ABSTRACT: The use of supplements eliminates deficiencies imposed by pasture, increases weight gain in animals and maximizes profits from the activity. The objective of this study was to evaluate the performance, carcass traits and meat quality of steers in grazing systems that received or did not receive a protein energy supplement at the level of 0.6 % body weight. The experiment lasted 160 days and included 36 Brangus × Zebu animals. Eighteen animals received supplementation and another eighteen did not receive supplementation. Carcasses were evaluated for yield, loin eye area, fat thickness and length. The assessment of meat quality evaluated the shear force, myofibril fragmentation index, color, exudative losses and collagen. The carcass traits of the supplemented animals showed higher values (p < 0.0001). Supplementation improved the color of the meat (p = 0.0434) and increased the amount of soluble collagen (p = 0.0456). The use of a protein energy supplement for steers in a pasture system increased the efficiency of muscle deposition of these animals and improved meat quality when compared to animals that were not supplemented.

ABSTRACT Eight rumen-cannulated steers were assigned to two 4 × 4 balanced Latin squares to evaluate degradability and kinetics of fiber particles from diets based on corn silage and supplements with or without addition of lipids. Dietary treatments were: only corn silage (T1), corn silage plus concentrate with no added lipids (T2), corn silage plus concentrate with added soybean oil (T3), and corn silage plus concentrate containing ground soybean seeds (T4). Kinetics of gastrointestinal transit of fibrous particles was evaluated based on chromium-mordanted fiber. Events of rumen degradation dynamics of fibrous carbohydrates were quantified using the in situ incubation procedure. The mixed models methodology from SAS was used to fit models and the Tukey test was used to compare means. The ruminal digestibility of fiber was lower in treatments T3 and T4 and, consequently, lower proportions of potentially digestible fraction of standardized fiber and higher proportions of indigestible fraction of standardized fiber for treatments T3 and T4 compared with T1 and T2 were observed. However, there were no differences in mean retention time of the rumen, total mean retention time, mean digestion time, and rumen fill among diets. Animals from T2, T3, and T4 showed higher dry matter intake, organic matter intake, and crude protein intake rates than animals receiving T1 diet, but there was no effect of the addition of lipid. Treatments did not differ regarding neutral detergent fiber intake. Animals from T1 had lower crude fat intake than animals from T2, which showed lower crude fat intake than those from T3 and T4. The addition of lipid to concentrate has no effect on passage rate, digestion rate, and intake, when a good quality roughage is used.

ABSTRACT The objective of this study was to evaluate the intake and digestibility of silages containing pineapple pulp and coast-cross hay, with or without addition of urea, and the recovery of the markers chromium oxide (Cr2O3), indigestible neutral detergent fiber (iNDF), indigestible acid detergent fiber (iADF), and indigestible dry matter (iDM), in a digestibility assay, in sheep. Treatments were as follows: two levels of pineapple pulp (818 and 758 g kg−1) and two levels of urea (with and without urea), in a completely randomized design. Twelve sheep (three per treatment) were used, kept in metabolic cages. Fecal excreta were determined by total collection or estimated by using the markers. Marker samples were obtained in morning and afternoon collections, with mean concentrations obtained for both daily activities. The level of silage pulp did not affect intake, while addition of urea increased the intake of crude protein (CP), but did not influence the intakes of dry matter, organic matter, neutral detergent fiber, or acid detergent fiber. The digestibility coefficients of all afore-mentioned fractions increased with the increase in pulp, the same happening with the addition of urea. The internal marker with lowest variability among the internal markers was iADF, with mean values near 100%. Mean recovery of Cr2O3 was approximately 107%, but with lower variability among treatments. Inclusion of pineapple pulp in silage does not influence intake, while addition of urea only increases the intake of CP. The levels of pineapple pulp in silage with or without urea increase the digestibility of the silage. Indigestible acid detergent fiber is the marker with lowest variability of recovery, with mean recovery for the four silages used very close to 100%.

ABSTRACTThe objective of this study was to evaluate the nutritive value of passion fruit by-product for cattle, contrasting the results with those found with sorghum silage. Four treatments were then constituted, comprising the combinations of the two roughages and the two levels of supplementation (with or without), in a completely randomized design with four animals per treatment. The considered variables included: feed intake, digestibility coefficients of the diets, and live weight gain of the animals. The experimental period lasted 70 days, preceded by a standardization period of 30 days. Chromium oxide was utilized to estimate the fecal output, in the digestibility trial. Treatments were compared by means of three orthogonal contrasts: between the two roughages and between the two concentrate levels within each roughage. Animals fed passion fruit by-product showed higher feed intake (total, per 100 kg of live weight (TLW), and per unit metabolic size) and had higher TLW gain than those fed sorghum silage (1.304 kg vs. 0.134 kg). The coefficients of apparent digestibility of dry matter (DM), organic matter (OM), and crude protein (CP) and the digestibility coefficient of neutral detergent fiber from passion fruit by-product were high, and much higher than those from sorghum silage. The concentrate supplement did not improve the TLW gain of animals fed passion fruit by-product and had a limiting effect on the digestibility coefficients of the diet. The concentrate supplement had a positive associative effect on intake and digestibility coefficients of DM, OM, and CP from sorghum silage. The by-product of fresh passion fruit is an excellent food for growing cattle as it provides high intake levels and weight gains, even when supplied as the only feed.

