Intake, digestibility and transit and degradation dynamics of neutral detergent fiber in cattle fed low-quality tropical forage and nitrogenous compounds

Objetivou-se avaliar os efeitos de compostos nitrogenados suplementares sobre o consumo, a digestibilidade, a síntese de proteína microbiana e as dinâmicas de trânsito e degradação da fibra em detergente neutro em bovinos alimentados com forragem tropical de baixa qualidade. Foram utilizadas cinco novilhas mestiças Holandês x Zebu, com peso vivo médio inicial de 209 kg, fistuladas no rúmen. A alimentação volumosa basal dos animais foi constituída por feno de capim-braquiária (Brachiaria decumbens Stapf.) (5,08% de PB, com base na MS), fornecido ad libitum. Os cinco tratamentos avaliados foram definidos de acordo com o nível de suplementação protéica (0, 3, 5, 7 e 9 pontos percentuais acima do nível de PB da forragem). Como fonte de compostos nitrogenados empregou-se mistura de uréia, sulfato de amônia e albumina, nas proporções de 4,5:0,5:1,0, respectivamente. O experimento foi constituído de cinco períodos experimentais, segundo delineamento em quadrado latino 5 x 5. Os níveis médios observados de PB nas dietas foram de 5,28, 8,08, 9,82, 11,87 e 13,63%, com base na MS. Verificou-se efeito quadrático (P0,10) entre os níveis de PB e a eficiência de síntese de proteína microbiana. Verificou-se elevação linear (P0.10). The potentially degradable fraction of NDF was linearly increased (P<0.10) according to CP levels in diet until 8.62% CP. From this point, there was stabilization of estimates (47.92% of NDF). On the other hand, the degradation rate of potentially degradable NDF showed a quadratic response (P<0.10) to CP levels, with maximal response on 13.39% of CP. The rumen rate of passage of fibrous particles, the mean retention time in the rumen, and the rumen fill effect of undegradable NDF showed a LRP (P<0.10) according to CP levels in the diet, with plateau beginning on 7.59, 7.68, and 8.00% of CP, respectively.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Nutritional performance of cattle under grazing during dry and rainy seasons supplemented with nitrogenous compounds and/or starch

