Apparent digestibility and nutrient balance in lambs fed different levels of flatpea hay

Apparent digestibility and nutrient utilization were studied in a digestion and balance trial with 30 wether lambs (BW 32 kg). Lambs were blocked by weight and allotted randomly to five diets with ratios of alfalfa (Medicago sativa L.) to 'Lathco' flatpea (Lathyrus sylvestris L.) hay of 100:0, 75:25, 50:50, 25:75, and 0:100. Alfalfa was harvested in the early bloom stage and flatpea was harvested in the vegetative stage. Digestibilities of DM, NDF, ADF, cellulose, hemicellulose, and energy decreased linearly (P less than .05) as the level of flatpea hay increased to values of 53.3, 32.4, 39.9, 46.0, 40.5, and 52.5%, respectively, for 100% flatpea hay. Nitrogen retention (9 to 15% of intake) was not affected by level of flatpea hay. Ruminal pH, NH3 N, and blood urea N increased linearly (P less than .001) as level of flatpea increased in the diet, apparently a reflection of dietary N level. Calcium excretion decreased linearly (P less than .01) with increased proportions of flatpea hay and was related to dietary intake of Ca. Apparent absorption and retention showed a cubic effect (P less than .05). No clinical signs of toxicity were observed in any of the lambs during the 20-d metabolism trial. Vegetative flatpea is potentially valuable as a forage for feeding ruminants.