Eight cecally cannulated Quarter Horse geldings were utilized in a crossover design with two 28 d periods with a 21 d washout period between. Horses were adapted to dietary treatments from d 1 to 19, dry matter intake was determined from d 20 to 24, and cecal fluid was collected on d 28. Horses were paired by age and body weight (BW) and randomly assigned to treatment. Treatments consisted of housing horses individually in stalls or group housed in a dry lot pen. Regardless of treatment, all horses were individually fed a pelleted concentrate at 1% BW (as fed) offered twice daily 12 h apart. All horses had ad libitum access to coastal bermudagrass hay. Hay was offered to stalled horses initially at 2% BW (as fed) then adjusted based on 120% of a previous 3 d average of voluntary intake. A dual marker system was utilized for estimation of voluntary intake in all horses using titanium dioxide (TiO2) as the external marker and acid detergent insoluble ash (ADIA) as the internal marker. Cecal samples were collected 4-h after the morning meal and immediately analyzed for pH. Samples were transported to the USDA/ARS laboratory to enumerate total anaerobic bacteria and lactic acid bacteria, and to determine methane and ammonia activity. Cecal pH was influenced by housing (P = 0.02) with group housed horses having lower cecal pH values when compared to stalled horses (6.52 +/- 0.04 and 6.69 +/- 0.04, respectively). The cecal pH values of this study are similar to other reported values when feeding similar diets (5). Populations of cecal total anaerobic bacteria and lactobacillus were not influenced by housing (P >= 0.21). Treatments did not affect the production of acetate, propionate, or butyrate (P >= 0.15). Additionally, methane and ammonia production were not affected by treatments (P >= 0.17). Forage intake was greater for group housed horses (P = 0.04) than stalled (8.47 +/- 0.89 kg DM/d and 5.17 +/- 0.89 kg DM/d, respectively). In conclusion, confinement housing did not greatly influence the cecal environment of a horse when similar diets were offered.

Previous research documented the fetus is sensitive to nutrition of the dam, but this has not been thoroughly investigated in horses. Objectives of the current studies were to determine effect of manipulation of maternal nutrition during the last third of pregnancy on mare performance, intake, hormones, foaling parameters, colostrum, and foal passive transfer of immunity and growth, and effects of supplemental arginine. Plane of nutrition influenced mare performance, and DMI was influenced by time with the first trial finding all mares consumed less in the 10th month of pregnancy compared to the 11th month, and the second trial finding all mares consumed less during the 11th month. Additionally, the second study determined arginine supplementation has no detrimental effects on DMI. Both studies indicated the dual marker system was sufficient at estimating DMI. Neither trial found an influence of treatment on foaling parameters or physical measurements obtained following parturition, and the second study determined arginine supplementation also did not affect foaling or measurements. The first study determined maternal nutrition did not affect foal growth or ADG. When colostrum quality was evaluated, the first study determined mares consuming only hay had increased specific gravity and Brix% indicating higher quality. This was confirmed by IgG analysis finding a tendency for increased IgG concentration. However, colostrum volume was not affected by nutrition, nor was total g IgG. The second study found contrasting results with greater specific gravity in mares on a high plane of nutrition, and a tendency for moderate plane of nutrition mares to have greater volume. Additionally, the second study determined that arginine supplementation does not influence colostrum volume or quality (measured by specific gravity or Brix %). In the first trial, maternal diets affected glucose and insulin AUC in mares, which altered insulin dynamics in the resulting foals. Foal insulin AUC and peak insulin concentration were greater in foals from mares supplemented with concentrate compared to foals from mares fed hay alone. These studies have provided a wealth of information to help elucidate the impact of maternal nutrition in late gestation on mares and their foals.

