Risk factors of lameness in sows in England

Lameness in pigs is a major welfare concern and one of the most commonly reported reasons for premature culling of breeding sows. In this study, the prevalence of lameness in sows was estimated using data from 76 pig breeding units in England and risk factors associated with the occurrence of lameness were examined. The prevalence of lameness in sows was 4.5% (farm median 5.0%, range 0–40%), with at least one lame sow being observed at 54% of the 76 farms. Relative risk (RR) of lameness was determined by multivariable Poisson regression analysis. Farms with high producing sows had a lower rate of lame sows than farms with a medium level of production (P = 0.01). However, medium levels of production on a farm were associated with higher levels of lameness than farms having the lowest level of production (P = 0.02). Farms where the stockman had responsibility for more sows resulted in an increased risk of lameness (P = 0.0062). When indoor units were considered, the area of the pen and younger sows (two parities or less) had higher risk of lameness (P = 0.001 and P = 0.026 respectively). An increased awareness of the risk factors behind lameness is essential in farm management and can be useful when designing housing areas as well as developing future prevention plans for lameness.     

Total loss and distribution of nitrogen and phosphorus in the outdoor run of organic laying hens

1. The objective of this study was to determine the level and variation of the total mass, and load of nitrogen (N) and phosphorus (P) excreted into the outdoor run of organic egg production systems.

2. Three egg production farms with an aviary system and an outdoor run were selected for this study. Four measurements, one per season, were executed on each farm.

3. Mean content of N and P of a manure dropping was 14·0?g N?kg^?1 and 3·12?g P?kg^?1, mean mass of a dropping was 6·36?g and mean dry matter content of a dropping was 238?g?kg^?1. Mean rate of excretion in the outdoor run was 2·99 droppings per hen per h. Mean percentage of hens outside during the time the outdoor run could be accessed was lowest on Farm 1 (1·7%), highest on Farm 2 (16·0%), and intermediate on Farm 3 (7·1%).

4. On all farms an exponential decrease of the number of hens and of the load of N and P with increasing distance from the hen house was found. Load of N exceeded the fertilisation standard (of 170?kg?ha^?1?y^?1) in the region at a 0 to 19?m distance from the hen house on Farm 1, 0 to 146?m on Farm 2 and 0 to 52?m on Farm 3.

5. It is concluded that the husbandry system should be redesigned to solve the problem of overloading, unwanted loss of N and P to the environment and loss of N and P from the organic production cycle.     

Serum acute phase proteins as biomarkers of pleuritis and cranio-ventral pulmonary consolidation in slaughter-aged pigs

The purpose of this study was to investigate the relationship between the existence of lung lesions in pigs at slaughter and the concentration of the serum acute phase proteins (APP), haptoglobin (Hp), pig-major acute protein (Pig-MAP) and C-reactive protein (CRP). A total of 24 pig farms were selected out of a larger farm database previously screened to study risk factors associated with pleuritis and cranio-ventral pulmonary consolidation (CVPC) lesions at slaughter-aged pigs in Spain. The farms were classified as “pleuritis negative (P−) or positive (P+)” and as “CVPC negative (M−) or positive (M+)” and divided into four groups according to a 2X2 factorial design (P−M−, P−M+, P+M−, P+M+). Also at slaughter, blood from 20 randomly selected pigs from each farm was collected. Obtained serum samples were used to measure acute phase proteins. All APP concentrations were significantly higher for M+ farms than for M− ones. However, only Hp and Pig-MAP showed significantly higher concentrations for P+ farms than for P− ones. Pig-MAP was the most sensitive biomarker since it was able to clearly discriminate between P−/P+ and M−/M+ groups (p < 0.001 in both cases). Hp was an excellent marker for pleuritis and good for CVPC lesions. CRP was able to discriminate for CVPC lesions but not for pleuritis. The present results indicate that Pig-MAP and, possibly Hp, may be used as potential markers to characterise and discriminate respiratory lesions in swine herds at slaughter.     

