Fathi Nasri, M. H., Danesh Mesgaran, M., Kebreab, E. and France, J. 2007. Past peak lactational performance of Iranian Holstein cows fed raw or roasted whole soybeans. Can. J. Anim. Sci. 87: 441–447. Responses of past peak lactating Iranian Holstein cows to feeding roasted whole soybean (SB), raw SB or soybean meal (SBM) supplements were evaluated. Treatments consisted of a total mixed ration (TMR) with 34% forage (21% alfalfa hay and 13% corn silage) supplemented with 11.9% SBM or 13.3% roasted SB or raw SB. Diets were offered to 18 multiparous cows assigned randomly to one of three experimental diets for a 49-d trial. Dry matter intake was not significantly different, but total and fat-corrected milk yields were higher for cows fed the roasted SB diet than the other treatments. Milk fat concentration was not significantly different among treatments, but milk fat yield was significantly higher for cows fed the roasted SB and SBM diets. Milk protein concentration was significantly decreased by the raw and roasted SB diets, but milk protein yield was unaffected. Feeding roasted SB significantly reduced rumen ammonia N, plasma urea N and milk urea N concentrations. Ruminal pH, plasma glucose and beta-hydroxybutyrate concentrations were not affected. Compared with the other treatments, roasted SB increased plasma concentration of most essential amino acids, except leucine and phenylalanine. Although caution must be taken in the interpretation of the results due to the limited number of observations in the experiment, feeding roasted SB in a diet with alfalfa hay as the primary forage was beneficial.

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