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Effects of an immunomodulatory feed additive on performance of transition cows.

C. S. Takiya




Effects of an immunomodulatory feed additive on performance of transition cows.
C. S. Takiya*1, L. K. Mamedova1,2, M. Garcia3, D. E. Nuzback3, B. J. Bradford1,2. 1Kansas State University Manhattan, KS, 2Michigan State University East Lansing, MI, 3Phibro Animal Health Teaneck, NJ.

The transition period is characterized by metabolic and hormonal changes to promote milk yield at the expense of body nutrient reserves. OmniGen-AF (OMN, Phibro Animal Health, Teaneck, NJ) is a commercial feed additive that has demonstrated positive impacts on productivity and metabolism of transition cows during stressful events such as heat stress. Thirty-four multiparous cows were blocked by expected calving date and assigned to control (305ME: 14,926 kg, 1.73 parities) or OMN (56 g/d top-dressed; 305ME: 14,325 kg, 1.46 parities) from dry-off (−67 � 3.0 d relative to actual calving date) until 49 d in milk. Dry matter intake (DMI) was measured daily from −30 to 49 d relative to parturition (RTP) and milk yield was recorded throughout the study. Blood samples were collected at enrollment, d −30, −14, −7, 1, 14, 28, and 42 RTP for assessment of plasma concentrations of glucose, free fatty acids (FFA), and β-hydroxybutyrate (BHB). Temperature-humidity index (THI) was measured throughout the study with data loggers. Models assessed fixed effects of 305ME, treatment, time, and their interaction, and random effects of cow and block; fixed effects of parity group, THI, and all interactions were also tested and retained if P < 0.15. Significance was declared at P < 0.05. Postpartum data from 6 cows were not considered in analysis due to illness. Treatment did not affect DMI either prepartum or postpartum. Cows fed OMN had lesser milk yields compared with CON (51.8 vs. 53.3 � 1.19 kg/d). However, when peripartum THI was greater than 66, OMN cows produced more milk than CON cows (THI2 � treatment P < 0.01). Treatments did not affect plasma glucose concentration either in pre- or postpartum periods. OMN decreased plasma FFA (482 vs. 331 � 52 �M) and BHB (562 vs. 464 � 43 �M) concentrations during the postpartum period. Feeding OMN from dry-off through 49 d in milk apparently slowed adipose tissue mobilization and modulated milk yield depending on environmental conditions.

Keywords: OmniGen-AF, heat stress, milk.