Field bean (Vicia faba var. minor) as a protein feed for growing lambs with and without protected lysine and methionine supplementation.

Thirty-two Appenninica lambs were submitted to a growth trial from day 60 to day 110 of age (on average) and the composition of gains was estimated by means of the comparative slaughter technique. Sixteen different diets, based on wheat straw as the forage and on field bean (Vicia faba var. minor) as the sole protein feed, were tested both by means of ANOVA and of response surface analysis, a multiple regression method designed to study additive and interaction effects. This study thus examined the combined effect of 4 levels of dietary CP (13, 15, 18, 20% DM) and 4 levels of rumen protected lysine and methionine, replacing 4 levels of field bean CP (0, 1, 2, 3 percent units), upon intakes, gains, digestibility and retentions of nutrients within gains. The animals had rather high gains (250 g/d on average) and retention efficiencies both of feed nitrogen and energy. Dietary CP levels higher than 18% and amino acid supplementation appeared of no use in improving the lambs’ performance. It is concluded that field bean may represent a valid alternative to soy bean as a protein feed for growing ruminants in the so-called “organic” animal production where transgenic soy is banned.