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

Piet Monegi; Ntuthuko Raphael Mkhize; Purity Thobekile Masondo; Khanyisile Rebecca Mbatha; Dibungi Luseba; Julius Tlou Tjelele

doi:10.3390/ani13223509

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

Animals (Basel). 2023 Nov 14;13(22):3509. doi: 10.3390/ani13223509.

Authors

Piet Monegi^{1

2}, Ntuthuko Raphael Mkhize^{1

3}, Purity Thobekile Masondo⁴, Khanyisile Rebecca Mbatha², Dibungi Luseba⁴, Julius Tlou Tjelele¹

Affiliations

¹ Agricultural Research Council, Animal Production, Range and Forage Sciences, Irene, Pretoria 0062, South Africa.
² Department of Agriculture and Animal Health, University of South Africa, Florida, Roodepoort 1709, South Africa.
³ Animal and Poultry Science, School of Agriculture, Earth and Environmental Sciences, University of KwaZulu-Natal, Scottsville, Pietermaritzburg 3209, South Africa.
⁴ Department of Animal Science, Faculty of Science, Tshwane University of Technology, Staatsartillerie Road, Pretoria West, Pretoria 0001, South Africa.

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.

Keywords: feed intake; macronutrients; nutrient–toxin interactions; secondary compounds.

Grants and funding

99405/National Research Foundation