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Seeking Genes For Robustness

In the not-too-distant future, beef producers may be able to add reduced disease susceptibility, also described as robustness, to the list of beef animal traits when making breeding and management decisions. A study involving the universities of Alberta and Calgary and GrowSafe Systems of Airdrie is moving along nicely into the second year of a two-year project to develop a molecular phenotype to select for robust beef cattle.

Molecular phenotype is actually a new term that describes precisely what the team is investigating, says project manager Dr. Graham Plastow of Livestock Gentec (former Alberta Ingenuity Centre for Livestock Genomics Technology) at the University of Alberta.

An animal s phenotype is what you see its physical characteristics resulting from its genetic makeup and the environment. In this project, the phenotype of importance is the state of the animal s health. At first sight, it s either ill or healthy, Plastow explains. At the molecular level, scientists will be studying gene products in the blood to define the gene expression of sick animals to look for genes that are switched on in response to infection.

They hypothesize that the gene expression profile, or blood transcript, of healthy animals will differ from that of sick animals and that it will also differ according to the cause of the illness, whether that be bacteria, viruses, toxins in the feed, or metabolic conditions such as bloat, he explains.

If it proves out and preliminary results from swine research suggest that it should researchers will be able to establish molecular phenotypes and group them according to the cause of the disease. The classification system could then be developed to provide a routine measure for health, which has been the missing link in making progress toward using genetics to improve animal health. In order to make genetic improvement in any trait, it has to be measurable.

Ultimately, the classification system would give researchers a tool to go on to find DNA markers to identify animals that are less likely to become ill when infected, in other words, animals that are more robust to various stresses so that their immune systems are likely to respond effectively to infection.

Plastow says the molecular phenotyping and classification project is on target to wrap up next May. The first year focussed largely on collecting the blood samples, which was accomplished under some rough working conditions throughout the winter months by the University of Calgary team and veterinary medicine students in co-operation with staff at feedlots involved in GrowSafe s related project.

GrowSafe Beef is a pen-monitoring system that electronically records data from individual animals 24 hours a day with the use of radio frequency identification tags and remote computer software. Each time an animal drinks from the GrowSafe Beef unit, the system calculates its weight, rate of gain and health profile. Variance from the normal water intake pattern is an early indicator of disease. The system has been programmed to visually mark an animal with altered water consumption behaviour for follow up. GSB also estimates a best-marketing date for each animal, that is, when the cost of gain begins to exceed the value of gain, and automatically marks market-ready animals to maximize profit. (CANADIAN CATTLEMEN, Feeding for Profit, fall 2010)

The validation project wrapped up with the cattle going to market in early July and GrowSafe is now in the process of analysing the GSB and carcass data, says GrowSafe co- CEO Alison Sunstrum, who has a new-found appreciation for the incredibly hard work that feedlot cowboys do. The entire report will be reviewed by Dr. Monty Kerely at the University of Missouri.

During the sampling for the molecular phenotype project, blood was drawn from individual animals marked by GSB and identified by pen checkers as having altered drinking, eating or behavioural patterns. A control sample was also collected randomly from a penmate regarded as healthy. More than 700 animals were part of the trial and more than 2,000 samples were collected for the various aspects of the study with multiple samples drawn from some animals.

Sick animals were examined by a veterinarian and their blood samples tested to diagnose the specifiailment and its cause for cross-referencing to determine whether each animal s genetic expression matches its apparent state of health. All animals were managed according to the feedlots standard operating procedures with the outcome noted, whether that was a speedy recovery, chronic illness and repeated treatments, or death.

The ball is now in Livestock Gentec s court to analyze the samples, define the genetic expression of each, and classify the genetic phenotypes. I certainly think we have a terrifi data set. With this number of samples we feel we will really be able to test the phenotype, Plastow says.

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