I demand! Lean Pork Please…
A glimpse within the growth hormone regulation of protein metabolism in pigs.
By Victor Allen M. Anas, DVM
The increase in consumer demand for lean meat has stimulated the need for technologies to reduce fat and increase lean in meat animals. Swine experts in genetics, nutrition and physiology have employed their respective fields of technology to achieve the continuing goal of the swine industry to produce fast growing pigs and increase the quantity of high-quality lean carcass. Supplementing growth hormone an anabolic agent increases muscle mass in pigs, while also improving the rate and efficiency in growth were demonstrated by various studies. Growth Hormone (GH) also known as Somatotropin (ST) viewed as the master hormone that regulates growth and performance has been shown to have impressive effects on nutrient partitioning between muscle and adipose tissue that leads to dramatic alterations in the growth of the tissues.
GH has markedly influenced Protein metabolism. Generally, growth hormone stimulates protein anabolism in many tissues. This effect reflect increased amino acid uptake, increased protein synthesis and decreased oxidation of proteins. One of the most important ways that it affects protein metabolism is to increase retention of nitrogen by the body. The loss of nitrogen into the urine as urea or other nitrogenous waste products is diminished indicating retention within the body. In addition, another and possibly more important effect of GH is to increase cell permeability to amino acids thereby favoring a buildup of the muscle mass of the body. Evidence suggests that GH favors protein synthesis by gene activation, mRNA synthesis and ribosomal RNA and transfer RNA production by liver cell.
Studies demonstrated the pig GH (pGH/pST) treatment increases protein deposition by increasing muscle protein synthesis in swine. Differences in the finding among the studies maybe due to length and/ or mode of GH treatment, species differences, tissue analyzed, developmental stages of the subject population, or nutrient status of the subject. Davis et al., 1996 annotates that feeding profoundly atimulates prorein synthesis and this response to GH treatment may potentially be affected if the animals were fasted or fed at the time of the study. Evidence suggested that 7 days of somatotropin (pST) treatment in young, growing swine (approximately 20 kg) enhances protein balance and metabolic efficiency by minimizing protein loss during fasting and protein gain during meal absorption (Vann et al., 2000a,b). Result of various studies also shows that GH treatment increases muscle protein synthesis may perhaps be tissue specifics or whole body. In the study in adult humans by Copeland and Nair,1994 the increased protein synthesis were observed in the whole body and reduced protein synthesis in the leg, while an opposite result were obtained in another study (Fryburg and Barrett 1993). A study to recognize the tissue-specific effect of protein synthesis and protein degradation to pST treatment were conducted by Bush et al., 2003a, it indicate that 7 days of exogenous pST administration in growing pig enhanced protein anabolism in the fed state by altering protein turnover in the whole body and amino acid kinetics in the hindquarter and portal drained viscera, with no effect on protein degradation. The increase in amino acid extraction and utilization for protein synthesis in the hindquarters was associated with an increase in blood flow to the hindquarters.
Pork maintains to be the most consumed meat around the world and the demand for quality and quantity for lean pork continue to rise. Supplementation pST in pigs improves the effectiveness and efficiency in the rate of growth generally associated with the increase in the muscle mass.
Marid Agribusiness Digest
Vol.17 No.11* April 2007