Trial 1

Crude protein and amino acid content were measured in the Bohatyr variety of peas grown at eight different rates of nitrogen fertilizer application. By altering the level of fertilizer use, peas were produced with crude protein levels ranging 22% to 26%. As more fertilizer was applied to the fields, the arginine and non-essential amino acids in the peas also increased. These amino acids make up the majority of the amino acids found in the storage proteins in peas. Most of the essential amino acids such as lysine only increased slightly as crude protein level increased. Methionine, the most limiting amino acid in peas, did not increase at all. When formulating pea diets, the estimated methionine values should not be increased even when feeding peas that test high in crude protein content.

Trial 2

The apparent protein digestibility was determined for one variety each of yellow, green and brown seed coloured peas (Impala, Radley and Sirius varieties). The apparent digestibility was measured by feeding diets containing 50% peas to commercial broilers. The yellow and green seeded varieties had moderate apparent digestibility of 75% and 73% respectively. The brown seeded variety, however, contained higher levels of tannins that could interfere with protein digestion and had an apparent protein digestibility of only 60%. The crude protein content of the three varieties of peas was similar but the amount of protein that the birds could digest was not. Choice of pea variety can significantly impact the performance of young birds on pea diets.

Trial 3

Samples of twelve different varieties of peas (8 yellow seed, 2 green seed and 2 brown seed varieties) were collected. Each sample was tested for crude protein and total amino acids. The availability of the amino acids was measured using the precision-feeding technique with fasted, adult cockerels. The samples were not all grown in the same location and some of the variety differences could have been due to different growing conditions.

The crude protein content of the peas was not related to seed colour. As would be expected from Trial 1, total lysine was slightly higher in varieties with higher crude protein but total sulphur amino acids did not vary noticeably. The availability of the lysine and total sulphur amino acids was noticeably depressed in the brown seed varieties (Carman and Sirius). These varieties contained much higher levels of tannins than any of the other varieties. Tannins were not the only factor affecting amino acid availability because the green seeded varieties (Radley and Trump) had below average lysine availability but low tannin levels. When formulating pea diets, it would be prudent to discount the estimated availability of amino acids in brown seeded varieties of peas.