Mitochondrial genomes show wide variation in their GC content. This study examines the correlations between mitochondrial genome-wide shifts in this feature and a fragment of the cytochrome c oxidase subunit I (COI) gene in animals, plants, and fungi. Because this approach utilizes COI as a sentinel, analyzing sequences from repositories such as GenBank and the Barcode of Life Data System (BOLD) can provide rapid insights into nucleotide usage. With this approach we probe nucleotide composition in a variety of taxonomic groups and establish the degree to which mitochondrial GC content varies among them. We then focus on two groups in particular, the classes Insecta and Aves, which possess the highest and lowest GC content, respectively. We establish that the sentinel approach provides strong indicators of mitochondrial GC content within divergent phyla (R values = 0.86-0.95, p < 0.001, in test cases) and provide evidence that selective pressures acting on GC content extend to noncoding regions of the plant and fungal mitochondrial genomes. We demonstrate that there is considerable variation in GC content of the mitochondrial genome within phyla and at each taxonomic level, leading to a substantial overlap zone in GC content between chordates and invertebrates. Our results provide a novel insight into the mitochondrial genome composition of animals, plants, and fungi and advocate this sentinel technique for the detection of rapid alterations in nucleotide usage as a measure of mitochondrial genome biodiversity.

Selective antimicrobial treatment strategies present a means to reduce antimicrobial use at the time of arrival at a veal or dairy beef operation. On-farm machine leukocyte differential cell counts (DCC) that can be acquired quickly may be useful to augment calf risk identification protocols. The objective of this study was to assess the utility of DCC taken at the time of arrival at a grain-fed veal facility and 72 h postarrival for determining morbidity risk, mortality risk, and growth during the production cycle. Data were collected between June and October 2018 from 240 calves upon arrival and from a subset of 160 calves 72 h postarrival at a commercial grain-fed veal facility in Ontario, Canada. Blood samples were evaluated using the QScout BLD test for leukocyte DCC (Advanced Animal Diagnostic, Morrisville, NC). All calves were screened using a standardized health examination, and a blood sample was collected to evaluate serum total protein and DCC. Cox proportional hazards models were constructed for both morbidity and mortality outcomes. Mixed linear regression models were constructed to evaluate average daily gain. Results from data collected at the time of arrival suggest that total protein values ≥5.2 g/dL reduced the hazard of mortality and that a rectal temperature >39.6°C was associated with an increased hazard of morbidity. Calves that were dehydrated gained less, whereas calves with an increased lymphocyte count had a higher rate of growth. Results from DCC collected 72 h postarrival suggest that lymphocyte counts between 4.8 and 5.8 × 10 9 cells/L decreased the hazard of mortality and counts >7.0 × 10 9 cells/L decreased the hazard of morbidity, whereas neutrophil counts >6.0 × 10 9 cells/L increased the hazard of mortality. This study demonstrates that machine DCC at the time of arrival and 72 h after arrival has potential for use in identifying high-risk calves that might require treatment, as part of selective antimicrobial therapy protocols, with the purpose of reducing antimicrobial use without sacrificing animal health in veal facilities.

No abstract

Recent advances in the understanding of risk factors and biomarkers in calves entering rearing facilities show promise for identifying high-risk calves on arrival at veal and dairy beef operations. Rapid automated leukocyte differential cell counts may be a good addition for augmenting or refining calf risk identification on-farm. The objective of this study was to validate an automated leukocyte cell counter, the QScout BLD test (Advanced Animal Diagnostics, Morrisville, NC), for its ability to determine leukocyte differential cell counts in neonatal Holstein calves. From June to July 2018, blood samples collected in EDTA anticoagulant from 235 calves upon arrival at an independent veal research facility in Ontario, Canada, were evaluated using the QScout BLD test and manually by microscopy. We compared these leukocyte differential counts using Lin's concordance correlation coefficient (ρ) and found very good agreement between tests for neutrophil counts (ρ = 0.83); fair agreement for lymphocyte counts (ρ = 0.32); fair agreement for the ratio of neutrophils to lymphocytes (ρ = 0.36); slight agreement for monocyte counts (ρ = 0.14); and slight agreement for eosinophil counts (ρ = 0.20). We further examined test results to determine if they differed in their classification of samples as being above, within, or below reported 95% reference intervals for neonatal Holstein calves. Classification between tests resulted in very good agreement for neutrophils and lymphocytes, with only 4.2% and 5.8% disagreement in classification, respectively. We observed moderate agreement for monocytes, with 23.3% classified differently, and poor agreement for eosinophils, with 70.3% classified differently. Further study is required to determine the role of leukocyte profiling in the risk assessment of calves arriving at calf-rearing facilities.

The objective of this case-control study was to determine if feeding behavior data collected from an automated milk feeder (AMF) could be used to predict neonatal calf diarrhea (NCD) in the days surrounding diagnosis in pre-weaned group housed dairy calves. Data were collected from two research farms in Ontario between 2017 and 2020 where calves fed using an AMF were health scored daily and feeding behavior data (milk intake (mL/d), drinking speed (mL/min), number of rewarded or unrewarded visits) was collected. Calves with NCD were pair matched to healthy controls (31 pairs) by farm, gender, and age at case diagnosis to assess for differences in feeding behavior between case and control calves. Calves were first diagnosed with NCD on day 0, and a NCD case was defined as calves with a fecal score of ≥2 for 2 consecutive days, where control calves remained healthy. Repeated measure mixed linear regression models were used to determine if there were differences between case and control calves in their daily AMF feeding behavior data in the days surrounding diagnosis of NCD (−3 to +5 days). Calves with NCD consumed less milk on day 0, day 1, day 3, day 4 and day 5 following diagnosis compared to control calves. Calves with NCD also had fewer rewarded visits to the AMF on day −1, and day 0 compared to control calves. However, while there was a NCD status x day interaction for unrewarded visits, there was only a tendency for differences between NCD and control calves on day 0. In this study, feeding behaviors were not clinically useful to make diagnosis of NCD due to insufficient diagnostic ability. However, feeding behaviors are a useful screening tool for producers to identify calves requiring further attention.