In the eastern Democratic Republic of the Congo (DRC), the integrated smallholder crop-livestock system is the dominant form of agricultural production (Maass et al., 2012). Its production is the primary source of food and income for rural households. Its expansion is thus desirable in alleviating poverty and enhancing food security. Smallholder dairying is particularly important as milk produced provides nutrients and income to the households. Despite its importance, feed quantity and quality are inadequate and rarely meet the nutrient requirements of lactating crossbred cows, especially during the dry season (Maleko et al., 2022). This is further exacerbated by the effects of rapid human population growth and the subsequent reduction in land available for pasture production, as well as climate change, negatively impacting pasture productivity shortage (Mugumaarhahama et al., 2021).
Consequently, inadequate nutrition of crossbred cows often culminates in substantial economic losses to the farmers due to low weight gain or milk production rates, poor body condition, reduced productive and reproductive performance, and susceptibility to pests and disease infestations Gebreyowhans and Zegeye, 2018). Alternative conventional supplements used by smallholder farmers, such as concentrates and agro-industrial by-products, are not readily available and, when available, are costly for most resource-poor smallholder farmers (Maass et al., 2012; Mutwedu et al., 2022). In response to this challenge, there is a need to provide alternative cheap-to-produce and locally available feed resources to supplement the feeds produced on smallholder farms.
Trees and shrubs are instrumental in delivering the triple-win strategy of enhancing livestock productivity, mitigating harsh climates in pastoral and agro-pastoral areas, and improving food security and rural livelihoods (Henry et al., 2018). This strategy is attributed to their multiple roles in contributing to the welfare of the cattle farming communities; and mitigating climate change through biological nitrogen fixation, carbon sequestration, and reduction of greenhouse gas emissions (Pello et al., 2021). Trees and shrubs are highly valued because of their high volume of biomass production, nutritional value, and adaptation to poor soil and harsh climatic conditions (Osuga et al., 2011, Barwani et al., 2022). Osuga et al. (2008) reported that tender shoots, leaves, pods, twigs, and fruits of trees and shrubs are rich in proteins, vitamins, and minerals compared to natural pastures. Integrating trees and shrubs into animal diets improves palatability, feed intake, digestibility, and lactation performance (Derero and Kitaw, 2018; Osuga et al., 2011). Although the benefits of trees and shrubs such as Leucaena (Leucaena leucocephala (Lam.) De Wit) and cassava (Manihot esculenta Grantz) are well known and used by smallholder farmers in the tropics (Franzel et al., 2014; Wanapat et al., 2003), the studies focusing on the utilisation of Leucaena and cassava as cattle feeds, notably in the eastern DRC context, remain a significant literature gap.
Leucaena is a plant that potentially improves soil fertility, introduced to eastern DRC 20 years ago. It is mostly used in soil fertility management as a source of green manure. The plant has the propriety of colonizing a wide range of soils due to its early year-round flowering and fruiting, abundant seed production, self-fertility, seed coat, and ability to regrow after burning or on being cut. These characteristics make the plant survive and multiply on farms, thus availing its resources all year round, which can be used in supplementing ruminants. Leucaena leaves are highly palatable, digestible (50–70%), and nutritious (22–40% of CP) (Katunga et al., 2014, Barwani et al., 2022). These good nutritional characteristics make the leaves suitable for supplementation in ruminant diets and have been shown to increase milk production, fat, and protein contents (De Angelis et al., 2021). Besides the Leucaena trees, cassava is also grown in the eastern DRC for its roots which constitute a staple food for more than 70% of the population, and its leaves are consumed throughout the year as a vegetable (Munyahali et al., 2017). However, for household consumption, most farmers (80%) cut only the young leaves without petiole to avoid fibrous stuff, leaving the other parts of the leaves as mulch or lost during root harvest (Munyahali et al., 2017). Wanapat et al. (2011) reported that cassava leaves at any stage of growth can still have good levels of protein (> 14%), vitamins, minerals, low condensed tannins (1.5–4%); and can be used as a source of nutrients to dairy animals after removing the hydrocyanic acid (HCN) content. However, the information about the nutritional and feeding characterisation of Leucaena and cassava leaves is inadequately addressed, which constitutes an obstacle to its utilisation in feeding the crossbred cows in the study region. Furthermore, scientifically generated information is useful in developing livestock feeds and feeding management policies. Therefore, this study investigated the effects of supplementing Guatemala grass with dried Leucaena and cassava leaves as nitrogen sources on feed intake, milk production, and milk composition of lactating Holstein Friesian x Ankole crossbred cows in the eastern DRC. The study findings would enable policymakers and farmers to design appropriate intervention strategies to improve livestock productivity and serve as a benchmark for future research.