A survey of manure management on pig farms in Northern Vietnam

Animal manure can provide nutrients for crop and fish production and input for biogas production but, if managed inappropriately, can also have a negative impact on the environment. The objective of this survey was to provide information about pig production and manure management practices in the Northern part of Vietnam in order to identify and prioritize research needs for future improvements in pig manure management. A survey was conducted by in-depth interviews on 54 pig farms in two Northern Vietnamese provinces, Thai Binh and Bac Giang. In addition to the survey, also key informant responses were obtained in the two provinces to help identify problems with existing manure management. The survey showed that large-scale pig producers (> 100 fatteners or 20 sows) had more pigs per hectare than medium-scale (19–99 fatteners, 5–19 sows) or small-scale (< 19 fatteners, < 5 sows) producers. Biogas was produced from 43% of the total manure produced on all surveyed farms, and was used for cooking. The proportion of total manure applied to crops was only 5% in Thai Binh and 35% in Bac Giang. Large-scale producers tended to operate smaller fishponds, and medium-scale farms operated larger ones. The farmers were of the opinion that fish in ponds fertilized with pig manure grew significantly faster than did fish in ponds supplied with other feed or types of fertilizer. Twenty percent of pig producers reported that they raised pigs just to provide manure to feed their pond fish. A large proportion (19%) of the total manure produced was discharged into public sewage systems, rivers and lakes. Of the 54 householders interviewed, 46 believed that animal manure caused serious damage to the environment. Farmers interviewed had little or no expertise in handling liquid manure, composting solid manure, or reducing contamination by means of microbial reduction of pollutants during manure management. In general, specialized pig production is seen as a commercial operation, while manure management remains non-commercial. The survey implied that more information to farmers, as well as stronger regulation of manure management, is needed in Vietnam.     

The effects of farm management practices on liver fluke prevalence and the current internal parasite control measures employed on Irish dairy farms

Fasciolosis caused by Fasciola hepatica is responsible for major production losses in cattle farms. The objectives of this study were to assess the effect of farm management practices on liver fluke prevalence on Irish dairy farms and to document the current control measures against parasitic diseases. In total, 369 dairy farms throughout Ireland were sampled from October to December 2013, each providing a single bulk tank milk (BTM) sample for liver fluke antibody-detection ELISA testing and completing a questionnaire on their farm management. The analysis of samples showed that cows on 78% (n = 288) of dairy farms had been exposed to liver fluke. There was a difference (P < 0.05) between farms where cows were positive or negative for liver fluke antibodies in (a) the total number of adult dairy cows in herds, (b) the number of adult dairy cows contributing to BTM samples, and (c) the size of the total area of grassland, with positive farms having larger numbers in each case. There was no difference (P > 0.05) between positive and negative farms in (a) the grazing of dry cows together with replacement cows, (b) whether or not grazed grassland was mowed for conservation, (c) the type of drinking water provision system, (d) spreading of cattle manure on grassland or (e) for grazing season length (GSL; mean = 262.5 days). Also, there were differences (P < 0.001) between drainage statuses for GSL with farms on good drainage having longer GSL than moderately drained farms. The GSL for dairy cows on farms with good drainage was 11 days longer than for those with moderate drainage (P < 0.001). The percentage of farmers that used an active ingredient during the non-lactating period against liver fluke, gastrointestinal nematodes, lungworm, and rumen fluke was 96%, 85%, 77% and 90%, respectively. Albendazole was the most frequently used active ingredient for treatment against gastrointestinal nematodes (57%), liver fluke (40%) and lungworm (47%), respectively. There was a difference (P < 0.05) in the use of triclabendazole and albendazole between positive and negative farms, with triclabendazole use being more common in positive farms. This study highlighted differences in dairy management practices between Irish farms with dairy herds exposed or not exposed to liver fluke and stressed the need of fine-scale mapping of the disease patterns even at farm level to increase the accuracy of risk models. Also, comprehensive advice and professional support services to farmers on appropriate farm management practices are very important for an effective anthelmintic control strategy.     

