Holzer, Z., Agricultural Research Organization, Newe Ya'ar Regional Experiment Station, Haifa, Israel
Tagari, H., Agricultural Research Organization, Newe Ya'ar Regional Experiment Station, Haifa, Israel, The Hebrew University, Faculty of Agriculture, Rehovot, Israel
Levy, J.D., Agricultural Research Organization, Newe Ya'ar Regional Experiment Station, Haifa, Israel
Volcani, R., Agricultural Research Organization, Newe Ya'ar Regional Experiment Station, Haifa, Israel, The Hebrew University, Faculty of Agriculture, Rehovot, Israel

Two levels of roughage in a complete fattening diet (25 and 45%), two particle sizes of the roughage component (6 and 12 mm diameter of sieve holes), and three levels of moisture (10, 50 and 75%) were examined in a feeding trial designed in a 2 × 2 × 3 factorial arrangement. Intact male Israeli-Friesian cattle were grown from an initial weight of about 300 kg to a slaughter weight of about 520 kg. Live-weight gains were 956, 1080 and 1025 g/day, and carcass gains were 516, 584 and 563 g/day for diet moisture contents of 10, 50 and 75%, respectively. The roughage content of the diet and particle size had no significant effects. Efficiency of conversion of metabolizable energy into live weight or carcass weight was directly related to the moisture content of the diet. Weight of gut fill was directly related to the roughage content of the diet, to diet particle size and to moisture content. Animals on the moist diets had less carcass fat but more depot fat than those on the dry ration. Total volatile fatty acid concentration in the rumen liquor of animals fed on moist diets was significantly higher, and the acetate: propionate ratio was significantly lower than that of animals on the dry control diet. The improvement in performance of animals fed on moist diets may be attributed to the accumulated effect of three factors, even though the effect of each separately may not be great: (a) Increased dry-matter intake; (b) Improvement in digestibility; and (c) Increased concentration of propionic acid and consequent reduction of the acetate: propionate ratio. © 1976, British Society of Animal Science. All rights reserved.