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| Forty-four transition Holstein cows were blocked by parity and expected calving date, and allocated to four treatments with a randomized complete block design to evaluate the effects of feeding glycerol-enriched yeast product (GYP) to transition dairy cow on lactation performance, blood metabolites, and rumen fermentation. Treatments were as follows: control (no additive), 2 L/d GYP (75.8 g/L glycerol and 15.3 g/L yeast), 150 g/d glycerol (G, 0.998 g/g glycerol), and 1 L/d yeast culture (Y, 31.1 g/L yeast). All additives were topdressed and hand-mixed into the upper one-third of total mixed ration in the morning feeding from -14 to +28 day relative to calving. Results indicated that dry matter intake, changes in body weights and body condition scores, as well as milk yield were not affected by treatments. However, cows fed GYP and Y had higher milk fat and milk protein percentages than control cows (P < 0.05). Compared with control, feeding GYP and G to cows increased the concentration of plasma glucose coupled with decreased concentrations of plasma beta-hydroxybutyrate acid and nonesterified fatty acid (P < 0.05). Additionally in ruminal parameters on 14 d postpartum, cows fed GYP and Y had higher total volatile fatty acids, and cows fed GYP and G had higher molar proportions of propionate than control cows (P < 0.05). In conclusion, GYP is a feasible feed additive of transition dairy cows, which can improve energy status and lactation performance and rumen fermentation via the effects of glycerol and yeast, respectively. |
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| Keywords:transition dairy cow; glycerol; yeast; blood metabolites |
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