产业转型期规模猪场建设工程防控技术思考

非洲猪瘟和环保的双重影响刺激了中国养猪业快速向集约化、高效化和自动化方向转型,而舍间交叉感染、疫病难控、环境污染等问题依然未能得到有效解决。在猪场建设和管理中,人们的关注重点主要有疾病控制、粪污臭气治理和无抗饲料三个方面,分别对应着生物安全、环保安全和食品安全三个安全底线。在重视猪场生物安全体系建设时,人们往往忽视工程防控技术措施的整体应用,其贡献尚无法得以很好的体现。文章从工程技术的角度,分析了隔离、合理分区和防止交叉感染等对猪场生物安全防控的作用,为猪场的工程防疫体系建设、守住三个安全底线提供指导。

海口地区商品猪场生产工艺和环境设计方法初探

地域气候差异、环境控制措施的选择对猪场设计及运行影响巨大。针对不同的养猪生产区,如何综合考虑气候特点对猪场进行标准化设计是满足猪场建成后正常运营的重要条件。海口市属华南地区,地处低纬度热带区域,年平均气温24℃,极端最高气温可达约41℃,平均相对湿度85%。文章针对海口地区特有的气候和地理环境特点,探讨了海口地区商品猪场在工艺设计、建筑设计和环境控制设计方面的设计思路,并通过案例分析进行了详细的说明。

Comparison of direct and indirect determinations of dynamic ventilation rate in a modern dairy free stall barn

Reliable estimation of the ventilation rate(VR)in intensive livestock buildings is necessary for studying building environmental control strategies and predicting indoor air quality and air emissions.As direct air exchange measurements are time-consuming and expensive,it is environmentally inefficient to measure livestock building VR continuously in practice.Hence,indirect VR estimation methods have been widely used in modelling environmental control and air emissions,and also to measure airflow in the field.The accuracy of indirect measurement methods needs to be evaluated by comparing with direct measurements.In this study,the direct and indirect methods of determining hourly and daily mean VRs were applied to a mechanically-ventilated dairy free stall barn monitored by the 24-month National Air Emissions Monitoring Study.The direct method was used to continuously monitor fan rotational speeds,and differential static pressures,coupled with periodic in-situ fan performance assessments,to calculate the VR.The indirect method consisted of estimating the VR using CO2 concentration measurements and the CO2 mass balance method.The average daily and hourly means(mean±SD)of directly measured barn ventilation rates for two years were(246±73)m3/s and(245±77)m3/s,respectively.The average daily and hourly means(mean±SD)of barn ventilation rates estimated by the CO2 mass balance method were(287±93.4)m3/s and(287±118)m3/s,respectively.Correlation analyses showed a strong correlation between the indirect CO2 mass balance method and direct measurement methods(r=0.93 for daily means and r=0.85 for hourly means).

Gases emissions estimation and analysis by using carbon dioxide balance method in natural-ventilated dairy cow barns

Contaminated gases emissions from livestock industry are becoming one of the most significant contributors to the increasingly serious environmental pollution.To find a way to reduce gases emissions,it is essential to reveal the factors that can affect the gases emissions.In this study,the concentrations of typical gases(including ammonia(NH_(3)),carbon dioxide(CO_(2)),hydrogen sulfide(H_(2)S),and sulfur dioxide(SO_(2)))generated from naturally-ventilated dairy cow barns were detected through the sample-data method in Tianjin,northern China.Indoor environmental conditions,such as temperature(T)and relative humidity(RH),were measured simultaneously.After applying the carbon dioxide mass balance method,ammonia,hydrogen sulfide and sulfur dioxide emissions were determined.The correlation analysis and regression analysis between the climate condition and gas emissions were conducted to assess the data collected in dairy cow barns during the whole study period.There was a significant relationship between environmental conditions and gas emissions.NH3,H2S and SO_(2) emissions from the building are in the range of 0.98-2.36 g/LU·h,0-0.034 g/LU·h,and 0-0.069 g/LU·h,respectively.The numerical analysis shows that the NH3 emission is highly correlated with the temperature and relative humidity.The ventilation rate shows a positive correlation with all the three gases.

Effects of ripple cross angles and turbulence models on wet curtain resistance

To study the influence of ripple cross angles on the resistance of wet curtains,wet curtains with different ripple cross angles(45°/45°,45°/15°)were tested on agricultural ventilation equipment performance testing benches,and the static pressure drop under different wind speeds(1-3 m/s)was determined.Four turbulence models(κ-ε,RNGκ-ε,κ-ω,SSTκ-ω)were adopted for numerical simulations of the two types of wet curtain,and the simulations’results were compared with those of experiments.The average errors found are 41.1%,48.7%,27.1%,and 27.8%,respectively,and theκ-ωmodel is found to be the most suitable one for the calculation of wet curtain resistance among the four turbulence models.By using theκ-ωturbulence model,the static pressure drop performances of wet curtains with ripple cross angles 45°/35°and 45°/25°were calculated.Resistance increases with wind speed and ripple cross angles,and a large ripple cross angle has a higher resistance growth rate with increasing wind speed.

Adaptability of pullets from cages to a large cage aviary unit system during the initial settling-in period

Pullets often raised in cage system from week 1 to week 13 in China,when transferred to aviary system after,there will be a problem with adapt.A large cage aviary unit(LCAU)system was developed,which allocated with facilities such as ramps to help cage reared hens to adapt to the multi-tier space.To investigate hens’adaptability to the new system,space use over time in the LCAU system during the first 10 days after hens transferred were recorded,instantaneous scan sampling and continuous focal sampling were used to assess the behavior difference of hens between the LCAU and conventional cage(CC)systems.On the first day of arrival,10.03% of hens reached the second tier(S2)and the third tier(S3)of the aviary.During the observation period,an average of 2.42% of hens climbed and stayed at the upper tiers every day.Space allowance on floor of the first tier(S1)increased from 444.62 cm^(2)/hen(91 d)to 586.32 cm^(2)/hen(100 d),which was more than 540 cm^(2)/hen in the CC system.Comfort behaviors in the LCAU system were significantly more than in the CC system(p<0.01)and hens performed more comfort behaviors with the increase of days after transferred.Hens ate and drank less in the LCAU system in the beginning,however,with the increasing use of upper space,hens ate and drank more and more in the LCAU system during the 10 days after transferred from CC system.Consequently,there were no difference of feed behavior between the CC and LCAU systems(p>0.05)on the last 5 days of the whole observing period.The results indicated that hens gradually learned to use the 3-dimensional space in the initial settling-in period and,gained a good welfare condition in LCAU system.Further studies are needed to investigate the three-dimensional preferences and behavior expression in difference period to bridge the gap in knowledge of space use capacity among adult laying hens.