Mouse gene makes cattle TB resistant?

Chinese scientists claim to have added a gene from mice to cattle that makes the GE cattle more resistant to Tuberculosis (TB).  This would -they say - allow the GE animals to stay in the herd longer and require less antibiotic use.  I wonder what the unintended consequences are?  In the US cattle with TB are slaughtered not treated. If the GE animals kept in the herd were not 100% resistant they could end up as carriers!

 I suspect that this experiment or press release is but a ploy to try to put a ‘good face’ on genetic engineering and to mask the sisnister aspects.