规模化猪场猪瘟、口蹄疫抗体水平监测和免疫效果分析

应用正向间接血凝试验检测45个规模化猪场共954份血清,其中母猪的猪瘟抗体水平大于和等于1∶16的血清占88.3%(362/410),育肥猪、保育猪的猪瘟抗体水平大于和等于1∶16的血清分别占80%(40/50)和65.2%(75/111),保育猪免疫效果最差;母猪的口蹄疫抗体大于和等于1∶128的血清占84%(583/694),育肥猪、保育猪的猪瘟抗体水平大于和等于1∶128的血清分别占66.7%(30/45)和47.7%(31/65),保育猪、育肥猪免疫效果较差。     

种猪群猪圆环病毒病的净化技术研究

为探究种猪群猪圆环病毒病(PCVD)的净化控制措施,通过对种猪群实施猪圆环病毒2型(PCV-2)灭活疫苗免疫(基础免疫2次,以后每隔4个月加强免疫1次),检测(基础免疫前、二免后20d和二免后3个月、加强免疫后3个月分别采集前腔静脉血,分离血清,采用ELISA检测PCV-2抗体、猪瘟抗体,PCR方法检测PCV-2核酸),淘汰加强免疫后PCV-2核酸仍为阳性的种猪,结合分析母猪PCV-2疫苗免疫前后繁殖性能的差异。为期1年净化措施实施的结果显示,种猪群的PCV-2核酸阳性率从33.33%显著下降到3.42%,其中后备猪的PCV-2核酸阳性率从39.02%下降到8.57%,种公猪从33.33%下降到0、经产母猪从15.38%下降到1.56%;母猪窝产仔数增加0.52头(P0.05),窝产活仔数增加0.78头(P0.01),窝产木乃伊胎数减少0.3头(P0.01);种猪群猪瘟免疫抗体合格率从53.73%提高到83.49%,平均阻断率从43.31%升高到63.46%,与种猪群PCV-2核酸检测阳性率呈现负相关。结果表明,实施免疫、检测、淘汰措施对于种猪群PCVD的净化成效明显,该技术可为规模化猪场开展PCVD的净化提供科学依据,具有推广应用价值。     

猪伪狂犬病-猪细小病毒病二联苗的安全性与免疫力试验

PRV-gE--PPV弱毒疫苗接种后备母猪和怀孕母猪,临床上未见不良反应,并且怀孕母猪在预产期内顺利产下健康仔猪,表明PRV-gE--PPV弱毒疫苗具有良好的安全性.PRV-gE--PPV弱毒疫苗免疫后备母猪,2周后,PPV抗体100%(8/8)转为阳性,PRV抗体85.7%(7/8)转为阳性,能产生良好的抗体反应.在免疫接种后2个月、4.5个月进行强毒攻击,免疫猪未见不良反应,对照猪未见或出现轻微的不良反应.从免疫猪的鼻、肛分泌物和血浆中未分离到PPV,而从对照猪的鼻、肛分泌物和血浆中分离到PPV和PRV.表明PRV-gE--PPV弱毒疫苗能抵抗PPV、PRV的攻击,具有良好的免疫保护力.     

河北省沧州地区猪场伪狂犬病毒感染情况调查与分析

为了解沧州地区猪场伪狂犬病疫苗免疫后伪狂犬病毒的感染情况,对本市13个注射过猪伪狂犬病gE基因缺失苗的猪场进行了猪伪狂犬病的血清学ELISA检测。结果表明,不同地区阳性率相差较大,沧县、盐山县、黄骅市、肃宁县血清阳性率较高,泊头市、河间市猪伪狂犬病阳性率较低;300头母猪以上的猪场阳性率(54.05%)低于平均阳性率(63.34%),100头母猪以下猪场阳性率最高达72.53%(66/91);1胎阳性率低于平均阳性率,而4胎以上的母猪高于平均阳性率;每年免疫2次的母猪阳性率明显高于每年免疫3次的母猪;30日龄内与31~60日龄的商品猪伪狂犬病阳性率相差不明显,60日龄以上的仔猪阳性率最小,低于平均值;未免疫疫苗的仔猪阳性率最高28.57%(12/42),而免疫2次的商品猪阳性率最低14.58%(7/48)。     

