Gut microbial colonization and establishment are vital to ruminant health and production. This review article focuses on current knowledge and methods used to understand and manipulate the gut microbial community in ruminant animals, with a special focus on probiotics treatment. This review highlights the most promising of studies in this area, including gut microbial colonization and establishment, effect of gastrointestinal tract microbial community on host mucosal innate immune function, impact of feeding strategies on gut microbial community, current probiotic treatments in ruminants, methods to manipulate the gut microbiota and associated antimicrobial compounds, and models and cell lines used in understanding the host immune response to probiotic treatments. As a lot of work in this area is done in humans and mice, this review article also includes up-to-date knowledge from relevant studies in human and mouse models. This review is a useful resource for scientists working in the areas of ruminant nutrition and health, and to researchers investigating the microbial ecology and its relation to animal health.

In mammals, microbial colonization of the digestive tract (GIT) occurs right after birth by several bacterial phyla. Numerous human and mouse studies have reported the importance of early gut microbial inhabitants on host health. However, few attempts have been undertaken to directly interrogate the role of early gut/rumen microbial colonization on GIT development or host health in neonatal ruminants through artificial manipulation of the rumen microbiome. Thus, the molecular changes associated with bacterial colonization are largely unknown in cattle. In this study, we dosed young calves with exogenous rumen fluid obtained from an adult donor cow, starting at birth, and repeated every other week until six weeks of age. Eight Holstein bull calves were included in this study and were separated into two groups of four: the first group was treated with rumen content freshly extracted from an adult cow, and the second group was treated with sterilized rumen content. Using whole-transcriptome RNA-sequencing, we investigated the transcriptional changes in the host liver, which is a major metabolic organ and vital to the calf’s growth performance. Additionally, the comparison of rumen epimural microbial communities between the treatment groups was performed using the rRNA reads generated by sequencing. Liver transcriptome changes were enriched with genes involved in cell signaling and protein phosphorylation. Specifically, up-regulation of SGPL1 suggests a potential increase in the metabolism of sphingolipids, an essential molecular signal for bacterial survival in digestive tracts. Notably, eight genera, belonging to four phyla, had significant increases in abundance in treated calves. Our study provides insight into host liver transcriptome changes associated with early colonization of the microbial communities in neonatal calves. Such knowledge provides a foundation for future probiotics-based research in microbial organism mediated rumen development and nutrition in ruminants.

Background: Nonambulatory cattle present therapeutic challenges in addition to animal welfare concerns. Flotation therapy is a treatment option, but more information regarding prognostic indicators for survival is needed to guide use of this modality. Hypothesis/Objectives: Evaluate historical and clinical variables assessed during hospitalization as prognostic indicators for survival in recumbent cattle undergoing flotation treatment in a referral hospital. Animals: A total of 190 nonambulatory dairy cattle. Methods: Retrospective case series. Medical records were analyzed from cattle undergoing flotation between 2000 and 2020. Univariable and multivariable logistic regression analyses were performed to assess the association of clinical variables with survival to discharge.Results: Eighty-nine of 190 (47%) recumbent cattle survived to discharge. For each additional day of hospitalization, cattle were 1.10 (95% confidence interval [CI], 1.02, 1.21) times more likely to survive. Cattle unable to walk out of the tank after their first float session were 0.11 (95% CI, 0.04, 0.28) times less likely to survive compared to cattle that could and inappetent cattle were 0.22 (95% CI, 0.07, 0.63) times less likely to survive compared to cattle with normal appetites. Cattle diagnosed with coxofemoral luxation or toxemia were 0.11 (95% CI, 0.02, 0.65) and 0.16 (95% CI, 0.02, 0.90) times less likely to survive, respectively, compared to cattle with causes of recumbency that were undetermined.Conclusions and Clinical Importance: Walking out of the tank after the first float session, appetite, diagnosis, and days of hospitalization are associated with outcome in nonambulatory dairy cattle treated by flotation. These findings can be used to determine likely outcome and guide treatment, referral, or euthanasia decisions.

