Dietary trends in the western world are favouring lean meat and less fat on our plates, and researchers are working at full capacity to satisfy consumer demands. Modern gene technology is creating opportunities to steadily and more efficiently improve meat and dairy products, overall food quality, and animal welfare.

Remarkable genetic progress

"A tremendous genetic development in Norwegian production animals has occurred in recent decades," asserts researcher Eli Grindflek. "The fat layer in Norwegian Landrace pigs, for instance, has been reduced from 30 millimetres to less than 10 millimetres in the course of 50 years. A cow produces over 4 000 litres of milk more per year than in 1959. And these feats have been accomplished without weakening the animals' health-related traits."

Dr Grindflek is employed by Norsvin, a Norwegian pig producers' cooperative, and located at the Norwegian University of Life Sciences (UMB). She has received funding for her work from a number of programmes under the Research Council of Norway, including the Programme on Functional Genomics in Norway (FUGE) and the Food Programme (MATPROGRAMMET).

Weeding out troublesome genes

Dr Grindflek, a molecular geneticist, carries out research on the ideal combination of gene variants for efficient production of pork while maintaining the best possible animal welfare.

Gene technology, a key element of modern breeding techniques, helps scientists to find specific genes in production animals in order to incorporate traits such as faster growth, more succulent meat, greater milk production, larger eggs or denser wool growth.

Gene technology also helps scientists to identify and avoid breeding disease-triggering genes.

"The halothane gene is an example of a problematic gene that was selectively bred out of Norwegian pigs in the 1990s using genetic testing," says Dr Grindflek.

"That gene variant led to pale, soft and exudative (PSE) meat. What's more, the pigs with both unfavourable alleles of this gene were dying from stress during transport to slaughter."

Sequenced genome opens up possibilities

Just 10 years ago, researchers were still studying one gene at a time to test for associations with desired traits. For pigs, which are so genetically similar to humans, genes were selected based on their corresponding function in people.

"Genetic variation is revealed in the form of mutations in the DNA," says Dr Grindflek, "and back then we were aware of a few thousand such variations in pigs. Now, the genome -- the complete genetic material -- has been sequenced for pigs, sheep, chickens and cattle. In pigs, we now know of millions of genetic variations."

International activity

Internationally, systematic selective breeding programmes on most production species have been underway for quite some time. Systematic breeding of pigs dates back to the 1950s.

Thanks to knowledge acquired through sequencing the entire pig genome, says Dr Grindflek, today's scientists are far better equipped to pinpoint genes associated with various traits.

"Since we now know of a large number of genetic variations across the entire genome, we can comparatively analyse these with traits already identified in the animals," she explains. "We hope that in the future it will be possible to sequence the entire genome of every broodstock individual in order to find most gene variants that are associated with each desired trait."

Speed breeding

Conventional selective breeding ranks each prospective broodstock individual on traits observed in the animal itself and in its relatives. Genomic selection is more accurate, based directly on the individual's DNA and variation at the genetic level. "First we establish a correlation between a number of genetic variations and the prospective animals' traits. Then we select for broodstock individuals based on these variations. We can, in other words, calculate breeding values based on individuals' DNA sequence without having to record every generation's traits in the conventional way. This method saves a good deal of testing and recording."

Environment also plays a role

An animal's environment, however, also has a major influence on its genetic development.

"An animal's development is affected by everything from feed and climate to its care and the pen it grows up in. So it's not always easy to determine whether a weakness is in the genes."

In addition, it is not sufficient to simply select for gene variants to enhance one trait, since this could have a negative impact on another trait. Dr Grindflek cites an example from pig breeding:

"If we select for only the genes that yield the fastest growth and highest meat quality, for instance, it may affect the pigs' bone quality. We have also seen that less fat in pigs can lead to sows with insufficient fat stores for suckling their piglets. With enhanced knowledge about the genome, we can select for broodstock individuals with the best combination of gene variants for all the relevant traits."

Strong focus on animal welfare

Regulation of selective breeding in Norway is currently based on objectives determined by national breeders' organisations in collaboration with the meat industry and the research community.

"Pig generations are short, so we can quickly achieve good results for a small number of traits," says Dr Grindflek. "The breeding objectives for pigs, however, currently include 26 different traits. This means we need to select animals with a strong overall combination of traits -- and accept that genetic progress goes more slowly when such high number of traits are to be improved simultaneously."

Note: If no author is given, the source is cited instead.

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