河南省某猪场圆环病毒病免疫程序制订及效果评估

为了解河南省某规模化猪场按规定的免疫程序接种猪圆环病毒2型(PCV2)灭活疫苗后猪体内的PCV2抗体水平,随机采集90份免疫猪的血液样品(后备母猪、1胎母猪、2胎母猪、3胎以上母猪、3周龄、6周龄、9周龄、11周龄、19周龄猪各10份),通过ELISA检测PCV2抗体。结果显示,除3周龄猪抗体阳性率为90%以外,其他各猪群抗体阳性率均为100%,猪群没有发生圆环病毒病和其他传染病,猪群生产性能正常。检测结果证明商品猪3周龄首免,3周后二免;后备母猪配种前免疫,间隔3周二次免疫;经产母猪产前1个月免疫的免疫程序是科学合理的。     

两种不同添加剂饲料对母猪血液生理指标及健康指数影响的研究

研究了饲喂新品母猪饲料和含A的母猪饲料后对母猪健康状况的影响。选用长白母猪26头,随机分为2组,分别饲喂新品母猪饲料和含A的母猪饲料,饲喂60 d,每间隔30 d采集血液,合计3次进行血液生理指标检测,确定产品效果。结果表明:饲喂新品母猪饲料后母猪的健康指数上升且第3阶段上升了24.8%(P0.05),应激水平第3阶段相比第1、第2阶段分别降低18.84%(P0.05)和19.01%(P0.05);免疫水平下降且第2阶段下降了了13.7%(P0.05)。含A的母猪饲料饲喂后猪健康指数无显著性(P0.05)差异,应激水平下降且第3阶段下降了15.8%(P0.05)。试验表明,饲喂新品母猪饲料能增加猪的健康指数且降低机体的应激水平、免疫水平,饲喂含A的母猪饲料能降低机体的应激水平。     

伪狂犬转阴方案在猪场实践和验证

正华东某猪场伪狂犬gE抗体高阳性率猪场,从2017年1月开始实施伪狂犬净化"CICA/3231"方案,结合使用猪伪狂犬耐热保护剂活疫苗(C株)免疫后,3个月gE抗体母猪阳性率下降60%,9个月以后趋于稳定,猪群gE抗体转阴。华东某猪场,1500头母猪。2016年因为引进携带伪狂犬病毒公猪,造成在繁母猪几乎全部感染,猪群出现流产、死胎、仔猪神经症状通过"CICA/3231"方案,即检测、"3231"免疫工程、选择猪伪狂犬耐热保护剂活疫苗(C株)、全     

规模猪场主要疫病抗体水平监测及免疫效果分析

采用血凝试验和酶联免疫吸附试验 (ELISA) ,检测了杭州市 2 4个规模猪场 91 1份血清中的猪瘟、猪伪狂犬病、猪繁殖和呼吸综合征 (蓝耳病 )抗体效价。结果表明 :规模猪场猪瘟免疫效果较好 ,免疫合格率达 85 6 % ,其中母猪免疫合格率 (92 6 % )高于种猪 (78 2 % )和肥育猪(62 4% ) ;猪伪狂犬病抗体阳性场达 2 0个 ,猪抗体阳性率为 40 0 7% ,其中母猪为 50 2 4 % ;猪蓝耳病抗体阳性血清数为 362份 ,占 39 74% ,其中 ,种猪最高 ,为 50 6 % ,其余依次为肥育猪 (48 3 % )和母猪 (35 4% ) ,猪蓝耳病抗体阳性场数为 1 7个 ,占 70 83 %。     

