Evaluation of mineral status in feed resources and effects of supplementation to farm animals in northern Ghana

Abstract

A survey was conducted on the mineral concentration of available feed resources at three locations in the northern Guinea Savannah Zone between 1992 and 1997. The feeds were categorized into cereal crop residues, legume crop residues, grass forages, legume forages, and legume browse and agro-industrial by-products. Experiments carried out involved balanced groups (age, sex and breed) of sheep using some of such forages and with or without access to commercial mineral licks. The animals were monitored for any changes in their live weight performance. Dry matter (DM) intake by sheep of supplementary fed rice straw was also determined. Average concentration of calcium (Ca) in the feed samples surveyed was highest in the browse forages (1.21%) and legume forages (1.13%). The lowest was recorded for the agroindustrial by-product (0.20%). However, phosphorus (P) was highest (1.6%) in the browse forages compared to that recorded in the cereal crop residues (0.06%). Copper (Cu) levels of 2.57, 7.1, and 7.6 mg kg-1 DM were observed for cereal forages, legume crop residues, legume forages and browse forages, respectively. The cereal crop residues contained 40.7 mg kg-1 of zinc (Zn) compared to 24.33 mg kg-1 in the browse forages. Manganese (Mn) concentration was 97.5, 143.3, 163.7, 231.4, 271.2, and 314.4 mg kg-1 DM for agro-industrial by-products, browse forages, grass forages, legume crop residues, forage legumes, and cereal crop residues in that order. Sheep exposed to commercial mineral lick consumed 4.7-8.0 g head-1 day-1. However, total supplementary rice straw intake was 7.0 per cent lower in animals on mineral lick. Sheep in the study generally consumed 13.5 per cent more of straw in the dry season (November-February) compared to the wet season (July -October). Sheep on natural grazing in the dry season and supplemented with rice straw with or without mineral lick gained 65.5 and 63.7 g head-1 day-1, respectively. A significantly (P< 0.001) lower daily gain of 26.7 g head-1 was recorded for sheep grazing natural pasture without any form of supplementation.