Case study data
We examined the effect of the feed used by three different egg producers. These egg producers are located in north-west and north-central Bulgaria. All three are specialised egg and poultry producers with their own feed mills. Two used imported soybean meal as the sole high-protein supplement source in the feed. The third producer (Producer 3) used own-grown (Bulgarian cv. Srebrina) cold-pressed soybean cake as the source of 50% of the soy-based protein in the feed, the other 50% provided by imported soybean meal. Feed samples taken from each of the three producers were analysed in a certified laboratory for energy (MJ/kg) and the contents (%) of protein, fat, starch, and total sugars (Figure 1).
Egg samples were taken from the producers for analysis of the content of amino acids and fatty acids. The analyses were performed separately on egg yolk and egg white by using gas chromatography/ mass spectrometry (GC/MS). The content of free AAs of egg yolk and egg white is presented in Figure 2 and Figure 3.
The content of free AAs in egg yolk indicated higher levels of each of the detected AAs in the egg yolk from producer 3 with the exception of lysine. Similar results were obtained for the content of free AAs in egg white. The contents of all detected AAs were higher in the egg samples from producer 3.
The content of the free FAs was also evaluated in the egg samples (yolk and white) collected from the producers 1, 2 and 3. Figure 4 shows the content of two saturated and five unsaturated FAs in egg white and egg yolk. The highest content of unsaturated FAs was detected in egg white and egg yolk samples from producer 3. The same trend was observed for saturated palmitic acid, and the only exception was the content of stearic acid in egg white where the value of stearic acid was higher in the egg white samples from producer 2.
Key practice points
Cold pressing of soybean grain is an easy process which does not require very expensive equipment. The inclusion of soybean cake in the animal feed on the other hand could benefit animal health and the quality of the final product. In our case study, we found that feed for laying hens in which 50% of imported soybean meal is replaced by soybean cake produced from locally grown soybean could increase the content of free AAs and FAs in thefinal product and benefit the quality of eggs.
The essential AAs (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine) and FAs (linoleic acid (an omega-6 fatty acid) and alpha-linolenic acid (an omega-3 fatty acid)) cannot be synthesised by humans and animals and must be taken in through the diet for normal development and healthier nutrition.
As part of the European project “Legumes translated” ID 817634, www.legumestranslated.eu, aiming to promote the cultivation and use of leguminous crops in Europe – the Bulgarian Legumes Network /BGLN/ performed this case study.