Made available in DSpace on 2014-06-11T19:33:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-11-10Bitstream added on 2014-06-13T20:45:12Z : No. of bitstreams: 1 vieira_br_dr_jabo.pdf: 745384 bytes, checksum: dc2143964d7559ca196e2a2ff2d18c49 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Objetivou-se avaliar a estrutura do dossel, o comportamento ingestivo, o consumo de forragem e o desempenho animal de novilhas, da raça Nelore, suplementadas em pastagens de Brachiaria brizantha cv. Marandu sob lotação contínua com taxa de lotação variável, durante o período das águas. Foram avaliados três alturas do dossel (15, 25 e 35 cm) e três suplementos (sal mineral, suplemento energético, e suplemento energético-protéico) em um esquema fatorial 3x3 totalizando nove tratamentos. Com exceção do sal mineral, que foi fornecido ad libitum, os suplementos foram fornecidos a 0,3% do PC/dia. O delineamento experimental foi inteiramente casualizado com duas repetições de piquete. As avaliações ocorreram entre os meses de janeiro e maio de 2009. Na época seca foi avaliado o impacto dos manejos da época de águas em dois sistemas de terminação (pasto ou confinamento) sobre o ganho de peso, o tempo de terminação e as características de carcaça dos animais. A maior altura do dossel determinou maior massa e oferta de forragem do pasto, superior consumo e menor tempo de pastejo dos animais. Entretanto, os suplementos não influenciaram essas características. O uso de suplementos energético e energéticoprotéico aumentou o desempenho animal, não havendo diferença entre os suplementos para nenhuma das vaiáveis estudadas, com exceção da concentração de amônia ruminal, que foi influenciada pelo suplemento energético-protéico em alguns horários do dia. O uso da suplementação energético-protéica, assim como as maiores alturas do pasto reduziram o tempo de terminação dos animais no período de seca, indiferente do sistema utilizado, mas não interferiu nos ganhos de peso e no consumo de matéria seca dentro de cada sistema. A terminação em confinamento aumentou a deposição de gordura nas carcaças / The objective was evaluate the canopy structure, the ingestive behavior, the forage intake and the performance of Nellore heifers supplemented in Brachiaria brizantha cv. Marandu pasture under continuous stocking and variable stoking rate during the rainy season. The treatments consisted of three canopy heights (15, 25 and 35 cm) associated with three types of supplements (a mineral, an energy supplement and a protein/energy supplement) on a factorial 3x3, totalizing 9 treatments. The mineral salt was provided ad libitum while the other supplements were provided at 0.3% of body weight/day. Experimental design was completely randomized with two paddocks replications. The evaluations were realized between January and May of 2009. In the following dry season were evaluated the impact of the previous treatment on finish systems (pasture or feedlot) on the performance, days to slaughtered and carcass quality. It was observed that the sward height affect forage mass, forage allowance, all the pasture structural features, animal intake and grazing time. However, the supplements did not affect these variables. The use of energy or protein supplement increased animal performance, without differences between the supplements for any variable evaluated, other than ruminal ammonia concentration, witch were affected by the protein supplement. The use of energy/protein supplement, as well as higher pasture height were positively related to time to slaughtered on the dry season, independent on the finish system, but did not affect the daily gain nor feed intake. The feedlot finish increased the fat deposition on the carcass

Orientador: Ricardo Andrade Reis / Banca: Flavio Augusto Portela Santos / Banca: Manoel Eduardo Rozalino Santos / Banca: Paulo Henrique Moura Dian / Banca: Ana Claudia Ruggieri / Resumo: Objetivou-se avaliar a estrutura do dossel, o comportamento ingestivo, o consumo de forragem e o desempenho animal de novilhas, da raça Nelore, suplementadas em pastagens de Brachiaria brizantha cv. Marandu sob lotação contínua com taxa de lotação variável, durante o período das águas. Foram avaliados três alturas do dossel (15, 25 e 35 cm) e três suplementos (sal mineral, suplemento energético, e suplemento energético-protéico) em um esquema fatorial 3x3 totalizando nove tratamentos. Com exceção do sal mineral, que foi fornecido ad libitum, os suplementos foram fornecidos a 0,3% do PC/dia. O delineamento experimental foi inteiramente casualizado com duas repetições de piquete. As avaliações ocorreram entre os meses de janeiro e maio de 2009. Na época seca foi avaliado o impacto dos manejos da época de águas em dois sistemas de terminação (pasto ou confinamento) sobre o ganho de peso, o tempo de terminação e as características de carcaça dos animais. A maior altura do dossel determinou maior massa e oferta de forragem do pasto, superior consumo e menor tempo de pastejo dos animais. Entretanto, os suplementos não influenciaram essas características. O uso de suplementos energético e energéticoprotéico aumentou o desempenho animal, não havendo diferença entre os suplementos para nenhuma das vaiáveis estudadas, com exceção da concentração de amônia ruminal, que foi influenciada pelo suplemento energético-protéico em alguns horários do dia. O uso da suplementação energético-protéica, assim como as maiores alturas do pasto reduziram o tempo de terminação dos animais no período de seca, indiferente do sistema utilizado, mas não interferiu nos ganhos de peso e no consumo de matéria seca dentro de cada sistema. A terminação em confinamento aumentou a deposição de gordura nas