Transmission of Actinobacillus pleuropneumoniae among weaned piglets on endemically infected farms

Clinical outbreaks due to Actinobacillus pleuropneumoniae occur recurrently, despite the wide-scale use of antimicrobials or vaccination. Therefore, new approaches for the prevention and control of these outbreaks are necessary. For the development of alternative measures, more insight into the transmission of the bacterium on farms is necessary. The aim of this cohort study was to quantify transmission of A. pleuropneumoniae amongst weaned piglets on farms. We investigated three possible transmission routes: (i) indirect transmission by infected piglets within the same compartment, (ii) transmission by infected pigs in adjacent pens and (iii) transmission by direct contact within pens. Additionally, we evaluated the effect of independent litter characteristics on the probability of infection. Two farms participated in our study. Serum and tonsil brush samples were collected from sows pre-farrowing. Serum was analysed for antibodies against Apx toxins and Omp. Subsequently, tonsil brush samples were collected from all piglets from these dams (N = 542) in three cohorts, 3 days before weaning and 6 weeks later. Tonsil samples were analysed by qPCR for the presence of the apxIVA gene of A. pleuropneumoniae. Before weaning, 25% of the piglets tested positive; 6 weeks later 47% tested positive. Regression and stochastic transmission models were used to assess the contribution of each of the three transmission routes and to estimate transmission rates. Transmission between piglets in adjacent pens did not differ significantly from that between non-adjacent pens. The transmission rate across pens was estimated to be 0.0058 day⁻¹ (95% CI: 0.0030–0.010), whereas the transmission rate within pens was ten times higher 0.059 day⁻¹ (95% CI: 0.048–0.072). Subsequently, the effects of parity and serological response of the dam and litter age at weaning on the probability of infection of pigs were evaluated by including these into the regression model. A higher dam ApxII antibody level was associated with a lower probability of infection of the pig after weaning; age at weaning was associated with a higher probability of infection of the pig after weaning. Finally, transmission rate estimates were used in a scenario study in which the litters within a compartment were mixed across pens at weaning instead of raising litter mates together in a pen. The results showed that the proportion of infected piglets increased to 69% if litters were mixed at weaning, indicating that farm management measures may affect spread of A. pleuropneumoniae.     

A Survey of Gastrointestinal Pig Parasites on Free-range,Organic and Conventional Pig Farms in The Netherlands

The prevalence of gastrointestinal parasites in suckling piglets, weaners, fattening pigs and sows was studied from November 2001 to October 2002 on 16 free-range farms (FRF), 11 organic farms (OF) and 9 conventional farms (CF) by means of faecal examinations of composite samples. Each farm was visited four times with a 3-month interval. Infections with coccidia were found on 43.8% of the FRF, 90.9% of the OF and 66.7% of the CF. Sows had the highest prevalence, particularly on FRF (87.5%) and OF (80%).Ascaris suum was present on 50% of the FRF, 72.7% of the OF and 11.1% of the CF, whereas fattening pigs on FRF (42.9%) and OF (54.5%) had the highest prevalence.Oesophagostomum spp. were observed on 25% of the FRF, 27.2% of the OF and 22.2% of the CF. The infection was most prevalent in the sows on all farm types: 37.5% on FRF, 30% on OF and 22.2% on CF.Trichuris suis was found on 37.5% of the FRF, 36.4% of the OF and 11.1% of the CF. Again, this infection was most prevalent in the sows, particularly on the FRF (50%) and OF (30%). No other gastrointestinal parasite species were found and no clinical signs were observed. No seasonal trends could be distinguished. In many cases, when an age group on a farm was positive for a certain parasite, it remained so during the whole study. This indicates that this parasite was really ‘endemic’ on that farm. The results of this study demonstrate that the prevalence of helminth infections of pigs on farms with outdoor facilities is higher than in pigs on conventional farms.     

