Effect of replacing soybean meal with marula nut meal on rumen dry matter and crude protein degradability
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Effect of replacing soybean meal with marula nut meal on rumen dry matter and crude protein degradability M. C. Muya 1 & I. M. M. Malebana 1
&
B. D. Nkosi 1
Received: 30 July 2019 / Accepted: 10 September 2020 # Springer Nature B.V. 2020
Abstract In situ rumen degradability of dry matter (DM) and crude protein (CP) in ruminant diets composed of graded inclusion levels of marula nut meal (MNM) as a protein source to replace soybean meal were evaluated. The five diets denoted as diet 1 (0.0 g kg−1 MNM: control), diet 2 (45.5 g kg−1 MNM), diet 3 (91.7 g kg−1 MNM), diet 4 (138.4 g kg−1 MNM), and diet 5 (185.9 g kg−1 MNM) were tested. Three cannulated mid-lactating Holstein cows were used to incubate triplicate subsamples of each diet for 2, 4, 8, 16, 24, and 48 h in polyester bags. The soluble fractions of DM and CP increased (P < 0.05) with increasing levels of MNM (138.4–185.9 g kg−1 MNM). However, the insoluble but degradable fractions of DM and CP increased (P < 0.05) with decreasing levels of MNM (45.5– 0.0 g kg−1 and 91.7–0.0 g kg−1 MNM, respectively). While the degradation rate of fraction and the effective degradability of DM increased (P < 0.05) with decreasing levels of MNM (91.7–0.0 g kg−1), those of CP increased with increasing levels of MNM (138.4–185.9 g kg−1 MNM) in the diet. These results suggest that dietary inclusion of MNM up to 91.7 g kg−1 in ruminant diets can provide undegradable protein to be absorbed in the small intestines and used for metabolic function, while an inclusion of up to 185.9 g kg−1 can be degraded in the rumen for microbial protein synthesis. Keywords Non-conventional feeds . Rumen disappearance . Nutrient degradability . Protein source
Introduction Soybean meal (SBM) is the most commonly used protein source for livestock and is regarded as the standard to which other plant protein sources used in feed are compared (Nezarati et al. 2014). The scarcity and current cost of SBM calls for alternative feed protein ingredients, especially those of plant origin. The production of oil from plants results in the availability of cakes/meals that contain valuable amounts of nutrients, notably proteins, fats and energy. These by-products can help to sort out feed shortages that can be incorporated in animal rations. Marula (Sclerocarya birrea caffra) nut meal is one of the by-products that emanates from oil production
* I. M. M. Malebana [email protected] 1
Agricultural Research Council-API, Private Bag X2, Irene, Pretoria 0062, South Africa
using marula nuts in the biodiesel industries in South Africa. According to Malebana et al. (2018), this by-product contains (g kg−1 DM) 411 fats, 391 crude protein, and 27.3 MJ metabolizable energy. Knowledge on the degradability of nutrients is essential when incorporating feed ingredients to formulate ruminant diets (Lei et al. 2017). Nkosi et al. (2019) reported MNM to have 23% of potentially degradable fraction of CP, which is lower than 96% reported in SBM by Lei et al. (2018). The evaluation of the two feed resour
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