carcaças / Abstract: The objective was evaluate the canopy structure, the ingestive behavior, the forage intake and the performance of Nellore heifers supplemented in Brachiaria brizantha cv. Marandu pasture under continuous stocking and variable stoking rate during the rainy season. The treatments consisted of three canopy heights (15, 25 and 35 cm) associated with three types of supplements (a mineral, an energy supplement and a protein/energy supplement) on a factorial 3x3, totalizing 9 treatments. The mineral salt was provided ad libitum while the other supplements were provided at 0.3% of body weight/day. Experimental design was completely randomized with two paddocks replications. The evaluations were realized between January and May of 2009. In the following dry season were evaluated the impact of the previous treatment on finish systems (pasture or feedlot) on the performance, days to slaughtered and carcass quality. It was observed that the sward height affect forage mass, forage allowance, all the pasture structural features, animal intake and grazing time. However, the supplements did not affect these variables. The use of energy or protein supplement increased animal performance, without differences between the supplements for any variable evaluated, other than ruminal ammonia concentration, witch were affected by the protein supplement. The use of energy/protein supplement, as well as higher pasture height were positively related to time to slaughtered on the dry season, independent on the finish system, but did not affect the daily gain nor feed intake. The feedlot finish increased the fat deposition on the carcass / Doutor

This study examined the nutritional responses of mule deer during winter on range subjected to a system of spring livestock grazing. The specific purposes were 1) to determine the quality (crude protein, digestible energy, and digestibility) of diets consumed by mule deer in winter on ranges grazed and ungrazed by sheep in spring, 2) to determine the level of forage intake, as determined by the external indicator chromic oxide, for deer under the same grazing regimes, 3) to compare forage intake estimates determined by the external indicator (chromic oxide) with results obtained by ocular estimation, and 4) to determine the forage intake level and quality consumed by fawns, adult does, and yearling male castrates used as experimental subjects during one season of the study. The study was conducted within the framework of a completely random experimental design with two treatments. Variables noted for each unit observed included treatment (previously grazed and not grazed by sheep), season (early-winter versus late-winter), weeks within season (four weeks per season), and sex-age class of animal (fawns, does, castrates). The study site , located at Hardware Ranch, Cache County, Utah, was a shrub:grass:forb community with sagebrush and bitterbrush as co-dominants. Two adjacent 2.4 hectare pastures were fenced. A sheep grazing treatment of 150 sheep days per hectare was applied in late May, 1974 and again in late May, 1975 to one pasture. Hand-reared mule deer were placed in each pasture at a stocking rate of about 100 deer days per hectare for three six-week seasons, two beginning in early November 1974 and 1975, and the other beginning near the middle of March, 1975. Artificial diets were carefully formulated for analyses of the forage quality indices. These formulations were based on the determined botanical composition of diets consumed by the mule deer. Forage intake was determined for two seasons by use of the external indicator method utilizing chromic oxide and these values derived were compared to intake levels determined by an ocular estimation method. No treatment differences existed for forage quality across the three seasons of this study. Mean values for the three qualitative parameters evaluated were: crude protein content, 9.9 percent; digestible energy content, 2.2 kcals/g forage consumed; and dry matter digestibility, 45.5 percent. There were no treatment differences in the level of forage intake, as determined by the external indicator, across two seasons of this study. Mean intake level was 38.1 g/kg body weight per day. No treatment differences existed for the ocular estimation method of determining forage intake and this method was judged to be inferior to the external indicator method of determining forage intake. Few temporal changes between treatments occurred in forage quality and quantity during the early-winter seasons. Some t emporal differences between treatments did exist for forage quality and quantity during the late weeks of the late-winter 1975 season. Deer displayed a marked shift from browse to herbaceous plant material during spring green-up. Deer on the pasture previously grazed by sheep began this shift about one week earlier than those deer on the pasture not grazed by sheep. Interpretation of the results of the forage quality and forage quantity evaluations suggest that deer on the sheep- grazed treatment deferred use of available browse plants and consumed more herbaceous plant material. Therefore, by shortening the length of time that over-wintering deer are dependent upon a browse-dominated diet of lower palatability, lowered quality, and lowered intake, the animals should survive the winter in better physical condition. Thus, this study has shown that sheep grazing of mule deer winter range caused no detriment to the nutritional well-being and may indeed benefit deer to a small degree, particularly at the time of spring green-up. This suggests that a greater animal production per unit area of rangeland can be realized through common use grazing.

