Digestibilidade intestinal verdadeira da proteína de alimentos para ruminantes

A digestibilidade intestinal verdadeira de diferentes classes de alimentos usados em dietas para ruminantes foi avaliada por meio das técnicas in situ e in vitro. Foram utilizados dois bovinos machos castrados (450 kg PV) com cânulas implantadas no rúmen para incubação in situ de concentrados protéicos de origens animal e vegetal e energéticos, resíduos da agroindústria e alimentos volumosos. Avaliou-se a digestibilidade intestinal verdadeira dos alimentos submetidos à digestão apenas com pepsina ou com pepsina + pancreatina, precedida ou não da incubação ruminal. A incubação ruminal diminuiu a digestibilidade intestinal verdadeira da proteína de 24 dos 30 alimentos testados, com exceção da farinha de penas, da aveia preta, do grão de milho triturado a 2,5 mm e dos fenos de aveia e tifton, para os quais ocorreu aumento, e do farelo de girassol, para o qual não houve efeito da incubação ruminal. A digestibilidade intestinal da proteína não-degradada no rúmen (PNDR), na maioria dos alimentos utilizados em dietas para ruminantes, é menor que a da proteína original do alimento. Entre os alimentos avaliados, 29 apresentaram maior digestibilidade intestinal verdadeira quando incubados com pepsina + pancreatina, evidenciando a importância da etapa de digestão abomasal sobre as proteínas dos alimentos (com exceção à aveia preta). A digestibilidade intestinal dos alimentos é variável e, portanto, deve ser considerada na formulação de dietas para atendimento das exigências de proteína metabolizável

DOSES AND SOURCES OF NITROGEN ON YIELD AND BROMATOLOGICAL COMPOSITION OF XARAÉS GRASS

This study evaluated the effect of nitrogen sources and doses on dry matter yield and bromatological composition of xaraés grass throughout the year. The experiment was carried out at the Agronomy Faculty of Rio Verde University from October 2008 to January 2010. The experiment consisted of a randomized complete block design in a 2 x 4 factorial arrangement with measures repeated in time, and four replications. We tested two nitrogen sources (ammonium sulfate and urea) and four nitrogen levels (0, 200, 400 and 600 kg ha-1). The evaluations were conducted on the same plots throughout the year and during all four seasons (autumn, winter, spring, and summer). The results demonstrated that the maximum grass production of dry matter and crude protein of xaraés grass for the sources of urea and ammonium sulfate were estimated at doses of 500 and 472 kg ha-1 and 407 and 396 kg N ha-1, respectively. And for TDN level the maximum dose was 404.74 kg ha-1 N, for the source of ammonium sulfate. This result indicates that, regardless of the source, the application of increasing doses of up to 400 kg ha-1 of nitrogen in xaraés grass is sufficient to maintain a high dry matter production, associated with the nutritional value of the forage. The source ammonium sulfate demonstrated higher efficacy for xaraés grass dry matter production in the seasons evaluated, however additional studies are needed to evaluate the economical feasibility of its use

<b>Performance of Nellore steers grazing on <em>Panicum maximum</em> Jacq cv. Mombaça receiving chopped sugar cane tops and protein supplementation</b> - doi: 10.4025/actascianimsci.v32i4.8142 <b>Performance of Nellore steers grazing on <em>Panicum maximum</em> Jacq cv. Mombaça receiving chopped sugar cane tops and protein supplementation</b> - doi: 10.4025/actascianimsci.v32i4.8142

