Effect of common vetch (Vicia sativa L.) seeds in organic diets for broiler chickens: acceptance and precaecal digestibility of crude protein and amino acids from raw, germinated and ensiled vetches

The common vetch (Vicia sativa L.) is a hardy legume mostly used as a catch crop, but it also produces seeds with high protein content. Due to anti-nutritional factors present in the seeds, their use in diets for monogastric animals is limited. In order to improve the usability of common vetch seeds (CVS) as a protein-rich component with a suitable amino acid profile in organic diets for broiler chicken, we compared raw CVS (cultivar Slovena) with a digestibility of 0.860 of crude protein and 0.960 of methionine with germinated and ensiled CVS in a digestibility trial and a feeding trial. We used a slow-growing genotype (Hubbard/Isa-JA-757) in both trials. In the digestibility trial, raw, ensiled and germinated CVS were fed at three inclusion levels: 0, 100 and 200 g CVS/kg of diet (as fed basis). A total of 972 day-old mixed-sex broiler chicks were used. During the experimental period of the feeding trial, a total of 640 mixed-sex birds were offered raw, ensiled and germinated CVS separately.The voluntary intake of raw CVS was 57 g/kg of total dry matter intake, and fattening performance did not differ from the vetch-free control diet. While germination did improve the digestibility of crude protein and almost all amino acids in CVS, this change did not translate into equally improved performance of the birds in the feeding trial. High voluntary intake of the separately offered germinated CVS (132 g/kg of total dry matter intake) resulted in an inferior feed conversion ratio in comparison to the vetch-free control diet. We can therefore state that germinated CVS are a very attractive feed for broilers that is eagerly consumed, but comes at the cost of decreased feeding efficiency, at least at the inclusion level applied in our study. Ensiling, on the other hand, resulted in a markedly decreased digestibility of crude protein and all amino acids compared to the unprocessed CVS. Moreover, the ensiled CVS were consumed at a much lower rate than germinated CVS (77 g/kg of total dry matter intake). Therefore, ensiling of CVS prior to feeding cannot be recommended. We conclude that feeding raw CVS at low inclusion levels is more recommendable than germination or ensiling, because of the observed disadvantages of the treatments.