Bovine respiratory disease (BRD), as one of the most common and costly diseases in the beef cattle industry, has significant adverse impacts on global food security and the economic stability of the industry. The bovine respiratory microbiome is strongly associated with health and disease and may provide insights for alternative therapy when treating BRD. The niche-specific microbiome communities that colonize the inter-surface of the upper and the lower respiratory tract consist of a dynamic and complex ecological system. The correlation between the disequilibrium in the respiratory ecosystem and BRD has become a hot research topic. Hence, we summarize the pathogenesis and clinical signs of BRD and the alteration of the respiratory microbiota. Current research techniques and the biogeography of the microbiome in the healthy respiratory tract are also reviewed. We discuss the process of resident microbiota and pathogen colonization as well as the host immune response. Although associations between the microbiota and BRD have been revealed to some extent, interpreting the development of BRD in relation to respiratory microbial dysbiosis will likely be the direction for upcoming studies, which will allow us to better understand the importance of the airway microbiome and its contributions to animal health and performance.

To investigate the effects of inorganic or amino acid-complexed sources of trace minerals (zinc, copper, manganese, and cobalt) on performance and morbidity of beef heifers during the receiving period, crossbred beef heifer calves (n = 287, initial body weight = 231 kg) arriving on 3 delivery dates were used in a 42-day receiving trial. Heifers were processed after arrival and stratified by day -1 body weights and allocated randomly to 8 pens (11 to 13 heifers/pen; total of 24 pens). Within truckload, pens were assigned randomly to dietary treatment (12 pens/treatment). Calves were housed on 0.42-ha grass paddocks, provided ad libitum access to bermudagrass hay and water, and fed grain supplements that served as the carriers of the dietary treatments. Treatments consisted of supplemental zinc (360 mg/d), copper (125 mg/d), manganese (200 mg/d), and cobalt (12 mg/d) from complexed (Availa 4, Zinpro Corporation, Eden Prairie, MN) or inorganic sources (sulfates). Cattle were observed daily for clinical bovine respiratory disease (BRD). If presenting symptoms of BRD and if rectal temperature was ≥ 40°C, cattle were deemed morbid and treated with an antibiotic according to a standard preplanned protocol. Six heifers/pen were bled to determine serum haptoglobin concentrations on days 0, 14, and 28. Statistical analyses were performed using the MIXED and GLIMMIX procedures of SAS 9.4 with truckload as a random effect and pen within truckload specified as subject. There tended to be a treatment by day interaction for body weights (P = 0.07). Body weights did not differ on day 0 (P = 0.82) and day 14 (P = 0.36), but heifers supplemented with complexed trace mineral sources had greater body weights on day 28 (P = 0.04) and day 42 (P = 0.05; 264 vs. 260 kg, SE = 1.8). Overall average daily gains were greater for heifers supplemented with the complexed trace mineral sources (P = 0.05; 0.78 vs. 0.70 kg, SE = 0.03). Cattle supplemented with inorganic trace mineral sources had greater BRD morbidity incidence than cattle supplemented with complexed trace mineral sources (P = 0.03; 58 vs. 46%, SE = 3.6). Medication costs were lower for heifers supplemented with complexed trace mineral sources (P = 0.05; $11.01 vs. $14.90, SE = 1.33). Haptoglobin concentrations decreased throughout the trial (day, P < 0.001), and cattle supplemented with complexed trace mineral sources tended to have lower haptoglobin concentrations (P = 0.07). In conclusion, supplementing cattle for the first 42 days after arrival with amino acid complexed trace mineral sources improved heifer performance as compared to heifers supplemented with inorganic trace minerals.

The objective of this study was to assess the effect of winter hair coat shedding for crossbred Angus dams (n = 544) on calf birth weights, calf weaning weights (WW), calf adjusted 205-day weaning weights (d205wt), artificial insemination (AI) pregnancy rates, overall pregnancy rates, cow pre-breeding body weights (PBW), cow pre-breeding body condition scores (PBCS) over a two-year collection period. Hair shedding data were collected on fall-calving crossbred cows from March to July using a visual hair shedding score of 1 to 5 was assigned to each cow, with 1 exhibiting 100% shedding of winter coat to 5 exhibiting 0% shedding of winter coat. Month of first shedding (MFS) was determined once a female reached a hair shedding score of ≤ 3 for any given month. Artificial insemination pregnancy and overall pregnancy was determined by rectal ultrasound. Data were analyzed using the MIXED procedure of SAS for calf performance, cow BW, and cow BCS, and the GLIMMIX procedure of SAS for AI pregnancy and overall pregnancy analyses. Statistical significance was declared at P ≤ 0.05 and tendencies declared at 0.05 < P ≤ 0.1. There was no effect of MFS on calf birth weights (P = 0.79), WW (P = 0.12), d205wt (P = 0.28), AI pregnancy (P = 0.76), overall pregnancy (P = 0.80), PBW (P = 0.11), and BCS (P = 0.69). The findings reported in this study indicate that MFS had no effect on cowherd performance during this two-year study in Arkansas; however, there is a need for continuing research to be performed to evaluate the effects of winter hair coat shedding in other environments.

