Investigations on the contents of crude protein and essential amino acids in various organically produced pea cultivars (Pisum sativum L.)

Summary

In organic farming, providing a diet with adequate amino acid (AA) contents and profiles for monogastric animals is particularly difficult. Feeding conventionally produced feedstuffs as well as some feed additives like crystalline AA is to be avoided or even prohibited. Therefore, knowledge about the AA and crude protein (CP) contents of valuable protein sources like peas (Pisum sativum) is of special interest regarding diet formulation. Therefore, samples of 13 pea cultivars have been collected in the years 2008, 2009, 2011, and 2012 from field trials of various organically managed experimental locations in Germany. CP and AA contents were measured using NIRS.
Wide variations of CP and AA contents within the observed cultivars were detected. On average, peas of the cultivar “Rocket” showed lowest contents of CP and all essential AAs. The average amount of cystine was slightly higher than in the cultivars “Alvesta”, “Auckland”, “Navarro”, and “Salamanca”. The cultivar “Casablanca” contained most CP and much lysine. “La Manscha KWS” showed highest lysine contents and relatively low CP contents. The table shows the contents of CP in % dry matter and essential AAs in g/kg dry matter of five selected cultivars which showed significant differences in either CP or AA contents. Correlation analyses revealed high correlation coefficients between the amount of CP and methionine (R=0.85), cystine (R=0.82), threonine (R=0.86), histidine (R=0.92), leucine (R=0.87), isoleucine (R=0.86), valine (R=0.90), phenylalanine (R=0.85), tyrosine (R=0.89), and arginine (R=0.94). Lysine content correlated less strongly with CP content (R=0.75) than the other AAs.
Targeting high CP contents may be detrimental referred to the protein quality due to relatively decreased amounts of limiting AA. The choice of the cultivar is important regarding variations in CP content and AA profile. Moreover, especially in organic farming, wide variations in the composition within cultivars partly result from temporal and spatial differences. They make it necessary to analyze the nutrient contents of harvested crops before formulating a diet.