Field peas: chemical composition and energy and amino acid availabilities for poultry

Twelve pea cultivars (yellow-, green- and brown-seeded) were evaluated for chemical composition and digestibility in poultry. The evaluation involved analyses for protein, amino acids (AAs), fat, starch, dietary fibre, ash, calcium, phosphorus and tannins. True metabolizable energy [nitrogen corrected (TME eta) and uncorrected (TME)] and true AA bioavailability values were also determined with adult cockerels. The cultivars showed a wide range of protein (207.5-264.0 g kg-1) and starch (385.3-436.8 g kg-1) contents which were not related to the seed coat colours. The concentrations of several AAs varied among the cultivars. With the exception of arginine, the concentrations of all other essential AAs on a protein basis decreased as protein levels increased. Out of 10 essential AAs including cystine, only arginine had a positive correlation (r = 0.79) with protein content. The dietary fibre contents varied between 190.7 and 223.1 g kg-1 and the values were slightly higher in the brown-seeded cultivars. The brown-seeded cultivars contained appreciable quantities of tannins, while the yellow- and green-seeded cultivars were devoid of tannins. The cultivars were almost devoid of fat and calcium but relatively high in phosphorus. Starch and dietary fibre were negatively correlated with protein content (r =-0.78 and -0.46, respectively), and accounted for the greatest difference in protein content. The TME values ranged from 11.6 to 13.3 MJ kg-1 while the TME eta values ranged from 11.0 to 12.9 MJ kg-1. The mean availabilities of AAs ranged from a high of 89.6 to a low of 75.9%, with total sulphur AAs (cystine and methionine) having the lowest value and glutamic acid having the highest value. There was a trend (P less than or equal to 0.05) towards lower AA bioavailability values in the brown-seeded cultivars. It can be concluded that these cultivars varied in chemical composition, metabolizable energy content and bioavailability of AAs.