Francisco A. Leal Yepes

Background: Heat stress (HS) poses a major challenge to the dairy industry by reducing milk production, yet its cell type-specific effects in the bovine mammary gland remain incompletely defined. In this study, we recorded production traits and collected mammary biopsies from cows under thermoneutral (TN), HS, and pair-fed (PF) conditions. Results: Clinical measurements confirmed HS-induced physiological alterations. Compared with TN cows, HS cows exhibited reduced dry matter intake (DMI), milk yield, and yields of fat, protein, and lactose, along with increased water intake and milk urea nitrogen. The use of PF controls indicated that decreased DMI accounted for 45% of the milk-yield reduction, whereas direct HS effects accounted for the remaining reduction. We applied single-nucleus RNA-seq (snRNA-seq) on mammary biopsies to generate cell-resolved HS responses. We identified 14 distinct cell clusters, including epithelial, immune, and stromal populations. Under the TN condition, casein genes (e.g., CSN1S1 , CSN2 ) were broadly expressed across luminal cells but were attenuated under HS, whereas luminal alveolar cells showed relative upregulation. Heat shock protein genes were strongly induced by HS, primarily in epithelial clusters. Gene-set enrichment analyses revealed increased ribosomal activities across HS-responsive clusters and enrichment of protein folding and metabolic pathways in luminal alveolar cells, suggesting elevated proteostasis demands under stress. Pseudotime analysis positioned luminal cells along a progenitor-to-secretory trajectory under TN, accompanied by increased casein gene expression, whereas under HS, mature luminal cells shifted toward a homeostasis regulatory state. Cell–cell communication analysis demonstrated HS-induced remodeling of interepithelial signaling, including altered ERBB4-mediated signaling from luminal hormone-sensing to alveolar lineages. Finally, transcription factor activity profiling highlighted cell type-specific HS-activated regulators and their downstream target genes. Conclusions: Together, this cell type-resolved atlas delineates how HS alters bovine mammary epithelial function, developmental state, and intercellular crosstalk. These findings point to proteostasis pressure, disrupted signaling pathways, and rewired regulatory networks as mechanistic contributors to reduced lactational performance under HS, offering insights for improving heat resilience in dairy cattle.

Summary: This study investigated whether calfhood and peripartum variables were associated with the development of postcalving intramammary infection (IMI) with Mycoplasma spp. in dairy cows. We analyzed data from 475 first-lactation animals using univariable logistic regression models. Cows that experienced their first episode of otitis at ≤23 days of age had 2.3 times higher odds of postcalving IMI with Mycoplasma spp. compared with cows that did not experience an otitis event. No significant associations were observed for other calfhood, reproductive, or management variables. These findings suggest that early-life otitis may serve as an important predictor of susceptibility to Mycoplasma spp. IMI after calving, underscoring the potential value of calfhood health monitoring as part of mastitis prevention strategies. The figure was created with BioRender.com.

Summary: An Internet of Things-based wireless sensor network was developed and validated to monitor greenhouse gas emissions and environmental conditions on dairy farms. Cost-effective sensing nodes measuring methane, carbon dioxide, and ammonia were first calibrated using standardized gases and then validated against gold-standard open-circuit respiration chambers with lactating cows. The calibrated sensing nodes were subsequently deployed across different areas of a dairy farm, including feed bunks, freestall beds, and dry cow pens, to capture real-time variations in spatial and temporal greenhouse gas emissions. This scalable solution enables continuous real-time environmental monitoring. The resulting data may support precision dairy management practices aimed at assessing and mitigating the environmental footprint of dairy production systems.

Background: Heat stress (HS) poses a major challenge to the dairy industry by reducing milk production, yet its cell type-specific effects in the bovine mammary gland remain incompletely defined. In this study, we recorded production traits and collected mammary biopsies from cows under thermoneutral (TN), HS, and pair-fed (PF) conditions. Results: Clinical measurements confirmed HS-induced physiological alterations. Compared with TN cows, HS cows exhibited reduced dry matter intake (DMI), milk yield, and yields of fat, protein, and lactose, along with increased water intake and milk urea nitrogen. The use of PF controls indicated that decreased DMI accounted for 45% of the milk-yield reduction, whereas direct HS effects accounted for the remaining reduction. We applied single-nucleus RNA-seq (snRNA-seq) on mammary biopsies to generate cell-resolved HS responses. We identified 14 distinct cell clusters, including epithelial, immune, and stromal populations. Under the TN condition, casein genes (e.g., CSN1S1 , CSN2 ) were broadly expressed across luminal cells but were attenuated under HS, whereas luminal alveolar cells showed relative upregulation. Heat shock protein genes were strongly induced by HS, primarily in epithelial clusters. Gene-set enrichment analyses revealed increased ribosomal activities across HS-responsive clusters and enrichment of protein folding and metabolic pathways in luminal alveolar cells, suggesting elevated proteostasis demands under stress. Pseudotime analysis positioned luminal cells along a progenitor-to-secretory trajectory under TN, accompanied by increased casein gene expression, whereas under HS, mature luminal cells shifted toward a homeostasis regulatory state. Cell-cell communication analysis demonstrated HS-induced remodeling of interepithelial signaling, including altered ERBB4-mediated signaling from luminal hormone-sensing to alveolar lineages. Finally, transcription factor activity profiling highlighted cell type-specific HS-activated regulators and their downstream target genes. Conclusions: Together, this cell type-resolved atlas delineates how HS alters bovine mammary epithelial function, developmental state, and intercellular crosstalk. These findings point to proteostasis pressure, disrupted signaling pathways, and rewired regulatory networks as mechanistic contributors to reduced lactational performance under HS, offering insights for improving heat resilience in dairy cattle.

