Holzer, Z., Agricultural Research Organization, Newe-Ya ar Experiment Station, PO Haifa 31-999, Israel
Drori, D., Agricultural Research Organization, Newe-Ya ar Experiment Station, PO Haifa 31-999, Israel
Brosh, A., Agricultural Research Organization, Newe-Ya ar Experiment Station, PO Haifa 31-999, Israel
Levy, D., Agricultural Research Organization, Newe-Ya ar Experiment Station, PO Haifa 31-999, Israel

The mineral balance of male calves given neutralized (with HC1) and unneutralized 35 g NaOH per kg treated wheat straw (WS), was determined in a digestibility trial in which WS was offered at inclusion levels of 300, 500 and 700 g/kg diet. The ratio of apparently retained sodium (Na) and potassium (K) increased with increasing proportion of straw in the diet and was lower on neutralized straw diets. The effect of supplementation with 3 and 6 g K per kg diet dry matter in a diet comprising approximately 500 g/kg of 35 g NaOH per kg treated WS, on performance, mineral status and acidbase balance was examined in a growth trial with 56 Israeli-Friesian male calves. The animals on the untreated WS diet had significantly (P < 0·05) less fat in the large depots and lower fat trim of carcass than did animals on the treated WS diets. No other differences in performance were significant. Ammonia concentration in rumen liquor and urea in blood were lower in the animals given alkali-treated WS. The concentrations of Na, K and chlorine in blood serum of the experimental animals were not affected by the treatment. The data on Na, K and magnesium (Mg) in muscle show depletion of Na and K and a trend towards a decrease in Mg concentration. K supplementation reduced the extent of depletion of Na and K. In bone, only Na was affected by the feeding of alkali-treated WS, the pattern being the same as in the muscle. The blood acid-base balance of the experimental animals was not significantly affected by treatments. The values of pH, actual bicarbonate and pCO2 of the animals given 35 g/kg alkali-treated WS indicate mild alkalosis in those animals. This alkalotic state did not affect performance. It appears that there is no Na loading problem which might interfere with growth. © 1991, British Society of Animal Science. All rights reserved.