规模化猪场猪粪中的营养素分析研究

以规模化养猪场中的保育猪、育肥猪和妊娠母猪为试验猪群,分别就各自粪样中的含水率、全氮、全磷、有机质、铜、锌等"营养素"指标,按照国家和环境保护行业检测分析标准方法进行了严格测定,并比较分析了这些指标在不同猪群、不同季节的变化规律。结果表明:(1)夏季猪粪中"营养素"除全氮指标外,其他各指标含量均处于最低状态,含水率、有机质二项指标秋冬季明显高于春夏季;全氮、全磷指标各季节存在明显差异;铜含量秋冬季明显高于夏秋季;锌含量春季最高,夏季最低。(2)保育猪粪样中铜、锌含量最高,育肥猪次之,妊娠母猪最低,相互之间差异极显著,其变化趋势表现为递减规律,含水率、全氮、全磷和有机质在不同猪群之间也有一定的差异。     

Productive response of grazing dairy cows to fresh chopped maize supplementation under a small farming system in the Mexican Highlands

The aim of this study was to evaluate the animal performance of late lactating grazing dairy cows in response to fresh chopped maize (FCM) supplementation under a small farming system. Twenty-four multiparous Holstein dairy cows were used in a rotational grazing on a mixed alfalfa–orchard grass sward. Three treatments were evaluated: 0, 4, and 8 kg dry matter (DM) of FCM cow⁻¹ day⁻¹. The experimental design was a crossover, with three periods lasting 19 days each. There were no differences on individual milk production nor on milk composition. Herbage DM intake decreased (P < 0.0001) from 8.4 to 5.2 and 3.1 kg DM when increasing FCM from 0 to 4 and 8 kg DM, respectively. Total DM intake increased (P < 0.0001) with 8 kg DM of FCM, averaging 14.8 kg. Substitution rate was 0.75 and 0.67 kg of pasture per kilogram of FCM with 4 and 8 kg DM of FCM, respectively. Consequently, stocking rate (STR) increased (P < 0.0001) from 3.8 to 6.2 and 8.8 cows ha⁻¹, and milk production per hectare increased (P < 0.0001) from 39.3 to 64.5 and 95.5 kg of milk, with 0, 4, and 8 kg DM of FCM, respectively. This means that STR increases 0.63 cows ha⁻¹, and 0.75 kg of milk ha⁻¹ when FCM is increased in 1 kg of DM. In conclusion, offering FCM as supplement to grazing dairy cows in their final lactation stage had no benefits in individual milk production or milk composition, but had benefits on milk production per hectare.     

Effect of plant height at cutting,source and level of fertiliser on yield and nutritional quality of Napier grass (Pennisetum purpureum (L.) Schumach.)

Napier grass (Pennisetum purpureum (L.) Schumach.) was studied using a 5 x 3 factorial experiment arranged in a randomised complete block design with three replications. The treatments were five fertiliser applications (0kg ha^-1 N, 46kg ha^-1 N and 92kg ha^-1 N, 1t ha^-1 and 2t ha^-1 cattle manure) and three plant heights at cutting (0.5m, 1m and 1.5m). The mean dry matter (DM) yield was 8.21t ha^-1 per cut but increased when the plant height at cutting increased and when the level of N fertilisation increased (P<0.05). Neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL), cellulose, calcium, in vitro dry matter digestibility (IVDMD) and metabolisable energy were significantly (P<0.05) affected by plant height at cutting while total ash, crude protein (CP), ADF-ash, hemicelluose and phosphorus were affected by both plant height at cutting and fertiliser level. As plant height at cutting increased from 0.5m to 1.5m, IVDMD declined from 71.74% to 61.03% (P<0.05). Correlations between IVDMD versus CP, NDF, ADF, ADL, cellulose and hemicellulose were high with r = 0.92, -0.94, -0.96, -0.98, -0.83 and 0.74, respectively. CP yield per hectare per day of growth was highest for the 0.5m height at cutting, whereas the digestible DM yield was highest at both the 0.5m and 1.0m cutting height. The results of the present study suggest that Napier grass could be categorised under medium to high quality forage if cut at 0.5m or 1.0m height.     

