Data/hora: 05/06/2024 00:02:19

Biblioteca(s): 	Embrapa Pantanal.	
Data corrente: 	25/02/1999	
Data da última atualização: 	23/09/2013	
Autoria: 	THEURER, C. B.; LESPERANCE, A. L.; WALLACE, J. D.; DENHAM, A. H.; CLANTON, D. C.; PRICE, D. A.; HARRIS, L. E.	
Título: 	Botanical composition of the diet of livestock grazing native ranges.	
Ano de publicação: 	1980	
Fonte/Imprenta: 	Arizona Agricultural Experiment Station Tecnical Bulletin, n.233, p.1-19, [ca.1980].	
Idioma: 	Inglês	
Conteúdo: 	Selective grazing by livestock markedly alters nutrient and botanical composition of forage ingested as compared to herbage available on native rangelands. Thus, direct pasture analyses are inadequate for determining nutrient or botanical composition of the diet of livestock grazing native grassland. The use of esophageal or rumen-fistulated animals appears to be the most accurate method for obtaining representiative samples of the grazing animal's diet even though species identification of masticated forage samples is tedious and time consuming and considerable variation exists between animals in dietary preferences. Under restricted circumstances, close visual observations (bite-count method) may provide a fairly reliable estimate of botanical composition for grazing cattle or sheep. Such restrictions include (1) relatively simple species composition of grazing area, (2) thorough familiarity of species available in their different growth stages and (3) gentle experimental animals. Various techniques (visual, manual separation, microhistological and microscope point) have been developed to estimate botanical composition of masticated forages or fecal droppings. The most promising methods appear to be microhistological and microscope point techniques. Species composition of masticated forage samples may be quantitatively determined by microscope techniques. the accuracy of both techniques in estimating percentage species composition of clipped forage mixtures has been demonstrated. The reliability and accuracy of the microscope point technique has been demonstrated with masticated forage samples, but not with the microhistological technique. Relating microscope points observed to volume of plant species in fistula samples appears to be a more reliable and accurate technique than directly relating microscope points observed to percentage weight of the species or the use of regression equations to relate points to weight. Analysis of fecal samples to estimate botanical composition of the diet has yielded inconsistent results in comparison to esophageal samples. It appears that fecal samples can be used to estimate many key dietary species but that their use may greatly under estimate forb content of the diet. Botanical composition of the diet may vary considerably within or among growing seasons. Grasses are usually the most important constituent in cattle diets, even on predominantly browse or shrub type ranges. Forbs, when available, are the major component of sheep diets. Browse seldom exceeds 20% of cattle or sheep diets, unless grass and forb availability is extremely limited. Cattle and sheep often selectively graze plant parts or plant species higher in protein content than the principal species in the available herbage. Leaf parts consistently dominate dietary components of cattle and sheep grazing native ranges. There is a definite need to understand more clearly the reasons why livestock select certain species over others so that our vast rangeland resources can be more effectively utilized for meat animal production.	
Palavras-Chave: 	Native ranges.	
Thesagro: 	Composição Botânica; Dieta; Gado; Pastagem Nativa.	
Thesaurus Nal: 	botanical composition; diet.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Pantanal (CPAP)	
Exemplares: 	CPAP - (36736-1) - ADC - SP - -- - SP3621 -  - 3621 - DIS