Abstract 390

Laredo-C,-MA; Ardila-G,-A; Alvarez-V,-JG

Instituto Colombiano Agropecuario, Bogota, Colombia.

Revista-Instituto-Colombiano-Agropecuario. 1983, 18: 2, 105-113; 21 ref.

In field trials in 1981-2 at Valledupar, Panicum maximum cv. Guinea I, II and III and Dichanthium aristatum cv. Angleton were grazed by 3 and 0.5 dairy cattle/ha in the wet and dry seasons, resp. Av. daily milk yields were 3.5 l/cow in a 260-day lactation. The grasses were sampled monthly from the grazed areas. CP concn. were low (5.72-9.31%) throughout the period and differences were not significant. Av. Ca concn. was 0.43 and 0.44% in the dry and wet seasons, resp., and was sufficient for animal requirements. P concn. only supplied 60% of the animal requirements and there was significant seasonal variation. Mg concn. were 0.18-0.2%, which was deficient with respect to the high K concn. (1.36-1.69%). Av. S concn. was 0.09%, with significant seasonal variation, being greater in the wet than in the dry season in P. maximum cv. and greater in the dry season in D. aristatum. Fe concn. were high, ranging from 173 to 386 p.p.m. Mn concn. were also high; mean values were 152 and 134 p.p.m. in the dry and wet seasons, resp. Cu concn. were 35-50% of animal requirements. Zn was deficient throughout the year. Mineral supplements for cattle in this area should include P, Mg, S, Cu and Zn.