PRRS净化中的封群管理
How to manage herd closure for PRRS elimination
为消除猪繁殖与呼吸综合征(PRRS)而封群的情况有所增加,部分原因是由于被鉴定为PRRS 1-4-4 L1C的强毒株。
Herd closures to eliminate porcine reproductive and respiratory syndrome (PRRS) are on the increase due in part to the virulent variant identified as PRRS 1-4-4 L1C.
明尼苏达州圣彼得市兽医中心,临床兽医博士(DVM)Paul Yeske报道说:“PRRS 1-4-4 L1C对人们的打击很大。消除这种变异株无异于我们净化PRRS病毒的做法,净化项目能够成功让猪群转为生产PRRS阴性猪。”
“PRRS 1-4-4 L1C has hit people hard,” reported Paul Yeske, DVM, Swine Vet Center in St. Peter, Minnesota. “The elimination process for this variant is what we’ve done for all PRRS viruses, and the program has been very successful at getting the herd to make PRRS-negative pigs.”
Yeske就PRRS净化期间,成功的封群管理提出建议。
Yeske offered suggestions for a successful herd closure to eliminate PRRS from a farm.
为封群做好准备
Prepare for herd closure
根据Yeske所言,首先增加初产母猪储备,覆盖整个封群期,通常为210至240天。
The first step is increasing gilt inventory to cover the full closure time, which typically runs 210 to 240 days, according to Yeske.
他说:“如场内有后备母猪舍,该场的后备取自隔离断奶猪,那他们已有6个月的初产母猪可用,只需再补充能满足数月需求的猪只数。如场内没有后备母猪舍,他们需另寻一处来安置这些动物,或填满可用的空间,以当前的储备量继续生产。
“If there’s an on-site gilt developer where the farm is getting the gilts as Isoweans, they already have 6 months of gilts and only need to increase capacity for a couple months,” he said. If the farm has no on-site gilt development, they must either find another site to hold these animals or be able to fill the space available and live with the current inventory.
封群前,Yeske建议对所有母猪和初产母猪实施返饲,以在封群的6-8个月内控制腹泻。他说:“我们从猪流行性腹泻(PED)中学到的一个教训是,我们可通过在封群初进行全群返饲来控制腹泻。”
Just prior to closure, Yeske recommended implementing a feedback program that’s given to all sows and gilts to provide scour control for 6 to 8 months of the closure. “A lesson learned from PED (porcine epidemic diarrhea) was that we can help ourselves on scour control by doing a whole-herd feedback at the beginning of a herd closure,” he said.
封群伊始
Closure begins
用猪场收集的血清暴露母猪后,封群便开始。在母猪群疾病刚暴发,缓过气儿来,正常吃喝后进行暴露。一些猪场甚至会等到所有后备入场后才进行。
Herd closure begins when sows are exposed with serum collected from the farm site. This occurs after the sow herd has recovered from the initial break and are eating and feeling good again. Some farms even wait until all replacements are on site.
他建议3周后在全场进行统计抽样,以确认群体呈阳性。必须测试所有猪舍,以确保所有动物都转阳。
He suggested following up 3 weeks later with a statistical sampling around the site to confirm the herd is positive. Make sure to obtain tests from all barns to ensure all animals are positive going forward.
Yeske说:“注射后开始计时240天,可能更长,这取决于检测结果。本质上来说,我们在等母猪的免疫力上升和排毒量降低。
“The injections start the clock ticking for 240 days and maybe longer, depending on how testing goes,” Yeske said. “Essentially, we wait for time to allow immunity to develop and shedding from sows to decrease.
他解释道:“我们的依据是,排毒一段时间后,免疫系统会清除母猪体内的病毒,畜群中没有可被感染的动物,理论上病毒会从猪场中消失,之后让阴性后备进入,也不会被感染。”
“The theory is the virus will shed for a period of time, and the immune system will clear the virus from the sows,” he explained. “Since there are no animals in the herd that can be infected, theoretically the virus should die out on the farm, allowing for negative replacements to enter and not become infected.”
Yeske说,整个封群期,猪场应重点清洁和消毒栋舍、走廊、出猪道和断奶猪去过的任何地方。此外,应尽量减少跨窝操作,工作人员在返回处理日龄更小的猪时应勤换靴子和工作服。他们应该按照从幼到长的顺序对猪进行处理,并在返回处理日龄更小的猪之前完成更换和清洁。
Throughout the herd closure, Yeske said the farm should focus on cleaning and disinfecting rooms, hallways, loadouts and any place weaned pigs move. Also, movement between litters should be minimized, and staff should be diligent about changing boots and coveralls when going back to handling young pigs. They should always work from youngest to oldest pigs, and change and clean up before going back to younger pigs.