A mathematical model based on Cornell Net Carbohydrate and Protein System (CNCPS) was developed and adapted in order to evaluate beef cattle rations at tropical climate conditions. The presented system differs from CNCPS in the modeling of insoluble particles' digestion and passage kinetics, which enabled the estimation of fiber mass in rumen and its effects on animal performance. The equations used to estimate metabolizable protein and net energy requirements for gain, net energy requirement for maintenance and total efficiency of metabolizable energy utilization were obtained from scientific articles published in Brazil. The parameters of the regression equations in these papers were estimated using data from Bos indicus purebred and crossbred animals reared under tropical conditions. The model was evaluated by using a 368-piece of information database originally published on 11 Doctoral theses, 14 Master's dissertations and four scientific articles. Outputs of the model can be considered adequate.

Foi avaliado o desempenho de novilhos mantidos em pastagens de capins elefante e mombaça no período de outubro a dezembro de 2006. Adotou-se o sistema de pastejo rotacionado, com oferta regulada de forragem. A área experimental consistia de duas repetições contendo 18 piquetes de 0,25 ha cada, divididos em nove piquetes formados de capim-elefante e nove com mombaça. Os efeitos de tratamentos foram as espécies forrageiras, a repetição de área, a interação entre estes, piquetes dentro da interação e o erro experimental. Este modelo foi usado para analisar os atributos do pasto. Para analisar o consumo, a digestibilidade e o ganho, foram aleatoriamente alocados 24 novilhos para as respectivas interações entre forragem vs. repetição vs. sistema de pastejo, o que totalizou três animais por interação tripla. Os sistemas de pastejo consistiram de pastejo ad libitum (AL) e restrito (PR). O capim-elefante apresentou maior biomassa de matéria seca total (BT) e biomassa de matéria seca verde foliar (BFV). Não houve diferença entre as forrageiras quanto à produção de biomassa de matéria seca verde foliar, no entanto a proporção de folhas foi maior no capim-mombaça. As extrusas apresentaram composição bromatológica semelhante. Apenas o consumo de proteína bruta diferiu entre as forrageiras, sendo este maior para o pasto de mombaça. A alimentação à vontade possibilitou maior consumo de todos os nutrientes em ambas as pastagens. A digestibilidade dos nutrientes foi maior para o capim-elefante, mas não diferiu entre os níveis de alimentação: apenas o teor em proteína bruta foi maior no pasto onde o pastejo foi restrito e o teor de energia bruta do pasto foi maior para o sistema de pastejo à vontade. Apesar das diferenças qualitativas e quantitativas entre as forrageiras, não foram encontradas diferenças quanto ao ganho em peso por animal e por área. Entre os animais com alimentação à vontade, o ganho médio em massa corporal foi de 850 g/dia e o ganho por área de 246 kg/ha durante o período experimental.

The performance of steers raised on elephant and mombasa grass pastures was evaluated from October to December 2006. A rotational grazing system with a regulated forage offer was adopted. The experimental area consisted of two repetitions containing 18 0.25-ha paddocks divided into nine paddocks with elephant grass and nine with mombasa grass. Forage species, area repetition, the interaction among these effects, paddocks within the interaction, and the experimental error were the effects of the treatments. This model was used to analyze pasture attributes. For analyses of intake, digestibility and gain, 24 steers were randomly assigned to the respective interactions among forage vs. repetition vs. grazing system, totaling three animals per triple interaction. The grazing systems consisted of ad libitum (AL) and restricted (PR) grazing. Elephant-grass showed the highest total dry matter biomass (TB) and green leaf dry matter biomass (GLDM). There were no differences among forage plants for production of biomass of green leaf dry matter; leaf proportion was the greatest in mombasa grass, however. Extrusas showed similar bromatological composition. Only crude protein intake, which was the highest for mombasa pasture, differed among forage plants. Ad libitum feeding enabled a higher intake of all nutrients from both pastures. Digestibility of nutrients was higher for elephant-grass but it did not differ among feeding levels: only crude protein content was the highest on pasture where grazing was restrict and gross energy content of pasture was higher for ad libitum grazing system. Despite qualitative and quantitative differences among forage plants, differences of weight gain per animal and per area were not found. For animal with ad libitum feeding, average body mass gain was 850 g/day and gain per area was 246 kg/ha during the experimental period.

