parameters and immune cells of their calves Abstract #17821 Effect of OmniGen-AF® supplementation to heat stressed cows during late gestation on blood parameters and immune cells of their calves AL Skibiel1, JL Powell1, TF Fabris1, YM Torres1, FN Corra1, JD Chapman2, DJ. McLean2, DJ. Kirk2, GE Dahl1, and J Laporta1 1 Department of Animal Sciences, University of Florida, Florida, United States 2 Phibro Animal Health Corporation, Quincy, IL Contact: jlaporta@ufl.edu Introduction Results Exposure to heat stress during the dry period negatively impacts cow immune status. Feeding OmniGen-AF® (OG) has been shown to improve the immune status of the HT cow during lactation, but the effect(s) on dry cows and on the gestating calf are unknown. Our objective was to evaluate the effect of OG supplementation pre-calving (56 g/d, for approx. 105 d) to cows under heat stress (HT, shade) or cooling (CL; shade, fans, soakers) environmental conditions during the dry period (~56d) on the immune, stress response and growth performance of their calves. 1 Colostrum IgG and apparent efficiency of absorption HT, P<0.05 Materials & Methods 24h 1st Feeding HT + Omnigen-AF (HTOG) Heat Stressed (HT) Cooled (CL) 28d 10d Calving Dry period CL + Omnigen-AF (CLOG) 2nd Feeding 56g OmniGen-AF/d No-OG Weaning pasteurized milk (6 L/d) 2 Hematology analysis Laser flow cytometry Optical fluorescence   CL HT P-value day No-OG OG SEM HT*OG HT*day OG*day RBC (M/µl) 7.29 7.75 7.61 8.31 0.35 0.08 0.03 <.0001 0.96 0.98 0.97 1 5.99 6.69 6.58 7.00   WBC (K/µl) 7.36 8.51 8.38 7.85 1.26 0.22 0.13 0.81 0.15 0.07 15.17 10.86 11.48 9.70 Neutrophils 0.62 0.72 0.65 0.59 0.01 0.52 <0.01 0.75 0.09 1.01 0.93 0.74 Lymphocytes 2.50 3.16 2.49 2.93 0.31 0.02 0.12 4.43 2.77 2.38 2.91 Basophils 0.20 0.36 0.29 0.06 0.10 0.60 0.95 0.66 0.17 Cows received OmniGen-AF starting at 60 days in milk (DIM) and during the entire dry period. At dry-off cows were assigned to HT or CL pens to yield a total of 4 treatments: HT (n=8 calves), CL (n=6 calves), HT with OG supplementation (HTOG, n=8 calves) and CL with OG supplementation (CLOG, n=7 calves). At birth calves were fed maternal colostrum. Calving day was consider day 0 of the experiment and heifers were kept until weaning. 3 Acute phase proteins HT, OG, DAY, P<0.05 OG*day, P<0.05 HT*day (tendency) OG, P < 0.05 DAY, P < 0.05 HT*OG, P < 0.05 Blood samples: At birth (0h), 24 h, 10 and 28 d after birth. Measurements: Acute phase proteins, neutrophil function, IgG, IGF-I, cortisol, WBC, RBC Statistical Analyses: The effects of Heat stress (CL vs HT), OmniGen-AF supplementation (OG vs No-OG), days (0, 10, 28) and their interactions were tested using mix models (SAS v9.4)

parameters and immune cells of their calves Abstract # 17821 Effect of OmniGen-AF® supplementation to heat stressed cows during late gestation on blood parameters and immune cells of their calves A Skibiel1, JL Powell1, TF Fabris1, YM Torres1, FN Corra1, JD Chapman2, DJ. McLean2, DJ. Kirk2, GE Dahl1, and J Laporta1 1 Department of Animal Sciences, University of Florida, Florida, United States 2 Phibro Animal Health Corporation, Quincy, IL Contact: jlaporta@ufl.edu Results (continued) 4 Neutrophil function 5 Body weight Rectal temperature DAY, P<0.05 HT*day, P<0.05 HT*OG*DAY, P<0.05 Days relative to calving Summary of findings OG, P=0.07 HT*day, P=0.06 HT*OG*DAY, P < 0.05 HT*day, P<0.05 HT*OG*DAY, P<0.05 Calves born to HS dry cows were 2.8 kg lighter and had higher rectal temperature. Calves born to dams supplemented with OmniGen-AF were 2.2 kg heavier and had lower rectal temperature at birth All dams produce good quality colostrum (> 50g/L, > 22% brix) and HTOG dams had higher brix% compared to HT dams. WBC increased and RBC decreased after maternal colostrum feeding for all groups. However, calves born to OG fed cows had greater RBC counts. There was no difference in total number of leukocytes. However, CL calves had lower lymphocytes but higher basophils than the HT calves and at birth OG calves had more lymphocytes than no-OG calves. Calves born to OG dams had increased circulating SAA and HPT. Specifically, SAA increased on d10 only for the HT and OG calves and then remained elevated compared to d0. HPT increased only on d10, and CLOG calves had higher levels compare to CL calves. There was no effect of maternal heat stress or OmniGen-AF supplementation on cortisol and IGF-1 concentrations. Cortisol decreased gradually with days and IGF-1 was elevated on d28 compared to birth. Calves born to OG fed dams tended to have higher phagocytosis capacity, and calves born to CLOG dams had elevated ROS produced by neutrophils and higher % of neutrophils undergoing phagocytosis, particularly on day 10. Days relative to calving Days relative to calving