A presente tese foi baseada em dois experimentos com bovinos de corte em pastagem composta por capim-braquiária (Uruchloa decumbens), sendo um conduzido durante o período da seca e o outro durante o período das águas. Objetivou-se avaliar os efeitos da suplementação protéica e/ou com amido sobre o desempenho nutricional de bovinos em pastejo. No primeiro experimento, conduzido no período da seca entre julho e setembro de 2008, foram utilizados cinco novilhos mestiços, Holandês x Zebu, com peso corporal médio (PC) de 396,8±13,4 kg, fistulados no rúmen e no abomaso. Foram avaliados os seguintes tratamentos: 1.controle (somente forragem basal); 2.suplementação com compostos nitrogenados supridos na proporção de 1 g de proteína bruta (PB) por kg de PC via administração ruminal; 3.suplementação com amido na proporção de 2,5 g/kg de PC via administração ruminal; 4.suplementação com compostos nitrogenados e amido na forma como descrito para os tratamentos 1 e 2; e 5.suplementação similar ao descrito para o tratamento 4 no qual o amido foi substituído por mistura de amido e compostos nitrogenados de modo que a porção energética do suplemento apresentasse 15% de PB. O experimento foi conduzido segundo delineamento em quadrado latino 5 x 5, adotando-se esquema fatorial 2 x 2 +1 (adição ou não de suplemento nitrogenado, adição ou não de amido, com tratamento adicional correspondente ao tratamento 5 descrito anteriormente). O consumo de pasto não foi afetado (P>0,10) por nenhum dos fatores avaliados. O consumo de nutrientes digestíveis totais (NDT) foi elevado (P0,10), com exceção da PB, no qual se observou efeito interativo (P0,10) nenhuma das demais variáveis associadas ao consumo voluntário. A suplementação com amido incrementou (P0,10) em relação ao controle quando nitrogênio ou amido foram fornecidos isoladamente, mas foi incrementado (P0,10) do fornecimento adicional de nitrogênio aos animais suplementados com compostos nitrogenados e amido. Os coeficientes de digestibilidade da MS e da MO e o nível dietético de NDT foram afetados de forma interativa (P0,10), a estimativa de BN se mostrou superior com a suplementação conjunta com amido e compostos nitrogenados em comparação à suplementação isolada com estes compostos. Diante dos resultados obtidos, concluiu-se que a suplementação com amido e compostos nitrogenados para bovinos mantidos a pasto durante o período das águas, considerando-se forragem com alto teor de proteína bruta, confere efeito interativo potencializando a digestão da matéria seca e o consumo de energia. Efeitos indiretos envolvendo aspectos metabólicos são observados, entre os quais se destaca a ampliação da retenção de nitrogênio no organismo animal.This study was prepared based upon two experiments with beef cattle in pasture constituted by Brachiaria grass (Uruchloa decumbens). One of them performed during the dry season, and the other during the rainy season. This work was carried out aiming to evaluate the effects of protein and/or starch supplementation relative to the nutritional performance of bovine under pasture during the dry and rainy seasons. The first experiment, performed during the months of July and September, five Dutch x Zebu half-breed young bulls with average body weight (BW) of 396.8 ± 13.4 kg, cannulated in the rumen and in the abomasum were used. The following experimental treatments were evaluated: 1. Control (for basal forage only). 2. Supplementation with nitrogen compounds supplied in the proportion of 1g of crude protein (CP) per kg of BW by ruminal infusion; 3. Supplementation with starch in the proportion of 2.5 g/kg of BW by ruminal infusion. 4. Supplementation with nitrogen compounds and starch as described for the treatments 1 and 2; and 5. Supplementation similar to the one described for the treatment 4 in which the starch was replaced by a mixture of starch and nitrogen compounds in such a way that the energetic portion of the supplement was 15% of the CP. The experiment was performed following the delineation in a 5 x 5 latin square, adopting a factorial scheme 2 x 2 +1 (addition or not of nitrogen supplement, addition or not of starch, and addition of energetic supplement containing 15% of the CP). The intake of pasture DM, pasture OM, NDFap, digested NDFap and NDFi were not affected (P>0.10) by any of the factors evaluated in this study. The CP consumption showed an effect of interaction of the supplement with nitrogen compounds and starch (P0.10) the CP consumption, while the additional supply of nitrogen compounds to animals supplemented with nitrogen and starch increased (P0.10), except for the CP, in which the interactive affect was observed (P0,10). Any of the other variables associated to the voluntary consumption. The supplementation with starch increased (P0.10) in respect to the control when nitrogen or starch were supplied separately, but was increased (P0.10) of the additional supply of nitrogen to the animals supplemented with nitrogen compounds and starch. The NB was increased (P<0.10) both by the supplementation with nitrogen compounds, as well as by the supplementation with starch. However, the relative nitrogen balance (RNB) was only increased (P<0.10) by the supplementation with nitrogen compounds. The effect of the additional supply of nitrogen to animals supplemented with starch and nitrogen compounds were only noticed on the NAR concentration and on the NB. In both cases, the additional supply of nitrogen increased (P<0.10) the obtained estimates. The effectively degraded portion of the NDF (FED) remained practically unchanged in respect to the control with the isolated supplementation with nitrogen compounds. However, it was depressed by the supplementation with starch. The joint supplementation with starch and nitrogen compounds resulted also in the DEF depression. However, in a less intense way when compared with the supplementation made only with starch. Considering these evidences, it can be concluded that the supplementation with starch and nitrogen compounds to beef cattle kept in pasture during the rainy season, considering high crude protein content in the forage, causes an interactive effect potentiating the digestion of dry matter and the consumption of energy. Indirect effects involving metabolic aspects are noticed, amongst which may point out the larger retention of nitrogen in the animal organism.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Rumen dynamics of neutral detergent fiber in cattle fed low-quality tropical forage and supplemented with nitrogenous compounds

