The potential of some sub-humid zone browse species as feed for ruminants

The overall objective of this study was to determine the most utilized browse species in the sub-humid zone in Burkina Faso, and to evaluate their potential as fodder for ruminants. The behaviour of sheep, goats and cattle was recorded on natural pasture using a direct observation method and farmers were interviewed concerning use of browse species. The phenological and chemical variations over the year were estimated through observations and collection of foliage samples every second week. The foliage biomass was evaluated using complete cutting and weighing. The nutritive value and the effect of feeding these foliages on growth performance were assessed in sheep using a completely randomised design. The browsing activity was about 25% of the total grazing time for all the animal species during the dry season. During the cool season the time spent browsing by goats (17%) was significantly higher than for sheep (7%) and cattle (5%). The plant species with the highest frequency of consumption by animals and most cited as fodder trees by farmers were Acacia dudgeoni Craib. ex Holl., Ficus gnaphalocarpa (Miq.) A. Rich, Dichrostachys cinerea (L.) Wight & Arn., Faidherbia albida A. Chevalier, Afzelia africana Sm. ex Pers., Khaya senegalensis (Desv.) A. Juss. and Pterocarpus erinaceus Poir. The foliage biomass per ha of the last three species differed significantly (0.3, 0.6 and 1.3 t dry matter (dm), respectively). The dm intake and apparent digestibility of dm for A. africana were the highest, 571 g/day and 582 g/kg, respectively. Significant relationships were found between the foliage biomass and the circumference of the crown for A. africana (R2=82%) and P. erinaceus (R2=81%). The growth rate was around 60 g/day when feeding a diet including A. africana and P. erinaceus, higher than with the diet with K. senegalensis (48 g/day). These browse species constitute an important source of nitrogen for domestic ruminants in sub-humid West Africa and should to be promoted in the agrosilvopastoral systems as a dry season fodder reserve and to avoid the risk of extinction.