Variations in nutrient digestibility and metabolisable energy corrected to zero nitrogen retention levels in cultivars of yellow lupin seeds for use as poultry feed have been examined in 2 independent trials.
Soybean meal (SBM) is the most common vegetable protein source in poultry diets, but dietary replacement of soybean products with home-grown legume seeds for non-ruminant animals has been receiving growing attention recently in countries that cannot produce soybean due to unfavourable climatic conditions
Nutritional value of lupin seeds
According to earlier research, protein from lupins is utilised to the same degree as of the SBM; with the metabolisable energy of yellow lupin meal (YLM) for poultry being around 9.5 MJ/kg of dry matter (DM). The nutritional value of lupin seeds for poultry depends mainly on their amino acid digestibility and metabolisable energy, which is positively correlated with the fat content and negatively with non-starch polysaccharides (NSP). The yellow lupin seeds contain approximately 272–353 g/kg of NSP, of which above 5% is water soluble, thereby limiting their application in poultry feeding. Nutrient composition and anti-nutritional factors in YLM depend on the cultivars and growing conditions.
2 experiments were conducted by researchers at the Poznan University of Life Sciences, Poland, to study the nutritional value of 4 or 7 cultivars of Lupinus luteus L. seeds. Experiments I and II were conducted on 150 and 240 16-day-old Ross 308 male chicks, respectively.
Dietary treatment groups allocated
The birds were allocated to 5 or 8 dietary treatment groups (10 replications in each, 3 birds per replication). Feeds in 4 treatments from Experiment I and 7 treatments from Experiment II, contained a lupin meal (different cultivars) and basal diet in a proportion of 30:70. Birds in one treatment (Experiments I and II) were fed only the basal diet. Crude protein content in lupin seeds ranged from 390 to over 440 g/kg of DM (in both experiments). In Experiments I and II, phytic-P content in lupin meal ranged from 5.6 to over 8 g/kg.
In Experiment I, water extract viscosity of seeds ranged from 1.21 to 1.61 cP. In Experiment II, non-starch polysaccharides ranged from 261 to 288 g/kg. The lowest content of oligosaccharides was 86 g/kg (Experiment I, cv. Mister) and the highest—128 g/kg (Experiment II, cv.Parys). Raffinose content in seeds ranged from 8 g/kg (Experiment II, cv. Baryt) to 16 g/kg (Experiment II, cv. Mister).
Energy and protein from yellow lupin seeds
The apparent metabolisable energy (AMEN) of yellow lupin seeds ranged from 8.33 to 10.2 MJ/kg; the lowest was determined for Mister and the highest for Baryt cultivars, both used in Experiment II. Ileal crude protein digestibility of yellow lupin seeds ranged from 0.759 to 0.85; the lowest was determined for Mister (Experiment I) and the highest for Perkoz (Experiment II) cultivars. Lupin AMEN negatively correlated with their raffinose content (Experiment I: r = −0.37; P ≤ 0.05; Experiment II: r = −0.67; P ≤ 0.01).
In Experiment II, sialic acid excretion correlated well with ileal digesta viscosity (r = 0.57, P ≤ 0.05) and raffinose content (r = 0.38, P ≤ 0.05). Negative correlations were observed between following: apparent ileal digestibility of dry matter and crude protein, ileal amino acid digestibility and water extract viscosity (Experiment I) – raffinose content (Experiments I and II) and – ileal digesta viscosity (Experiment II).
In Experiments I and II, there were no correlations between the alkaloids contents and digestibility of any nutrient or AMEN values of the seeds (correlations coefficients not presented). The current alkaloid levels in L. luteus cultivars are low and have negligible effect on nutrients’ digestibility.
The inherent variability of seeds may partially explain why birds did respond differently across trials (including this experiment) after being fed with a similar dose of YLM seeds. It seems that the nutritional value of yellow lupin seeds for broilers depends, to a considerable extent, on raffinose content and ileal digesta viscosity. Examining concentrations of nutrients (CP or EE), we found no informative variables for predicting yellow lupin seeds’ AMEN. Therefore, L. luteus seeds characterised by low sNSP and a raffinose content have a high nutritional value.
The full results were published in Science Direct