The aim of this work was to evaluate the effects of supplementation with nitrogenous compounds on rumen dynamics of neutral detergent fiber (NDF) in cattle fed low-quality tropical forage. Five crossbred heifers with average live weight of 180 kg and fitted with rumen cannulae were used. The animals were fed ad libitum with signal grass (Brachiaria decumbens Stapf.) hay, which had crude protein (CP) content of 4.86% of dry matter (DM). The five treatments were proposed in order to raise the CP level of diets to 0, 2, 4, 6, and 8 percentile points above the CP level of the forage. The supplement was a mixture of urea, ammonium sulfate, and albumin (4.5:0.5:1.0, respectively). The experiment was carried out according to a 5 &#215; 5 Latin square design, with five experimental periods. The average CP levels in the diets were: 5.19, 7.11, 8.60, 11.67, and 13.02% on DM basis. The potentially degradable NDF was linearly increased according to the CP levels in diet up to 6.97% of CP. From this point, there was stabilization of estimates (47.87% of NDF). The degradation rate of potentially degradable NDF was linearly increased with the CP levels in diets. The rumen flow of fibrous particles (L) showed a linear-response-plateau pattern according to the CP levels in diets. The plateau (maximum estimate) began on 7.24% of CP. The mean retention time in the rumen and the rumen fill effect of undegradable NDF were affect by the CP levels similarly to L, with plateau (minimum) beginning on 6.90 and 6.97% of CP, respectively

Intake and digestibility in cattle fed low-quality tropical forage and supplemented with nitrogenous compounds

The objective of this study was to evaluate the effects of supplementation with nitrogenous compounds on intake, digestibility, and rumen microbial synthesis in cattle fed low-quality tropical forage. Five crossbred heifers, averaging 209 kg and fitted with ruminal fistulla, were used. The animals were fed ad libitum with signal grass (Brachiaria decumbens Stapf.) hay, which had crude protein (CP) content of 5.08%, as dry matter (DM) basis. The five treatments were defined according to the increasing level of CP in the diet (0, 3, 5, 7, and 9 percentile points above the forage CP level). The supplement consisted of the following nitrogen sources: urea, ammonium sulfate and albumin (4.5:0.5:1.0, respectively). The experiment was carried out according to a 5 &#215; 5 Latin square design, with five experimental periods. The average CP levels in the diets were: 5.28, 8.08, 9.82, 11.87, and 13.63% on DM basis. The intakes of DM, organic matter (OM), and neutral detergent fiber (NDF) showed a quadratic response according to CP levels in the diet, with maximum responses at 10.83%, 10.78%, and 10.37% CP, respectively. The digestibility coefficients of OM and NDF showed a linear-response-plateau response according to CP levels, with the plateau beginning (maximum response) at 7.93% and 7.55% CP, respectively. The average daily concentration of rumen ammonia nitrogen (RAN) was positively related with CP levels. The RAN estimate associated with the maximum DM intake was 15.33 mg/dL. It was observed that intestinal flow of microbial nitrogenous compounds and nitrogen intake became equivalent to each other at 7.13% of CP

Macro mineral requirements by grazing zebu bovines

The objective of this study was to determine requirements of calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K) and sodium (Na) for grazing zebu bovines. The experiment area was composed of Brachiaria decumbens paddocks. Twenty-seven non-castrated animals, with initial live weight of 311.0 kg and at an average age of 14 months were used. Three animals were slaughtered, after adaptation period, so they were used as control for estimates of empty body weight and initial body composition of animals in the experiment. Out of the 24 remaining animals, four were sent to the maintenance group with restrict grazing time to limit energy intake close to the maintenance level. The other 20 animals were distributed in four treatments: mineral mixture, self-control intake and three-times-a-week-offer frequency (offered on Mondays, Wednesdays and Fridays) and daily. Concentrations of all studied macro elements in empty body and empty body gain decreased as live weight increased. The ratios obtained for g Ca/100 g of retained protein and g P/100 g of retained protein were 9.18 and 4.72, respectively. Total dietary requirement of calcium was lower than the one recommended by NRC (2000), but P requirement was very close to that

