Effects of replacing soybean meal with heat-treated soybean meal in diets varying in preotien content on performance of dairy cows under mild heat stress

This study examined the effects of partial replacement of soybean meal (SBM) with heat-treated soybean meal (HSBM) in heat-stressed cows. 32 multiparous Holstein cows (DIM = 110 ± 20; milk yield = 40 ± 4.1 kg) were used in a complete block randomized design with a 2×2 factorial arrangment of treatments. Treatments included two dietary crude protein levels (i.e. 17 and 15.5%) each combined with HSBM partially replaced for SBM. The experiment was conducted in two periods of 28 days with the last seven days for sampling and collection of data of tempreature, nutrient intake and digestibility and blood variables. Average THI showed that cows were in mild heat stress (70.60 and 71.50 for periods 1 and 2, respectively)(p > 0.05). Diets with 15.5% CP and based on HSBM increased intakes of dry and organic matter (p 0.05). Butyric and isovaleric acid were increased in cows received HSBM (p