规模化猪场免疫程序调整前后抗体变化及分析

本文针对某规模化猪场免疫程序调整前后的猪群进行了血清学检测。对两个季度共计177个样本进行了猪瘟抗体、猪肺炎支原体抗体、猪圆环病毒2型抗体、猪蓝耳病抗体的检测和分析。结果显示,该场商品猪猪瘟免疫调整后免疫效果不佳,猪蓝耳和猪圆环调整后免疫表现良好;后备母猪虽未修改计划,但蓝耳病抗体滴度下降,猪瘟和圆环两个季度表现一致,主要呈现猪肺炎支原体中等程度(42%)感染;母猪猪瘟免疫计划调整后免疫良好,蓝耳病免疫方案调整后阳性率和抗体滴度均有下降。结合两个季度的抗体表现,表明本场对商品猪的猪圆环、猪蓝耳免疫程序调整较为理想,可继续保持;对经产母猪进行的猪瘟和猪蓝耳病免疫调整也基本可行,可继续实施;同时需调整商品猪的猪瘟免疫程序;并考虑通过保健或免疫措施提升后备母猪抵抗猪肺炎支原体的能力。     

规模化猪场猪伪狂犬病野毒感染的调查

为了解北疆部分规模化猪场伪狂犬病野毒感染情况,本试验于2016年6月-2017年7月共采集北疆5个不同规模的规模化猪场567份血清,采用gE-ELISA和全病毒ELISA方法进行伪狂犬野毒及免疫抗体的检测。结果表明,北疆地区猪伪狂犬病全病毒抗体总阳性率为99.32%(290/292),gE抗体总阳性率为52.74%(154/292);其中B、D、E三场全病毒抗体阳性率都达到了100%,C场阳性率最低,为98.15%(53/54),D场gE抗体阳性率最高为83.33%(20/24),B场gE抗体阳性率最低为35%(14/40);不同猪群调查结果显示,怀孕母猪gE抗体猪阳性率最高为68.18%(30/44),公猪较高为59.38%(19/32),保育猪阳性率最低为35.14%(26/74);A场在2016年6月-2017年7月3次检测中,gE抗体阳性率总体呈下降趋势,其中生产母猪和怀孕母猪下降明显,其他猪群阳性率波动较大。检测结果揭示,北疆地区伪狂犬野毒感染净化工作的压力依然很大,需要进行严格的检疫、免疫以及净化。     

Worm control practices of pig farmers in Greece

Information concerning worm control practices of pig farmers in Greece was collected through a questionnaire survey by visiting farms and interviewing farmers. Questionnaires from 93 farmers were collected. The most commonly treated age groups of pigs were sows (87%), followed by fatteners (59%) and weaners (57%). Most of the farmers treated their sows twice per year (78%). The preferred method for calculating anthelmintic dosages was visual estimation (77%) of an average body weight (97%). Drug administration was by mixing anthelmintics with 1-day ration (97%) in two doses with an interval of 4-5 days (94%). The most commonly used group of anthelmintic was benzimidazoles and probenzimidazoles (37-46%), followed by avermectins (7-14%) and tetrahydropyrimidines (8-14%). Febantel was the most commonly used individual drug (34-40%), followed by ivermectin (7-14%) and pyrantel (9-14%). A small number of pig farmers used more than one group of anthelmintics (1-4%) or individual drug (2-6%) in the same year. The majority of the farmers (60%) used the same anthelmintic group for 3 or more years. When gilts/sows or boars were brought, 55% of the pig farmers did not treat with an anthelmintic. Most of the farmers evaluated the efficacy of an anthelmintic by inspecting the general appearance of the pigs or by inspecting for the presence of worms expelled in the faeces after treatment. Planning of the anthelmintic treatment strategy for most of the farms was the responsibility of veterinarians. However, most of the farmers considered the magnitude of worm infection in their own farm as insignificant.     

浙江省家蚕新品种选育科研投资收益的定量评价

引用农业科研投资收益计量模型,对浙江省1981-2005年家蚕新品种选育的科研投资收益进行定量评价。结果表明,浙江省在此期间对家蚕新品种选育研究投资所获得的经济收益达4 164.8万元(以1981年为基期),投资的内部收益率为35.09%,远高于全社会投资项目基准收益率8%,总体投资收益十分显著。然而在具体的投资收益流中,由于2000年以后没有选育出经济性状具有突破性改进的新品种在生产上推广应用,因而其投资收益逐年大幅下降,从2000年的197.02万元下降到2005年的64.83万元。根据评价结果,提出了加大科研投资力度、加快育种材料和育种手段与方法的创新、深化家蚕育种体制改革和激发育种人员积极性等政策性建议。     

