Comparative analysis of the porcine IGF2-G3072A mutation and reduced myostatin function on meat quality and unexplained mortality in pigs

Burris, Elli Shae

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https://hdl.handle.net/2142/129161 Copy

Description

Title

Comparative analysis of the porcine IGF2-G3072A mutation and reduced myostatin function on meat quality and unexplained mortality in pigs

Author(s)

Burris, Elli Shae

Issue Date

2025-02-07

Director of Research (if dissertation) or Advisor (if thesis)

• Harsh, Bailey N
• Dilger, Anna C

Committee Member(s)

Dilger, Ryan N

Department of Study

Animal Sciences

Discipline

Animal Sciences

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• myostatin
• IGF2
• loss of function
• meat quality
• mortality

Abstract

Myostatin, a growth and differentiation factor, plays key roles in regulating muscle growth both prenatally and postnatally. Additionally, insulin-like growth factor-2 (IGF2) is a key regulator of myogenesis via promotion of myoblasts in the cell cycle. Gene editing of both myostatin and IGF2 has the potential to increase muscle mass in production animals. This increase in muscle mass could provide a solution to a major challenge in the United States: rising meat demand coupled with stagnant production levels. Therefore, the objectives of the first study were to determine the relative effects of the porcine IGF2 mutation and a novel, gene editing derived, myostatin loss of function mutation on carcass and meat quality characteristics in pigs. Pigs were either IGF2 paternal G allele (Gpat) and wild-type (WT) for myostatin (n=13), Gpat and heterozygous (HET) for myostatin (n=10), IGF2 paternal A allele (Apat) and WT (n=11) or Apat and HET (n=10). Pigs were raised in mixed sex pens of 10-15 pigs per pen, given free access to age-appropriate diets that met or exceeded nutrient recommendations, and slaughtered at 175 d (±5 d) of age. Loin eye measurements, loin quality, and belly quality were recorded. Data were analyzed using the MIXED procedure of SAS with a model including the effects of sex, IGF2, myostatin, and all interactions; means were separated using the PDIFF option and considered different at P ≤ 0.05. Loin muscle area was greater (P < 0.001) in HET pigs regardless of IGF2 genotype compared with WT pigs. The longissimus dorsi (LD) was different (P < 0.05) in all 4 genotypes. Loins from myostatin HET pigs were paler than those from WT pigs, regardless of IGF2 genotype, as evidenced by an increased (P < 0.01) L* value of approximately 5 units. However, L* did not differ (P = 0.21) between IGF2 Apat and Gpat pigs. Bellies from IGF2 Gpat pigs had a greater (P < 0.003) flop distance compared with all other genotypes. These data suggest that the partial loss of myostatin or IGF2 increased lean muscle deposition but resulted in poor loin color quality. Additionally, both mutations resulted in poorer belly firmness. The objective of the second study was to evaluate the effects of myostatin loss of function mutation on piglet organ and muscle development and blood parameters to determine potential causes of excess mortality. Piglets (n=50) resulting from matings of sows and boars both heterozygous for the mutation were euthanized at postnatal d 3. Piglets were weighed, dissected, and select organs and muscles were collected for further evaluation. Loin samples were used to genotype piglets into one of three groups: wild type (WT) (unmutated myostatin, n=13), heterozygous (HET, n=21), and myostatin mutant (MKO, n=10). Data were analyzed as a two-way ANOVA using the MIXED procedure of SAS to determine the effect of sex, genotype, and their interaction. Back girth was reduced (P = 0.04) in MKO by 2.3 cm compared with WT and by 2.1 cm compared with HET piglets. MKO piglets had lighter (P ≤ 0.03) weights of the heart, liver, kidneys, pancreas, spleen, stomach, and small intestine compared with HET and WT piglets, on both an absolute basis and as a percentage of body weight. In general, compared with other genotypes, MKO organs were 5-19% lighter. Surprisingly, muscle weights, both longissimus dorsi and semitendinosus, were not different (P ≥ 0.15) by genotype, either on an absolute basis or as a percentage of body weight. White blood cell count was not different; however, neutrophil count was increased (P < 0.01) in MKO compared with other genotypes. These data suggest that underdeveloped or undersized organs in MKO piglets may compromise their survivability. Additionally, increased neutrophil counts may be indicative of a stress response in MKO piglets. Overall, partial myostatin loss of function has a positive effect on muscle accretion and a negative effect on loin and belly quality. However, complete myostatin loss of function results in poor ability to thrive.

Graduation Semester

2025-05

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129161

Copyright and License Information

Copyright 2025 Elli Burris

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