Whole soybeans (SB) are mostly used in feeding of dairy cows, but protein in raw SB is degraded readily by rumen microbes and cannot meet the high demand of rumen undegradable protein (RUP) in early lactation. Heat treatment of SB, especially roasting, reduces ruminal protein degradation and improves the nutrient balance for cows. However, there have been conflicting results regarding animal response to feeding heat treated SB. In many studies, increase in milk yield may be related to type of forage in the diet, as improved performance is usually achieved by diets with lucerne silage as the forage because of the high solubility of its protein, but mixed lucerne hay-maize silage as the primary forage source of diets that are used widely in tropical areas like Iran, was not tested. So, the main objective of this study was to investigate the performance responses of Iranian Holstein cows in early lactating to the feeding of Iranian roasted SB, raw SB and SBM in combination with lucerne hay-maize silage diets.

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