Holzer, Z., Agricultural Research Organization, Institute of Animal Science, Newe Ya'ar Experiment Station, PO Haifa, 31-999, Israel
Levy, D., Agricultural Research Organization, Institute of Animal Science, Newe Ya'ar Experiment Station, PO Haifa, 31-999, Israel
Samuel, V., Agricultural Research Organization, Institute of Animal Science, Newe Ya'ar Experiment Station, PO Haifa, 31-999, Israel
Drori, D., Agricultural Research Organization, Institute of Animal Science, Newe Ya'ar Experiment Station, PO Haifa, 31-999, Israel

Four groups of 12 beef heifers were each given either straw treated with 35 g sodium hydroxide per kg (TS) or untreated straw (US) and were either supplemented with 35 mg monensin per kg (Ms) or not supplemented (Ns). The diet consisted of approximately 0·40 of a concentrate mixture that contained 12·8 MJ metabolizable energy and 243 g crude protein per kg dry matter, and 0·60 straw. Feeding was ad libitum. The average initial weight of the heifers was 207·2 kg and the experiment lasted 86 days. The average dry matter consumed was 2·3g/kg live weight. Average daily gain (±s.e.) was 505±31·6, 371±33·8, 380±26·2 and 257±32·7g/day for treatment groups TS-Ms, TS-Ns, US-Ms and US-Ns, respectively. These findings indicate that monensin may counteract some ill-effects of diets high in sodium hydroxide-treated straw and thus further research is warranted. © 1982, British Society of Animal Science. All rights reserved.