Bovine viral diarrhea virus (BVDV) is a critical disease negatively impacting many facets of the cattle production system. Cattle infected with the persistent (PI) form of BVDV are the primary reservoirs and source of transmission and may be implicated with an increased risk of bovine respiratory disease (BRD) to exposed calves in feedlots. To date, little to no data exists regarding characterization of the effects PI-BVDV has on the bovine nasal microbiome, an important feature for bovine health. To investigate these effects, Angus-crossbred beef calves were selected and randomly assigned to either continuous exposure (E, n = 3) or non-exposure (NE, n = 3) to an auction market sourced PI-BVDV positive (PI, n = 1) calf from weaning to 112 days post-weaning. Nasal swab samples were collected upon weaning, 56 days post-weaning, and 112 days post-weaning. Next generation sequencing was used to measure the effects of PI-BVDV on the nasal microbiome. Alpha diversity, including Shannon Index and Observed OTUs, and beta diversity, including Bray-Curtis and Jaccard distances, were not different (P > 0.05) between treatments. Next, community structure was assessed at the amplicon sequence variant (ASV) level and LEfSe was used to identify the bacterial biomarkers for each treatment. Results indicated that ASV5-Mycoplasma could be a biomarker for the PI and E treatments due to its high relative abundance in each when compared with the NE treatment. Overall, ASV5-Mycoplasma was identified as a potential biomarker for the prediction and diagnosis of persistently infected bovine viral diarrhea virus among both calves infected with and exposed to the virus and may be an additional biomarker for the increased risk of bovine respiratory disease in exposed feedlot cattle.

The objective of this experiment was to further investigate the effects of phosphorus intake on beef heifer growth performance and conception rates. An increase in phosphorus soil concentrations from use of livestock manure as fertilizer in Northwest Arkansas has led to greater phosphorus concentrations available in forages. This study was designed to determine if phosphorus supplementation is warranted when adequate phosphorus soil concentrations exist. This experiment was conducted over 2 years using two separate groups of weaned crossbred Angus heifers (n=72/year). Approximately 30 d after weaning, heifers were stratified by body weight (average initial weight 262kg) and allocated randomly to 14 groups (8 in Year 1, 6 in Year 2). Groups were assigned randomly to 1 of 2 treatments: 1) a free-choice-mineral mix that contained no supplemental phosphorus (CON), or 2) a free-choice-mineral mix with 4% supplemental phosphorus and identical concentrations of other supplemental minerals (4PMIN). Heifers grazed 2.24 ha mixed grass pastures with a history of livestock manure application and were supplemented with soy hulls (0.5% of body weight) daily. On d 112, heifers > 273 kg body weight had an ultrasound evaluation of reproductive tracts (1= infantile, 5= cyclic). Heifers were determined pregnant or open via rectal ultrasonography. Data were analyzed using the MIXED or GLIMMIX procedures of SAS 9.4 with group within year as the experimental unit. There were no differences in gain for either treatments for the 224-day period (P ≥ 0.14). Reproductive tract scores did not differ (P = 0.95). There were no differences for conception rates (AI or natural bred) (P ≥ 0.55). Overall pregnancy was 79% for CON and 83% for 4PMIN. Heifers grazing pastures with a history of livestock manure application did not benefit from adding supplemental phosphorus in the free choice mineral offered.

The objective of this experiment was to evaluate the effect of maternal phosphorus intake on growth and health of their calves. Treatments were 1) a free-choice mineral containing no supplemental P or 2) a free-choice mineral with 4% supplement phosphorus. Primiparous crossbred Angus beef cows (n = 36) were stratified by body weight and pregnancy status (bred by artificial insemination or natural service) then assigned to pasture groups (4 groups, 2/treatment, 9 heifers/group). These bred heifers had been receiving these same dietary treatments from 30 days after weaning until confirmation of pregnancy. Eighteen bred heifers from each treatment were selected randomly to continue into this experiment. At calving, colostrum and blood samples were collected from a subset of 12 heifers/treatment (6/group) and evaluated. Body weights and calf viability scores were obtained for all cattle. Data were analyzed using the MIXED (for continuous data) and GLIMMIX (for scoring data) procedures of SAS using group as the experimental unit. Cows grazed mixed grass pastures; monthly forage samples ranged from 0.28 to 0.36% P. There were no differences (P > 0.10) for cow body weight during gestation, calf birth weight, calf viability scores at birth, or calf weight at an average age of 21 days. There were also no differences (P > 0.10) in colostrum components (fat, protein, lactose, and IgG), or in the serum IgG or plasma mineral concentrations for both cows and calves 48 hours after parturition. All calves were sampled at approximately 21 days of age and there were no treatment differences (P > 0.10) in serum IgG concentrations. There were no benefits to supplementing gestating heifers with phosphorus when they grazed pasture with a history of fertilization with livestock manure.

