Nursery mortality monitored with statistical process control over 2 years in a farm, which faced an acute PRRS outbreak and implemented changes in the vaccination program

  • 10 minutes
  • Expertise article
  • Dražen Hižman, Rebecca Morgenstern, Vladan Miljković
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Dražen Hižman1, Rebecca Morgenstern2, Vladan Miljković3

1Belje Agro-Vet plus, Croatia; 2Boehringer Ingelheim RCV GmbH & Co. KG, Austria; 3Boehringer Ingelheim Serbia d.o.o., Serbia E-mail: drazen.hizman@belje.hr

 

Introduction

Infection with porcine reproductive and respiratory syndrome virus (PRRSV) may lead to significant losses in productivity of breeding and growing pig herds1,2. Performance data was monitored over two years in a commercial farm in Croatia, which faced an acute PRRS outbreak and subsequently implemented changes in the vaccination program. The present abstract presents the results of nursery mortality. Sow performance is presented in a second abstract.

Materials and Methods

The study was conducted on a one site, farrow-to-finish farm with 2000 sows in Croatia. The farm is PRRSV positive since 2014, however, the first introduction never caused noticeable changes in performance and production was stable. A new, acute and severe PRRS outbreak occurred in late 2018, which negatively influenced reproduction (from week 44/2018) and shortly after the growing pig performance (from week 48/2018). Piglets were vaccinated against porcine Circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae (Mhyo). No PRRS vaccination was implemented prior to this new outbreak. A PRRS control program was initiated early 2019. The herd was loaded with gilts and closed for six month. In week 8/2019 vaccination against PRRSV was initiated. The breeding herd, including all gilts, was vaccinated twice four weeks apart with ReproCyc PRRS EU®, followed by routine mass vaccination every three month. Concurrently with the first mass vaccination of the breeding herd, all piglets in the farrowing unit at the age of 14 days and older were vaccinated with Ingelvac PRRSFLEX® EU, followed by routine vaccination at three weeks of age. Piglets were concurrently vaccinated against PCV2 and Mhyo. Starting with week 39/2019, previous PCV2/Mhyo vaccines were replaced by FLEXcombo . No other major changes of vaccination, management, feeding or housing were implemented during the observational period.

Mortality in nursery was analyzed via statistical process control (SPC) starting from week 20/2018 until week 20/2020. Weekly data was compared for four different periods, respecting the different vaccination protocols and the phase of the acute PRRS outbreak until the start of the PRRS control program. Transition periods, during which results could not be assigned to one or the other treatment, were excluded.

Results and Discussion

Figure 1 presents the data over the period of two years, split in four different comparison periods, and two transitionperiods.

Figure 1: Nursery mortality (%) in the different periods presented in an I-MR chart. Period 1: PCV2/Mhyo vaccination; Period 2: acute PRRS outbreak; Period 3: PRRSFLEX + PCV2/M.hyo; Period 4: PRRSFLEX + FLEXcombo. The mean is calculated for each period (x̅ ) and indicated by the green line. Red lines indicate the upper and lower control limits. Transition periods are blended out.

Figure 1 Image

A significant increase of nursery mortality (p<0.001) was noticed along with the acute PRRS outbreak. After the start of the PRRS vaccination program mortality dropped significantly (p<0.001), but did not reach the pre-outbreak level (p<0.001). After additional change of vaccines against PCV2 and Mhyo, the mean and the standard deviation of nursery mortality dropped again significantly (p≤0.003) to the pre-outbreak level (p=0.619).

Conclusions

Vaccination is a key measure to prevent and control diseases in modern swine production. Three major pathogens in pig production, PRRSV, PCV2 and Mhyo, do influence each other and may all be controlled, but not eliminated by vaccination3. Consequently, as presented, changes in the vaccination program and/or individual vaccines within the program may change the overall disease situation and the associated performance. Statistical process control is a valuable tool to analyze large continues data sets, taking into consideration mean and variation of the data associated with process changes.

References

  1. Zimmerman et al. 2019. Diseases of Swine, 11th edition: 685-708.
  2. Nathues et al. 2017. Preventive Veterinary Medicine 142: 16-29.
  3. Yaeger and Van Alstine 2019. Diseases of Swine, 11th edition: 393-407.