Objetivou-se determinar os vícios de estimação da excreção fecal com base nos indicadores internos matéria seca indigestível (MSi), fibra em detergente neutro indigestível (FDNi), fibra em detergente ácido indigestível (FDAi) e do indicador externo óxido crômico (Cr2O3) em ensaio de digestão com ruminantes. Foram utilizados cinco bovinos mestiços Holandês × Zebu com peso médio de 240 kg. O experimento constituiu de três períodos experimentais de 12 dias, os seis primeiros destinados à adaptação dos animais. Os animais foram alimentados à vontade com silagem de sorgo e mantidos em baias individuais. Foram adotados seis esquemas de amostragem: 16 coletas diárias, em intervalos de 1 hora e 30 minutos; oito coletas no período diurno a partir das 7 h, em intervalos de 1 hora e 30 minutos; oito coletas no período noturno, a partir das 19 h, em intervalos de 1 hora e 30 minutos; quatro coletas no período diurno, de 3 em 3 horas; quatro coletas no período noturno, de 3 em 3 horas; duas coletas, às 7 h e às 16 h. O óxido crômico foi o indicador com o menor vício de longo prazo, mas superestimou a produção fecal. Os indicadores internos subestimaram esta variável e a FDNi foi o que apresentou menor vício. Para os vícios de curto prazo, todos os indicadores superestimaram a produção fecal: o menor vício de curto prazo foi registrado para a MSi. Dos indicadores testados, a FDNi apresenta o menor vício total, mesmo subestimando a produção fecal.

The objective of this study was to determine the biases in estimating fecal excretion from the internal markers indigestible dry matter (DMi), indigestible neutral detergent fiber (NDFi) and indigestible acid detergent fiber (ADFi) and the external marker chromic oxide (Cr2O3) in a digestion trial with ruminants. Five crossbred Holstein-Zebu castrated males with 240 kg average weight were used. The research consisted of three twelve-day experimental periods, from which the first six days were assigned to animal adaptation. The animals were fed sorghum silage ad libitum in individual pens. Six sampling schedules were adopted: 16 daily collections, at 1.5 hourly intervals; eight collections made during daylight starting at 7 a.m. at 1.5 hourly intervals; eight collections made at night starting at 7 p.m. at 1.5 hourley intervals; four collections made in the day every three hours; four collections at night every three hours and two collections, at 7 a.m. and 4 p.m. The chromic oxide was the indicator with the smallest bias in the long term, but underestimated fecal production. The internal markers overestimated this variable and the NDFi presented the smallest bias. For the short term biases, all the indicators over estimated fecal production: the smallest short term bias was registered for MSi. The NDFi was the indicator that presented the smallest total bias, even though it underestimated fecal production.

O experimento foi conduzido com o objetivo de avaliar a influência da irrigação sobre as disponibilidades de matéria seca total (DMST), matéria seca verde (DMSV) e matéria seca residual (DMSR); a altura; a densidade volumétrica da forragem (DV); a porcentagem de folhas e a composição química da lâmina foliar dos capins napier e mombaça. Avaliaram-se as combinações das duas forrageiras com dois níveis de irrigação (presença e ausência). A irrigação foi realizada repondo 100% da evapotranspiração (ET0) média diária observada em dez anos. Adotou-se o sistema de lotação intermitente, com quatro dias de ocupação e 32 de descanso e carga animal variável, mantendo-se pressão de pastejo de 4 kg de matéria seca foliar disponível (MSFD)/100 kg de peso vivo, utilizando-se novilhos. Os maiores valores de disponibilidade de matéria seca total e matéria seca verde e matéria seca residual, nas duas épocas do ano, foram obtidos com as forrageiras irrigadas e o capim-napier. A irrigação trouxe maior aumento nas disponibilidades de matéria seca total e matéria seca verde no capim-mombaça que no capim-napier. Na época seca, a irrigação elevou a porcentagem de folhas, a altura e a densidade volumétrica de forragem. Nas épocas seca e chuvosa, o capim-napier, irrigado ou não, teve menor porcentagem de folhas e maior altura que o capim-mombaça, mas a densidade volumétrica de forragem não diferiu entre as duas forrageiras. Na época chuvosa, as forrageiras sob irrigação apresentaram maior altura, mas a porcentagem de folhas e a densidade volumétrica de forragem foram semelhantes às obtidas com as forrageiras não irrigadas. A irrigação não influenciou os teores de matéria orgânica, proteína bruta e fibra em detergente neutro. O capim-napier, irrigado ou não, apresentou maior teor de proteína bruta e menores teores de matéria orgânica e fibra em detergente neutro em comparação ao capim-mombaça, nas duas épocas.