No description available.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Heifers rearing is a determinant step of efficiency in beef cattle production systems on pastures. Several experiments have tested alternative uses for tropical grasses to heifers rearing. In order to summarize results and making not visible relationships evident in these individual experiments an analysis was performed in a set of data from six experiments dealing with beef heifers rearing from 15 to 18 months of age on Pearl Millet (Pennisetum americanum), Alexandergrass (Urochloa plantaginea) and Coastcross (Cynodon dactylon) pastures. Canopy structure, herbage intake patterns, performance and body development of heifers were studied. Forage mass (3,000.4 kg DM/ha) and leaf blade mass (668.1 kg DM/ha) were similar between pastures while leaf blade: stem ratio of sward vertical strata was different. In Pearl Millet, higher forage allowance and canopy height were observed as well as less stems mass. The leaf blade allowance was higher in Pearl Millet (4.4%), intermediate in Alexandergrass (2.8%) and lower in Coastcross (1.8%). The daily intake of DM was lower in Coastcross (5.6 kg) compared to Alexandergrass (6.5 kg) and these values were similar to the value in Pearl Millet (6.1 kg). The bite mass and biting rate were similar in Pearl Millet and Alexandergrass. The main compensatory mechanism for smaller bite masses and reduced intake rates in Coastcross was increasing grazing time. The biting rate variations happened as a response to constraints imposed by the canopy architecture. Surface utilization on Alexandergrass and Coastcross was increased by the searching for leaf blades which influenced the increase of the number of feeding stations visited and displacement rate. Average daily gain was similar in Pearl Millet and Alexandegrass (0.864 kg) and less in Coastcross (0,610 kg). Daily weight gain per area was higher in Pearl Millet (8.1 kg/ha/day), which resulted in a higher production of total body weight (668.0 kg/ha). The body weight gain was mainly determined by forage mass and neutral detergent fiber in the three pastures. Body weight, body condition score, reproductive tract score, pelvic area and hip height were similar among heifers in the three grasses at 18 months of age. It suggests an adequate body development of heifers for mating at the end of pastures occupation, when the animals are at 18 months of age. To beef heifers rearing (from 14 to 18 months of age), Coastcross and Alexandergrass pastures are alternatives to Pearl Millet pasture. / A recria das novilhas constitui uma etapa determinante da eficiência dos sistemas de produção de bovinos de corte a pasto. Diversos experimentos têm testado alternativas de uso de gramíneas tropicais na recria de novilhas. Com o objetivo de sumarizar resultados e evidenciar relações não visíveis nestes experimentos individuais, foi realizada análise conjunta de dados provenientes de seis experimentos (n=436) que envolveram a recria de novilhas de corte, dos 15 aos 18 meses de idade, em pastagens de milheto (Pennisetum americanum), papuã (Urochloa plantaginea) e Coastcross (Cynodon dactylon). Foi analisada a estrutura do dossel, os padrões de ingestão de forragem, o desenvolvimento corporal e do trato reprodutivo das novilhas. A massa de forragem (3000,4 kg MS/ha) e de lâminas foliares verdes (668,1 kg MS/ha) foram similares entre as espécies forrageiras enquanto a relação lâmina foliar:colmo nos estratos verticais da pastagem foram diferentes. Houve maior oferta de forragem e altura do dossel e menor massa de colmos na pastagem de milheto. A oferta de lâminas foliares foi maior em milheto (4,4%), intermediária em papuã (2,8%) e menor em Coastcross (1,8%). A ingestão diária de MS foi menor em Coastcross (5,6 kg) em relação à papuã (6,5 kg) e esses valores foram similares à milheto (6,1 kg). A massa e a taxa de bocados foram similares em milheto e papuã, e menores em Coastcross. O aumento do tempo de pastejo foi o principal mecanismo compensatório da menor massa de bocados e reduzida taxa de ingestão em Coastcross. A variação na taxa de bocados foi uma resposta às limitações