The aim of this study was to evaluate protein supplementation on the performance of steers grazing on Mombaça grass and receiving chopped sugar cane tops at a level of 0.80% of live weight (dry matter (DM) basis), during the dry season. Forage availability and quality of the experimental pasture were also evaluated. Thirty-two Nellore steers, weighing 300 kg (&plusmn; 25.80) of initial live weight, eight per treatment, were used. The statistical design was completely randomized and each steer group was allocated to one of four paddocks (1.125 ha paddock^-1). All steers received a protein supplement at 0.40% of live weight (DM basis) and the four treatments consisted of the following four crude protein (CP) concentrations in supplements: 12.5, 25.0, 37.5 and 50.0% CP (DM basis). Average forage mass availability and green leaf blades availability were 10,069 and 2,195 kg of DM ha^-1, respectively. Average CP, neutral fiber detergent (NDF) and <em>in vitro</em> dry matter digestibility (IVDMD) in forage mass were 6.87, 62.63 and 49.80%, respectively. Average daily gain was 0.61 kg steer^-1 day^-1 and these results show that the strategy of feeding steers in pasture, with chopped sugar cane tops (0.80% LW) and protein supplement with 12.50% CP (0.40% LW), during the dry season, allows high gain per area (363 kg live weight ha^-1).<br>The aim of this study was to evaluate protein supplementation on the performance of steers grazing on Mombaça grass and receiving chopped sugar cane tops at a level of 0.80% of live weight (dry matter (DM) basis), during the dry season. Forage availability and quality of the experimental pasture were also evaluated. Thirty-two Nellore steers, weighing 300 kg (&plusmn; 25.80) of initial live weight, eight per treatment, were used. The statistical design was completely randomized and each steer group was allocated to one of four paddocks (1.125 ha paddock^-1). All steers received a protein supplement at 0.40% of live weight (DM basis) and the four treatments consisted of the following four crude protein (CP) concentrations in supplements: 12.5, 25.0, 37.5 and 50.0% CP (DM basis). Average forage mass availability and green leaf blades availability were 10,069 and 2,195 kg of DM ha^-1, respectively. Average CP, neutral fiber detergent (NDF) and <em>in vitro</em> dry matter digestibility (IVDMD) in forage mass were 6.87, 62.63 and 49.80%, respectively. Average daily gain was 0.61 kg steer^-1 day^-1 and these results show that the strategy of feeding steers in pasture, with chopped sugar cane tops (0.80% LW) and protein supplement with 12.50% CP (0.40% LW), during the dry season, allows high gain per area (363 kg live weight ha^-1)

<b>Protein fraction and digestibility of marandu, xaraes and campo grande grasses in monocropping and intercropping systems under different sowing methods</b> - doi: 10.4025/actascianimsci.v35i1.15134

<p class="aresumo">A study was carried out to evaluate the protein fraction and <em>in vitro</em> dry matter digestibility of marandu, xaraes grasses and campo grande in monocropping and intercropping systems under different planting methods, for a period of two years. The experimental design was a complete randomized block with four replications. The treatments consisted of the following crop systems: campo grande in monocropping; xaraés grass in monocropping; marandu grass in monocropping; xaraés intercropped with campo grande in rows; xaraés intercropped with campo grande, broadcast; marandu grass intercropped with campo grande in rows; and marandu intercropped with campo grand, broadcast. The evaluations were conducted for two years, consisting of seasonal evaluations (autumn, winter, spring and summer) in the same plots, with repeated measurements over time. The results showed that xaraes and marandu grasses were similar between crop systems, indicating that both can be intercropped with campo grande. The intercropping of campo grande with <em>Brachiaria brizantha</em> cultivars improved the protein fraction and digestibility. The row method of planting provided better protein fractions and <em>in vitro</em> dry matter digestibility.</p> <p class="apalavrachave"><em> </em></p

Efeito do período experimental na absorção aparente de macroelementos minerais em bovinos alimentados com dois níveis de volumoso

The objective of this study was to evaluate the effects of forage levels in diet (30% and 70%) and experimental periods (14 and 21 days) on the total and partial apparent absorption (AA) of calcium (Ca), phosphorus (P), magnesium (Mg) and potassium (K) and on the partial and total coefficient of apparent digestibility (CAD) of dry matter (DM) in cattle. Four Holstein steers fitted with ruminal and duodenal cannulas were used. The experimental design was a 4 x 4 Latin square. High concentrated diets showed higher intestinal and total CAD (p < 0.01) to DM and ruminal and total AA (p < 0.01) to P. The experimental period affected intestinal and total (p < 0.05) AA of Ca that was higher for of 21 days experimental period. There was interaction between forage level and experimental period where higher intestinal and total AA of Ca (p < 0.05) for diets with low forage was observed.O objetivo deste trabalho foi avaliar os efeitos do nível de volumoso na dieta (30% e 70%) e da duração do período experimental (14 e 21 dias) sobre a absorção aparente (AA) parcial e total de cálcio (Ca), fósforo (P), magnésio (Mg) e potássio (K) e sobre o coeficiente de digestibilidade aparente (CDA) parcial e total da matéria seca (MS) em bovinos. Utilizaram-se 4 novilhos da raça Holandês-Preto-e-Branco implantados com cânulas ruminal e duodenal. O delineamento experimental utilizado foi o quadrado latino 4 x 4. A dieta rica em concentrado apresentou maior CDA intestinal e total (p < 0,01) para MS e AA ruminal e total (p < 0,01) para P. A duração do período experimental afetou a AA intestinal e total (p < 0,05) de Ca, que foi maior para o período experimental de 21 dias. Houve interação entre o nível de volumoso na dieta e a duração do período experimental, em que observou-se maior AA intestinal e total (p < 0,05) de Ca para dietas com baixo volumoso