PSI-11 Effects of a supplemental water source and trace-mineral based electrolyte drinking solution on intake and blood cell count of newly received feedlot calves

Oral hydration therapy has been used to improve performance and health of newly received feedlot calves; however, little is known regarding water intake (WI) following arrival at the feedlot. Our objective was to evaluate WI of newly received feedlot calves provided a supplemental water source or a novel nutritional rehydration solution during initial 3 days following arrival. Crossbred heifers (n=180; initial BW = 237 ± 23 kg) were individually weighed after 16 h fasting and sorted into 12 pens (4 pens/treatment). Treatments were: 1) Control (CON): water provided through standard in-pen automatic waterer only (Richie CM480; one waterer/pen); 2) Supplemental water (SUPW): CON + water provided with one additional stock tank/pen; 3) Novel nutritional rehydration solution (NRS): trace-mineral based drinking solution provided with one stock tank/pen as the only water source. Treatments were provided from days 0 to 3 after which supplemental tanks were removed. From days 4 to 14 all heifers had access to the standard in-pen automatic waterer only. The WI was measured daily throughout the trial and BW was recorded at days 0 and 14. Whole blood was collected (5 heifers/pen) on days 0, 3, and 14. Treatments had no effect on DMI or ADG (P ≥ 0.15). SUPW and NRS had greater WI than CON from days 0 to d 3 (P ≤ 0.001), but not from days 4 to 14 nor from days 0 to 14 (P = 0.69). No treatment effect or treatment × day interactions were observed for total red (RBC) or white blood cell counts (WBC; P ≥ 0.19); however, a day effect was present (P < 0.001) and RBC and WBC linearly decreased from day 0 to 14 (P < 0.05). Our preliminary results indicate that providing a supplemental source of water during the initial 3 d after arrival increased total WI and may facilitate rehydration in stressed calves following transit.

Importance and Antimicrobial Resistance of Mycoplasma bovis in Clinical Respiratory Disease in Feedlot Calves

Bovine respiratory disease (BRD) is an important viral and/or bacterial disease that mainly affects feedlot calves. The involvement of Mycoplasma bovis in BRD can lead to chronic pneumonia poorly responsive to antimicrobial treatment. Caseonecrotic bronchopneumonia is a pulmonary lesion typically associated with M. bovis. In Spain, M. bovis is widely distributed in the feedlots and circulating isolates are resistant to most antimicrobials in vitro. However, the role of this species in clinical respiratory disease of feedlot calves remains unknown. Furthermore, available data are relative to a fixed panel of antimicrobials commonly used to treat BRD, but not to the specific set of antimicrobials that have been used for treating each animal. This study examined 23 feedlot calves raised in southeast Spain (2016–2019) with clinical signs of respiratory disease unresponsive to treatment. The presence of M. bovis was investigated through bacteriology (culture and subsequent PCR), histopathology and immunohistochemistry. The pathogen was found in 86.9% (20/23) of the calves, mainly in the lungs (78.26%; 18/23). Immunohistochemistry revealed M. bovis antigens in 73.9% (17/23) of the calves in which caseonecrotic bronchopneumonia was the most frequent lesion (16/17). Minimum inhibitory concentration assays confirmed the resistance of a selection of 12 isolates to most of the antimicrobials specifically used for treating the animals in vivo. These results stress the importance of M. bovis in the BRD affecting feedlot calves in Spain.

Effect of sealing on the feed out face of trench silos on the performance of confined calves

ABSTRACT This study aimed to evaluate the productive performance, dry matter intake, apparent digestibility and ingestive behavior of feedlot calves fed corn silage from the feed out face of trench silos with different types of sealing. The animals were divided into three treatments with four repetitions: Conventional seal - double-sided polyethylene of 110µm thickness; Double-sided seal - double-sided polyethylene of 200µm thickness; and Double seal - composed of double face polyethylene with a thickness of 80µm superimposed on a polyamide translucent vacuum film with a thickness of 20µm. The use of double face sealing provided 12.63% increase in average daily gain and improved food conversion by 0.62 percentage points. The apparent digestibility of the diet with double-face sealing system silage was 4.30% higher than the diet with double-face sealing silage and 11.00% higher than the diet with conventional sealing silage. It is recommended to use the double face sealing with 200µm polyethylene and double face sealing with 80µm thick polyethylene on top of a 20µm thick polyamide translucent vacuum film.

Mycoplasma Bovis-pneumonia and Polyarthritis in Feedlot Calves in Argentina: First Local Isolation

Bovine respiratory disease (BRD) is one the most frequently occurring clinical problem in weaned calves after their arrival at the feedlot. Infectious pneumonia usually has complex causes, involving several microorganisms. Mycoplasma is frequently detected in BRD, especially Mycoplasma bovis. This work reports the first local isolation of M. bovis from feedlot calves with pneumonia and polyarthritis in Argentina. Twenty four out of 545 calves showed progressive, subacute to chronic respiratory distress, coughing, and fever. Thirty percent of the affected calves also showed lameness and swelling of elbow or carpal, and knee or tarsal joints. Five necropsies were performed and severe multifocal to coalescent pulmonary nodules, containing white-yellowish caseous exudate encircled by fibrous tissue, and fibrinonecrotic arthritis and tenosynovitis were detected. Mycoplasma was isolated from lung and joint samples. The 16S-23S rRNA ITS consensus sequence obtained from these isolates showed 100 % similarity with the same region of M. bovis strains. This work should alert practitioners about the presence of mycoplasma infections as the cause of BRD in the region. Since there are no commercially available vaccines in the region for the prevention and control of M. bovis pneumonia and arthritis, surveillance is a priority to reduce the source of disease to naïve animals.

280 Relationship of gene markers to residual feed intake, ADG, and marbling of four years of MSU Steer-A-Year steers

Feeding cattle is one of the largest expenses in beef production systems. Genetic testing has been proposed as a tool to help select livestock that are the most efficient, with greater performance and/or carcass yield or quality. Improved beef cattle performance, increased feed efficiency, and increased carcass value are ongoing goals for beef cattle production. For this study, 118 mix breed feedlot calves were genetically tested with The Merial Ltd (Deluth, GA) Igenity GGP Bovine 50K. We compared genotypic and phenotypic average daily gain (ADG), residual feed intake (RFI) and marbling. Igenity scores were not related to ADG in years 1, 2, and 3 (P > 0.14), but were correlated in year 4 (P < 0.01; r = -0.58). Steer RFI displayed no relationship to the Igenity RFI score (P ≥ 0.29). No linear relationships were observed between actual and predicted marbling but did display tendencies to rank animals similar to actual marbling in years 3 and 4 (P ≤ 0.08; P = 0.34, 0.31, respectively). In summary, we did not see a strong relationship between genetic marker predictions and actual performance characteristics. However, relationships appear to be stronger in later years, suggesting more work is needed to validate genetic markers correlation to feedlot performance.