Evaluation of feeding immunoglobulin-Y to Holstein feeder cattle for the control of liver abscesses

An immunoglobulin-Y (IGY) feed additive that targets Fusobacterium necrophorum and Trueperella pyogenes was compared to tylosin phosphate (TYL) for effect on liver abscess prevalence, severity, bacterial DNA, and antibiotic-resistant (AMR) Enterococcus fecal load in Holstein steers (n = 64; body weight = 388 ± 3.37 kg). Secondary objectives included abscess detection via liver chemistry blood panel and evaluation of bacterial DNA from healthy and abscessed livers. Steers were used in a completely randomized design and allocated to 1 of the following treatments: TYL (tylosin phosphate; daily intake: 90 mg/hd; n = 32) or IGY (daily intake at 2.5 g/hd; n = 32); with a basal ad libitum high concentrate diet for 188 d and individual intake was recorded to determine feedlot performance. After 150 d fecal samples were randomly obtained from each treatment (n = 40) and cultured on Enterococcosel (ENT) agar and ENT amended agar with erythromycin (8 μg/mL) to define the proportion of AMR Enterococcus excreted. Within 48 h of harvest, venous blood was collected for a liver chemistry panel analysis. At harvest, carcasses and livers were graded. Purulent material from liver abscesses and tissue of healthy livers were collected for bacterial DNA analysis. Continuous data variables were analyzed using the MIXED procedure of SAS and ordinal data variables via the FREQ procedure. Treatment did not affect feedlot performance or carcass characteristics, except for greater dry matter intake (P = 0.015) and fat thickness (P = 0.015) for TYL group. Proportion of macrolide-resistant Enterococcus growth from feces was greater for TYL than IGY (42.6 vs. 21.9%, respectively; P < 0.04). Treatment did not affect liver abscess prevalence (TYL = 63% vs. IGY = 52%; P = 0.40), severity (P = 0.23). Abscessation lowered albumin (P = 0.04) but not other blood analytes. Bacterial DNA data indicated that alpha and beta diversity metrics were different between liver abscess severity scores. No difference in relative abundance of F. necrophorum (P = 0.23) or T. pyogenes (P = 0.76) was observed in abscessed livers. In normal livers, relative abundance of T. pyogenes was lesser for IGY than TYL (0.039 vs. 0.44% respectively; P = 0.03), but F. necrophorum was not affected (P = 0.58). Providing IGY rather than TYL did not affect the liver abscess prevalence, severity, and decreased the proportion of AMR Enterococcus shedding in feces by half indicating IGY could be a viable antibiotic alternative.