Citation: Pepeta, B.N.; Moyo, M.; Adejoro, F.A.; Hassen, A.; Nsahlai, I.V. Techniques Used to Determine Botanical Composition, Intake, and Digestibility of Forages by Ruminants. Agronomy 2022, 12, 2456. https://doi.org/10.3390/ agronomy12102456 Academic Editor: Kevin F. M. Reed Received: 19 August 2022 Accepted: 7 October 2022 Published: 10 October 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). agronomy Review Techniques Used to Determine Botanical Composition, Intake, and Digestibility of Forages by Ruminants Bulelani Nangamso Pepeta 1,2 , Mehluli Moyo 2 , Festus Adeyemi Adejoro 1,3 , Abubeker Hassen 1, * and Ignatius Verla Nsahlai 2, * 1 Department of Animal Science, University of Pretoria, Private bag X20, Hatfield, Pretoria 0028, South Africa 2 Animal and Poultry Science, School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, Private Bag X01, Pietermaritzburg 3209, South Africa 3 School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, Leicestershire, UK * Correspondence: abubeker.hassen@up.ac.za (A.H.); nsahlaii@ukzn.ac.za (I.V.N.) Abstract: The botanical and chemical composition of diets consumed by ruminants is different from the composition of plant species available in the rangeland or pastures on which they graze. Exploring alternative and improving existing methods of estimating botanical composition (diet selection) is imperative in advancing sustainable feeding practices in extensive production systems. The ability to predict the intake and digestibility of the diet consumed is important in designing grazing management for different feeding systems as well as supplementation strategies. This facilitates the efficient use of feed resources for optimal animal performance. This review assesses the merits, limitations, and potential advancements in techniques used to estimate botanical composition, forage intake, and digestibility in ruminants. Supplements containing sufficient quantity and identifiable n-alkanes can be used to determine the total forage intake in grazing ruminants without dosing the animals with synthetic even-numbered n-alkanes. When the botanical composition, intake, and digestibility of diet are estimated using internal markers, the results should be validated with those of faecal near-infrared reflectance spectroscopy (NIRS) or plant cuticular compounds to enhance the prediction accuracy. This should be done to determine the degree of error in the use of internal markers. Conclusively, the use of internal markers with automated solver routine software is a prudent approach to predicting botanical composition due to the analytical ease of the markers involved and the associated model assumptions. Keywords: diet selection; grasslands; internal markers; NIRS; plant cuticular compounds; solver routine software 1. Introduction Natural grasslands and crop residues are the major feed resources for ruminants across Sub-Saharan Africa [1]. Although the nutritional value of feed resources is highest during the wet season, it varies widely across seasons, and often, the nutrients available are inade- quate to sustain optimal animal performance [2]. Forages selected by grazing ruminants are usually different in composition and quality compared to the average available within the rangeland. Therefore, the knowledge of the nutritive value and intake of selected dietary components is important for managing different feeding systems and facilitates the choice and quantity of supplement feed required by the animals [3]. The quantity and quality of herbage selected and consumed in rangelands are influ- enced by several factors, which include but are not limited to the nutritional status and post-ingestive feedback of grazing herbivores, the presence of hair on and leaf size of the plant species, forage availability, as well as the botanical composition of the pasture and furthermore, differences in plant distribution, presence of chemicals as herbivory tolerance mechanism, and the number of plant species [4]. The magnitude of the influence caused Agronomy 2022, 12, 2456. https://doi.org/10.3390/agronomy12102456 https://www.mdpi.com/journal/agronomy