Nutrient intake, digestibility, and utilization in goats fed graded levels of hempseed cake finisher diets

Tropical Animal Health and Production (2024) 56:21 https://doi.org/10.1007/s11250-023-03864-1 REGULAR ARTICLES Nutrient intake, digestibility, and utilization in goats fed graded levels of hempseed cake finisher diets Farouk Semwogerere1 Cletos Mapiye1 · Obert C. Chikwanha1 · Chenaimoyo L. F. Katiyatiya1 · Munyaradzi C. Marufu2 · Received: 14 August 2023 / Accepted: 7 December 2023 © The Author(s) 2023 Abstract Globally, the price of soybean meal, the most common proteinaceous ingredient in livestock diets, has become highly expensive prompting a search for alternative ingredients. Hemp seed cake is a promising alternative but could be limited by its high neutral detergent fiber and ether extract contents which impede nutrient intake and digestibility. However, some ruminant species such as goats have superior ability to digest high fiber and ether extract diets. Thus, the current research evaluated nutrient intake and digestibility, rumen fermentation, and microbial protein synthesis of goats fed hempseed cake as a substitute for soybean meal in finisher diets. A total of 25 Kalahari Red castrates (27 ± 3 kg, 4–5 months old) were assigned to five dietary treatments (5 goats/ diet) in a completely randomized design. A maize-lucerne-based finishing diet was formulated with hempseed cake substituting soybean meal as the primary protein ingredient at 0, 25, 50, 75, or 100 g/kg dry matter. Ether extract intake exhibited a positive linear trend (P ≤ 0.05) while crude protein intake and microbial nitrogen supply exhibited a negative linear trend (P ≤ 0.05) with dietary inclusion of hempseed cake. However, feeding hempseed cake did not influence (P > 0.05) apparent nutrient digestibility, rumen fermentation parameters and nitrogen use efficiency. In conclusion, the substitution of soybean meal for hempseed cake decreased crude protein intake and microbial nitrogen supply in goat finisher diets without compromising nutrient digestibility and nitrogen use efficiency. The study recommends partial or full replacement of soybean meal with hempseed cake in goat finisher diets. Keywords Hempseed cake · Nutrient digestibility · Purine derivatives · Volatile fatty acids Introduction Globally, the production of hemp (Cannabis sativa L.) is increasing due to the legalization of its cultivation and revived fiber, food and medicinal uses (Siano et al. 2019; Horne 2020; Leonard et al. 2020). About 143 metric tons (MT) of hempseed are produced annually yielding about 50 MT of oil and 93 MT of cake worldwide (FAOSTAT 2022). Hempseed by-products (i.e., cake and hulls) have potential economic uses, including feed, human food and * Cletos Mapiye 1 Department of Animal Sciences, Faculty of AgriSciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa 2 Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Onderstepoort 0110, South Africa beverages (Frassinetti et al. 2018; Leonard et al. 2020; Aloo et al. 2022). Valorization of hempseed by-products as animal feedstuff provides a potential alternative to increasing their economic value, thus improving the importance of hempseed by-products in the circular bioeconomy (Moscariello et al. 2021; Aloo et al. 2022; Winders et al. 2023). Hempseed cake (HSC) has the highest potential among the hemp by-products to be used as animal feedstuff owing to its high crude protein (CP; 341 ± 50.4 g/kg dry matter; DM), neutral detergent fiber (NDF; 395 ± 40.7 g/kg DM) and ether extract (EE; 116 ± 15.5 g/kg DM) with the NDF and EE almost triple that of soybean meal (SBM; NDF: 125 ± 17.6; EE: 40 ± 15.9; g/kg DM) (Pojić et al. 2014; Paula et al. 2018; Leonard et al. 2020; Semwogerere et al. 2023a). Apart from having high protein and energy contents, HSC contains bioactive compounds such as cannabinoids, tocopherols and polyunsaturated fatty acids (PUFA) (Leonard et al. 2020; Sainz Martinez et al. 2023; Semwogerere et al. 2023b). 13 Vol.:(0123456789) 21 Page 2 of 10 Previous reports in ruminants indicate that high NDF (> 355 g/kg DM) and EE (> 50 g/kg DM) rich in PUFA inhibit nutrient intake, digestion and utilization among ruminants (Pantoja et al. 1994; Harper and McNeill 2015; Wang et al. 2017; Embaby et al. 2019). However, goats might be able to digest HSC diets better than other ruminants as they have better feed grinding ability and spend more time chewing and ruminating, which gives them the capacity to digest fibrous diets (Domingue et al. 1991; Lu et al. 2008). More so, goats tend to have more Butyrivibrio fibrisolvens that enhance fibre digestion in the rumen than the other ruminants (Candyrine et al. 2017). Soybean meal, the primary protein source in goat finisher diets is normally included at 120 g/kg DM (Brand et al. 2020; Kustantinah et al. 2020; Dahmer et al. 2022). Replacing SBM with HSC (100 g/kg DM) linearly decreased in vitro DM digestibility but maintained the DM intake of goats (Abrahamsen et al. 2021; Semwogerere et al. 2022). More importantly, there is an information gap on the level of HSC in goat diets beyond which nutrient intake, digestibility and utilization efficiency are compromised. It was hypothesized that replacing SBM with increasing proportions of HSC up to 100 g/kg DM in goat finishing diets could maintain nutrient supply, digestion, and utilization. Thus, the current study investigated nutrient intake and digestibility, ruminal fermentation parameters, and microbial protein synthesis in goats fed pelleted finisher diets containing HSC substituting SBM. Materials and methods Research site Welgevallen Experimental Farm, Stellenbosch University, Stellenbosch, South Africa, hosted the research study during June and July 2021. The experimental site experiences a Mediterranean climate and was characterized by an average temperature of 12°C, rainfall of 141 mm, and humidity of 77% during the experimental period. Goat diets and management A local oilseed processing company ( SeedOilSA, Somerset West, Cape Town) supplied cold-pressed HSC (Cannabis Sativa L. Fedora 17) which was used to formulated five maize-lucerne based goat finisher diets to satisfy the dietary needs for growing goats (CP: 120 g/kg DM and ME: 11.0 MJ/kg DM; National Research Council 2007). The milled (1.5-mm sieve) HSC was included at levels of 0, 25, 50, 75 and 100 g/kg DM replacing SBM and pelleted (5 mm × 30 mm) at 45°C (Table 1). The hay and straw were milled through 4 mm sieve prior to mixing. A local goat producer 13 Tropical Animal Health and Production (2024) 56:21 Table 1  Feed ingredient proportions in experimental diets Ingredients (g/kg DM) Soybean meal Hempseed cake Maize white fine Lucerne hay Hominy chop Molasses syrup Wheat straw Wheat bran Soybean hulls Savannah Lime Vitamin-mineral premix* Ammonium sulfate Coarse salt Urea Hempseed cake inclusion level (g/kg DM) in the diet 0 25 50 75 100 100 0 400 200 93.5 70 50 49 10.6 7 7 5 4.9 3 75 25 400 200 93.5 70 (...truncated)