The decisive role of metallic cations in the formation of supramolecular clusters involving lignin, cellulose, and hemi-cellulose and its relationship to energy losses in ruminants associated with fibrous feed resources is still not well understood. Indeed, interactions between lignin, cellulose and metallic cations generate highly stable clusters that significantly decrease the capability of cellulase to break bonds between sugar units in order to facilitate the absorption of a great quantity of cellulose, which is ingested by ruminants as forage. Furthermore, several metallic cations cannot be absorbed as a consequence of the formation of coordinated ligations with the oxygen atoms of the lignocellulosic cluster. The loss of lignocellulose-metal clusters by ruminants is responsible for a substantial waste of nutrients, which is a significant problem in animal science. Moreover, the chemical structure of these relevant supramolecular systems is poorly understood. In the present review, we discussed this topic in detail in reference to relevant literature from the chemical and animal sciences in order to analyze the perspectives associated with the improvement of nutritional absorption from feed resources by ruminants.

The present study was carried out with the objective to evaluate the productive and qualitative characteristics of forages produced in systems of intercropping of corn, brachiaria grass and different leguminous plants. Productivity, bromatological composition and the fermentative profile of the silages from the following treatments were evaluated: corn in exclusive cultivation (CEC); intercropping of corn with brachiaria grass (CB); intercropping of corn, brachiaria grass and Calopogonium mucunoides (CBCal); intercropping of corn, brachiaria grass and Macrotyloma axillare (CBMac); and intercropping of corn, brachiaria grass and Stylozanthes capitata (CBSty). The experimental design utilized was completely randomized. For each type of cultivation, five plots or replications of three linear meters were harvested, and the material was separated. The variables assessed were: dry matter productivity per area; dry matter productivity of corn per area; crude protein production per area and productivity of total digestible nutrients per area. The material originated from the cultures was ensiled, with dry matter between 28 and 32%. After, the material was placed and compacted appropriately in bucket silos. A sample was collected from each replication for determination of the contents of DM, crude protein (CP), ether extract (EE), lignin, neutral and acid detergent fibers (NDF and ADF) and TDN. A fraction of the sample of silages from each treatment was compressed for extraction of the juice and determination of the silage quality. There was difference between the forms of cultivation for the dry matter production per hectare. The CEC with production of 11920.1 kg DM/ha did not differ from CB (8997.41 kg DM/ha) or CBCal (10452.10 kg DM/ha); however, it was superior to CBMac (8429.75 kg DM/ha) and to CBSty (8164.83 kg DM/ha). The contents of DM, CP, NDF, ADF, lignin and TDN did not differ between the silages from the different treatments. All the silages presented good quality with good fermentation patterns

Com o objetivo de estudar o comportamento produtivo do consórcio capim-braquiária e milho, foram avaliadas as características bromatológicas da planta inteira e das frações folha e colmo do capim-braquiária produzido de diferentes arranjos de semeadura. Avaliaram-se as produções de matéria seca (MS), proteína bruta (PB) e nutrientes digestíveis totais (NDT) por área e os teores de PB, proteína bruta digestível (PBD), proteína insolúvel em detergente neutro (PIDN), fibra em detergente neutro (FDN), lignina (LIG) carboidratos não-fibrosos (CNF) e NDT na MS da forrageira e a relação folha:colmo (F:C) em diferentes arranjos de semeadura e idades das culturas. Os arranjos de semeadura testados foram: duas fileiras do capim-braquiária nas entrelinhas do milho; semeadura a lanço do capim-braquiária nas entrelinhas do milho; uma fileira do capim-braquiária na mesma fileira do milho; uma fileira do capim-braquiária nas entrelinhas do milho; capim-braquiária em cultivo exclusivo e milho em cultivo exclusivo. O efeito da idade das culturas foi avaliado em amostras de plantas colhidas aos 128, 141, 174 e 199 dias após o plantio. As maiores produções de MS, PBD e de NDT por hectare foram obtidas com o capim-braquiária em cultivo exclusivo. Durante o período em que o sombreamento da cultura do milho sobre o dossel do capim-braquiária foi mais intenso, a relação folha:colmo do capim-braquiária em consórcio foi menor que a do capim cultivado na forma exclusiva. As forrageiras oriundas dos arranjos com maior sombreamento (capim-braquiária semeado a lanço nas entrelinhas do milho e uma fileira de capim-braquiária na mesma fileira do milho) foram menos produtivas e apresentaram maiores teores de PB na MS. Em média, a fração folha apresentou maiores teores de PB e menores teores de FDN e lignina em comparação à fração colmo, independentemente do arranjo de semeadura. O consórcio capim-braquiária e milho não influenciou os teores de lignina, carboidratos não-fibrosos e nutrientes digestíveis totais na matéria seca do capim-braquiária, no entanto, a idade teve efeito sobre essas variáveis. A produtividade do milho não foi afetada pelo consórcio em nenhum dos arranjos.

