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Effect of a live yeast supplement and altered ruminal fermentability of dietary starch on the yields of milk and milk components of mid- to late- lactation dairy cows.

U. Abou-Rjeileh

Abstract:

416
Effect of a live yeast supplement and altered ruminal fermentability of dietary starch on the yields of milk and milk components of mid- to late- lactation dairy cows.
U. Abou-Rjeileh*, A. N. Negreiro, A. L. Lock. Michigan State University East Lansing, MI.

We evaluated the effect of a live yeast supplement and changes in ruminal fermentability of dietary starch on feed intake and the yields of milk and milk components of mid- to late-lactation dairy cows (158 � 76 DIM). Thirty-two multiparous Holstein cows (45.5 � 5.1 kg/d) were used in a crossover design with two 28-d periods. A fermentable starch challenge (FSC) on the last 7 d of each period was utilized as a split-plot within period. Cows were blocked by milk yield and randomly assigned to 1 of 2 treatments. Treatments were: 1) control diet with no live yeast supplementation (CON); and 2) diet supplemented with a live yeast supplement (Saccharomyces cerevisiae from Phileo by Lesaffre) at 0.03% diet DM (YEAST). Diets were formulated to contain (% DM) 19.8% NDF, 28.8% starch, 16.9% CP, and 4.5% fat. Diets containing a 2:1 ratio (DM basis) of dry ground corn (DGC) to high-moisture corn (HMC) were fed from d 1—21 of each period. During the last 7 d of each period the ratio of DGC to HMC was switched to a 1:2 ratio to increase ruminal starch fermentability. Response variables were averaged for d 17—21 (before the FSC period) and d 27 and 28 (during the FSC period). The statistical model included the random effect of cow and fixed effects of treatment, period, challenge, and their interactions. There was no effect of treatments on DMI or the yields of milk and milk components (all P > 0.13). While there was no main effect of the FSC on DMI or the yields of milk and milk components (all P > 0.30), effects on milk fat content and yield varied for CON and YEAST. During the FSC, milk fat yield decreased from 1.69 to 1.62 kg/d for CON but was not different for YEAST (1.68 to 1.66 kg/d; interaction P = 0.06). Milk fat content decreased from 3.55 to 3.39% for CON but was not different for YEAST (3.51 to 3.47%; interaction P = 0.05). Overall, the live yeast supplement did not impact DMI or the yields of milk and milk components. Results demonstrate that a live yeast supplement may help prevent milk fat depression during transition to a diet with increased ruminal starch fermentability.

Keywords: live yeast, starch, milk fat.

Biography: My name is Ursula Abou-Rjeileh. I was born and raised in Beirut, Lebanon and moved to the US to attend MSU. I'm currently an undergraduate research assistant in Dr. Lock's lab in the Animal Science Department, and in Dr. Contreras's lab in the College of Vet Med at MSU. I plan on pursuing a graduate degree in Dairy Science starting Fall of 2020 to build a stronger foundation in an area that I love. In the future, I see myself working with a team of researchers, making advances in animal health and medicine.