. 2003. Feeding value of peas for backgrounding beef heifers. Can. J. Anim. Sci. 83: 779-786. Four diets in which peas progressively replaced barley [0% (0P), 30% (30P), 50% (50P), and 100% peas (100P)] and one in which canola meal (CM) replaced 10% of the barley, were fed to 90 beef heifers (initial weight 215.8 ± 13.8 kg). The heifers achieved average daily gains (ADGs) of 0.72, 0.80, 0.79, 0.83, and 0.76 kg d -1 on the five diets, respectively, with the difference between the 0P group and the 100P group being significant (P = 0.028). The total feed costs of gain were $0.786, 0.779, 0.799, 0.860, and 0.817 kg -1 for the five groups, respectively, with the cost of gain being significantly greater (P < 0.05) for the 100P group than for the 0P, 30P or 50P groups. The latter three were not significantly different from each other. Three rumen-cannulated steers (575 ± 56.3 kg) were used to estimate the degradability of the dry matter (DM) and N in the barley straw (BS), CM, barley grain (BG) and peas used in the feeding trial. The rumen undegradable protein (RUP) levels supplied by the five diets were 17.5, 19.0, 19.9, 21.5, and 22.5%, respectively, and all of them met the requirements of these cattle. The RUP content of peas ground through a 1-mm screen was lower than that of peas ground through 2-or 4-mm screens (P < 0.01), which were themselves not significantly different from each other (P = 0.67). The low RUP content of peas was not a limiting factor for growth in backgrounding cattle. La teneur en PND du pois moulu et passé au tamis de 1 mm était inférieure à celle de la farine de pois passée au tamis de 2 ou de 4 mm (P < 0,01), qui ne présentaient pas de variation significative (P = 0,67). La faible concentration de PND du pois n'entrave pas l'engraissement des bovins en semi-finition.Mots clés: Bovins, pois de grande culture, ingestion de matière sèche, valorisation des aliments, métabolisme du rumen Western Canada is one of the main pea-growing areas in the world, and a major pea exporter to the European Union (EU). Field peas (Pisum sativum) were traditionally grown in Canada for human use, and only downgraded peas were used as animal feed, but with more cultivars available and increased production levels, more and more peas are being used in animal feeds. Western Canada (Manitoba, Saskatchewan and Alberta) produces almost all of Canada's dry peas and is also Canada's main cattle-producing region (Statistics Canada 2001). Thus, feeding peas to cattle presents a realistic, on-farm value-adding opportunity for pea growers, many of whom background beef steers and replacement heifers.In recent years, some work has been done to explore the utilization of peas in ruminant feeds. However, most of the work has been done with dairy rather than beef cattle (Corbett 1997;Ellwood 1998). Therefore, our objectives were to compare diets with different inclusion levels of peas with an all-barley diet and a canola meal diet when fed to backgrounded beef cattle (exp. I). A second experiment (exp. II) was designed to investi...