Nutrient Contents of Major Food Plants Eaten by Cattle in the South Texas Plains

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Abstract
From May, 1975-Nov. 1977, whole plant samples of 6 native [Aristida roemeriana, Bouteloua repens, Brachiaria ciliatissima, Chloris cucullata, Eragrostis oxylepis and Paspalum setaceum] and 2 introduced grass species [Cenchrus ciliaris and Cynodon dactylon], and top pads of 1 browse (pricklypear cactus) species, Opuntia lindheimeri, were collected monthly; the samples were analyzed for crude protein (CP), P, Na, K, Ca, Mg contents and digestible energy (DC) to determine their nutritive value as range forage. Digestible energy, CP and P levels were deficient, especially in winter and early spring for lactating cows but were near to marginal for dry cows. All other elements, except Na, were present at amounts adequate to meet all cattle requirements. Na levels were low, but probably would not pose a problem if free choice salt was provided. Any deficiencies may be alleviated by cattle selection of higher quality plants, such as forbs and short-lived annual grasses. Pricklypear cactus had low levels of CP, P and Na but high levels of estimated DE (2900 K cal/kg); pricklypear cactus is high in soluble ash (20%) and, if expressed as in vitro digestible organic matter, DE is considerably reduced. Protein should be supplemented to lactating cows in winter and early spring while P probably should be supplemented all year.