Effects of partial replacement of solvent-extracted soybean meal by amino resin-treated soybean meal in the concentrate supplement of high producing grazing dairy cows

Abstract We aimed to determine the effects of partially replacing conventional solvent-extracted soybean meal by amino resin-treated soybean meal in the concentrate supplement of lactating dairy cows grazing Guinea grass (Panicum maximum cv. Mombaca) on dry matter intake, milk production and composition, feed and nitrogen use efficiency, and nutrient digestibility. Eighteen Holstein x Gyr crossbred multiparous cows (79 ± 38 days in milk and 37.4 ± 4.69 kg/d of milk yield) were used in a replicated 3×3 Latin square design study with three experimental periods of 21 d. The solvent extract soybean meal of the control diet (CON) was replaced by 1.0 (TSBM1.0) and 1.5 (TSBM1.5) kg as-fed basis of amino resin-treated soybean meal (29 and 43% as dry-matter basis, respectively) in the treatment diets. Dry matter intake, milk casein, protein, and fat contents, feed efficiency, nitrogen use efficiency, and nutrient digestibility did not differ among treatments (P > 0.05). The metabolizable protein was not increased by the treatments; however, cows fed with TSBM1.5 tended to produce 1.2 kg/d more milk (P = 0.09) and 64.3 g/d more lactose (P = 0.06) than CON cows. Although the supply of metabolizable protein was not affected by treatments, increasing rumen undegradable protein supply by 43% by replacing conventional solvent-extracted soybean meal with amino resin-treated soybean meal tended to increase milk production of high producing grazing cows.