Assessing the role of sow parity on PRRSv detection by RT-qPCR through weekly processing fluids monitoring in breeding herds.

The use of processing fluids to monitor the breeding herd's porcine reproductive and respiratory syndrome (PRRS) status has gained industry acceptance. However, little is known about PRRS virus RT-qPCR detection dynamics in processing fluids and factors that may contribute to maintain PRRS virus in the herd after an outbreak. This study aimed to describe weekly RT-qPCR processing fluid results in breeding herds after an outbreak and to evaluate the proportion of RT-qPCR positive results among parity groups. Processing tissues of 15 first parity (P1), 15 second parity (P2), and 15 third parity or higher (P3+) litters (parity groups) were collected weekly for between 19 and 46 weeks in nine breeding herds. Processing fluids were aggregated, and RT-qPCR tested by parity group weekly. Additionally, a subset of 743 processing fluid samples of litters that formed 50 parity groups, as previously described, were RT-qPCR tested individually at the litter level. The agreement between RT-qPCR results of processing fluid samples of parity groups (15 litters) and results based on individual litter testing was assessed using overall percent of agreement, Kappa statistic, and McNemar test. The association between RT-qPCR results and the parity group was evaluated using a generalized estimating equations model, after accounting for the effects of sampling week, breeding herd PRRS control strategy (i.e., open to replacements v/s closed) and herd. An autoregressive correlation structure was used to account for the repeated samplings within a herd in time. The overall agreement was 98 %, and Kappa statistic 0.955 (McNemar p = 1.0). Sensitivity of parity group processing fluid samples was estimated at 100 % (95 % CI 89-100 %), while specificity was estimated at 94 % (95 % CI 71-100 %). Although P1 aggregated litters had on average a higher proportion of RT-qPCR positive results from outbreak week 25 onwards, the proportion was not significantly different to the one observed for P2 and P3+ aggregated litters (p > 0.13). Additionally, herds that interrupted gilt entry had lower odds of PRRS RT-qPCR positivity than herds that continued entering gilts (OR = 0.35, 95 % CI 0.16-0.78). PRRS virus persistence in processing fluids was not affected by the sow parity effect in most of the breeding herds studied. No evidence of disagreement between RT-qPCR results of an aggregated sample of 15 litters and those of individual litters was observed. This level of litter aggregation testing strategy may be of particular use at the last stages of an elimination program under low PRRS virus prevalence.

Evaluation of cross-grazing deer with sheep or cattle, as means to reduces anthelmintic usage to control gastrointestinal and pulmonary nematodes in farmed red deer (Cervus elaphus) in New Zealand.

Recent reports indicate that gastrointestinal nematodes (GIN) are contributing to significant losses in deer productivity and that anthelmintic resistance has become an issue of concern for deer farmers in New Zealand. The aim of this study was to evaluate cross-grazing of deer with sheep or cattle as an aid for control of gastrointestinal and pulmonary nematode parasites of farmed red deer (Cervus elaphus) in New Zealand. This was a field study replicated over two years (2012 and 2013) for 16 weeks each year at two locations (Massey University, Palmerston North and Invermay AgResearch Centre, Mosgiel). Each farm replicate included four groups (19-20 deer) at each location: red deer cross-grazing with cattle (Deer/Cattle); red deer cross-grazing with sheep (Deer/Sheep); red deer grazing on their own (DeerOwn); and red deer grazing on their own and treated with anthelmintics every two weeks to suppress worm burdens, as a positive control (DeerSup). The key outcome was the number of anthelmintic treatments (AT) given to deer. The decision to treat individual resident deer in Deer/Cattle, Deer/Sheep and DeerOwn groups was based on "trigger" criteria including faecal egg count (FEC)≥250 eggs/g or Dictyocaulus faecal larval count (FLC)≥100 larvae/g or when growth rate was less than 80 % of the mean of the DeerSup group in the previous two weeks. In addition, to quantify the species of parasites cycling in each group, sets of three "tracer" deer were introduced to graze with each group at the mid-point and again at the end of each 16 week period in both years at both locations. Least squares means (LSM) of the number of AT given per animal for Deer/Sheep (3.4) and DeerOwn (3.3) groups were significantly higher than for the Deer/Cattle (2.7) group (p < 0.001). In tracer animals, the LSM of abomasal Trichostrongylus spp. were significantly fewer in the DeerOwn (17), Deer/Cattle (37) and DeerSup (54) groups than in the Deer/Sheep (952; p < 0.001) group. The LSM of the nematodes in the subfamily Ostertagiinae (=Ostertagia-type) were significantly more in the DeerOwn (1950) than in Deer/Sheep (370; p = 0.003) and DeerSup (238; p < 0.001) groups, but the number in the Deer/Cattle group (689) was not different to DeerOwn (p> 0.05). The LSM of lungworm were fewer in Deer/Sheep (3), Deer/Cattle (4) and DeerSup (3; p < 0.001) groups than in DeerOwn (40) group. The Deer/Cattle and DeerSup groups had significantly higher LSM of liveweight gain over the 16 weeks (p < 0.001) than the other two groups. This study demonstrated that cross-grazing with either sheep or cattle aided control of lungworm and gastrointestinal nematodes in young deer during autumn. However, the advantages varied between the use of sheep or cattle and in the ability to control different species of parasites.