The increasing rate of woody plant encroachment in grasslands or savannas remains a challenge to livestock farmers. The causes and control measures of woody plant encroachment are of common interest, especially where it negatively affects the objectives of an agricultural enterprise. The objectives of this study were to determine the effects of gut passage (goats, cattle), dung (nutrients), fire, grass competition and trampling on establishment of A. nilotica and D. cinerea seedlings. Germination trials were subjected to the following treatments: 1) seed passage through the gut of cattle and goats and unpassed/ untreated seeds (i.e. not ingested), 2) dung and control (no dung), 3) grass and control (mowed grass), 4) fire and control (no fire), 5) trampling and control (no trampling). The interaction of animal species, grass and fire had an effect on seedling recruitment (P < 0.0052). Seeds retrieved from goats and planted with no grass and with fire (6.81% ± 0.33) had a significant effect on seedling recruitment than seeds retrieved from goats and planted with grass and no fire (2.98% ± 0.33). Significantly more D. cinerea and A. nilotica seeds germinated following seed ingestion by goats (3.59% ± 0.16) than cattle (1.93% ± 0.09) and control or untreated seeds (1.69% ± 0.11). Less dense grass cover, which resulted in reduced grass competition with tree seedlings for light, space and water, and improved seed scarification due to gut passage were vital for emergence and recruitment of Acacia seedlings. These results will contribute considerably to the understanding of the recruitment phase of woody plant encroachment.

Goats can act as dispersal agents by consuming seed pods of woody plants and dispersing the seeds in feces. Concerns that goats might thereby promote encroachment by woody plant species such as Dichrostachys cinerea (sickle bush) have not been addressed. The objective of this study was to determine the recovery rate and germination of D. cinerea seeds that pass through the digestive tract of goats. We hypothesized that 1) D. cinerea seeds will remain intact and viable after passage through the digestive tract of goats and that 2) D. cinerea seeds will be scarified by such passage, resulting in improved germination percentages. The first trial measured the recovery rate of 1 500 D. cinerea seeds that were consumed by indigenous goats, either voluntarily after mixing them with feed pellets (mixed) or by force-feeding (gavaged). Seed recovery for the gavaged treatment (32.7%) was significantly higher than for the mixed treatment (9.9%; P , 0.001). The second trial determined germination percentages of D. cinerea seeds recovered from the feces of animals in the two treatments of the first trial as well as scarified and control (untreated) seeds. The germination percentage of mechanically scarified seeds (53.0%) was significantly higher than that of seeds that passed through the digestive system in the mixed (35.5%) or gavaged (31.2%) treatments or were untreated (19.0%; P , 0.001). Seeds that passed through the digestive tract (mixed and gavaged treatments) had a significantly higher germination percentage than untreated seeds (P , 0.001). A nonnegligible proportion of D. cinerea seeds remained intact after ingestive chewing and passage through the digestive system, and their germination percentage was even elevated. This suggests that goats have a potential to facilitate woody plant encroachment through dispersal of viable and scarified seeds. ResumenLas cabras pueden actuar como agentes dispersores de semillas de plantas leñ osas al consumir las vainas de estas. No se ha discutido la preocupación de que las cabras de este modo podrían propiciar la invasión de plantas leñ osas tales como Dichrostachys cinerea (arbusto hoz). El objetivo de este estudio fue determinar la tasa de recuperación y germinación de semillas de D. cinérea que pasan a trave´s del tracto digestivo de las cabras. Planteamos la hipótesis de 1) Las semillas de D. cinerea permanecerán intactas y viables despue´s de haber pasado por el tracto digestivo de las cabras, y 2) Las semillas de D. cinérea serán escarificadas por tal pasaje resultando, en el mejoramiento de el porcentaje de germinación. El primer experimento se midió la tasa de recuperación de 1 500 semillas de D. cine´rea que fueron consumidas por cabras criollas ya sea de manera voluntaria o después de mezclarlas con bolas de alimento o por alimentación forzada. La recuperación de semillas por medio del tratamiento de alimentación forzada (32.7%) fue significativamente mayor que la del tratamiento de la mezcla (9.9%; P , 0.001). El segundo experimento determino el porcentaje de germinació...