用生物经济模型对我国不同类型猪场的模拟研究——模型的构建和初步结果

根据我国当前养猪生产繁育体系,将我国集约化养猪生产概括为5类典型猪场,并利用农场模型的方法,构建了不同类型猪场的生物经济模型,并考虑了模型的生物学效率。模拟的600头母猪的商品猪场、猪苗场、杂种扩繁场、杜洛克育种场和长白（或大约克）育种场每年总利润分别为56.01、12.99、100.53、134.09和164.10万元,净能利用效率分别为27.69、32.98、28.25、28.32和28.48 MJ/kg。模型还输出了不同类型猪场的成本结构、收入组成和生产综合指标。对模型的敏感度分析表明,模型对不同市场形势、生产水平和管理措施变化的反应是灵敏的。     

Implementation of Nutrient Management Planning on a Dairy Farm

Environmental policy and highly variable margins are requiring major changes on dairy farms. A case study was conducted on a commercial dairy farm over a 5-yr period to evaluate the impact of implementing methods designed to improve environmental and economic sustainability. Six Sigma (Pande et al., 2000) principles were utilized in conjunction with the Cornell University Nutrient Management Planning System (cuNMPS) to develop a system for precision farming to improve nutrient management. Critical components were the development and implementation of plans for herd nutrient management and crop, soil, and manure nutrient management. Implementation of this precision farming system resulted in increases in animal numbers (26%), milk per cow (9%), total milk sold daily (45%), and decreases in purchased feed cost (48%), feed cost per kilogram of milk sold (52%), and total manure N (17%) and P (28%) excretion. These results were attributed to improvements in forage production, quality, and storage (38% increase in proportion of diets homegrown) and precision feeding of high forage diets using the Cornell University Net Carbohydrate and Protein System (CNCPS) for diet formulation. Implementation of this approach on other farms requires management commitment and training. Training must include providing background information and tools for making continuous improvement in quality control and management and the use of root cause analysis. The adoption of the precision farming system by the case study farm management team has improved the business financially and decreased the accumulation of manure nutrients per hectare.     

基于畜禽粪便养分含量的畜禽承载力研究

为了减少畜禽养殖带来的环境污染,许多发达国家规定畜牧场周围必须配备农田来消纳畜禽粪便,同时也有成熟的畜禽承载力的研究方法。根据我国区域养殖畜种较多、农田分散、农牧脱节等情况,本研究确定了适合我国国情的用特定地理区域范围消纳畜禽粪便氮(N)、磷(P2O5)能力的方法来确定畜禽承载力。本研究根据不同畜种平均每头(只)存栏动物每年的粪便养分产生量、每公顷作物每年的养分移走量,计算出每公顷大田作物地、蔬菜地和园地每季所能承载的各种畜禽数量,然后根据各地区的复种指数估算出作物地每年承载的畜禽数量。结果表明:牛、羊的年产粪便N/P2O5较大,禽类比值较小,其他畜种比值居中;蔬菜地可以承载的畜禽数量最多,大田作物地次之,园地承载的最少;以N作为承载标准时,农用地所承载的畜禽数量比以P2O5作为标准时多(最高为6.6倍)或者两者持平。可以根据区域需要,通过提高作物对肥料的利用率、调整化肥与粪肥用量、调整种植结构等方式改变畜禽承载力的大小。     

Comparison of two milk pricing systems and their effect on milk price and milk revenue of dairy farms in the Central region of Thailand

A study was conducted to investigate determinates of how milk pricing system, farm location, farm size, and month and year affected farm milk price (FMP), farm milk revenue (FMR) and loss in FMR of dairy farms in the Central region of Thailand. A total of 58,575 milk price and 813,636 milk yield records from 1034 farms were collected from November of 2004 to June of 2006. Farms were located in the districts of Muaklek, Pak Chong, Wang Muang, and Kaeng Khoi. A fixed linear model was used to analyze milk price of farms. Two pricing systems were defined as 1 = base price plus additions/deductions for milk fat percentage, solids-non-fat, and bacterial score, and 2 = same as 1 plus bulk tank somatic cell count (BTSCC). Farm size (small, medium, and large) was based on the number of cows milked per day of farms. Results showed that FMP were lower (P < 0.05) in pricing system 1 than pricing system 2. Most small farms had higher (P < 0.05) milk prices than medium and large farms across both pricing systems. Large farms lost more milk revenue due to deductions from bacterial score and BTSCC than small and medium farms.     

