Diet Mixing and Supplementation Present an Opportunity to Increase the Use of Encroaching Woody Plants by Goats

SIMPLE SUMMARY: Without strategies to increase the use of chemically defended trees as forage, feeding 9 billion people by 2050 becomes impossible. In response to the challenge of trees encroaching on grasslands and the growing demand for meat, this study conducted experiments to support sustainable solutions for future animal protein needs. The research focused on enhancing goat consumption of tannin-defended woody plants through supplementing their diets with nutrients and polyethylene glycol. It also explored the impact of diverse diet ingredients and plant species on goats’ intake of chemically defended woody plants. The results highlight the effectiveness of incorporating various plant species and nutrient-rich options in goat diets to help them consume chemically defended woody plants. This research provides valuable insights for sustainable livestock farming, enabling us to meet the increasing meat demand while conserving our evolving ecosystems. ABSTRACT: Along with the woody plant expansion that is predicted to continue at the expense of the grassy layer is the increasing societal demand for animal protein and livestock products. Unless concerted efforts by land users, ecologists, and animal scientists are made to increase the utilization of trees and shrubs as forage, it will be impossible to meet future demand for meat and meat products. We conducted two short-term pen experiments to determine the effects of (1) supplementation with polyethylene glycol (PEG-a polymer purported to bind and neutralize the negative effects of tannins), a high-protein source (soybean meal), and a high-energy source (yellow maize grain) and (2) diet mixing (single-species vs. multispecies diets) on the intake of condensed tannin-rich woody plants (i.e., Searsia lancea, S. pyroides, and Euclea crispa) by goats. While all three forage species were used in the diet mixing experiment (Exp. 2), only E. crispa was used in the supplementation experiment (Exp. 1). Supplementing goats with energy- and protein-rich sources significantly increased the intake of E. crispa (p < 0.05), 713.4 g ± 13.5 and 760 g ± 28.9, respectively, whereas those on the control diet maintained their intake at 540.32 g ± 11.2. Although PEG tended to increase the consumption of E. crispa by goats, the observed increase was not significant (p > 0.05) from that observed in other treatments. In the diet mixing experiment, goats offered a combination of all three forage species attained substantially higher dry matter intakes compared to the goats offered these species individually (p < 0.05). While longer-term field experiments are needed in the African savannas, we postulate from the current results that management strategies that provide animals with (1) a variety of species in the diet vs. monocultures and (2) a combination of nutrient-rich and tannin-rich species may improve the ability of goats to consume chemically defended woody plants.