Survey among Belgian pig producers about the introduction of group housing systems for gestating sows

There is a global move from individual to group housing of gestating sows. In the European Union, individual gestating stalls will be banned by 2013. Just like in other industrialized regions, these stalls have been the standard housing system for intensively kept sows from the 1960s onward in the Flemish region of Belgium. Because the socioeconomic consequences for the pig industry may be far-reaching and because farmer attitude may influence the realization of the hoped-for improvement in animal welfare in practice, we conducted a survey from 2003 until 2009 among representative samples of Flemish pig producers every 2 yr. The share of farms with group housing increased from 10.5% in 2003 to 29.8% in 2007, but then dropped to 24.6% in 2009. It appears that after 2005 users of old group housing systems in particular stopped farming. Because sow herd size increased more on farms with vs. without group housing and because the proportion of the herd that was group-housed also tended to increase between 2003 to 2009, the change to group housing took place faster when expressed at the level of the sow (from 9.1% in 2003 to 34.1% in 2009) instead of farm. The percentage of farmers planning to convert to group housing within 2 yr was 4.1% in 2003, and 6 to 7% thereafter. These were typically young farmers (P = 0.006) with a large sow herd (P < 0.001) and with a likely successor (P = 0.03). Free access stalls were the most common group housing system (31% of farms, 37% of sows). Their popularity is expected to increase further at the expense of electronic feeding stations, ad libitum feeding, and stalls/troughs with manual feed delivery. User satisfaction was generally high but depended on whether or not all gestating sows were kept in group (P < 0.001), the provisioning of environmental enrichment (P = 0.057), and the age (P = 0.012) and type (P = 0.016) of system. The main criteria for choosing a certain group housing system were the investment costs and sow health and welfare. The importance of economic reasons (P = 0.007) and type of labor (P = 0.043) decreased with the age of the system. In 2003 and 2005 the main reason for not having converted to group housing was that farmers would stop keeping sows by 2013. In 2007 and 2009 the reasons mainly concerned uncertainty about the future and maximally delaying the conversion. Belgium is one of the European Union countries where the pig industry is expected to undergo drastic changes during the few years remaining before the ban on individual housing.     

Characterisation of smallholder pig production in Kikuyu Division, central Kenya

A three-phase study was conducted in high-potential farming and peri-urban area in Kikuyu Division central Kenya to obtain farm and management data and to monitor health and productivity of pigs in smallholder farms. The first phase was a cross-sectional study in which 87 farms (that had been selected from a total of 179 farms using a simple random selection) were visited once and data on important farm and management factors were gathered using semi-structured questionnaires. The second phase was a pilot study that was conducted in the 87 study farms for a period of 3 months to pretest the data-collection tools and to evaluate the general research methodology for the longitudinal study. The third phase was a prospective 12-month observational study in which health and productivity of pigs were monitored monthly in 76 herds that were still active and had participated in the previous studies.

The initial voluntary enrolment among the eligible farms was 99%. The median farm size was 1 acre. All the farms kept crossbreed pigs of Large White or Landrace (median nine pigs per farm). The median number of sows per herd was one. Most farmers engaged in farrow-to-finish pig-production system and most (60%) did not keep a breeding boar. The pigs were stall-fed the year round. Guard rails/piglet devices were present in 22% of the herds. Few (8%) farmers disinfected pig pens (especially the farrowing area). None of the farmers reported the use of vaccination against pig diseases. Most farmers (84 and 96%) indicated that they controlled for mange and worm infestations, respectively. To control mange, 50% of the farmers used acaricides, 34% used engine oil and 12% used both. Anthelmintics were used to control worms. No farmer had a particular control programme in place for both worms and mange. Artificial heating for piglets was not used in any of the farms. High costs of feeds (which were of variable qualities) lack of credit and genetically high-quality breeding boars and diseases were ranked highly by the farmers as the main production constraints. Thirteen percent (11/87) of farmers withdrew during the pilot study; 10 farmers had sold their pigs and one had died. Thirty-three percent (25/76) of the farms withdrew during the longitudinal study for various reasons that included death of pigs (3%; 2/76) and sale of the pigs (30%; 23/76)—mainly because of financial need.     