The research was carried out aiming to evaluate the influence of irrigation on total dry matter (TDMA) and green dry matter availability (GDMA) and on residual dry matter (RDM), forage height, forage density (FD), leaf percentage and chemical composition of leaf blades of the Napier grass and Mombaça grass. The treatments were the combinations of the two grasses and two irrigation levels (presence and absence). The irrigation supplied the previous ten-year mean evapotranspiration (ET0). It was adopted the rotational grazing, with grazing period of four days, rest period of 32 days and variable stocking, with grazing pressure of four kg of leaf dry matter per 100 kg live weight. Irrigated forages, in relation to non irrigated, and Napier grass, in relation to Mombaçagrass, showed higher TDMA, GDMA and RDM in both seasons of the year. Mombaça grass showed higher response to irrigation in TDMA and GDMA than Napier grass. During the dry season, irrigation increased percent of leaves, forage height and forage density. Napier grass, irrigated or not, in both seasons, was taller, showed lower proportion of leaves, but did not differ from Mombaça grass with respect to density. During the rainy season, irrigated forages were taller, but did not differ from the non irrigated ones regarding to percent of leaves and density. Irrigation had no influence on organic matter (OM), crude protein (CP) and neutral detergent fiber (NDF) content of forages. Napier grass, irrigated or not, had higher CP and lower OM and NDF than Mombaça grass, in both seasons.

Objetivou-se avaliar a eficiência de conversão da matéria seca (MS) e da energia metabolizável (EM) da dieta em ganho de peso e em peso de bezerro desmamado por vaca. Utilizaram-se 13 vacas Nelore, 13 mestiças F1 Simental × Nelore (SN) e 13 F1 Limousin × Nelore (LN) com 5 a 9 anos de idade e suas respectivas crias. Entre 15 e 210 dias pós-parto, as vacas foram mantidas em baias individuais, juntamente com os bezerros. Utilizaram-se rações contendo, na MS, 30% de concentrado e 70% das silagens de milho e sorgo na primeira e segunda metades do período experimental, respectivamente. O conteúdo de energia metabolizável das dietas foi obtido utilizando-se o fator 0,82 na conversão da energia digestível, determinada experimentalmente, em energia metabolizável. A produção de leite foi determinada mensalmente utilizando-se o método da diferença de peso dos bezerros. A eficiência foi avaliada considerando as relações: kg de bezerro desmamado e kg de ganho de peso de bezerro por kg de MS; ou por Mcal de EM ingeridos pela vaca; ou pelo par vaca/bezerro no período de lactação: ou foram estimadas para todo o ano. Foi ainda considerada a relação peso do bezerro/peso da vaca (PB/PV) à desmama. As vacas mestiças apresentaram maior eficiência de conversão da MS e da energia alimentar em peso de bezerro desmamado e em ganho de peso de bezerro. Apresentaram ainda as mais elevadas relações PB/PV à desmama. Os dois grupos de mestiças não diferiram quanto à eficiência. A utilização de matrizes obtidas por cruzamento entre bovinos de raças européias e bovinos Nelore possibilita elevar a eficiência do sistema na fase de cria.

The objective was to evaluate the efficiency of conversion of dry matter (DM) and metabolizable energy (ME) of the diet on weight gain and weight of calf weaned per cow. A total of 13 Nellore, 13 crossbred F1 Simental × Nellore (SN) and 13 F1 Limousin × Nellore (LN) cows with 5 to 9 years of age and their offspring was used. Between 15 and 210 days post calving, the cows were kept in individual stalls, with the calves. Diets contained 30:70% (% DM) concentrate to corn or sorghum silages ratio, in the first and second half of the experimental period, respectively. The metabolizable energy content of the diet was obtained using the 0.82 factor in the conversion of digestible energy, experimentally determined, in metabolizable energy. The milk production was determined monthly using the calf weigh-suckle-weigh method. The efficiency was evaluated considering the ratios: kg of calf weaned and kg weight gain of calf per kg DM, or by Mcal of EM consumed by the cow, or by cow/calf pair in the period of lactation or were estimated for all the year. The relationship of calf weight/weight of the cow (CP/LW) at weaning was also considered. The crossbred cows showed higher efficiency of conversion of the DM and the feed energy in weight of weaned calf and in weight gain of calf. They showed also the highest relations CP/LW at weaning. The two crossbred groups did not differ on the efficiency. The use of matrices obtained by crossing European breeds and Nellore cattle enables raising the efficiency of cow-calf enterprise.