Phosphorus Intake and Excretion on South Carolina Dairy Farms

The objective of this study was to survey dairy farmers to determine P levels in feed and manure. Feed and manure samples were collected from 19 Holstein, six Jersey, and two Guernsey farms in South Carolina. Samples from the Jersey and Guernsey herds were pooled. Samples were dried and analyzed for N and P. Amounts of all feeds were recorded; then, nutrient intake was determined. Dairy Herd Improvement records were used to determine the milk yield and fat content and, subsequently, the P requirement. Nineteen of 27 herds (70%) were fed more P than required according to nutrient requirements established by the NRC. The average P intake was 94.9 g (0.48% of diet DM) compared with the average requirement of 78.3 g (0.41% of diet DM). There were correlations between dietary and fecal P (R² = 0.46) and between CP and P intake (R² = 0.62). There was not a significant correlation between excess P intake and milk yield. In summary, many dairy producers overfeed P. Feeding dietary P at recommended levels will optimize milk yield and reduce P excretion on dairy farms.     

北京市规模化奶牛场粪污综合管理模式分析——以北京延庆区大地群生养殖专业合作社为例

北京是都市奶牛养殖业发展的典型代表,拥有规模化奶牛场49 家,存栏规模5.68 万头。得益于资金和技术支持,北京市奶业稳步发展,但受资源、环境、政策等因素影响,当地规模化奶牛养殖企业也面临管理难度大、环保压力大、养殖成本高等问题。优化规模化奶牛场综合管理是解决奶牛养殖区域性难题的有效途径。本文在充分调研北京市奶牛奶牛场粪污处理现状的基础上,以北京市延庆区大地群生养殖专业合作社为例,介绍科学养殖-高效粪污资源化利用综合管理方案,以期为都市型农业提供粪污管理方案提供参考。     

Manure as a key resource within smallholder farming systems: Analysing farm-scale nutrient cycling efficiencies with the NUANCES framework

Smallholder farmers in Africa recognise the important role of manure in maintaining soil fertility. For smallholder farmers who use little fertiliser, efficient management of nutrients in manure is key for crop production. We describe a simple model to analyse the effect of manure management on the efficiency of mass and nutrient retention. We used on-farm data on manure excreted and manure management, experimental results, literature and fuzzy logic to model losses during manure storage. The model was used to analyse N cycling efficiency (NCE) within smallholder farms in western Kenya. Simulations showed that manure management during collection and storage had a large effect on the efficiency of C and nutrient retention. Differences in NCE between farmers of different wealth classes arose due to differences in resource endowment. For poorer farmers, large N losses occur at all stages of manure recycling. Urinary-N losses occurred on all farms but their impact on NCE for poor and medium-class farmers was larger due to the smaller amount of N recycled. With current management the poor farmer recovered < 1 kg N y^− 1 in composted manure from 15 kg N y^− 1 excreted. Improved manure storage had little effect on increasing overall NCE for the poor farmer due to large losses before storage. For the wealthier farmer improvement of manure storage increased NCE and allowed recycling of 30% of N excreted (ca. 30 kg N y^− 1) with small investment in infrastructure. Covering manure heaps with a polythene film reduced mass and N losses considerably. For the poor to increase overall NCE, investment in cattle housing and recycling of urinary-N is required. Increasing cattle numbers or improved feeding would have a larger effect on manure availability but this is constrained by feed scarcity and investment capacity. The absolute amounts of N recycled (1–6, 4–17 and 7–18 kg N y^− 1 for poor, medium and wealthier farmers) were small compared with maize N demand (> 50 kg N ha^− 1), but significant given the small farm sizes (0.1–1.1 ha). Although absolute amounts of N recycled with improved manure management may have little immediate impact on crop productivity, manure is often the only input available. Manure provides other nutrients for crops and maintains soil organic matter — both vital to guarantee efficient use of fertiliser N — which justifies the search for interventions to assist farmers make better use of manure.     