Reproductive, metabolic, and endocrine responses to feed restriction and GnRH treatment in primiparous, lactating sows

The current experiment was carried out to determine whether exogenous GnRH treatment in primiparous, lactating sows undergoing feed restriction would improve reproductive performance after weaning. Sows were allocated to one of three treatments: AA sows (n = 8) were fed to appetite throughout a 28-d lactation, AR (n = 12) and AR + GnRH (n = 12) sows were fed as AA sows from farrowing to d 21 of lactation, and feed intake was reduced to 50% of the ad libitum intakes from d 22 to 28. The AR + GnRH sows received 800 ng of GnRH i.v. every 6 h from d 22 to 28 of lactation, and AA and AR sows received saline. Sow weight, backfat, and litter weight were recorded weekly. Within 2 d after farrowing, litter size was standardized to 8 to 10. At d 17 of lactation, an indwelling jugular catheter was surgically implanted in each sow. Blood samples were taken for characterization of plasma LH, FSH, insulin, IGF-I, and leptin by RIA at d 21 and before and after weaning on d 28 of lactation. After weaning, all sows were given ad libitum access to feed, checked for onset of standing estrus twice daily with mature vasectomized boars, and inseminated 12 and 24 h after onset of standing estrus with pooled semen from the same fertile boars (3 x 10(9) sperm/AI). After breeding, feed allowance was reduced to NRC (1988) requirements for gestation. At d 28 +/- 3 of gestation, sows were killed and ovulation rate and embryo survival were determined. Restricted sows lost more weight during lactation than AA sows (P < .02). During the period of feed restriction, plasma IGF-I and postprandial insulin and leptin in AR and AR + GnRH sows, and LH pulse frequency in AR sows, were lower than those in AA sows (P < .04). Associations (P < .004) between plasma insulin and leptin and between leptin and mean LH concentrations were established. The LH pulse frequency in AR + GnRH sows did not differ from that in AA sows before weaning. After weaning, maximum, mean, and minimum LH concentrations in the AA and AR sows, and FSH concentrations in AR sows, increased (P < .05) in response to weaning. Paradoxically, GnRH treatment in lactation seemed to suppress the expected LH and FSH responses to weaning. Ovulation rate and embryo survival were not different among the three groups. In conclusion, although exogenous GnRH therapy restored LH secretion in feed-restricted sows, it did not improve overall reproductive performance.     

Protection against neonatal Escherichia coli diarrhoea in pigs by vaccination of sows with a new vaccine that contains purified enterotoxic E. coli virulence factors F4ac, F4ab, F5 and F6 fimbrial antigens and heat-labile E. coli enterotoxin (LT) toxoid

The efficacy of a new vaccine against neonatal Escherichia coli diarrhoea in piglets containing purified F4ab, F4ac, F5 and F6 fimbriae and detoxified heat-labile toxin (LT) was tested in challenge experiments by the method described by the European Pharmacopoeia (3rd edn, EDQM, Council of Europe, Strasbourg, France). A group of 11 young sows from a herd without E. coli problems was vaccinated 6-8 and 2-4 weeks prior to expected farrowing and another group of nine young sows were non-vaccinated controls. Escherichia coli antibody titres were determined in serum samples taken from the sows before first vaccination and before farrowing and in colostrum samples. The newborn piglets were allowed to suckle colostrum from their mother immediately after birth. The piglets were marked with individually numbered ear tags. Approximately 12 h after birth, 118 piglets from vaccinated sows and 79 piglets from non-vaccinated control sows were challenged by oral instillation of 5 ml of a freshly prepared culture of one of the challenge strains [O8:K87:F4ab (LT+) or O149:K91:F4ac (LT+) or O9:K30:F5 or O9:K103:F6 respectively]. The challenge cultures contained as a mean 6.8x10(9) CFU/ml. After challenge the piglets were observed for 7 days and mortality and morbidity were recorded. Vaccinated sows developed significant levels of antibody titres in colostrum and serum. Control sows stayed at a low/seronegative level. The protective efficacy was excellent because 66.7-87.5% of the piglets from vaccinated sows remained without clinical signs after challenge. Only 0.0-28.0% of the piglets from non-vaccinated sows remained healthy and more than 47.1% of the piglets in this group died after challenge. It is concluded that the new vaccine is very effective in protection of piglets against neonatal E. coli diarrhoea.     