O experimento foi conduzido em uma época chuvosa e duas épocas secas com o objetivo de avaliar a influência da irrigação na taxa de lotação (TL), no ganho de peso (GPV), no consumo de nutrientes e na digestibilidade in vivo em pastagens rotacionadas de capim-elefante e capim-mombaça. Avaliaram-se combinações de duas forrageiras e dois níveis de irrigação (com e sem), além das épocas chuvosa e seca, analisadas separadamente. A irrigação foi realizada repondo-se 100% da evapotranspiração (ET0) média diária de dez anos. Como animais experimentais fixos, utilizaram-se 40 e 16 novilhos mestiços Europeu × Zebu nas épocas chuvosa e seca, respectivamente. Animais semelhantes foram utilizados como reguladores da biomassa de folhas verdes. Nas épocas chuvosa e seca, a irrigação possibilitou aumento da taxa de lotação nas duas forrageiras. Na época seca, a irrigação reduziu o ganho de peso vivo em ambas as forrageiras, enquanto, na época chuvosa, aumentou o ganho de peso no capim-mombaça. A irrigação não influenciou o consumo em nenhuma das épocas avaliadas, mas afetou a digestibilidade de matéria seca, que reduziu na época chuvosa e aumentou na época seca. As maiores taxas de lotação foram obtidas no capim-mombaça, ao passo que, no capim-elefante, obtiveram-se valores superiores de ganho de peso vivo, consumo e digestibilidade. As taxas de lotação médias nas épocas chuvosa e seca para o capim-elefante com e sem irrigação e para o capim-mombaça com e sem irrigação foram de 5,6; 4,5; 7,7; e 4,9 animais/ha e os valores de GPV de 0,64; 0,68; 0,50 e 0,60 kg/dia. O efeito da irrigação é mais pronunciado na taxa de lotação que no ganho de peso dos animais e, em sistemas intensivos de produção a pasto, a produtividade animal (kg/ha) obtida com os capins mombaça e elefante é similar.

The research was carried out comprising one rainy season and two dry seasons. The objective was to evaluate the influence of irrigation on stocking rate (SR), weight gain (WG) intake, nutrient intakes and in vivo digestibility in elephantgrass and mombaçagrass, under rotational grazing. Combinations of the two grasses and two irrigation levels (with and without) were evaluated. Data from dry season and rainy season were analyzed separately. Irrigation was performed restore up 100% mean evapotranspiration (ET0) of the last ten-year. A total of 40 and 16 crossbred steers European × Zebu was used as tester experimental animals in the rainy and dry seasons, respectively. Similar put-and-take animals were used as to adjust grazing pressure of the green leaves biomass. In the rainy and dry seasons, irrigation has enabled the rise in the stoking rate in both forages. In the dry season, irrigation reduced the weight gain in both forages, while in the rainy season, increased the weight gain in the mombaçagrass. Irrigation did not affect intake in any of the periods evaluated, but affect the digestibility of dry matter, which reduced in the rainy season and increased in the dry season. The highest stocking rates were obtained in the mombaçagrass, while, in the elephant grass, higher values were obtained for weight gain, intake and digestibility. The means stocking rates during the rainy and dry season for the elephant grass with and without irrigation and for the mombaçagrass with and without irrigation were 5.6, 4.5, 7.7, and 4.9 anim/ha and the values of WG of 0.64, 0.68, 0.50 and 0.60 kg/day. The effect of irrigation is more evident in the stocking rate than in weight gain of animals, and in intensive grazing production systems, animal productivity (kg/ha) is similar for mombaçagrass and elephantgrass.

Objetivou-se avaliar nutricionalmente a grama-estrela (Cynodon nlemfuensis) cv. Africana utilizada sob pastejo rotacionado por vacas leiteiras. Dez vacas mestiças foram manejadas em 2 ha de grama-estrela e divididas em 11 piquetes/ha. O período de pastejo foi de três dias e os 30 subseqüentes foram destinados à recuperação da pastagem. Durante o período experimental, os animais foram ordenhados duas vezes ao dia e receberam suplementação com 2 kg de concentrado. Amostras representativas do pasto ingeridas (extrusa) foram colhidas para determinação de sua composição nutricional. O consumo de matéria seca (MS) pelos animais foi estimado utilizando-se cromo e a MS indigestível como indicadores externo e interno. O desempenho individual das vacas foi avaliado pela produção de leite diária e pela pesagem dos animais. A dinâmica da matéria alimentar foi estimada com base nas técnicas in vitro gravimétricas, de produção cumulativa de gases da fermentação microbiana e da estimativa da cinética de passagem das fases sólida e líquida. A quantidade de energia líquida total (ELt), em MJ/dia, atendeu à demanda energética exigida pelos animais. Os valores de proteína metabolizável (PM) preditos corresponderam ao suprimento de 91% da PM exigida por esses animais. As predições das exigências em macrominerais atenderam apenas 75% do Ca exigido, mas atenderam às exigências dos demais macrominerais. A grama-estrela atende à demanda energética nutricional de mantença e produção de 11,7 kg de leite por dia. Nas circunstâncias estudadas, é necessário suplementar nutrientes que complementem a PM e Ca não atendidos completamente. O teor e as características cinéticas da fibra não causam repleção ruminal e restrição sobre o consumo de vacas leiteiras em pastejo.

