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.