This study evaluated pre-to postweaning ruminal structural development, fermentation characteristics, and acute-phase protein levels in calves with a high milk replacer (MR) feeding rate prior to weaning. Six ruminally cannulated Holstein bull calves were fed MR (150 g/L) at 15% of body weight (BW) in 2 equal volumes daily. Volumes were adjusted weekly based on BW. Calves were weaned using a 1-step weaning method, with MR decreased by 50% at the end of wk 5 and full weaning at the end of wk 6. Calf starter, chopped straw, and water were offered ad libitum. Intake was recorded daily, and BW was recorded weekly. From wk 5 to 12, ruminal pH was continuously measured using a ruminal pH bolus. Ruminal fluid was collected weekly from wk 5 to 12 for measurement of short-chain fatty acid concentrations and quantification of total bacteria and protozoa. Rumen papillae were obtained at wk 5, 6, 7, 8, and 12 for histological analysis. Serum amyloid A and lipopolysaccharide-binding protein were measured weekly. Data were analyzed using GLIMMIX procedure of SAS (SAS Institute Inc., Cary, NC), with week as a fixed effect and calf as a random effect. During the weaning step-down, starter intake was 3-fold higher and continued to increase until wk 12. Body weight increased from birth to wk 12; however, BW did not change during wk 6, 7, and 8, possibly due to low metabolizable energy intake caused by the weaning strategy. Preweaning ruminal pH was below 5.8 for approximately 936.3 ± 125.99 min/d, implying ruminal acidosis. Furthermore, ruminal pH below 5.8 reached a peak at wk 8 with 1,203.9 ± 227.65 min/d below pH 5.8 and slowly decreased to 388.1 ± 189.82 min/d below pH 5.8 at wk 12. Papillae surface area, length, and width increased during wk 12 compared with wk 5. Corneum thickness increased by week, whereas spinosum/basale thickness only increased during wk 8 compared with wk 5. The acute-phase protein concentration was highest at wk 1 and then decreased and remained constant until wk 12. In conclusion, even before step-down weaning, calves experienced ruminal acidosis despite low starter intake. Further, the observed prolonged ruminal pH depression suggests that dietary rumen adaptation after weaning can take several weeks in calves with a high MR feeding rate preweaning. The prolonged depressed ruminal pH did not affect acute-phase proteins and this finding, along with the other results, suggests that rumen epithelium barrier integrity is not compromised during weaning.

The objectives of this study were to develop a methodology for biopsying the rumen and colon of young dairy calves and to collect suitable quality tissue samples for microscopic and gene expression analysis. Six Holstein dairy bull calves (45.0 ± 1.5 kg birth weight) were ruminally cannulated during the second week of life and weaned at the end of wk 6. Ruminal and colon tissue samples were collected at the end of wk 5, 6, 7, 8, and 12. Calves were not sedated but were restrained in a chute for sampling. The endoscope (100 cm length, 9.8 mm diameter) was introduced through the rumen cannula to harvest ruminal tissue. Endoscopic biopsies of the rumen with endoscopic biopsy forceps were unsuccessful 85% of the time because they were unable to shear the ruminal tissue. Thereafter, an Allis clamp was used to retrieve the blind sac through the rumen cannula to perform direct tissue biopsying with surgical scissors. To biopsy the colon, the lubricated distal tip of an endoscope was slowly inserted into the calf's anus. A total of 6 colon tissue samples (12.6 ± 0.74 mg) were collected per calf per time point from the distal colon 30 to 40 cm from the calf's anus using endoscopic biopsy forceps, which were inserted through the instrument channel. A new forcep was used between sites and calves. Between calves, the outside of the endoscope was washed with 4% chlorohexidine and rinsed with water and the instrument channel was washed with distilled water and 70% ethanol. Colon and ruminal samples were processed for histological measurements, and RNA was isolated and sequenced. High-quality RNA (RNA integrity number 8.8 ± 0.08) was collected from samples, and light and electron microscopy was performed on samples. In conclusion, endoscopic biopsying can be used for tissue harvest in the colon of young calves. However, it was found that collecting ruminal tissue by retracting the rumen from the cannula and taking samples with surgical scissors was more successful than an endoscopic biopsy. This method allows for tissue collection of the same animal throughout time, which can help the research community investigate the effect of weaning regimens, feed rations, and age on the structure and function of the gastrointestinal tract.

Background Sleep-disordered breathing (SDB) is an important risk factor for developing atrial fibrillation (AF), and treatment of concomitant SDB can improve AF rhythm outcomes. Diagnosis of SDB requires sleep studies which can pose a significant time and resource burden. We sought to develop a prediction score based on clinical characteristics that can help identify AF patients who require further assessment for SDB. Methods Prospectively-collected data for 442 consecutive patients treated for AF from 2009 to 2017 were analysed. All patients were considered candidates for rhythm-control and therefore referred for sleep studies. The diagnosis of SDB was confirmed using in-lab polysomnography and classified using the apnoea-hypopnoea-index (AHI), with cut-offs of ≥15/hr and ≥30/hr indicating moderate-to-severe and severe SDB respectively. Patients treated up to 2015 formed the derivation cohort (n=311) and the remainder (n=113) formed the validation cohort. Multivariate logistic regression analysis was used to identify clinical variables predictive of moderate-to-severe SDB. A risk score model was developed based on regression coefficients and tested using receiver-operating-characteristics analyses on the validation cohort. Results Overall, mean age was 60±11 years, mean body mass index (BMI) was 30±5 kg/m2 and 69% were men. The prevalence of moderate-to-severe SDB was 33.7%. There were no significant differences in baseline characteristics between the derivation and validation cohorts. Male gender (score=1), overweight (BMI: 25–29 kg/m2, score=2), obesity (BMI≥30 kg/m2, score=3), diabetes (score=1), and stroke (score=2) were significantly independently predictive of moderate-to-severe SDB and formulated the score. The score performed well to predict moderate-to-severe SDB with a C-statistic of 0.73 (95% CI: 0.67–0.79, P<0.001) in the derivation cohort, and 0.67 (95% CI: 0.57–0.77, P<0.001) in the validation cohort. As a rule-out test, a score of ≤3 had a negative predictive value of 77% for moderate-to-severe SDB (91% for severe SDB). A score of ≥4 had an intermediate positive likelihood ratio (PLR) of 2 for moderate-to-severe SDB (2.2 for severe SDB), while a score of ≥5 had a high PLR of 6.5 and 6.8 for moderate-to-severe SDB and severe SDB respectively. Sensitivity and specificity table Conclusion A novel risk score comprising clinical characteristics can identify patients with AF likely to benefit from further assessment for SDB. Application of this model may aid optimise resource utilisation and facilitate timely patient care.

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