An nutritional analysis of stargrass cv. Africana fed dairy cattle under rotational grazing was evaluated in this research. Ten Holstein-Zebu crossbred cows were managed in 2 ha covered with the grass and divided in 11 paddocks /ha with three grazing days 30 days of resting period. During the experimental period the animals were milked twice a day for 16 days and were feed two kg of concentrate. Representative samples of the pasture consumed (extrusa) were taken and determined the nutritional composition. The dray matter intake of the animals was estimated by means of chromium and indigestible DM as external and internal markers. The individual performance of the cows was evaluated by daily milk production and by weighting the animals. The food matter dynamics was estimated with gravimetric in vitro techniques, cumulative gas production from microbial fermentation and estimates of the passage kinetics of solid end liquid phases. The amount of total net energy (NEt) in MJ/d meet the energetic requirement by the animals. The predicted values for metabolizable protein (MP) corresponded to the supply of 91% of the MP required by those animals. The predictions for macrominerais met only 75% of the Ca required, however met the requirements by other macrominerals. The stargrass pasture meet the nutritional requirements for maintenance and production of 11.7 kg of milk per day. In the studied circumstances, it is needs to supplement nutrients that complement MP e Ca not fully met. The content and kinetic characteristics of stargrass fiber caused niether rumen fill effect nor constrained int1ake of grazing dairy cows.

O trabalho foi realizado com o objetivo de avaliar as curvas de lactação de vacas Nelore e mestiças F1 Limousin-Nelore (LN) e Simental-Nelore (SN) e o desempenho de suas progênies. Foram utilizadas 13 vacas de cada grupo genético, com 5 a 9 anos de idade, e as suas respectivas crias. A partir do 15º dia após o parto até a desmama dos bezerros (210 dias), as vacas foram mantidas com suas crias em baias individuais. No arraçoamento procurou-se atender 100% das exigências de mantença e lactação das vacas; a mesma ração foi fornecida aos bezerros a partir dos 90 dias de idade visando atender no máximo 30% de suas exigências nutricionais. A ração foi formulada com 30% de concentrado e 70% de silagem, na MS. A produção de leite das vacas foi determinada mensalmente pelo método da diferença de peso dos bezerros. Por meio de um modelo não-linear, estimaram-se o tempo necessário para as vacas atingirem o pico de lactação, a produção no pico, a persistência de produção de leite e as produções total e média diária. As vacas Nelore tiveram, em comparação às mestiças, menores produções no pico de lactação, total e média diária, mas apresentaram maior persistência de lactação. As produções no pico de lactação, total e média diária, nas vacas SN foram maiores que nas vacas LN, no entanto, não houve diferença entre esses grupos quanto à persistência de lactação. Os bezerros das vacas Nelore apresentaram menores ao nascer e à desmama e ganharam menos peso no período de aleitamento em comparação aos de vacas mestiças, que não diferiram entre si. Vacas mestiças têm maior habilidade materna que vacas Nelore.

The research was carried out to evaluate the lactation curves of Nellore and Crossbred F1 Limousin-Nellore (LN) and Simmental-Nellore (SN) cows and the performance of the progeny. Thirteen cows from each breed group, with age ranging from 5 to 9 years, and the respective calves were used. From 15 days after calving until weaning of the calves (210 days), the cows and calves were kept in individual pens. The nutritional requirements of the cows for maintenance and lactation were met. The same ration was offered to the calves from the 90 days of age, in limited amounts to supply 30% of the nutritional requirements. The ration was formulated with 30% of concentrate and 70% of silage, DM basis. Monthly, milk production of the cows was estimated, utilizing the weigh-suckle-weigh method. By means of nonlinear model, it was estimated the time needed for the cows to reach the peak of lactation, the production at the peak of lactation; the persistence of milk production and total and daily average milk production. Nellore cows showed lower production at the peak of lactation, total and daily average milk production, but higher persistency than crossbred cows. The productions in the lactation peak, total and daily average, in cows SN, were higher than in cows LN, however, no difference was observed between these groups for lactation persistence. Calves from Nellore cows had lower birth weight, weaning weight and preweaning weight gain than those from crossbred cows. There was no difference between calves from the two crossbred groups. It is concluded that crossbred cows have higher maternal ability than Nellore cows.

