Utilization of low quality roughages: effects of alkali treatment of wheat straw on intake by and growth rate of cattle, with and without a supplement of cotton-seed meal

Abstract

SUMMARYEffects of treating wheat straw with caustic soda solution and of providing a cottonseed meal supplement were studied with 40 Friesian heifers (280 kg live weight) in individual pens. Responses were measured in terms of food intake, growth rate and food conversion ratio.Wheat straw was coarsely-milled and fedad libitum, untreated (U) or alkali-treated (T); both types of straw were supplemented with urea and minerals. Half the animals on each type of straw were fed 500 g cotton-seed meal (C/day.Straw intake was higher with T than with U (P< 0·01) and unaffected by the cotton-seed meal supplement, being 4·53, 4·71, 6·58 and 6·56 kg/day on treatments U, UC, T and TC respectively. Alkali treatment and the cotton-seed meal supplement improved live-weight change (P< 0·001), being –6, 189, 334 and 495 g/day respectively.In vivodigestible organic matter in the dry matter, calculated from lignin ratios, was 59, 60, 64 and 64 respectively.Rumen VFA concentrations were significantly higher, molar proportions of acetic acid lower, propionic andn-butyrie acids higher in animals on T than on U. Plasma urea and rumen ammonia concentrations were lower on treatment T than on U.It was concluded that wheat straw which is coarsely-milled, NaOH-treated and sprayed with urea and minerals provides sufficient nutrients to allow cattle to grow and that additional gain obtained by feeding cotton-seed meal was predictable in terms of its energy contribution to the diet.