impostas pela estrutura do pasto. A busca por lâminas foliares ocasionou o aumento da exploração da área em papuã e Coastcross, com maior número de estações alimentares visitadas/minuto e maior taxa de deslocamento. O ganho médio diário foi similar em milheto e papuã (0,864 kg) e menor em Coastcross (0,610 kg). O ganho de peso por área foi maior em milheto (8,1 kg/ha/dia), o que resultou em maior produção total (668,0 kg/ha). Nas três espécies o ganho de peso corporal foi determinado principalmente pela massa de forragem e teor de fibra em detergente neutro do pasto do pasto. O peso corporal, escore de condição corporal e do trato reprodutivo, área pélvica e altura da garupa foram similares, nas três espécies forrageiras, aos 18 meses de idade das novilhas. Essas variáveis indicaram a possibilidade de acasalamento dos animais ao final do período de utilização das pastagens de verão, no sistema 18/20 meses de idade. Pastagens de Coastcross ou papuã constituem alternativas à pastagem de milheto para a recria de novilhas de corte dos 14 aos 18 meses de idade.

Submitted by Claudia Rocha (claudia.rocha@udesc.br) on 2018-03-15T13:27:54Z No. of bitstreams: 1 PGCA16MA208.pdf: 759581 bytes, checksum: 66fd12477aaa280fa6f6beece50c33c0 (MD5) / Made available in DSpace on 2018-03-15T13:27:54Z (GMT). No. of bitstreams: 1 PGCA16MA208.pdf: 759581 bytes, checksum: 66fd12477aaa280fa6f6beece50c33c0 (MD5) Previous issue date: 2016-07-29 / Feeding systems based on mixed diets comprising grazed pasture and conserved forages are useful during times of low pasture accumulation rate and/or to increase stocking rate and milk production per area. This work aimed to evaluate DM intake and milk production of dairy cows strip-grazing a mixed perennial pasture (Festuca arundinacea, Trifolium repens) without supplementation (control, C) or supplemented with corn silage (CS) or partial mixed ration (PMR). Twelve Holstein cows and F1 (Holstein × Jersey), in the middle third of lactation (133 ± 43 days in milk), were divided into six lots and distributed in a Latin square 3 × 3 replicated twice, with three periods of 15 days, with the last six days for measurements. The treatment C had access to pasture for 21 h/day, with a herbage allowance (PA) of 35 kg DM/day at ground level. Supplemented treatments had access to pasture for 7 h/day (from 0830 to 1530 h), with a PA of 25 kg DM/day. The herbage intake was measured by difference between pre and post-grazing pasture mass. The total DM intake (+ 7.3 kg DM), milk production (+ 4.7 kg/day) increased in cows that received PMR compared to unsupplemented cows, but these variables were similar between treatment C and CS. The DM herbage intake (+ 2.8 kg DM/day) and the proportion of time spent grazing (+ 25%) were higher in animals with CS supplementation compared to animals receiving PMR supplementation. It is concluded that, to dairy cows grazing mixed perennial species, CS supplementation is a tool to increase milk production per area without reductions on a milk production per cow basis, whereas PMR supplementation is a tool to improve total DM intake and milk production per cow and per area / Sistemas baseados em dietas mistas que compreendem pastagem e forragens conservadas são úteis durante os períodos do ano onde se tem uma taxa de acúmulo do pasto baixa e / ou para aumentar a taxa de lotação e produção de leite por área. Este trabalho teve como objetivo avaliar o consumo de MS e a produção de leite de vacas leiteiras em pasto perene de inverno composto por um consórcio de festuca e trevo-branco Festuca arundinacea, Trifolium repens), submetidas a três tratamentos, um controle sem suplementação (SS) ou suplementadas com silagem de milho (SM) ou ração misturada parcial (PMR). Doze vacas da raça Holandesa e F1 (Holandês × Jersey), no terço médio da lactação (133 ± 43 dias em lactação), foram divididos em seis lotes e distribuídos em um quadrado latino 3 × 3 replicado duas vezes, com três períodos de 15 dias, com os últimos cinco dias para as medições. Os animais do tratamento SS tiveram acesso a pastagens durante 22 h / dia, com uma oferta de forragem de 35 kg de MS / dia no nível do solo. Os