The present study evaluates the efficiency of different sulfur sources for ruminant nutrition. The fiber digestibility and the amino acid profile were analyzed in the duodenal digesta of crossbred steers fed Brachiaria dictyoneura hay. The sources utilized were elemental sulfur (ES70S), elemental sulfur (ES98S); calcium sulfate in hydrated (HCS), CaSO4.2H₂O, and anhydrous (ACS), CaSO₄, forms; and ammonium sulfate (AS), (NH₄)₂SO₄, keeping a nitrogen:sulfur ratio of 11:1. The iso-protein supplements had 50% of protein in the total dry matter (DM). Five Holstein × Zebu steers, which were fistulated in the rumen and abomasum, were distributed in a 5 × 5 Latin square. The different sulfur sources in the supplement did not affect any of the evaluated nutritional factors, such as intake of hay dry matter and protein supplement, crude protein (CP), neutral detergent fiber corrected for ash and protein (NDFap), organic matter (OM), non-fibrous carbohydrate (NFC), ether extract (EE), total digestible nutrients (TDN), NDFap and CP digestibility coefficients, ruminal pH, and ruminal ammonia concentration. The concentrations of amino acids available in the abomasal digesta did not differ significantly in the tested diets. The sulfur sources evaluated in the present study are suitable as supplement for cattle, and their employment may be important to avoid environmental contaminations.

Nesta pesquisa, o objetivo foi avaliar as diferenças entre silagens de culturas exclusivas ou do consórcio de milho e capim-braquiária, além de dois arranjos de semeadura do consórcio (duas fileiras de capim-braquiária nas entrelinhas do milho; e semeadura de capim-braquiária a lanço nas entrelinhas do milho). Avaliaram-se as produções de matéria seca (MS), proteína bruta (PB) e nutrientes digestíveis totais (NDT) por área e as características qualitativas das silagens (teores de PB, NDT, FDN, lignina e carboidratos não-fibrosos, nitrogênio amoniacal, ácidos butírico e lático e o pH). O milho em cultivo exclusivo, semeadura de duas fileiras do capim-braquiária nas entrelinhas do milho e semeadura do capim-braquiária a lanço nas entrelinhas do milho não diferiram com relação à produção de MS, PB e NDT, e nem com relação a variáveis qualitativas como teores de PB, NDT, FDN, lignina, pH, nitrogênio amoniacal, ácidos lático e butírico na MS das silagens, mostrando-se melhores desempenhos que o capim-braquiária em cultivo exclusivo quanto a essas variáveis. Porém, a recuperação do dossel forrageiro na área, após a colheita do material, foi mais rápida no arranjo com duas fileiras do capim-braquiária nas entrelinhas do milho.

The objective of this study was to evaluate the performance of F1 (Holstein × Zebu) cows in lactation according to different levels of substitution of soybean meal for a protein equivalent non-protein nitrogen originated from slow-release urea (SRU). Eight F1 (Holstein × Zebu) cows in the first third of lactation, with an average milk yield of 12.7 kg (±3.1 kg)/day and a live weight of 552 kg (±30 kg), were used. The experimental design was composed of two simultaneous 4 × 4 Latin squares, with the following treatments: 100% soybean meal and 0% SRU; 66% soybean meal and 34% SRU; 34% soybean meal and 66% SRU; and 0% soybean meal and 100% SRU. Sorghum silage, used as roughage, was supplied together with the concentrate. Feed intake and digestibility as well as milk yield and milk composition were measured. The obtained data were subjected to analysis of variance, adopting a 5% probability level. No intake variable showed significant differences among the treatments, and the mean values for the intakes of dry matter (DM), crude protein (CP) and neutral detergent fiber (NDF) were 18.35 2.62 and 5.85 kg/day, respectively. The results for apparent digestibility also did not show differences among treatments, with DM, CP and NDF averaging 58.16, 58.64 and 36.21%, respectively. Milk yield and composition were similar among the treatments. The average 4%-fat-corrected milk yield was 13.39 kg/animal day. Intake, digestibility and milk yield and composition variables are not changed according to the substitution of the soy protein for slow-release urea. Thus, for average-milk-yield crossbred.animals, this substitution depends on economic variables only.