The primary objective of this randomized controlled challenge study was to investigate the effect of ampicillin on ultrasonographic (US) lung consolidation after experimental challenge with Pasteurella multocida in preweaned dairy calves. The secondary objectives were to determine whether ampicillin affected respiratory score, gross consolidation, or the detection of P. multocida in lung tissue at postmortem exam (PME). Holstein bull calves (n = 39) were transported to the University of Wisconsin-Madison School of Veterinary Medicine isolation facility at the mean (±SD) age of 52 ± 6 d. After a 7-d acclimation period, 30 calves were inoculated intratracheally with 10 10 cfu of ampicillinsensitive P. multocida. Lung US and respiratory scoring were performed 2, 6, 12, and 24 h post-challenge, then US once daily and respiratory scoring twice daily until d 14. Calves were randomized to receive ampicillin [n = 17, treatment (TX), 6.6 mg/kg i.m. once daily for 3 d] or placebo [n = 11, control (CON), saline, equal volume, i.m. once daily for 3 d] when ≥1 cm 2 of lung consolidation was observed and ≥6 h had elapsed since challenge. Lung lesions ≥1 cm 2 were considered positive for consolidation. Calves were respiratory score positive if ≥2 in 2 or more categories based on the Wisconsin respiratory health score chart. Area under the curve (AUC) was calculated for US score and respiratory score as a proxy for time with consolidation and clinical respiratory disease, respectively. Gross lung lesions and pathogens were quantified following PME. At the time of first treatment, consolidation had developed in 28/30 calves (TX, n = 17; CON, n = 11) and 6% (1 out of 17) of TX and 9% (1 out of 11) of CON calves had a positive respiratory score. The TX calves had a significantly lower median (interquartile range given in parentheses) AUC for US score [TX: 23 (20, 29), CON: 47 (33, 53)], whereas mean AUC for respiratory score was not different between groups (TX: 93 ± 28, CON: 96 ± 17). On d 14, 70% (12 out of 17) of TX and 100% (11 out of 11) of CON calves had lung consolidation, and 24% (4 out of 17) of TX and 27% (3 out of 11) of CON calves had clinical respiratory disease. On PME, median consolidation was 10% (6, 15) for TX and 10% (2, 28) for CON calves. Lung cultures were positive for P. multocida in 77% (13 out of 17) of TX and 91% (10 out of 11) of CON calves. Lung health benefited from a 3-d ampicillin therapy, but benefits were short-lived. Treatment failures might be due to incomplete resolution of the initial lung infection. Future studies are needed to optimize TX strategies to improve long-term lung health.

The primary objective of this randomized controlled trial was to determine whether anti-IL-10 egg yolk antibodies fed upon arrival to a calf ranch would lower the prevalence of Cryptosporidium parvum shedding in naturally challenged preweaned dairy calves. The secondary objectives included measuring the effect of anti-IL-10 antibodies on calf health, performance, and shedding of less common diarrheal pathogens. A total of 133 calves, enrolled at 24 to 72 h of age, received a daily dose of 0.96 g of egg yolk powder with anti-IL-10 antibodies (MAB, n = 71) or without anti-IL-10 antibodies (MEP, n = 62) split between 2 feedings for the first 11 d on feed at a calf ranch. Daily health evaluations were completed for 15 d after arrival and on d 56. Digital weights were collected at enrollment and d 56, and hipometer weights were collected at enrollment and d 7 and 56. Packed cell volume and serum total protein concentration were measured at enrollment and on d 7 and 14. Fecal pH was measured at enrollment and on d 5 and 14, and fecal pathogen (C. parvum, coronavirus, rotavirus, and Salmonella spp.) shedding was assessed at d 5 and 14. Continuous outcomes were compared between groups using a Student's t-test or Wilcoxon rank sum test. Fecal pathogen shedding at d 14, respiratory disease at d 56, and antibiotic usage were compared using relative risk (RR) and chi-squared test. Fecal pH (median and interquartile range) on d 14 was 6.65 (6.39-6.99) and 6.52 (5.97-6.81) for MAB and MEP, respectively. On d 56, the risk of respiratory disease was lower for MAB compared with MEP (RR = 0.40; confidence interval = 0.16-0.99). The risk for antibiotic treatment was lower for MAB- compared with MEP-treated calves (RR = 0.38; confidence interval = 0.17-0.88). The risk of shedding rotavirus was higher in MAB (RR = 1.38; confidence interval = 1.10-1.81) calves. After multivariable analyses, hipometer weights (least squares means ± standard error) were 1.7 ± 0.8 kg greater on d 56 in MAB compared with MEP; however, ADG was 0.04 ± 0.02 kg/d lower in MAB calves. Total health score, diarrhea days, average respiratory score, packed cell volume, and serum total protein were not affected by feeding anti-IL-10 egg antibodies. In summary, feeding anti-IL-10 antibodies was associated with increased fecal pH, reduced risk of respiratory disease later in the preweaning period, and decreased antibiotic usage despite higher rotavirus infection. These findings might be associated with improved mucosal immunity, enhanced host defenses, or reduced susceptibility and warrant further investigation.