Post-grazing sward height imposed during the first 10 weeks of lactation: Influence on early and total lactation dairy cow production,and spring and annual sward characteristics

Increasing the proportion of grazed grass in the diet of the dairy cow is the main target of grass-based milk production systems. Imposing a severe post-grazing sward height (PGSH) in early lactation is one strategy to increase grass utilisation. A grazing experiment was undertaken to investigate the direct and carryover effects of PGSH imposed in early lactation on sward and dairy cow lactation performance. Ninety Holstein–Friesian dairy cows (mean calving date: February 13) were randomly assigned to one of three target PGSH treatments: 2.7 cm (severe; S), 3.5 cm (low; L) and 4.2 cm (moderate; M) from February 14 to April 24, 2011 (period 1; P1). This was followed by a carryover period (period 2; P2) during which cows were randomly re-assigned within their P1 treatment across two PGSH treatments: 3.5 or 4.5 cm until November 13. Sward utilisation (>2.7 cm) during P1 was significantly improved by decreasing PGSH from M (0.74) to L (0.82) and further to S (0.94). At the end of the entire grazing season, the M treatment swards had produced +1.4 t dry matter (DM)/ha than the S and L treatment swards which had similar total DM yields (14.1 t DM/ha). Treatment had no immediate or carryover effect on the proportions of leaf, stem and senescent material in the sward or the quality of herbage selected by the animals. During P1 the cows in S had greater bodyweight loss (−18 kg), reduced milk (−2.1 kg/day) and milk solids yields (−0.21 kg/day) as well as lower grass DM intake (−1.7 kg DM/day) compared with the cows in L and M, which performed similarly (−5 kg, 24.1 kg/day, 1.94 kg/day, and 13.0 kg DM/day, respectively). There was no carryover effect of early lactation PGSH on milk and milk solids yields, fat and protein concentrations during P2. This indicates that cows restricted in P1 were able to adjust production in accordance with the higher PGSH imposed during the remainder of the lactation. The S treatment had numerically lower, though not significantly lower, total lactation milk and milk solids yields, reflecting their significantly reduced yields in early lactation. It was concluded that grazing to 2.7 cm in early lactation is too restrictive for dairy cows. Cows in L and M had very similar total cumulative production performance. As a result, grazing to 3.5 cm during the first 10 weeks of lactation contributes to achieving both high milk output from pasture and high grass utilisation.     

规模化奶牛场粪污危害、处理及循环利用模式

随着我国奶牛养殖业发展规模的壮大,规模化奶牛场数量持续增加,但奶牛场粪污污染问题也日益凸显。本文结合自身工作经验,首先分析了规模化奶牛场粪污的危害性,然后从雨污分离、固液分离和干清粪工艺对规模化奶牛场粪污处理方式进行概述,最后从厌气（厌氧）发酵获得沼气、微生物发酵用作饲料和生产生物有机肥三种不同模式介绍模化奶牛场粪污的循环利用操作,以期为规模化奶牛场粪污高效利用提供借鉴。     

Effect of solid–liquid separation on anaerobic digestion of dairy manure in semi‐continuous stirred tank reactors: Process performance and digestate characteristics

The objective of this study was to investigate the effect of solid–liquid separation on anaerobic digestion of dairy manure in semi‐continuous stirred tank reactors. Reactors fed with liquid fraction of dairy manure (screened liquid manure) were kept in water baths at mesophilic (Run 1) and thermophilic (Run 3) temperatures, respectively, while reactors fed with water diluted manure and kept at mesophilic (Run 2) and thermophilic (Run 4) temperatures as control reactors. The performances of reactors were compared in terms of biogas and methane production, and digestate characteristics. The methane yields obtained from screened manure were higher than those from diluted manure at both mesophilic and thermophilic temperatures, while the highest methane yield was 185 L/kg VS_added under thermophilic temperature. Solid–liquid separation also had improved the effect on digestate fertilizer characteristics. Among four digestates from reactors, the highest contents of nutrients, N (4.12 g/kg) and P (2.36 g/kg) were found in Run 3, while the highest content of K (3.42 g/kg) was found in Run 1. These results showed the benefits of solid–liquid separation of dairy manure on process performance and digestate characteristics.