M.R. AL-MASRI

Atomic Energy Commission, Damascus, Syria

Abstract

A field experiment was carried out in 2 consecutive years to study the changes in the values of cell wall constituents and the digestibility of some nutrients in forages subjected to 2 harvest regimens. Vetch (Vicia sativa) and barley (Hordeum vulgare) were grown in a mixed culture and a monoculture system under rainfed conditions in a semi-arid region. Plants were either harvested at 3 sequential times (H1, H2 and H3; 115, 146 and 167 d after planting), or harvested once (H0; 167 d after planting), at physiological maturity. The results indicated that the quality of harvested material declined from the first to the second of the sequential harvests for all cropping systems, with minimal change between the second and third harvests. Material harvested only once at physiological maturity consistently had higher levels of crude fibre and cell wall constituents than material from any of the sequential harvests. In vitro organic matter digestibility and digestible energy values were lower in later harvests than in the first of the sequential harvests. In vitro digestible crude protein (IVDCP) values were consistently higher for vetch than for barley, declining progressively from H1 to H2, H3 and H0 in the case of vetch. With barley, IVDCP values for H3 were significantly higher than for other harvests. A single cut at physiological maturity yielded more digestible energy and protein/ha than serial cuts. The mixed cropping of vetch and barley produced much more forage than barley alone and the quality of the material was much higher than that from barley alone.