Feeding okara, a soybean by-product, to dairy cows as partial protein source enhances economic indexes and preserves milk quality, intake, and digestibility of nutrients

This study was carried out to evaluate the potential of dietary inclusion of okara (a soybean by-product) on feed intake, apparent in vitro digestibility of dry matter, production and milk quality of dairy cows, and economic indexes. Four lactating Holstein cows were assigned to a 4 × 4 Latin square design. Treatments were control diet with no okara, diet with 35 g/kg okara, diet with 65 g/kg okara, and diet with 95 g/kg okara in dry matter basis. There was no effect of the inclusion of okara in the diet on the intake of dry matter, crude protein, and ether extract. The inclusion of okara did not affect the in vitro digestibility of nutrients either. However, neutral detergent fiber intake differed between levels 0 and 35 g/kg of okara in the diet, with lower (8.15 kg/day) and higher (9.30 kg/day) values for these treatments, respectively, with values intermediates for the other treatments. There was no significant difference for milk production, fat, protein, lactose, milk urea, somatic cell score, and conjugated diene. However, there was an effect of including okara on thiobarbituric acid reactive substance content in milk. Regarding the economic analysis, the inclusion of 95 g/kg of okara in the diet (dry matter) showed the best results for average feed cost, gross margin, breakeven, and profitability index. Okara can be included in diets of lactating dairy cows up to 95 g/kg of total mixed ration on dry matter basis without interfering on milk production, milk solids, nutrient digestibility, and providing beneficial economic indexes, being economically feasible.