Bovine Respiratory Disease (BRD) is the most devastating disease affecting cattle producers in North America. Vaccines and antimicrobials are commonly used to prevent and treat BRD. However, it is still a growing problem. The four common BRD opportunistic pathogens, Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis, are present in the upper respiratory tract of healthy cattle as well, and how they move to the lung are unknown. The apparent role of the respiratory microbiome in BRD has led to many microbiome studies. However, most culture-independent studies have focused on the opportunistic pathogens, and little is known about the potential bacterial probiotics in the prevention and treatment of BRD. This study aims to identify potential probiotics to treat and prevent BRD by analyzing respiratory microbiotas (nasal swabs (NS): healthy: n=94, BRD: n=94; nasopharyngeal swabs (NPS): healthy: n=25, BRD: n=36; and bronchoalveolar lavage (BAL): healthy: n=22, BRD: n=29) from clinically healthy calves at feedlot entrance and calves at BRD diagnosis. Amplicon sequence variants (ASVs) were classified as potential probiotics if selected as a top predictor by a machine learning technique (random forest) and significantly more abundant in healthy controls (log2fold change ≥ 2 and P<0.05) based on DESeq2. ASV98_Corynebacterium was a potential probiotic in all three locations. ASV121_JG30-KF-CM45_unclassified, ASV32_Corynebacterium, and ASV64_Serinicoccus were potential probiotics in NPS and BAL. Additional taxa were potential probiotics in a single location, including ASV114_Streptococcus_luteciae and ASV233_Facklamia in NS; and ASV150_Facklamia, ASV26_Corynebacterium, ASV306_Facklamia, and ASV44_Dietzia in NPS. SPARCC network analysis revealed that ASV114_Streptococcus_luteciae was the top hub taxa in healthy calves’ NS, and ASV32_Corynebacterium and ASV26_Corynebacterium were in the top five hub taxa of healthy calves’ NPS, indicating that these ASVs are key members of their respective communities. Furthermore, SPARCC found ASV32_Corynebacterium is negatively correlated with ASV2_Mycoplasma (-0.25) in NS and ASV5_Mycoplasma_hyorhinis (-0.23) in NPS (P <0.05). Additionally, ASV26_Corynebacterium is negatively associated with ASV62_Ureaplasma (-0.37) and ASV5_Mycoplasma_hyorhinis (-0.21) in NPS and ASV12_Histophilus_somni in (-0.29) in BAL (P <0.05).

Crossbred beef calves (n = 30) were stratified by gender and BW and placed into 1 of 16 dry lot pens. Pens were allocated to either: 1) the control treatment (CON) with calves fed a basal ration containing 31 mg of zinc/kg DM; or 2) Zn supplemented treatment (SUP) with calves fed the basal ration supplemented with 30 mg of zinc/kg DM (provided as zinc amino acid complex). Growth performance was recorded every 28-d during the 143-d study. On d 115, cattle were given a commercial vaccine containing M. bovis and M. bovoculi bacterins. Blood samples were collected and analyzed for serum zinc, alkaline phosphatase activity (ALP, 28-d intervals), and vitamin A (d 0 and 143). Samples for serum and tear IgG concentrations specific for M. bovis and M. bovoculi were taken on d 115, 129, and 143. Data were analyzed as repeated measures, where appropriate, using the MIXED procedure of SAS. Dietary zinc status did not impact liver or zinc concentrations (P ≥ 0.36), BW (P ≥ 0.66) or ADG (P ≥ 0.14). There was no effect of treatment (P ≥ 0.16) or treatment by time interaction (P > 0.39) on tear IgG specific for either M. bovis or M. bovoculi. However, serum IgG concentrations specific for M. bovis were greater (P = 0.02) in CON calves compared with SUP calves, and serum IgG concentrations specific for M. bovoculi tended (treatment by time, P = 0.08) to increase more in CON calves. Both serum and tear IgG concentrations specific for either bacterin increased (day effect, P < 0.001) from d 115 to 143. Results did not support a relationship between dietary Zn and eye health in cattle. However, this could be explained by the similarity in liver and serum zinc concentrations.