MILK-PRODUCTION AND INTAKE OF LACTATING COWS FED RAW OR EXTRUDED PEAS

Primiparous (n = 9) and multiparous (n = 18) Holstein cows averaging 5 84 +/- 15 kg of body weight ((X) over bar +/- SE) were allotted at 2 w k postpartum to nine groups (3 primiparous and 6 multiparous) of 3 cow s each to determine the effects of pea extrusion on ruminal degradabil ity and milk production. Cows were fed a total mixed diet based on tim othy silage and concentrate for ad libitum intake. The experiment was carried out between wk 4 and 15 of lactation. Cows within each group w ere assigned randomly to isonitrogenous and isoenergetic concentrates based on corn plus soybean meal, raw peas, or extruded peas. Extrusion of peas increased the ruminal degradability of starch but had no effe ct on the ruminal degradability of crude protein. Cows fed extruded pe as had higher dry matter intakes and plasma urea N concentrations than did those fed soybean meal; no differences were detected between cows fed extruded and raw peas. Production of 4% fat-corrected milk and mi lk composition generally were similar for cows fed the various diets. Digestibilities of dry matter and N were higher for cows fed extruded peas than for cows fed soybean meal or raw peas. These data suggest th at peas can substitute for soybean meal as the protein source in diets of early lactation cows without adverse effects on production and tha t, in this study, the extrusion of peas had no beneficial effect on mi lk production.