Intramuscular fat or marbling is an important sensory quality of pork that affects consumer preference and premiums for pork. As a result, improving the marbling quality of pork meat is of great interest to pig nutritionists, breeders and geneticists for health and economic reasons.
Several factors, such as the pig’s genetic makeup, sex, age, dietary micronutrients, and environmental conditions, affect fat metabolism and phenotypic response in pigs. Furthermore, recent studies have found that fat metabolism and marbling are regulated by several genes involved directly or indirectly in fatty acid metabolism, cell proliferation and differentiation. Nutrigenetics and nutrigenomics are two different scientific fields that provide a general approach to understanding the complex mechanisms of interaction between genes and nutrients and the environment throughout the genome.
Nutrigenetics vs. Nutrigenomics
Nutrigenetics and nutrigenomics are two different terms that are often confused; therefore, it is essential to clearly distinguish between them. ‘Nutri’ (or nutrient) refers to the chemical compounds in a diet necessary for cellular functions. Genetics is the study of individual genes, while genomics is the study of the entire genome, which is the totality of an organism’s genes, their interactions, and how they are affected by the environment.
Nutrigenetics studies the impact of individual differences at the genetic level in the response to a specific dietary pattern, functional food or supplement on a specific health outcome; while nutrigenomics assesses the influence of nutrient intake on gene expression and related molecular and biological events thereafter.
Impact of genetic makeup on response to nutrient intake
Most of the genes related to fat metabolism indirectly influence the intramuscular fat content of pork. However, its effects have shown variability with respect to muscle localization and fat synthesis mechanisms. Intramuscular fat content and meat quality traits differ between pig breeds due to diverse expressions of genes and enzymes involved in fatty acid synthesis and fat metabolism. Several studies have reported that the following genes are associated with fat metabolism and intramuscular fat content in pig breeds.
PPAR genes
Mainly PPARΞ± and PPARΞ³ that are associated with metabolic pathways related to fat metabolism. higher concentrations of PPARΞ± are mainly found in organs such as the liver, while PPARΞ³ is more concentrated in fatty tissues.
FABP genes
First of all A-FABP Y H-FABP that are involved in fat metabolism and carry out intracellular transport of fatty acids from the cell membrane to sites of fatty acid oxidation.
DCS gene
DCS is a functional gene associated with the fatty acid composition of the pig and acts as an important regulator of the genetic mechanism of fat deposition and fatty acid synthesis.
LEP gene
Porcine leptin is involved in feed intake and energy homeostasis and affects the rate of intramuscular fat accumulation.
ACACA Y FASN genes
Both genes regulate the synthesis of fatty acids and their expression level varies between pig breeds.
MSTN either GDF8 gene
This gene is responsible for the double muscularity in Belgian domestic pig breeds.
SREBF-1 gene
This gene has a fundamental role in the mechanism of gene transcription and the regulation of muscle fat deposition.
Impact of dietary nutrient supply on gene expression
Protein, amino acid, fat and micro/macronutrient supplements are applied during the different stages of growth and development of pigs. Protein levels in the diet have a regulatory mechanism on gene expression related to fat metabolism. A high supply of 18% dietary protein significantly reduced mRNA expression, enzyme activity, and expression levels of fat and marbling genes in pigs.
Altering the level of lysine in the diet can have a major nutrigenetic impact in pigs
Furthermore, amino acids such as methionine, lysine, histidine, isoleucine, leucine, phenylalanine, threonine, tryptophan, and valine are essential in various metabolic and gene expression pathways. Altering the level of lysine in the diet can have a major nutrigenetic impact on pigs. A low supply of lysine in the diet of heavy fattening pigs promotes intramuscular fat deposition and better marbling. Studies have shown that a 0.78% lysine supply results in a higher intramuscular content in growing pigs.
Micronutrients influence the expression pattern of various genes and modulate gene signaling pathways and their regulatory elements during growth and development. Furthermore, dietary fatty acids have a vital regulatory effect on DNA receptors and enzymes during DNA transcription and translation.
To sum up
The scientific fields of nutrigenetics and nutrigenomics are effective and accurate in describing changes in gene sequences that predispose individual pig breeds to respond in a certain way in terms of health, performance and meat quality. Based on the principles of nutrigenetics and nutrigenomics, the complex mechanisms of gene-nutrient interaction and the environmental effect on the entire genome can be explained. This makes it possible to measure nutritional effects with the aim of tuning gene expressions and regulating genome responses in pigs, to optimize growth performance, backfat thickness, intramuscular deposition, disease resistance and breeding traits. meat quality. However, given the wide variability in pig genetics, the environment, and the quality and quantity of nutrients in any given diet, it remains a challenge to establish the individual effect of all nutrients on genetic responses. This means that more research is required to be able to integrate the scientific principles of nutrigenetics and nutrigenomics as a tool in pig nutrition and feeding.