Factors influencing farmers' responses to welfare legislation: A case study of gestation sow housing in Flanders (Belgium)

In the light of the EU ban on individual confinement of gestating sows which will have to be fully implemented by 2013, a survey was conducted among a representative sample of Flemish pig producers. The questionnaire was sent by post to 250 farmers in 2003 and 352 farmers in 2005 of which 219 and 296, respectively, provided valid responses via telephone. The percentage of respondents housing (some of) their sows in group was 10.5% in 2003 and 16.2% in 2005. These farmers were more likely to have a successor than farmers housing their sows individually. The most common group housing systems were free access stalls (24%) followed by electronic feeding stations (21%), ad libitum feeding (20%), feeding stalls/troughs (18%), and drop/trickle feeding systems (13%). Interval (4%) and electronic feed dispensers (0%) were very rare in Flanders. The main criteria for having chosen a particular group housing system related to sow health and welfare, investment costs and amount of labour. The relative importance of economic reasons has increased over time. Users were generally rather satisfied with their group housing system. Farmers using group housing for all their sows were more satisfied than farmers using both group and individual housing. Users of ad libitum feeding systems (and feeding stalls/troughs) were more satisfied than users of electronic feeding stations. A minority of respondents was planning to change to group housing within two years time (4.1% in 2003 and 7.4% in 2005). These tended to be young farmers with a large sow herd and 58% reported to opt for free access stalls. The main reason why the remaining respondents were not planning to change to group housing yet is that they will stop farming activities before 2013. This reason was particularly important for older small-scale farmers without a successor. In contrast, the lack of financial resources and security was particularly important for young farmers of a large sow herd with a likely successor. An increasing group of farmers (often without a successor) reported to delay changing to group housing because they consider individual housing more profitable. These results show that, in Flanders, the conversion to group housing is taking place slowly, that the reasons for not converting yet vary according to the farmers' age, the likelihood of a successor and herd size, and that there are differences between operational group housing systems concerning herd size, age of the system, sow management and user satisfaction.     

Efficacy, safety, and residue evaluation of levamisole gel formulation in sows

Anthelmintic efficacy, safety, and residue studies were conducted in sows and gilts with a levamisole gel containing 11.5% levamisole HCl. In 12 sows and 12 gilts, 8 mg of levamisole HCl equivalent/kg of body weight orally was 100% (resinate) and 91.1% (gel) effective against 55-day-old Ascaris suum and 100% (gel) and 96.1% (resinate) effective against Oesophagostomum dentatum. In 20 sows given levamisole gel (8 mg of levamisole HCl/kg) orally just before breeding, 4 to 6 weeks after breeding, 4 to 6 weeks before farrowing, and just before farrowing, there were no adverse effects. Transient salivation was noticed in five sows after treatment. In 4 groups of 4 sows each given levamisole gel orally to provide 8, 24, 40, or 80 mg of levamisole HCl/kg, adverse clinical signs were not observed in sows treated with 8 mg/kg. Transient salivation was noticed in one sow given 24 mg/kg, two sows given 40 mg/kg, and four sows given 80 mg/kg. Multiple emesis and chomping occurred in one sow given 80 mg/kg. Levamisole residues in edible tissues from sows given 8 mg of levamisole gel/kg orally were less than 0.1 mg/kg of muscle and fat in sows killed on posttreatment day (PTD) 3 and less than 0.1 mg/kg of kidney in sows killed on PTD 5. Liver residues averaged 0.78 mg/kg in sows killed on PTD 3 and were reduced to 0.31 mg/kg in sows killed on PTD 5. The 99% upper tolerance limit with 95% confidence on the withdrawal time to assure levamisole residues of less than 0.10 mg/kg in liver tissue was 11 days.     

