Milk yield and composition of lactating dairy cows fed diets supplemented with a probiotic extract

Thirty-six lactating Holstein cows from the Dairy Research Center at the University of Georgia Tifton Campus were used in a 10-wk randomized-design trial to determine the effects of feeding a nonviable probiotic extract (PD; ProDairy, Donaghys Industries Ltd., Christchurch, New Zealand) on DMI, milk yield, and milk composition. During the first 2 wk of the trial, all cows were fed the control diet, and data collected were used as a covariate in the statistical analysis. At the end of wk 2, cows were assigned randomly to 1 of 2 treatments: 0 (CONT) or 10 mL/d of PD per cow for the following 8 wk. A basal diet was fed to cows once daily behind Calan gates as a TMR in amounts to provide at least 5% refusal. The probiotic extract was added to the TMR and mixed for 10 min before feeding. No differences were observed in DMI between treatments, which averaged 25.3 and 25.6 kg/d for CONT and PD, respectively. Yields of milk (P = 0.001), protein (P = 0.05), and solids-not-fat (P = 0.002) were greater for cows fed diets supplemented with PD compared with CONT. Interactions of treatment and week were observed for each variable because the difference between PD and CONT increased as the trial progressed. Milk urea nitrogen concentrations tended to be reduced (P = 0.10) for PD compared with CONT. No differences were observed among treatments in concentration of milk components or change in BW or BCS. The probiotic extract used in the trial supported greater yield of milk, protein, and solids-not-fat apparently through improved utilization of nutrients consumed.