Rapidly and stably measuring the total nitrogen (TN) and total phosphorus (TP) contents of dairy slurry was a critical step before the field application, which was a key component of sustainable agriculture and slurry resource utilization. In present study, near-infrared spectroscopy (NIRS) models were established for swiftly determining TN and TP contents in the slurry from diverse dairy farms under various conditions. A total of 828 samples were gathered from 33 intensive dairy farms in Tianjin City throughout spring, summer, autumn and winter. The analysis initially explored the seasonal influences on the distribution characteristics of TN and TP in slurry and the effects on NIRS. Subsequently, the study employed partial least squares (PLS) regression to establish the single-season models for predicting slurry TN and TP contents. The results demonstrated that the TN models were excellent in all the seasons, with Rp2 values ranging from 0.94 to 0.95 and RPD values between 3.88 and 4.29. The TP models were superior during spring, summer, and winter compared to autumn. Lastly, the global models of four seasons (GMFS) were developed to predict TN and TP contents. For TN, the Rp2 and RPD values were 0.85 and 2.38, which were deemed very good. For TP, the Rp2 and RPD values were 0.76 and 1.87, indicating good performance. Consequently, the GMFS incorporating data from diverse seasons exhibited a broader applicability scope, albeit with reduced precision and accuracy compared to the single-season models. These models accommodated various situational needs during slurry reapplication to farmland, providing a theoretical basis for the precise and scientifically-informed reuse of dairy farm slurry in agricultural fields.

There is an urgent need for accurate measurement for emissions of ammonia (NH3) and hydrogen sulfide (H2S) in dairy barns in order to obtain reliable emission inventories and to develop and evaluate abatement strategies. This experiment was performed on three dairy farms in central China during 14 consecutive days in the winter 2020. Concentrations of NH3 and H2S were measured every two hours. The samples were taken inside and outside of barns from 7 sites at two heights (at floor and 1.5 over the floor). The results show that the average NH3 concentration was 2.47 mg/m3 with a maximum of 4.62 mg/m3, while the average H2S concentration was 0.179 mg/m3 with a maximum of 0.246 mg/m3. Lactating cows produced significantly more NH3 (3.73 mg/m3 versus 2.34 mg/m3) and H2S (0.24 mg/m3 versus 0.14 mg/m3) than non-lactating cows. NH3 and H2S concentrations were higher at 0 m than at 1.5 m, especially during the day. In addition, the average daily emission rates per animal unit (AU = 500 kg weight) were 23.5 g and 0.21 g for NH3 and H2S, respectively. The emission rate for NH3 was then used to extrapolate the NH3 emission from the Chinese dairy production. Our estimation for 2016 was 0.45 Tg, and it could reach 1.35 Tg by 2050. These numbers reflected our first attempt to calculate emission inventories for the Chinese dairy industry. Our results also suggest that more concrete measures must be taken to reduce the uncertainties of NH3 emissions from dairy cow production in China.

Field monitoring technology plays a vital role for returning the animal manure back to the cropland with high-efficiency and accuracy, particular in the complex rotation system of manure management in Chinese intensive farms. The comprehensive quantitative analysis models were proposed and built for determining the content of the nitrogen (N) and the phosphorus (P) through the whole chain of manure management in different dairy farms under multiple conditions. 249 manure samples were collected from 31 intensive dairy farms in Tianjin both in summer and autumn. The effect of seasons on the distribution characteristics of the N and P in the manure was analyzed. Near infrared spectra were collected and principal component analysis (PCA) was performed. Partial least squares (PLS) was used to establish the intra-season and inter-season models. It was found that the contents of the N and P in the manure varied with seasons. The prediction performance of intra-season models was better than that of inter-season models. Fusion model of two seasons were also established. The coefficient of determination of external validation (R2pred) for the N and P were 0.972 and 0.901, respectively. The residual predictive deviations (RPD) were 5.98 and 3.18, respectively. The results showed that the fusion model could enhance the universality and stability for predicting the N and P contents through the whole chain of manure management under the influence of various factors. The study not only supports for the development of on-spot detecting instrument but also guides for the rational recycling of manure in practice as well.

This study investigated the occurrence and resistance rates of Staphylococcus aureus strains isolated from raw milk in the dairy farms over two seasons (spring and autumn) and across four regions that included 11 provinces in China. In total, 750 raw milk samples from the 405 dairy farms were collected. Fifteen antimicrobial agents were tested for antimicrobial resistance via disk diffusion tests, and PCR tests were performed to identify drug resistance genes of S. aureus isolates. Out of 750 samples, 276 (36.8%) were positive for S. aureus, with 150 (41.1%) being positive in spring and 126 (32.7%) being positive in autumn. The occurrence rate of S. aureus in northeastern China (45%) was higher than that in western China (33%) and southern China (31.9%), respectively, and the rate significantly (p < 0.05) differed from those of western China and southern China. Of 276 isolates, 261 (94.6%) strains were resistant to more than 1 antimicrobial drug, and 193 (69.9%) strains were multidrug resistant. The blaZ (46.3%), dfrG (35.5%), and tetM (27.2%) genes were detected at a high frequency in the S. aureus strains. Our data revealed a variation (p < 0.05) in the resistance patterns in the different regions and across the two seasons. The occurrence and drug resistance rates of S. aureus isolated from raw milk obtained from dairy farms may still cause severe problems in China.

Manure management is an important aspect of urban livestock production that has a profound impact on metropolitan living. Data were collected from 28 dairy farms in peri-urban Beijing and analysed to determine farm nitrogen and phosphorus flows and costs associated with various manure management options to reduce nutrient losses. Dairy production in peri-urban Beijing was characterized by its use of high protein diets (16.3-17.0% crude protein), high reliance on imported feeds (92-98%), and low manure recycling (3.0-10.8%). Farms of 900-2000 cattle showed lower use efficiencies than farms of <900 cattle. Costs of manure handling ranged from 0.1 to 1.0 Yuan kg-1 milk. Among various manure treatment options, biogas digesters with aerobic lagoons had the lowest N losses and costs, justifying their investments. In conclusion, peri-urban dairy production systems were contrasting with traditional systems and within their own systems in nutrient use efficiency and losses, which was mainly decided by their farm size. To improve the nutrient use efficiencies and reduce losses, farmers and managers of peri-urban dairy production system should have a full awareness of different feed intake and manure management.

Two hundred milk samples from 20 randomly selected dairy farms were screened for the incidence of organochlorine pesticide residues to evaluate the safety of milk in Faisalabad region. The results revealed that overall buffalo milk samples in winter (85 %) and in summer (78 %) were more contaminated as compared to cow milk samples 83 and 75 % in respective seasons. The residues of cyhalothrin were found only in summer season in milk of both species. Permethrin residues were detected at higher levels than perfinofos while DDT and methamedophos were found undetectable. The mean levels of permethrin were 0.042 and 0.033 mg kg-1in buffalo milk samples and 0.045 and 0.043 mg kg-1 in cow milk in winter and summer season, respectively. Perfinofos residues were found to be the least contaminated pesticides with mean values of 0.0006 and 0.0013 mg kg-1, respectively in winter season, and 0.004 and 0.0025 mg kg-1 in summer season. All analysed pesticide residues in milk samples in both seasons were below the maximum residual limit (MRL) values as described by European Union (EU) but milk samples contaminated with α, β-endosulfan and endosulphate exceeded their respective Food and Agriculture Organization\'s (FAO) established MRLs both in winter and summer.