CASE STUDY: Effects of a supplemental enhanced yeast product on digestion and milk production in dairy cows

This research evaluated the effects of an enhanced yeast product (EY) on in sacco and total digestion of nutrients and milk production by lactating cows. For the in sacco study, 4 rumen-cannulated, lactating Holsteins received a common TMR for 1 wk. Thirty grams of EY per day was topdressed daily to 2 of the 4 cows. Corn silage, alfalfa silage, timothy hay, corn grain, and soybean meal were incubated in sacco. Digestion kinetics were calculated. The EY reduced lag to digestion for the corn silage (P < 0.05) and alfalfa silage (P < 0.10). Digestion rates of NDF were greater for corn grain and soybean meal (P < 0.10) with EY. Solubility of DM was greater with EY than control for corn grain and soybean meal. For the digestion trial, 8 lactating Holsteins were divided equally into 2 groups. Thirty grams of EY per day was topdressed after a.m. feeding for the test group, and this group was compared with the control. There were no differences (P > 0.05) in total-tract nutrient digestibility. Urinary N losses were reduced (P < 0.10) by EY. Fourteen on-farm feeding experiments were conducted. In 5 trials in which the control diet contained no yeast, 150-d milk increased in 4, fat percentage increased in 2, and protein percentage increased in 2 trials with EY (P < 0.10). In 9 trials in which EY replaced a yeast product, 150-d milk increased in 6, fat percentage increased in 2 and declined in 2, and protein percentage increased in 1 and declined in 1 study. The EY alters fermentation, which can positively but inconsistently influence milk production.