Methane emission, nitrogen and energy utilisation of beef cattle when replacing or omitting soybean meal in a forage-based diet
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2022-08
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Journal Article
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Abstract
Replacing imported soybean meal (SBM) by domestic protein sources such as grain legumes, food industry by-products or novel resource-efficient feeds is a current research focus to enhance the sustainability of ruminant production systems. In addition, grass silage replacing maize silage can contribute to dietary crude protein (CP) supply as well and complies with the natural diet of ruminants. An experiment with 30 Limousin-sired beef bulls was performed with diets in which SBM was replaced by alternative protein sources when feeding a diet composed of, per kg dry matter (DM), 500 g grass silage, 300 g maize silage and 200 g concentrate. In the concentrate, SBM (control diet) was replaced by faba beans, pumpkin seed cake, or spirulina (Arthrospira platensis) to result on average in 226 g CP/kg concentrate dry matter (DM). A fifth group served as negative control, which received a grain-based concentrate with only 135 g CP/kg DM. Bulls were fed the experimental diets for the entire fattening period starting from an initial body weight (BW) of 164 ± 2.3 kg and 4.3 ± 0.06 months of age. At an average body weight (BW) of 275 ± 5.6 kg and 7.4 ± 0.17 months of age, each animal underwent a 9-day sampling period to determine individual N and energy intake and excretion (7 days of urine and faeces collection) as well as methane emission (2 days in respiration chambers). The diet had no effect on DM and nutrient intake. Apparent fibre digestibility was significantly affected by diet, being numerically lowest with faba beans instead of SBM. Compared to the other groups, the bulls fed no additional protein had the lowest urinary N excretion (25.1 vs. 40.3 g/bull/day; 366 vs. 460 g/kg total faecal and urinary N). Digestive and metabolic energy utilisation were comparable among diets. Methane (CH4) production adjusted to body weight differed significantly among groups, being numerically highest in bulls fed faba beans (547 vs. 513 mg CH4/kg BW/day in the other diets). These results show that none of the tested protein sources, including SBM, was of benefit when feeding a diet containing 500 g/kg DM grass silage complemented with maize silage and concentrate. Feeding such a diet seems to provide an adequate supply with metabolisable protein. Omitting the common protein supplementation therefore mitigated urinary N losses and thus likely N emissions from the manure at unchanged N and energy utilisation.
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published
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Volume
290
Pages / Article No.
115362
Publisher
Elsevier
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Subject
Spirulina; Faba beans; Pumpkin seed cake; Soybean; Grass silage; Urinary nitrogen
Organisational unit
03428 - Kreuzer, Michael (emeritus) / Kreuzer, Michael (emeritus)
09747 - Niu, Mutian / Niu, Mutian