Neste trabalho, foram estimadas as exigências de mantença de energia líquida (ELm) e metabolizável (EMm) e as mudanças na composição corporal e no ganho de vacas adultas não-gestantes e não-lactantes confinadas. Foram utilizadas 36 vacas, 12 Nelore (NEL), 12 F1 Pardo-Suíço-Nelore (PSN) e 12 F1 Red Angus-Nelore (RAN). As alterações na composição corporal dos animais durante o período experimental foram estimadas utilizando-se a técnica do abate comparativo: quatro animais de cada grupo genético foram alocados, aleatoriamente, nos tratamentos abate inicial (AI), alimentação restrita (AR) e alimentação ad libitum (AL). Os animais AR receberam, no período experimental, níveis de proteína e energia 15% acima da mantença e os AL, ração ad libitum, para ganho de 1,1 kg/dia. Os animais AI foram abatidos no início do experimento e os AR e AL 120 dias depois. Em todos os animais abatidos, foram estimadas as proporções corporais dos tecidos muscular, adiposo e ósseo, além dos conteúdos corporais de proteína, gordura e energia. Na estimação da ELm e da EMm, foram empregados modelos linear e não-linear. Os grupos genéticos não diferiram quanto às exigências de ELm e EMm, expressas em peso vivo em jejum (kcal/kg0,75/dia PVJ). Quando utilizados os modelos linear e não-linear, os valores de ELm encontrados foram de 80,7 e 83,6 kcal/kg0,75/dia PVJ e os de EMm, 109,9 e 128,0 kcal/kg0,75/dia PVJ, respectivamente. Os conteúdos de proteína por unidade de peso corpo vazio (PCVZ) e do ganho (GPCVZ) não diferiram entre os grupos genéticos, porém, os animais NEL apresentaram maior concentração de gordura e energia por kg PCVZ e GPVCZ para mesmo peso vivo.

This research aimed to estimate the maintenance requirements of net energy (NEm) and metabolizable energy (MEm), and the changes in body and gain composition of confined adults non-pregnant and non-lactant beef cows. Thirty six cows were used, 12 were Nellore (NEL), 12 F1 Brown Swiss-Nellore (BSN) and 12 F1 Red Angus-Nellore (RAN). The comparative slaughter method was utilized to estimate the changes of animal body chemical composition during the experimental period. Four animals from each breed group were randomly allocated to the treatments: initial slaughter (IS), restrict feeding (RF) and ad libitum feeding (AL). The RF animals received levels of energy and protein 15% above maintenance during the experimental period, while the AL group was fed ad libitum, to gain 1.1 kg liveweight (LW) daily. The IS animals were slaughtered at the beginning of the experimental period, and those from RF and AL treatments were slaughtered 120 days latter. The proportions of muscle, adipose tissue and bone beyond body content of protein, fat and energy were estimated in all slaughtered animals. Linear and non linear models were fitted to estimate the NEm and MEm requirements. There was no difference among breed groups for NEm and MEm requirements expressed fast body weight (kcal/kg0.75 FBW). When the linear and the non linear models were fitted, it was observed values of NEm requirements of 80.7 and 83.6 kcal/kg0.75 FBW, and the MEm requirements of 109.9 and 128.0 kcal/kg0.75 FBW, respectively. Breed groups did not differ with respect to protein content per unit of empty body weight (EBW) and of empty body weight gain (EBG). However, NEL animals showed higher fat and energy concentrations per kg EBW and EBG, at a given live weight.

Objetivou-se com este trabalho avaliar a dinâmica de excreção fecal dos indicadores internos matéria seca indigestível (MSi), fibra em detergente neutro indigestível (FDNi), fibra em detergente ácido indigestível (FDAi) e do indicador externo óxido crômico (Cr2O3). Foram utilizados cinco bovinos mestiços Holandês × Zebu, com peso médio de 240 kg, em três períodos experimentais de 12 dias (os sete primeiros destinados à adaptação dos animais). Antes do início do período experimental, os animais passaram por um período de adaptação à dieta e ao manejo, com duração dez dias, no qual foram mantidos em baias individuais e alimentados à vontade com silagem de sorgo. O Cr2O3 foi fornecido diariamente em duas porções de 5 g, às 8h e 17h, durante todo o período experimental. Procedeu-se à caracterização do padrão diurno de excreção fecal dos indicadores, por meio do algoritmo de Gauss-Newton, em um modelo em série de Fourier. A avaliação descritiva das funções ajustadas evidenciou que a amplitude total dos ciclos foi menor para FDAi que para outros indicadores, com valores de 4,71; 1,83; 2,42 e 1,74% para Cr2O3, MSi, FDNi e FDAi, respectivamente, em relação à concentração média estimada para cada um desses indicadores. Por sua vez, o período fundamental de excreção dos indicadores em estudo foi significativo e evidenciou duração do ciclo de 3,25; 3,47; 3,46 e 3,74 horas para o Cr2O3, MSi, FDNi e FDAi, respectivamente. A concentração média fecal dos indicadores pode ser obtida por meio de duas coletas diárias de fezes, mantendo-se o espaço de tempo entre duas coletas consecutivas de 3, 9, 15 ou 21 horas.

