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

Abstract

From May 1975 to November 1977, whole plant samples of 6 native and 2 introduced grass species, and top pads of 1 browse (pricklypear cactus) species were collected monthly and analyzed for crude protein (CP), P, Na, K, Ca, Mg contents, and digestible energy (DE) 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. Sodium 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); however, pricklypear cactus is high in soluble ash (20%) and if expressed as in vitro digestible organic matter, DE is considerably reduced. These data suggest that protein should be supplemented to lactating cows in winter and early spring while P probably should be supplemented all year.