IGF1 IN BROILERS

Insulin like Growth Factor-1 (also called IGF-1 or somatomedin C), is a highly conserved molecule similar to the molecular structure of insulin. It is made up of 70 amino acids encoded by the IGF1 gene.

IGF-1 has many effects on the body.

It plays a key role in the control of skeletal characteristics, metabolism, and growth of adipose tissue and deposition of fat in chickens. IGF1 promotes cell division and cell growth in the body. It also plays a role in cellular repair in the brain, heart and muscles of the animal. The perturbation of IGF1 can cause many consequences to the animal. IGF-1 is a major mediator of effects of growth hormone (GH) produced in the pituitary gland, then released into the blood stream, later triggers the liver to produce IGF-1.

Few studies have shown no direct correlation between GH levels and the growth rate in chickens; hence this has led to study IGFs as mediators of the functions of GH. The action of mechanism is initiated by binding of IGF1 to its receptor called IGF1 receptor which is present on many cell types in many tissues. This mediates intracellular many cellular signal transductions at the molecular level. The mechanisms of involvement of these proteins in
insulin/IGF signaling pathways are largely speculative and require further study. The IGF1 produced in the muscle offers main benefits to the gain of the muscle. They trigger different protein activities involved in the muscle protein synthesis.

There are multiple factors associated with the production of IGF1, such as low levels of glucose or deficiency of protein can trigger a significant decline of the IGF1, vice versa. full Endocrinology in birds has always been an unfamiliar subject to the researchers, even though endocrinopathy in birds have high occurrence. Hormones such as the growth hormone, IGF, thyroid hormones and insulin, play important and diverse roles in animal growth.

Very few information is available that explains the nutrient-IGF relationship in poultry industry. However, IGF1 have been sensitive to the alteration in the nutrition in domestic fowl. Studies performed by two separate groups shows food deprivation for 5 day depresses circulating IGF1 concentration and upon re-feeding, concentration return to near initial concentration.

Other studies in contrast reported that a complete return to normal IGF1 was observed following depriving from feeding suggesting that the extent of nutrient deprivation determines the rate at which IGF1 synthesis and
secretion return to normal following periods of nutrient modification. The study led by Del vesco and its colleagues in 2013, has evaluated the effects of different dietary methionine levels on IGF1 and GH gene expression in liver and muscle tissues. The IGF1 and GH gene expression in muscle tissues was not affected by methionine supplementation. However, IGF1 gene expression in the liver was higher in broilers fed methionine diet. They further demonstrated the effect of heat stress and supplementation of methionine on the GH and IGF1gene expression in the liver and found that methionine supplementation increased IGF1 and GH expression.

They observed that the highest GHR expression occurred at normal temperature and not at heat stress in supplementation of methionine in the diet. This suggests that the protein degradation is induced by the heat stress but supplementation of methionine triggers protein deposition because it increases the expression of gene related protein synthesis and reduces the expression of genes related to protein catabolism.
Jaromir Kadlec along with other workers has found IGF1 as a potential candidate gene responsible for various metabolic traits in chickens. They have identified single variable gene known as single nucleotide polymorphism (SNP) in total 132 birds using molecular techniques
and have correlated the genotype frequencies with growth and fat deposition in chickens.

The results depict identical IGF1 amino acid sequences among chickens, rats and human peptides. In spite of the wealth of knowledge that has accumulated concerning IGF1 in past few decades, still many details of IGF1 in broilers remain to be clarified about the role of different pathways.

What is The Term Matrix Related to The Poultry Feed Industry?

Matrix is a term people will generally relate to the Keanu Reeves; even google will present you with this as a first page result. However matrix in the feed analogy is more related to something mathematical. The words digestible nutrients of feed ingredients and matrix are generally used as synonyms.  But matrix actually represents the nutrients available in the feed additive together with the nutrients spared or made available by use of the same additive in the feed formulation.  It represents the total nutrition provided to the animal body directly or indirectly by affecting the digestibility of feed. So, what is the use of matrix? We all remember our schooling days in mathematics and associate with a name called as Linear programming problems acronym as LPP. These are mathematical equations to link variables together to extract optimum results. One can set the key parameters such as price, dosage, availability, standards as variables with monetary profits as realistic outcomes. To give an example of LPP, let’s try this, for what combination of three machines A, B and C can work together with efficiency using each other’s limitations on different levels of time, use, power and accuracy to obtain an algorithm best suitable to manufacture maximum units of D in the least possible time, consuming least electricity and maintaining quality standards by reducing standard deviation. In layman terms it will give you a method of best utilization of available resources. So a matrix will enable us to use  LPP, which are now-a-days coded in software’s that help in formulating feed.

So how does one calculate the matrix of a feed additive? The answer is to run digestibility trials. These trials evaluate the nutritional availability from the ingredient to the animal. The availability can be further refined as in case of terms in energy as gross energy, metabolizable energy and so on. The digestibility trials also are needed to be refined on the basis of species, age, breed, sex and diet. A mature broiler breeder will have an ability to digest nutrients from corn which will be a different for a layer chick and a corn-soy diet with fishmeal will have different matrix then a corn-soy-bran diet with lupins. Once individual ingredient digestibility values are calculated the nutrional content can be corrected with these fractions to determine their true potential in feed formulations. Many phytogenic origin products have tried to replace certain high cost matrix products in the feed. But very few have succeeded to relate the plant sourced additive in terms of a compatible matrix value. The matrix can be also formed on the basis of growth studies where ingredient for ingredient replacement can be tested by using performance parameters. A correlation graph can be utilized to compare the new ingredients which fit better in an LPP for cost reduction with the old ones, falling short on the price front or other long term frontiers. In case of certain additives like phytase enzymes which result in mobilization phosphorus, the tibial ash content comparisons are also used to form matrix.

An in vivo digestibility assay in case of poultry ideally focuses of ileal sampling of digesta and deductively analyzing the same with oral fed feed. The birds are sacrificed and digesta is sampled at different levels of the gut to understand the digestibility of ingredients. As ileum is the terminal region of the small intestine and digestion is considered at its optimum here, the feed sampled in these zones is used for developing a matrix. The fecal collection is generally contaminated with renal excretions and is not considered as ideal to evaluate digestibility of precision fed feed. The most accurate theoretical method to estimate digestibility values is to use cecectomized roosters. Only few attempts to replicate the digestive values in vitro are successful and are not as accurate as in vivo methods. Most of the values tested in vitro were based on activity of enzymes on a certain feed grain and do not replicate real time complexities of in vivo trials.

Research is now moving to the molecular level, and ultimately it is the nutrients that are utilized at a cellular level that matter the most. Current digestibility studies focus on the nutrients absorbed from the intestinal lumen to the blood, whereas growth studies compare the net benefits from the additive. In the future our goal should be a point of intersection between these two studies with molecular markers used to light up our path to the least cost matrix for success.