Intake and digestibility in cattle under grazing supplemented with nitrogenous compounds during dry season Consumo e digestibilidade em bovinos em pastejo durante o período seco recebendo suplementação com compostos nitrogenados

The objective of this work was to evaluate the effects of supplementation with nitrogenous compounds on intake and digestibility in cattle under grazing during dry season. It was used five Holstein × Zebu steers with average initial live weight of 236 kg, kept in five Brachiaria decumbens Stapf. paddocks (0.34 ha). The experiment was carried out according to a 5 × 5 Latin square design, with five supplementation levels and five experimental periods. The supplementation levels were the following: 0; 0.35; 0.70; 1.05, and 1.40 g of crude protein/kg live weight. A mixture of urea, ammonium sulfate and albumin (4.5:0.5:1.0, respectively) was used as nitrogen supplement. The average crude protein levels in the diet were 7.39; 8.92; 10.98; 12.55; and 13.62%, as dry matter basis, for the respective supplementation levels. Linear-response-plateau relationships were observed between intake estimates and diet crude protein levels. The linear-response-plateau pattern showed that intake was increased up to crude protein levels close to 9%, as dry matter basis. The estimates became unchangeable from this level. The total and ruminal digestibility coefficients of dry matter and neutral detergent fiber, and diet level of total digestible nutrients presented a positive linear pattern according to diet crude protein levels. The rumen ammonia nitrogen concentration was linearly increased by diet crude protein levels. This variable assumed the value of 8.00 mg/dL when the intake estimates reached the maximum values. Supplementation with nitrogen compounds in quantities that raise the crude protein content in the diet to levels close to 9% optimizes the use of low-quality forage by cattle under grazing.<br>Objetivou-se avaliar os efeitos da suplementação com compostos nitrogenados sobre o consumo e a digestibilidade em bovinos em pastejo durante o período seco do ano. Foram utilizados cinco novilhos mestiços Holandês × Zebu, com peso vivo (PV) médio inicial de 236 kg, mantidos individualmente em piquetes de Brachiaria decumbens Stapf. (0,34 ha). Utilizou-se delineamento em quadrado latino 5 × 5, com cinco níveis de suplementação (0; 0,35; 0,75; 1,05; e 1,40 g de proteína bruta (PB)/kg PV) e cinco períodos experimentais. Como fonte de compostos nitrogenados empregou-se mistura de ureia, sulfato de amônia e albumina (4,5:0,5:1,0, respectivamente). Os níveis médios de PB nas dietas foram de 7,39; 8,92; 10,98; 12,55 e 13,62%, com base na matéria seca (MS), para os respectivos níveis de suplementação. Verificou-se relação do tipo linear-response-plateau (LRP) entre as estimativas de consumo e os níveis de PB da dieta. O comportamento do tipo LRP permitiu evidenciar aumento no consumo até níveis próximos a 9% de PB, com base na MS, a partir do qual houve estabilidade das estimativas. Os coeficientes de digestibilidade total e ruminal da MS e da fibra em detergente neutro e o nível de nutrientes digestíveis totais na dieta apresentaram relação linear e positiva com os níveis de PB na dieta. A concentração de nitrogênio amoniacal ruminal (NAR) aumentou de forma linear e positiva de acordo com os níveis de PB na dieta, com valor estimado de 8,00 mg NAR/dL, equivalente à otimização do consumo voluntário. A suplementação com compostos nitrogenados em quantidades que permitam elevar o teor de PB da dieta a níveis próximos a 9% proporciona otimização na utilização de forragem de baixa qualidade por bovinos em pastejo