Vaccination of pregnant sows against transmissible gastroenteritis with two attenuated virus strains and different inoculation routes

Summary Two attenuated transmissible gastro-enteritis (T. G. E.) virus strains were used for vaccination experiments in sows. Four different experiments were carried out (see Table 1). In each experiment, 9 sows were vaccinated during pregnancy and 3 sows served as controls. They were kept together in one farrowing house. The sows were due to farrow at about the same time. The sows and their litters were challenged shortly after farrowing by exposing 3 piglets of 2 control litters to virulent TGE virus. The following vaccination schedules were used (see Table 1): twice intramuscularly with TGE-vac (a commercially available TGE-vaccine), one oral administration followed by an intramuscular vaccination with an attenuated TGE Purdue (Pu) strain, twice orally with Pu strain in enteric coated capsules, and one direct intra intestinal administration followed by 2 intramuscular vaccinations or 3 intramuscular vaccinations with the Pu strain. All sows, except most of those treated with enteric coated capsules, seroconverted demonstrably (Table 2). The geometric mean seroneutralization (SN) titer log 2 varied from 4.1 to 7.5 after the first vaccination and from 7.6 to 10 after the second vaccination. None of the vaccination schedules resulted in an effective lactogenic immunity. The morbidity in the piglets was 100% within 3 to 5 days after challenge. The mortality rate varied from 44 to 80% in litters from vaccinated sows and from 71 to 100% in litters from control sows (see Table 3). Clinical signs were observed in 33,3% of the control sows and in 36% of the vaccinated sows. No correlation was found between the titer of SN antibodies in the sera of the piglets and their survival rate (Table 4). A rapid decrease in antibody concentration was observed, during the first week of lactation in milk samples collected from 4 orally and intramuscularly vaccinated sows (Table 5).     

Factors influencing estrus and ovulation in weaned sows as determined by transrectal ultrasound.

Characterization of factors influencing estrus and ovulation in sows may facilitate development of procedures for improving reproductive performance. The experiment was conducted in confinement during 1997 to 1999 using 174 Large White x Landrace sows. After weaning, sows were checked for estrus twice daily. In the 1st yr, transrectal ultrasound was performed once daily and in the 2nd yr twice daily at estrus and on every day until ovulation. The effects of lactation length (< or = 16 d, 17 to 24 d, 25 to 31 d or > or = 32 d), parity (1, 2, or > or = 3), season (winter, spring, summer, or fall) and weaning-to-estrus interval (3, 4, 5, or 6 to 8 d) and their interactions on estrual and ovulatory responses were studied. There was no effect of frequency of ultrasound on any response variable, so data across years were pooled. Percentage of sows expressing estrus within 8 d of weaning was influenced by lactation length (P < 0.001), with sows lactating < or = 16 d (35.2%) less likely to express estrus than sows lactating > or = 17 d (94%). A parity x season interaction was observed (P < 0.001) for estrus, with the lowest expression in parity 1 (73.0%) and parity 2 sows in fall (67.2%), compared with > or = parity 3 sows (98.1%). No explanatory variable had a significant effect on weaning-to-estrus interval (4.4 d) or on follicle size at estrus (8.1 mm). Ovulation hour after onset of estrus was affected by weaning-to-estrus interval (P < 0.01), with sows returning in 3 d ovulating at 46.2 h and between 6 and 8 d at 30.2 h. For sows that expressed estrus within 8 d of weaning, the percentage of sows ovulating was influenced by lactation length (P < 0.001) and weaning-to-estrus interval (P < 0.001). Sows that lactated < or = 16 d were less likely to ovulate (78.0%) than those lactating > or = 17 d (> 92%). Sows that returned to estrus in 3 d were also less likely to ovulate (79.5%) than sows returning > or = 4 d after weaning (> 92%). A parity x season interaction was also observed on ovulation (P < 0.001), with parity 1 and 2 sows less likely to ovulate after expressing estrus in fall and spring compared with parity 3 and greater sows. The data suggest lactation length, early return to estrus, and parity by season effects are associated with risk of failure to express estrus and ovulate.