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Effects of OmniGen Pro on performance, digestibility, and rumen fermentation of Holstein heifers.

Y. Jiang



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Effects of OmniGen Pro on performance, digestibility, and rumen fermentation of Holstein heifers.
Y. Jiang*, M. Garcia, H. A. Roberts, J. D. Chapman, D. J. McLean. Phibro Animal Health Corporation Teaneck, NJ.

OmniGen Pro (OGPRO; Phibro Animal Health, Teaneck, NJ) is a new OmniGen-family feed additive, developed to maintain the immunological foundation of OmniGen-AF while improving rumen functionality and nutrient utilization. This study aimed to examine the effects of OGPRO on performance, digestibility, and rumen fermentation of dairy heifers. Fourteen Holstein heifers (229 kg BW) were randomly assigned to 1 of 2 treatments: Control (no additive, n = 7) or OGPRO (top-dressed at 4.5 g/45.4 kg BW, n = 7). A single TMR representing a late lactation diet (14.7% CP, 31% NDF, 21% starch, 1.56 Mcal/kg NEL) was offered ad libitum for 16 d before the start of the study and during the 56-d study. Dry matter intake was measured daily and BW recorded every other week. Rumen fluid (d 0, 14, and 28) was collected 4 h after morning feeding via rumenocentesis to quantify fermentation via VFA and pH analyses. On d 29 and 30, fecal grab samples were taken to estimate digestibility using uNDF240 as an internal marker. Data were analyzed with the GLIMMIX procedure of SAS, with significance declared at P ≤ 0.05 and trend at 0.05 < P ≤ 0.10. Treatment did not affect ADG, DMI or D14 rumen fermentation parameters (P > 0.10). At d 28, there were no treatment differences in ruminal pH, propionate and butyrate concentrations and molar proportions, nor ammonia-N concentrations. However, feeding OGPRO numerically increased ruminal concentrations of total VFA (133 vs. 115 mM, P = 0.15) and acetate (90.8 vs. 78.2 mM, P = 0.14) and significantly increased total branched-chain fatty acids (1.44 vs. 1.02 mM, P = 0.04), primarily via an increase in isobutyrate (0.80 vs. 0.51 mM, P < 0.01). In addition, OGPRO tended to increase total-tract DM digestibility (73.3 vs. 67.7%, P = 0.08) compared with Control. These findings suggest that the inclusion of OmniGen Pro in lactating diets may improve nutrient utilization by altering rumen fermentation and DM digestibility.

Keywords: OmniGen Pro, lactating diet, rumen fermentation.