tratamentos suplementados tiveram acesso ao pasto durante 7 horas /dia (08:30-15:30 h), com um oferta de 25 kg / dia de MS. O consumo de forragem foi medida pela diferença entre a massa pasto pré e pós-pastejo. O consumo de MS total (+ 7,3 kg de MS), e a produção de leite (+ 4,7 kg / dia) aumentaram nas vacas que receberam PMR em comparação com vacas não suplementadas, mas estas variáveis foram semelhantes entre os tratamentos SS e SM. O consumo de MS de forragem (+ 2,8 kg de MS / dia) e a proporção de tempo gasto pastoreio (+ 25%) foram maiores nos animais de SM em comparação com animais de RPM. Conclui-se que, para vacas leiteiras em pasto perene de inverno, a suplementação com silagem de milho é uma ferramenta para aumentar a produção de leite por área sem reduções em uma produção de leite por vaca, enquanto que a suplementação PMR é uma ferramenta para melhorar o consumo de MS total e produção de leite por vaca e por área

Made available in DSpace on 2016-12-08T16:24:09Z (GMT). No. of bitstreams: 1 PGCA11MA075.pdf: 737868 bytes, checksum: 5473c383aab70553ce6a1f7fcce2d52c (MD5) Previous issue date: 2011-11-11 / The aim of this study was to validate the use of n-alkanes C31, C32 and C33 on estimates of intake and digestibility and assess the accuracy of the use of indicators and acid detergent fiber (ADF), compared to the lignin in the studies of duodenal flow of nutrients. In addition, was to studied the use of indicators of fecal content in the estimation of digestibility and forage intake in lambs receiving ryegrass green. Two assays were conducted digestibility "in vivo" with 16 days each (11 for adaptation and 5 collection). The treatments consisted of diets composed by Italian ryegrass (Lolium multiflorum Lam.), in two successive cycles of grazing (28 and 35 days regrowth). The n-alkane C33 showed fecal recovery close to 1,0 in both tests and was more accurate in predicting the digestibility of C31. The intestinal flows of dry matter (DM) estimated from the C31, FDA or lignin were similar. In addition, the flow estimates obtained by internal ADF and lignin markers proved closely associated (linear coefficient = 1,016, r2 = 0,809). In local validation of the use of n-alkanes to estimate the consumption pair C33: C32 showed better relationship with the observed dry matter intake, since it held the correction for recovery rate of fecal C32. For the study of fecal indicators index the best estimates of consumption of organic matter (IOM) were obtained when using the amounts excreted nitrogen (g / day) and neutral detergent fiber (NDF, g / day) associated with the content forage NDF (r² = 0,78, rsd = 0,095). In conclusion, estimates of consumption and / or digestibility using the technique of n-alkanes should be preceded by local validation tests, studies of the intestinal flow of nutrients the FDA can be used instead of the lignin and estimates of forage intake in sheep may be made depending on the amount of nitrogen excreted per day and NDF / Os objetivos deste trabalho foram validar o uso dos n-alcanos C31, C32 e C33 em estimativas de consumo e digestibilidade e avaliar a exatidão do uso destes indicadores e da fibra em detergente ácido (FDA), em comparação à lignina, nos estudos de fluxo duodenal de nutrientes. Além disso, foi estudado o uso de indicadores de índice fecal na estimativa da digestibilidade e do consumo de forragem em ovinos recebendo azevém anual verde. Foram conduzidos dois ensaios de digestibilidade in vivo com 16 dias de duração cada (11 de adaptação e 5 de coleta). Os animais utilizados foram oito ovinos machos, castrados, mantidos em gaiolas de metabolismo. A dieta fornecida foi composta exclusivamente de azevém anual (Lolium multiflorum Lam.) verde em dois ciclos de desenvolvimento (28 e 35 dias de rebrote). O n-alcano C33 apresentou recuperação fecal próxima de 1,0 em ambos os ensaios e se mostrou mais exato na predição da digestibilidade aparente que o C31. Os fluxos intestinais de matéria seca (MS) estimados a partir do C31, FDA ou lignina foram semelhantes. Além disso, as estimativas de fluxo obtidas pelos marcadores internos FDA e lignina se mostraram estreitamente associadas (coeficiente linear = 1,016; r2 = 0,809). Na validação local da utilização dos n-alcanos para estimativa do consumo o par C33:C32 mostrou melhor relação com o consumo de matéria seca observado, desde que realizada a correção pra taxa de recuperação fecal do C32. Para o estudo com indicadores de índices fecais as melhores estimativas do consumo de matéria orgânica (CMO) foram obtidas quando se utilizou as quantidades excretadas de nitrogênio (g/dia) e fibra em detergente neutro (FDN, g/dia) associados ao teor de FDN na forragem (r² = 0,78; dpr = 0,095). Em conclusão, estimativas do consumo e/ou digestibilidade aparente utilizando a técnica dos n-alcanos devem ser precedidas de ensaios de validação local; nos estudos do fluxo intestinal de nutrientes o FDA pode ser utilizado em substituição a lignina e estimativas do consumo de forragem em ovinos podem ser efetuadas em função da quantidade de nitrogênio e FDN excretados por dia

A trial was conducted to evaluate forage production potential, forage intake and milk production in two perennial tropical grasses under continuous grazing of lactating cows, in the growth seasons of 2003/04 and 2004/05, in Palmeira das Missões/RS. Twelve tester animaIs were distributed in two paddocks per treatment, using "put-and-take" technique to adjust stocking rates. Evaluated treatments were Dwarf Elephantgrass (Pennisetum purpureum cv. Mott) and Tifton 85 (Cynodon dactylon x C. nlemfuensis) pastures. Under the proposed management criteria (4 % of leaf lamina allowance), Tifton 85 demonstrates to be less sensible to forage production and stocking rate reduction under adverse climate conditions, with relative stability of forage mass available. Its superiority in individual animal performance, in more favourable conditions (2003/04 growth season), when compared to Dwarf Elephantgrass, should be related to the allowance used. Maintaining low levels of leaf lamina on offer could be limiting to cows' individual performance, rebounding negatively over persistency of the pastures. The evaluated species presented different structures and forage densities in the most accessible strata to grazing by the animaIs. However, those differences didn't affect the chemical composition of these layers nor of its respective of its respective "hand-plucking" samples, causing similar forage intake. Higher individual animal production indices were found, indicating a little known potential for perennial tropical grasses in milk from pasture systems. / Para avaliar o potencial forrageiro, o consumo de forragem e a produção de leite em duas gramíneas perenes tropicais sob pastejo contínuo de vacas em lactação, foi conduzido um experimento nos anos agrícolas de 2003/04 e 2004/05, em Palmeira das Missões/RS. Foram utilizados 12 animais testes, distribuídos em dois piquetes por tratamento, adotando-se a técnica dos animais reguladores para ajustes da carga animal. Os tratamentos avaliados foram pastagens de Capim Elefante Anão (Pennisetum purpureum cv. Mott) e Tifton 85 (Cynodon dactylon x C. nlemfuensis). Sob o critério de manejo proposto (oferta de 4 % de lâminas foliares), o Tifton 85 demonstra ser menos sensível à redução da produção forrageira e capacidade de carga sob condições adversas de clima, com relativa manutenção da massa de forragem disponível. Sua superioridade em produção individual por animal, em condições mais favoráveis (ano agrícola 2003/04), quando comparado ao Capim Elefante Anão, deve estar relacionada à oferta utilizada. A manutenção de níveis reduzidos de oferta de lâminas foliares pode ter sido limitante ao desempenho individual das vacas, repercutindo também de forma negativa na persistência produtiva das pastagens. As espécies estudadas apresentaram distintas estruturas e densidades de forragem nos estratos mais acessíveis ao pastejo pelos animais. Contudo, tais diferenças estruturais não afetaram a composição química destas camadas ou das respectivas simulações de pastejo, acarretando em consumo de forragem similar. Foram registrados elevados índices de produção animal individual, indicando um potencial pouco conhecido das gramíneas tropicais em sistemas de produção de leite a pasto.