DNA Basics

Strive for Consistency
The future demand for beef as a food product in the 21st Century will depend on the ability of segment of the beef industry to respond collectively to the changing needs of our customer, the beef-eating consumer. Modern consumers demand improved product quality and consistency. Improvements in production, nutrition, management, processing, as well as handling and cooking techniques all play an important part in achieving future customer satisfaction.

Consistency, or uniformity in beef production has long been a goal for cattlemen. Uniformity at the sale barn has meant higher prices, uniformity in the feedlot relates to a higher percentage of correctly finished cattle and ultimately a higher price. Lack of consistency of beef was identified as a major problem in the 1991 Beef Quality Audit conducted by the National Cattlemen's Beef Association. Although the 2001 audit showed improvement, commercial cow-calf producers as well as their seedstock suppliers are looking for selection and management practices that will result in continued improvement through more consistency and less variation in the cattle they produce for beef.

Diversity and Variation
There are three types of variation that impact uniformity among cattle including genetic, phenotypic and environmental. All three have a compounding effect. Genetic variation in a calf crop relates to the diversity of genotypes for a particular trait, such as birth weight. Phenotypic variation is the actual variation that the calf expresses, or shows like eye color, or amount of body fat. Environmental variation (or how that calf is managed) impacts the ability for that animal to express it's genetic potential.

The opportunity for genetic change in any population is dependent on the genetic diversity, which exists in that population. There is no more powerful technology for making genetic progress than selecting the best animals in the population and making them parents. Some genetically inherited traits in cattle are more important to producers than others because cattle that have those traits are more in demand. The continued application of breeding technologies will contribute significantly to maintaining gains made and achieving continued improvements in production efficiency, as well as quality and consistency.

Role of DNA Analysis
DNA is the substance of which most genes are made and is chiefly responsible for the transmission of inherited characteristics. Every animal has a unique genetic makeup or DNA profile. DNA testing or "fingerprinting" provides a method for determining with high accuracy the parentage of cattle based upon this profile. DNA, or Deoxyribonucleic acid, is found in the nuclei of all living cells, which make up Chromosomes. A Chromosome is made up of DNA molecules tightly coiled around proteins.

Making genetic progress is not as simple in commercial beef production settings. Although some operators are able to identify the dam side of the parentage equation, more often than not multi-sire matings confuse the issue for identifying the sire. Exact identification of parentage of calves resulting from unknown matings or from a multi-sire pasture matings is a challenge, but technology offers the tools to resolve this problem. DNA testing or "fingerprinting" provides a method for determining with high accuracy the parentage of cattle. The characteristics of all living things, including cattle are determined by information contained within the DNA inherited from their parents. DNA directs how the cells develop and controls the way characteristics are passed on from parent to progeny.

DNA Parentage Verification
Parentage testing is basically achieved by detecting certain "markers". Any attribute that can be easily detected and its inheritance traced can serve as a marker. Parentage and paternity testing relies on two basic principles:
1. On the detection of genetically inherited markers that remain the same throughout the animal's life, and 
2. On the knowledge that all animals possess two copies of every gene (or marker), one of which was inherited from the sire and the other from the dam. 
If the marker shows variation, then the copy inherited from the dam may be different to that inherited from the sire. This provides the foundation for parentage and paternity testing. That is, if one variant of a genetic marker is present in a calf but absent in both alleged parents, the calf must be excluded as the offspring of that mating. 
Parentage and paternity tests always work by exclusion since no test can with 100% accuracy positively identify an animal's parentage. That is, testing can exclude a sire or dam as a possible parent or an offspring can be excluded as being possible from a nominated mating or parent and these exclusions are absolute, however, if an animal or mating qualifies, this does not prove it absolutely. At best we can provide a probability that the qualification is correct, but this will never be 100%.

How it is done?
The process of DNA fingerprinting requires DNA to be extracted from a tissue sample. Blood, semen, muscle and hair follicles are all examples of tissue that can be used to extract DNA. All tissue samples need to be relatively fresh in order to extract DNA of sufficient quality for testing. 
A commercially viable DNA-based parentage or paternity test requires the identification of groups of markers (three or four markers per group) that can be tested simultaneously and that show a high degree of variability across different cattle breeds. Currently a standard set of 12 DNA markers tested in three separate marker groups is used for DNA fingerprinting. 
Extra groups of markers are available if further resolution is required. The combined results of all markers produce a DNA profile for each animal and the chances of any two animals having the same profile lies somewhere between three in 10 million to three in 100 billion, depending on the breed.

Applications for the beef industry
For commercial breeders Cow Sense Genetic Services offers a powerful tool for collecting parentage information on their animals for enhanced management decision making capabilities. The identification of those sires and dams producing progeny with desirable or even undesirable traits can assist in making management decisions with regard to bull selection, replacement heifer selection and or culling decisions. The ability to sample many and actually test only those that are outliers provides additional economy.

For the seedstock producers, DNA typing offered by Cow Sense Genetic Services provides greater accuracy than blood typing although the costs of the two procedures are similar. As the DNA parentage verification process is more exact (each animal has a unique genetic profile), there is less chance for error. The DNA parentage identification process allows for cost effective means of pedigree verification for breed associations. In addition testing of young sires can be accelerated by multi sire matings, while maintaining the ability to verify parentage. In the future identification of markers for traits of economic importance will also help in the selection of superior animals.

For processors and harvest industry Cow Sense Genetic Services provides the tools to verify that the "in house" animal - to - product tracking systems are accurate. In addition broader application can be implemented to provide traceability of product to carcass and true source verification for their customers.