ABSTRACT
The extended storage of feed ingredients has been suggested as a method to mitigate the risk of pathogen transmission through contaminated ingredients. To validate the approach of extended storage of complete swine feed for the inactivation of swine viruses, an experiment was conducted wherein swine feed was inoculated with 10 mL of 1 × 105 TCID50/mL of porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), and Senecavirus A (SVA) and stored for 58 d at 23.9 °C. Measures of feed quality were also evaluated at the initiation and conclusion of the storage period including screening for mycotoxins, characterization of select microbiological measures, and stability of phytase and dietary vitamins. Storing feed for 58 d under either ambient or anaerobic and temperature-controlled storage conditions did not result in substantial concerns related to microbiological profiles. Upon exposure to the feed following 58 d of storage in a swine bioassay, previously confirmed naïve pigs showed no signs of PEDV or SVA replication as detected by the PCR screening of oral fluids and serum antibody screening. Infection with SVA was documented in the positive control room through diagnostic testing through the State of Minnesota. For PRRSV, the positive control room demonstrated infection. For rooms consuming inoculated feed stored for 58 d, there was no evidence of PRRSV infection with the exception of unintentional aerosol transmission via a documented biocontainment breach. In summary, storing feed for 58 d at anaerobic and temperature-controlled environmental conditions of 23.9 °C validates that the extended storage of complete swine feed can be a method to reduce risks associated with pathogen transmission through feed while having minimal effects on measures of nutritional quality.
ABSTRACT
Introduction: Most male pigs are surgically castrated to avoid puberty-derived boar taint and aggressiveness. However, this surgical intervention represents a welfare concern in swine production. Disrupting porcine KISS1 is hypothesized to delay or abolish puberty by inducing variable hypogonadotropism and thus preventing the need for castration. Methods: To test this hypothesis, we generated the first KISS1-edited large animal using CRISPR/Cas9-ribonucleoproteins and single-stranded donor oligonucleotides. The targeted region preceded the sequence encoding a conserved core motif of kisspeptin. Genome editors were intracytoplasmically injected into 684 swine zygotes and transferred to 19 hormonally synchronized surrogate sows. In nine litters, 49 American Yorkshire and 20 Duroc liveborn piglets were naturally farrowed. Results: Thirty-five of these pigs bore KISS1-disruptive alleles ranging in frequency from 5% to 97% and did not phenotypically differ from their wild-type counterparts. In contrast, four KISS1-edited pigs (two boars and two gilts) with disruptive allele frequencies of 96% and 100% demonstrated full hypogonadotropism, infantile reproductive tracts, and failed to reach sexual maturity. Change in body weight during development was unaffected by editing KISS1. Founder pigs partially carrying KISS1-disruptive alleles were bred resulting in a total of 53 KISS1 +/+, 60 KISS1 +/-, and 34 KISS1 -/- F1 liveborn piglets, confirming germline transmission. Discussion: Results demonstrate that a high proportion of KISS1 alleles in pigs must be disrupted before variation in gonadotropin secretion is observed, suggesting that even a small amount of kisspeptin ligand is sufficient to confer proper sexual development and puberty in pigs. Follow-on studies will evaluate fertility restoration in KISS1 KO breeding stock to fully realize the potential of KISS1 gene edits to eliminate the need for surgical castration.
