This study evaluated responses of early lactation Iranian Holstein cows to feeding roasted whole soybean (SB) or raw SB in diets with lucerne hay and corn silage as the primary forage source. Treatments consisted of a total mixed ration that included 387 g/kg forage supplemented with 1) 120 g/kg of roasted SB and 82 g/kg of cottonseed meal (CSM), 2) 120 g/kg of raw SB and 82 g/kg of CSM or 3) 120 g/kg of soybean meal (SBM) and 82 g/kg of cottonseed (CS), on a dry matter (DM) basis. The diets which were formulated to be iso-nitrogenous and iso-caloric were offered to fourteen multiparous Holstein cows (body weight = 617.0 kg, days in milk = 16.9) that were assigned randomly to one of three experimental diets for a 45-d trial. Roasted SB were obtained by roasting seeds for 1.5 to 2 min in a commercial roaster (exit temperature of seeds was about 140-145°C) and immediately placing, without cooling, in covered wooden barrels for 45 min. A dietary effect on rumen pH values, glucose and beta-hydroxy butyrate (BHB) concentrations were not detected among cows fed different diets (Table 1). Rumen ammonia N concentration were significantly lower for the cows fed roasted SB compared with those fed raw SB. The lower ruminal ammonia concentration in cows fed roasted SB diet compared with raw SB diet, possibly arose as a consequence of lower ruminal protein degradability of roasted SB. Plasma urea nitrogen (PUN) concentrations were also significantly (p<0.031) lower in cows fed roasted SB than in cows fed raw SB that confirms the reducing of ruminal protein degradability of roasted SB.

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