RESUMO -Foram conduzidos dois ensaios para medir os fluxos portal e visceral total de metabólitos em ovinos (peso vivo (PV) médio de 35 ± 3 kg) recebendo feno de capim-arroz (Echinochloa sp.) cortado aos 32, 46, 72 ou 90 dias de rebrota.Um dos ensaios foi realizado em quadrado latino 4 × 4 (ensaio 1) para avaliação dos quatro fenos e outro em quadrado latino 3 × 3 (ensaio 2), sem o feno do capim cortado aos 32 dias de rebrota. Os animais foram implantados com cateteres permanentes nas veias mesentérica e hepática. Sangue arterial foi acessado através de cateteres temporários na carótida. O fluxo de sangue portal e visceral foi estimado com base na diluição de paraminohipurato infundido continuamente em uma veia mesentérica.Na refeição prévia às amostragens, o consumo de matéria orgânica (MO) total e digestível não foi afetado, mas o consumo de nitrogênio total e digestível diminuiu linearmente com o aumento da idade de rebrota do capim-arroz em ambos os ensaios. fed rice-grass (Echinochloa sp.) hay cut at 32, 46, 72 or 96 days of regrowth age, two assays were carried out. One of them was a 4 × 4 Latin Square experiment (Assay 1) where the four hays were evaluated and the other was a 3 × 3 Latin square experiment (Assay 2) that did not include the 32-day hay. Animals were surgically implanted with permanent catheters into mesenteric and hepatic blood vessels. Arterial blood was sampled using temporary catheters into carotid artery. Portal and visceral blood flow was estimated based on continuous infusion of paraminohippurate in a mesenteric vein. On the sampling day, total and digestible organic matter (OM) intakes were not affected, but total and digestible N intakes decreased linearly with the increased forage regrowth age in both assays. The portal and visceral blood flow, net visceral flux of glucose, urea and amino acids and the net portal flux of glucose and urea were not affected by forage regrowth age. The net portal flux of amino acids and ammonia which was markedly higher in lambs fed 46-day hay and that ingested more digestible N.Most nutrients absorbed by lambs fed rice-grass hay were metabolized by visceral tissues such as peripheral availability of amino acids and glucose only account to a small proportion of N and OM intake. In general, the visceral metabolism of lambs is not clearly affected by forage regrowth age.Key Words: amino acids, ammonia, Echinochloa sp., glucose, metabolism, urea IntroduçãoO desempenho dos ruminantes é altamente dependente do consumo de matéria orgânica (MO) digestível e da eficiência como os nutrientes absorvidos são utilizados pelos animais. No entanto, a regulação da disponibilidade de nutrientes para os tecidos periféricos é afetada pelo metabolismo visceral. O sistema visceral é representado pelos tecidos drenados pela veia porta (trato gastrintestinal, gordura mesentérica, pâncreas e baço) mais o fígado.
The changes in chemical composition of hay of kikuyu grass (Pennisetum clandestinum) harvested at 50, 70 and 90 d of regrowth, and its effect on intake, digestibility, fermentation and microbial protein synthesis in the rumen (Experiment 1) and oxygen uptake by portaldrained viscera (PDV) (Experiment 2) were evaluated. The experiments were carried out with Polwarth · Texel crossbreed lambs with a mean live weight (s.e.m.) of 35(3AE0) kg housed in metabolic cages. Organic matter (OM), neutral-detergent fibre (NDF) and nitrogen (N) intake, as well as rumen ammonia-N concentration, decreased linearly with age of regrowth (P < 0AE05). Acid-detergent fibre (ADF) and indigestible NDF intakes were similar for all treatments. Apparent digestibility of organic matter (OM), NDF and N, as well as true digestibility of OM, microbial protein synthesis in the rumen, N retention, pH of rumen fluid and sugars, amino acids and peptide concentrations in rumen fluid were similar for all treatments. Age of regrowth also did not affect the kinetics of passage of the particulate phase through the digestive tract nor oxygen uptake by PDV. Heat production by PDV represented an average of 0AE039 of digestible energy (DE) intake. Increasing the age of regrowth of kikuyu grass from 50 to 90 d did not affect digestibility nor the efficiency of DE use by PDV tissues of lambs but it reduced the nutritive value of the hay due to a lower intake of OM. Intake of hay appeared to be most limited by the ADF and indigestible NDF concentrations of the hay.
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