The life-cycle carbon emissions (LCCE) assessment of dairy barns is crucial for identifying low-carbon transition pathways and promoting the sustainable development of the dairy industry. We applied a life cycle assessment approach integrated with building information modeling and EnergyPlus to establish a full life cycle inventory of the material quantities and energy consumption for dairy barns. The LCCE was quantified from the production to end-of-life stages using the carbon equivalent of dairy barns (CEDB) as the functional unit, expressed in kg CO₂e head⁻¹ year⁻¹. A carbon emission assessment model was developed based on the “building–process–energy” framework. The LCCE of the open barn and the lower profile cross-ventilated (LPCV) barn were 152 kg CO₂e head⁻¹ year⁻¹ and 229 kg CO₂e head⁻¹ year⁻¹, respectively. Operational carbon emissions (OCE) accounted for the largest share of LCCE, contributing 57% and 74%, respectively. For embodied carbon emissions (ECE), the production of building materials dominated, representing 91% and 87% of the ECE, respectively. Regarding carbon mitigation strategies, the use of extruded polystyrene boards reduced carbon emissions by 45.67% compared with stone wool boards and by 36% compared with polyurethane boards. Employing a manure pit emptying system reduced carbon emissions by 76% and 74% compared to manure scraping systems. Additionally, the adoption of clean electricity resulted in a 33% reduction in OCE, leading to an overall LCCE reduction of 22% for the open barn and 26% for the LPCV barn. This study introduces the CEDB to evaluate low-carbon design strategies for dairy barns, integrating building layout, ventilation systems, and energy sources in a unified assessment approach, providing valuable insights for the low-carbon transition of agricultural buildings.

Automated milk feeders (AMFs) offer significant advantages in promoting natural feeding behavior in calves and reducing manual labor. With widespread use, the impact of AMF hygiene on calf health has attracted increasing research attention, as inadequate cleaning protocols may lead to bacterial accumulation on calf-contact surfaces and subsequent health risks for calves. This study aimed to quantify bacterial contamination on AMF surfaces, evaluate the cleaning efficacy of slightly acidic electrolyzed water (SAEW) compared to warm water and chemical disinfectants (n = two total samples), and optimize SAEW cleaning parameters using response surface methodology (RSM). Results revealed that bacterial loads on five high-frequency calf-contact surfaces ranged from 5.48 to 8.21 log₁₀ CFU/cm². SAEW at 60 mg/L achieved significantly higher cleaning efficacy than warm water and chemical disinfectants under field conditions (p < 0.01). Through RSM optimization (highly significant (p < 0.001)), the optimal SAEW cleaning parameters were determined as follows: cleaning time of 35 s, cleaning temperature of 78 °C, and available chlorine concentration (ACC) of 108 mg/L. Under the optimized parameters, bacterial and adenosine triphosphate (ATP) removal rates reached approximately 98%. These findings suggest that SAEW is a promising alternative sanitation agent for AMFs, provide preliminary parameters for rapid sanitation under the tested conditions, and hold the potential to support the standardized hygiene control of calf feeding equipment.

Calves raised in barns are usually kept in individual pens separated by either solid or mesh partitions. To quantify the effects that the two types of partition have on airflow speed in an axial-ventilated-barn, the indoor environment of a calf barn was simulated using computational fluid dynamics (CFD) with validation accomplished by means of direct measurement. To ascertain the effects that two types of partition have on the physiological parameters and health of pre-weaned calves, 24 calves (3–11-day-olds) were selected, equally divided into four groups and sequestered as follows: calves placed in pens separated by solid partitions receiving “low-speed” or “high-speed” airflow; calves separated by mesh partitions receiving “low-speed” or “high-speed” airflow. The results of the CFD simulation showed that the percentage of airflow speed that exceeded 0.5 m s⁻¹ at a height of 0.4 m above the floor of the animal occupied zone where calves were separated by mesh partitions was 88%, while the speed was 66–70% for calves separated by solid partitions. The duration of treatment provided to the calves in the MP-LA (mesh partitions and subjected to a low-speed airflow) and MP-HA (mesh partitions and subjected to a high-speed airflow) groups, were both lower than the SP-LA (solid partitions and subjected to a low-speed airflow) and SP-HA (solid partitions and subjected to a high-speed airflow) groups. We conclude that when the fan is operating, contact between calves separated by mesh partitions produces no negative impact on the health of calves; furthermore, this arrangement can provide a higher airflow speed than that delivered to calves raised in pens separated by solid partitions, especially to those calves in pens farther from the fans.

To enhance energy utilization efficiency, dairy farmers have increasingly adopted photovoltaic (PV) panels on barn roofs. However, there is currently a general separation between the barn construction and the additional aspects of the PV system. It is unclear to dairy farmers whether rooftop PV panels will have an impact on the dairy barn, particularly on the thermal environment. This study investigated the influence of air layer properties, specifically thickness and ventilation conditions, on the thermal performance of PV dairy barn roofs. Utilizing the harmonic analysis method, the study quantified its dynamic thermal properties. The results demonstrated that increasing the air layer thickness in ventilated roofs decreases heat flux and improves thermal resistance (1.67–2.15 times higher than non-PV roofs). In contrast, sealed air layers exhibit consistently high thermal resistance (up to 3.33 times higher). Optimizing ventilated air layer thickness (0.20–0.30 m) effectively minimizes heat ingress and prevents PV efficiency degradation. These results provide valuable insights for optimizing the design of energy-efficient PV dairy barns, enhancing thermal comfort, and contributing to low-carbon energy solutions in livestock facilities.

To investigate the associations between genes involved in fatty acid composition and volatile flavor compounds (VOCs), Dabieshan (DBS) cattle were selected and stratified into high (H: 0.018–0.024 g) and low (L: 0.007–0.012 g) groups according to the fatty acid content in the longissimus dorsi (LD). Integrated analysis using two-dimensional gas chromatography–time-of-flight mass spectrometry (GC×GC-TOF-MS) and transcriptomics systematically revealed differences in VOCs and gene expression profiles, along with their associations with fatty acid composition. The relative contents of aldehydes, esters, and hydrocarbons were significantly higher in the group H, whereas the group L exhibited elevated levels of alcohols, acids, and heterocyclic compounds. Among 54 differentially abundant VOCs identified, (E)-2-Nonenal (ROAV = 100) was established as the key flavor contributor. Transcriptomic analysis identified 678 differentially expressed genes (DEGs), with eight candidate genes implicated in fatty acid composition pinpointed through GO and KEGG enrichment analyses. Further correlation analysis showed that the expression levels of SGPL1, KLF15 and SLC27A6 were significantly correlated with the contents of polyunsaturated fatty acids (C22:5n-3, C18:3n-3, C18:2n-6, C18:1n-9c). There was also a significant correlation between the above fatty acids and characteristic flavor compounds including 3-Hexanone, (E)-2-Nonenal, (E,E)-2,4-Octadienal and Butanal. This study suggested potential links among fatty acid composition, key genes and characteristic flavor compounds in Dabieshan cattle, providing new insights into the genetic improvement of flavor quality of local cattle breeds.