Variation in apparent and true ileal amino acid digestibility in barley using a rat model

The study aimed to determine ileal amino acid and total tract energy digest ibility coefficients for a range of barleys, The laboratory rat served as a model nonruminant animal and digesta samples were obtained using the slaug hter method with chromic oxide being used as a dietary marker. In a prelimi nary study the effect of time interval after the feeding of a single meal o f ground barley and before sampling of ileal digesta on the apparent ileal digestibility of total nitrogen (N) and of the effect of the length of term inal ileum sampled were investigated, There was no significant effect of ti me of sampling but there was an effect (p<0.001) of site in the ileum. The final 10 cm of ileum was considered appropriate for the sampling of ileal d igesta for barley-fed rats. In the main study 20 barley samples comprising 14 different cultivars which had been grown in the same year but in three d istinct geographical locations in New Zealand were given as sole sources of protein to growing rats (n=120). Digesta were collected (final 10 cm of il eum) 4 h after the commencement of a single meal. The barley samples had va riable contents of crude protein, amino acids, neutral detergent fibre, aci d detergent fibre, acid detergent lignin and gross energy. The mean (n=6) a pparent ileal N digestibility ranged from 0.74 to 0.85 while the equivalent range for true N digestibility was 0.84 to 0.94, Apparent and true ileal a mino acid digestibility showed considerable between-sample variation. Diges tible energy ranged from 13.0 to 15.1 MJ/kg dry matter, There was a signifi cant effect of the geographical locality where the barleys were grown on am ino acid digestibility for most of the cultivars studied, (C) 1998 Elsevier Science B.V.