Utilization of biotechnology, including CRISPR/Cas9, to improve production efficiency in swine
Date
2023-12
Authors
Schultz, Ronald Blythe
Major Professor
Advisor
Ross, Jason W
Essner, Jeffrey
Gabler, Nicholas
Keating, Aileen F
Reecy, James
Committee Member
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Abstract
The global demand for meat, particularly pork, is steadily rising with the growing global population, as well as an increasing emphasis from governments and consumers for more sustainable production. Gene editing, using CRISPR/Cas9 technology, has provided producers with a novel approach to achieve rapid gains in production and efficiency in the swine industry. The vast majority of the current avenues being pursued related to gene editing in the livestock industry up to this point have been focused on disease resistance and welfare concerns, but very few have explored the possibilities related to growth performance and efficiency.
Somatotropin or growth hormone (GH) is a crucial component in the growth and development of pigs, and the regulation of GH production and release is tightly controlled in part by the negative feedback of somatostatin (SST) and SST receptors (SSTR) in the brain. Decades of research focused on increasing GH in pigs, primarily through the administration of exogenous GH, has demonstrated that increases in circulating GH in pigs improves growth performance, decreases feed intake, decreases fat, and increases lean tissue accretion.
Given our understanding of the interplay between GH and the negative feedback exerted by SST, the studies presented in this dissertation focused on the creation of an SSTR2 model in pigs that was used to create multiple generations of offspring to evaluate the phenotypic and molecular effects of pigs lacking one or both copies of SSTR2. We hypothesized that SSTR-1bp/-1bp pigs would demonstrate improved growth and efficiency advantages when compared to SSTR2WT/WT pigs, and that SSTR2WT/-1bp pigs would express an intermediate phenotype. To test this, founder boars were created using CRISPR/Cas9 to modify somatic cell lines, somatic cell nuclear transfer, and embryo transfers (Chapter 3). Three litters of F1 piglets were produced by breeding one of the founder boars to wildtype gilts (Chapter 3). Based on the results from the F1 generation of male SSTR2WT/-1bp pigs being heavier than male SSTR2WT/-3bp pigs (Chapter 3), two SSTR2WT/-1bp boars were bred to 20 commercial gilts to further evaluate phenotypic and molecular effects of a modification in the SSTR2 gene in a commercial genetic line (Chapter 4). This study also provided a much larger sample size and collected data from birth through to market weight. Body weight data from both of these studies (Chapter 4 and 5), suggests that modifying a single allele in the SSTR2 gene may improve growth performance in pigs. Finally, an F2 generation of pigs containing all three genotypes was created by making half sibling crosses in boars and gilts from the F1 generation (Chapter 5). No differences in body weight were observed in the pigs in the F2 generation.
In addition to body weight, several blood biomarkers, body composition measurements, and production metrics that are commonly associated with exogenous GH induced growth were measured across all three studies (Chapters 3, 4, and 5). In all three cases, no pattern of differences in any of the secondary characteristics measured were observed that corresponded with what was hypothesized based on previous research supplementing pigs with GH. Collectively, these data suggest that improving growth performance in pigs using gene editing is a viable option for genetic improvement in the swine industry, modifications in the SSTR2 gene may positively impact growth in pigs, and that more research is needed to understand the complex molecular interactions in SSTR2 modified pigs in addition to modifications in other members of the SSTR family.
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dissertation