Response of High Producing Dairy Cows in Early Lactation to the Feeding of Heat-Treated Whole Soybeans

Abstract

Fifty-eight multiparous cows were assigned randomly to one of two rations. Control cows received a concentrate mixture that contained 20% soybean meal as the protein supplement, and the experimental cows were fed a concentrate that contained 25% heat-treated whole soybeans. The experimental period started 10 d after calving and continued for 15 wk. Experimental cows peaked later in milk production (5 vs. 3 wk) but at a higher level (39.8 vs. 39.4 kg/d) than control cows. Although milk production was less during the first 4 wk, experimental cows surpassed the controls in wk 5 and increased the advantage to 2.0 kg/cow/d by wk 15. For the total 15-wk period, average milk production was 37.0 kg/d for the experimental cows compared with 36.2 kg/d for the controls. Total dry matter intake, lactation efficiency, body weight, and reproductive performance were similar for both treatments. Cows fed heated soybeans consumed more metabolizable energy, 61.6 vs. 60.4 Mcal/d for controls. Cows on experimental diet also had higher free fatty acids in plasma (5.6 vs. 4.8 mg/100 ml) and triglycerides (25.0 vs. 20.9 mg/100 ml). The acetate-to-propionate ratio of rumen acids was significantly lower in the experimental group (3.36 vs. 3.61).