1984) with a fit parameter. Data of production were collected from 12 primiparous cows with a mean live weight of 359 kg (± 8) and its offspring. The milk production was estimated weighing the calf before and after suckling, from birth to 180 days of age. Measurements were made twice a day in a weekly period after 6 hour fasting of liquid and solids. The mathematical models of Sikka, Jenkins & Ferrell, Nelder and Wood failed to describe lactation curve appropriated due to over or underestimation of milk yield peak. Better adjustement was found for the model of Jenkins & Ferrell with a fitting parameter. Cow and calf intake evaluated separately was no correlated with milk yield. Conversely at evaluating both cow and calf together, it was found a positive and a negative correlation with milk yield, respectively. Milk yield is is closely correlated wiht cow and calf intake, and the capacity of the calf to ingest non-dairy solids results in reduction of milk needs from dam.

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.