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Yeast Additive Effects on Dry Matter Intake, Milk Production, Milk Composition, and Ruminal Metabolism in Lactating
Michaela R Plowman1, Barry D Lambert1, James P Muir2,3
1Department of Animal Science, Tarleton State University, Stephenville, TX 76402, USA.
None:
Saccharomyces cerevisiae yeast products are used to stabilize dairy cattle rumen environments. In this study, multiparous lactating Holstein-Jersey cross cows in late lactation (n = 12; ±150 DIM) were used in a replicated 4 × 4 Latin square design over four 21 d periods to evaluate yeast supplementation on dry matter intake (DMI), milk production, milk components, rumen pH, and redox potential (Eh). A subset of four ruminally cannulated cows were selected for rumen measurements. Treatments included no additive (CON), 14 g yeast culture additive (YCA), 5 g active dry yeast (ADY), and 5 g ADY + 5 g yeast extract additive (YEA) top-dressed once daily. Data were analyzed using GLIMMIX in SAS 9.4, with significance at p ≤ 0.05 and tendencies at p ≤ 0.15. Dry matter intake did not differ among treatments (p > 0.15) but decreased over time (p < 0.05). Milk production, efficiency, lactose, and total solids were not affected (p > 0.15). YCA tended to increase milk fat and fatty acid fractions compared with CON (p < 0.15). Protein in milk was greater in CON (p < 0.05; p < 0.05) than YCA and YEA. Active dry yeast treatments increased the frequency of a buffered rumen (p < 0.05) and promoted a more reducing ruminal environment, characterized by lower redox potential and conditions favorable for anaerobic fermentation (p < 0.05). Overall, supplementing active dry yeasts to dairy cows in late lactation did not affect DMI, production efficiency, or milk quality, but may maintain rumen pH stability.
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