Milk production and intake of lactating cows fed raw or extruded peas

Primiparous (n = 9) and multiparous (n = 18) Holstein cows averaging 584 +/- 15 kg of body weight (mean +/- SE) were allotted at 2 wk postpartum to nine groups (3 primiparous and 6 multiparous) of 3 cows each to determine the effects of pea extrusion on ruminal degradability and milk production. Cows were fed a total mixed diet based on timothy silage and concentrate for ad libitum intake. The experiment was carried out between wk 4 and 15 of lactation. Cows within each group were 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 effect on the ruminal degradability of crude protein. Cows fed extruded peas 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 milk 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 that peas can substitute for soybean meal as the protein source in diets of early lactation cows without adverse effects on production and that, in this study, the extrusion of peas had no beneficial effect on milk production.