Summary: Blood samples (n = 182) were collected from Holstein lactating cows and preweaning heifers (n = 26) at a single time point. One whole blood sample was analyzed as the baseline, and the remaining 6 samples were stored at 4°C for analysis of blood gases, electrolytes, and metabolites at different time points. Additionally, plasma samples were analyzed as baseline, and 2 aliquots were stored at −80°C for analysis. Whole blood measurements of electrolytes, blood gases, and metabolites remained stable for up to 48 hours after collection when stored at 4°C. Potassium and lactate were less stable in whole blood; however, they showed greater stability and agreement in plasma samples. Created in BioRender.

Objective: We hypothesized that dehydrated calves treated with IV fluids containing 14 g of sodium bicarbonate, combined with oral electrolytes, would reduce mortality and improve recovery of anion gap compared to calves treated with IV fluids containing 14 g of sodium bicarbonate only or IV fluids with 14 g of sodium bicarbonate combined with milk replacer feeding. Methods: In a randomized control study, dairy and beef-on-dairy cross calves (n = 460) were enrolled into the following groups at diagnosis of dehydration: sick controls treated with IV fluids only (Con-IV), calves treated with IV fluids plus oral force-fed electrolytes (ELE), calves treated with IV fluids plus oral force-fed milk replacer (MILK), and healthy controls (Con-Health). Mortality and IV fluid treatment counts were analyzed. Blood metabolites and fecal dry matter were measured (n = 80). Results: Mortality for each group was as follows: Con-Health, 5.31% (95% CI, 2.4% to 11.3%); Con-IV, 13.91% (95% CI, 8.6% to 21.5%); ELE, 10.43% (95% CI, 6.0% to 17.5%); and MILK, 11.3% (95% CI, 6.6% to 18.5%). Bicarbonate concentrations in the Con-IV group returned to normal levels 1 hour after treatment. Anion gap in MILK calves was the highest after treatment. The relative risk of additional IV treatments for dehydration was 1.5 (95% CI, 1.2 to 1.8), 1.3 (95% CI, 1.1 to 1.6), and 2.1 (95% CI, 1.8 to 2.4) for the Con-IV, ELE, and MILK groups, respectively. Conclusions: IV fluid with 14 g of sodium bicarbonate alone or combined with oral electrolytes was the most effective treatment for changes in acid-base balance in dehydrated bovine neonates in this study. Clinical Relevance: IV therapy with sodium bicarbonate may practically rehydrate diarrheic calves in the field and correct acid-base balance. The use of forced feeding of ororuminal milk may not be beneficial for dehydrated and diarrheic calves.

Our study aimed to compare Bovine Respiratory Disease (BRD) morbidity, mortality, and growth in dairy and dairy beef cross-bred calves during the commingle period, 81–120 days of age, using two different BRD prevention strategies. The calves (n = 1799) were randomly assigned into groups: (1) Control (CON; received no vaccine or metaphylaxis); (2) Tulathromycin metaphylaxis (TUL; Increxxa^TM, Elanco Animal Health Inc., Greenfield, IN, USA); and (3) Mannheimia haemolytica vaccine (VACC; Nuplura^® PH, Elanco Animal Health Inc., Greenfield, IN, USA). Calves were individually weighed three times during the study to estimate average daily gain (ADG). Deep nasopharyngeal swabs, thoracic ultrasonography, health scores, and treatment records were collected during the study. Ultrasound and health score results were not different across treatments. In this study, the TUL group had a lower cumulative BRD incidence than CON. The cumulative incidence and 95% CI of BRD during the commingle period, 81–120 days of age for CON, TUL, and VACC were 0.43 (0.38 to 0.47), 0.36 (0.38 to 0.40), and 0.39 (0.35 to 0.43), respectively. The ADG for CON, TUL, and VACC were 0.25 ± 0.15, 0.32 ± 0.15, and 0.17 ± 0.15 kg, respectively. There was no difference among the treatment groups for ADG. Management and environmental conditions were variable at this operation throughout the study period and likely impacted the calves. Earlier interventions may be needed when the BRD incidence is elevated in high-risk calves.

This study developed and evaluated an algorithm for processing thermal-RGB video feeds captured by an unmanned aerial vehicle (UAV) to automate heat stress monitoring in cattle housed in the drylots. The body surface temperature (BST) of individual cows was used as an indicator of heat stress. UAV data were collected using RGB and thermal infrared imagers, respectively, at 2 and 6.67 cm per pixel spatial resolution in Spring 2023 (dataset-1) and Summer 2024 (dataset-2). Study sites were two commercial drylots in Washington State. The custom algorithms were developed to: (1) detect and localize individual cows using a Mask R-CNN-based instance segmentation model combined with centroid tracking; and (2) extract BST by averaging the thermal-imagery pixels for each of the segmented cows. The algorithm showed higher detection accuracy with RGB images as input (F1 score: 0.89) compared to thermal (F1 score: 0.64). BST extraction with combined RGB and thermal imaging approach required corrections for alignment problems associated with differences in optics, imaging field of view, resolution, and lens properties. Consequently, thermal imaging-only approach was adopted for assessing real-time cow localization and BST estimation. Operating at one frame per second, algorithm successfully detected 72.4% and 81.65% of total cows in video frames from dataset-1 (38 s) and -2 (48 s), respectively. The mean absolute difference between algorithm output and ground truth (BST_GT) was 2.1 °C (dataset-1) and 3.3 °C (dataset-2), demonstrating satisfactory performance. With further refinements, this approach could be a viable tool for real-time heat stress monitoring in large-scale drylot production systems.