The goal of the present study was to evaluate the dynamics of fecal excretion of the following digestion markers: indigestible dry matter (DMi), indigestible neutral detergent fiber (NDFi), and indigestible acid detergent fiber (ADFi) as internal markers and the external marker chromic oxide (Cr2O3). Five Holstein-zebu steers with 240 kg average weight were used in three 12-day experimental periods, being the first seven days for animal adaptation. Previously to the beginning of the experimental period, the animals were submitted to a 10-day period of adaptation to facilities and experimental management. They were fed ad libitum with sorghum silage and maintained in individual pens. The Cr2O3 was offered twice daily at 08:00 and 17:00 h, 5 g each, during the whole experimental period. Then, the daily marker fecal excretion pattern was characterized by means of the Gauss-Newton algorithm to fit a Fourier series model. A descriptive graphic evaluation of the fitted function showed that the total amplitude of cycles was lower for ADFi than the other markers, with values of 4.71%, 1.83%, 2.42% and 1.74% for Cr2O3, DMi, NDFi and ADFi, respectively, in relation to the estimated mean concentration of each. In turn, the fundamental period of the markers excretion patterns were significant showing cycle lengths of 3.25, 3.47, 3.46 and 3.74 hours for Cr2O3, DMi, NDFi and ADFi, respectively. As a conclusion, the mean fecal concentration of all markers might be obtained through two daily samplings at intervals from each other of 3, 9, 15 or 21 hours.

Avaliou-se a influência da restrição alimentar durante um período de pastejo de 104 dias (fase 1) sobre o consumo e a conversão alimentar, o conteúdo de digesta no trato gastrintestinal e os ganhos de peso corporal, da carcaça e dos constituintes não-carcaça em bovinos durante o período de realimentação em confinamento (fase 2). Foram utilizados 39 novilhos mestiços Holandês-Gir, com idade inicial de 19,3±5,1 meses e 202,0±49,1 kg de PV, distribuídos em três grupos segundo o regime alimentar proposto: controle - pastejo ad libitum na fase 1 e ração ad libitum na fase 2 (nove animais); ganho compensatório - pastejo restrito na fase 1 e ração ad libitum na fase 2 (15 animais); mantença - pastejo restrito na fase 1 e níveis de proteína e energia 15% acima da mantença na fase 2 (15 animais). Nos dias 1, 28, 56, 84 e 112 de confinamento, foram abatidos três animais do regime ganho compensatório e três do regime de mantença. Nos dias 1, 28 e 112, foram igualmente abatidos três animais do grupo controle. Em comparação aos animais do grupo controle, os novilhos do ganho compensatório ganharam mais peso corporal durante os primeiros 28 dias de confinamento (ganharam mais peso dos constituintes não-carcaça), porém, não diferiram quanto ao ganho de peso da carcaça. Após o início do confinamento, com a ingestão de alimentos concentrados, verificou-se redução contínua do conteúdo de digesta (em % PV) nos animais dos três regimes de alimentação, mas não foi observada diferença entre os regimes de alimentação. Nos grupos controle e ganho compensatório, os 28 dias iniciais de confinamento constituíram o período de melhor conversão alimentar, pois coincidiram com o período de maior consumo por unidade de tamanho metabólico e em porcentagem do peso vivo.

The objective of this trial was to evaluate the effect of feed restriction during a grazing period of 104 days (phase I) on intake, feed conversion, and digesta load as well as body weight (BW) change and weights of carcass and non-carcass components during a feedlot period (phase II) in crossbred steers. Thirty nine crossbred Holstein-Gyr steers averaging 19.3±5.1 months of age and 202.0±49.1 kg of BW at the beginning of the study were used. Animals were assigned to one of the following three treatments: 1 - control - ad libitum grazing in phase I and ad libitum concentrate in phase II (nine animals); 2 - compensatory growth - restricted grazing in phase I and ad libitum concentrate in phase II (15 animals); or 3 - maintenance - restricted grazing in phase I and protein and energy supplementation 15% above maintenance in phase II (15 animals). At 1, 28, and 112 days of feedlot, three animals from treatments 1, 2 and 3 were slaughtered. In addition, three animals from treatments 2 and 3 were also slaughtered at 56 and 84 days of feedlot. Animals from the compensatory growth treatment gained more BW than those from the control during the first 28 days of feedlot because of the greater weight gain of non-carcass components. However, carcass weight gain did not differ between both treatments. Gut fill as percentage of BW decreased in all three treatments when animals were fed concentrate in phase 2 but no significant differences were observed across treatments. Animals on control and compensatory growth treatments had improved feed conversion during the first 28 days of feedlot, which was associated to greater intake either expressed per unit of metabolic size or as percentage of BW.