永利皇宫手机版:Fat fish

 作者:南郭姥     |      日期:2019-03-07 06:10:07
By Claire Ainsworth Trying to grow bigger farm animals by genetically engineering them to produce more growth hormone may be harder than we thought, say researchers in Canada. Animals that have been bred to grow fast have hit a metabolic glass ceiling, and any attempts to boost their growth further might only result in physical deformities, they say. They started by engineering a slow-growing wild strain of rainbow trout. The transgenic trout grew much faster than their non-engineered siblings, and were over 17 times as heavy and over twice as long at 14 months of age. However, spectacular as this seems, the transgenic wild trout still lagged behind their domesticated counterparts – a strain bred for fast growth that is commonly used in aquaculture. When the team introduced the gene into the domesticated strain, they found that it had no effect on the fish’s growth. Worryingly, both sets of engineered fish developed skull abnormalities, and the GM domesticated fish all died before reaching sexual maturity. “Genetic selection has pushed metabolic systems to their max already,” says Devlin. Although growth hormone is in abundant supply, other factors are limiting growth. For instance, animals are finding it impossible to churn out enough proteins to continue growing healthily. Intriguingly, when Devlin and his team added the gene to a partly domesticated strain of salmon, it did result in extra growth. He suspects this is because the salmon strain had not yet reached its growth “plateau”. Researchers tinkering with the metabolic pathways of different species and breeds will need to be careful. “Genetic background is a big issue,” says Devlin, and scientists need to think twice before diving in with transgenes. “Ideally,