检测方案
Testing regimens
闭群10-12周后,开始收集和检测仔猪处理液,这告知我们仔猪的病毒血症水平。他说:“我们仍呈阳性,还是趋于阴性?我们关注Ct值(循环阈值),希望该值上升。数值越低意味着样本中病毒越多。”
After 10 to 12 weeks of closure, collecting and testing piglet processing fluids begins, which will indicate the level of viremia in piglets. “Are we still positive or are we going negative?” he said. “We watch the Ct (cycle threshold) values and hope to see them go up. A lower number means more virus in the sample.”
Yeske建议使用处理液,因为样品相对易得,且比其它检测方法便宜。此外,它其实检测了所有仔猪的一份混样。大多数猪场将一整周的样品进行混样以降低成本,依然可监控净化项目进程。
Yeske recommended using processing fluids because samples are relatively easy to obtain, and it is less expensive than other testing methods. Plus, it essentially tests all piglets in a pooled sample, he added. Most farms pool a week’s worth of samples to reduce cost, yet still monitor to see if the herd is progressing.
处理液转为PRRS阴性后,对断奶猪进行检测,以确定它们是否在哺乳期保持阴性。此时,以产房或日为单位,采样检测处理液,以定位阳性位点。
When processing fluids start testing PRRS-negative, then piglets should be tested at weaning to see if they have remained negative through lactation. At this point, processing-fluid samples should be tested by room or day to help isolate the positive locations.
Yeske说 “断奶前,大多数人会做血液检测,但也可用母仔口腔液。母仔口腔液,可把麻绳悬于栏内,母猪会先去咀嚼,仔猪也会跟着咀嚼。一些窝的母仔口腔液采集易于其它窝,这就是为什么大多数还是会使用血样。
“Before weaning, most do blood testing, but you can use family oral fluids,” Yeske said. “With family oral fluids, hang the rope so the sow can chew on it first, and the piglets will chew on it too. Some litters respond better to family oral fluids than others, which is why most will use blood samples.
他补充道:“另一种选择是每周或每月对30-60只差猪进行血检,以确定断奶时猪是否呈阴性。”
“The other option is to blood test the poorest-quality pigs, 30 to 60 a week or month, to establish if pigs are negative at weaning,” he added.
何时解封
When to open herd
Yeske说,依场而异,有些在断奶猪转阴后60天,有些90天后解除封群。
Depending on the farm, some use 60 days of negative tests at weaning, and others use 90 days of negative tests before ending the closure, according to Yeske.
他说:“我们认为210天是封群的最佳时长,我们尝试过180天,但没有成功。采用210天,对之后开始引入PRRS阴性初产母猪的信心更足。
“What we’ve seen is 210 days is the sweet spot for herd closures,” he said. “We tried 180 days and didn’t have good success. If you use 210 days, you have higher confidence that the herd is ready to take PRRS-negative gilts.
“如果在第210天仔猪未转阴,那我们就继续等待。有些需要240天或更久。谨记净化项目中,时间是你的朋友,过早解封不是。”
“And if you don’t get the piglets testing negative at 210 days, then we just wait. That’s when some people go to 240 days or longer. Remember, time is your friend in elimination programs versus ending the closure too soon.”
封群结束
Closure ends
封群结束,最后一步是填群。若一个种猪场可以为场内自带后备母猪舍的猪场提供分段的动物群体,Yeske建议用这种方式补充后备。
Once the closure is finished, the final step is repopulating. If a genetic supplier for a farm with an on-site gilt developer can provide a staged population, Yeske recommended refilling the gilt developer that way.
若供应商只能提供断奶猪来填群,猪场将需要一个干净的地方来饲养阴性动物。他说道:“这是在筹备净化时需考虑的一个潜在限制”。
If only weaned pigs are available from the supplier to repopulate the herd, the farm will need a clean place to raise clean animals. “That’s a potential limitation, and you must think about that going into an elimination,” he said.
“总的来说,PRRS净化相对便宜。它能够将野毒驱逐出群,”Yeske补充道:“在猪密集区的一些猪场将继续接种疫苗。它们野毒阴性,但PRRS疫苗可以帮助他们在新病毒来袭的情况下保持一定的群体免疫力。”
“Overall, the process of PRRS elimination is relatively inexpensive. And it’s been able to push the field virus out of herds,” Yeske added. “Some farms in pig-dense areas will maintain a vaccination status. They will be negative to the field virus but have a PRRS vaccine to have some herd immunity in case of a new virus exposure.”
原文链接:https://pighealthtoday.com/how-to-manage-herd-closure-for-prrs-elimination/