How would the efficiency of cattle production be affected if producers could only use breeds from one country?

Production would be very biased and inefficient. There would be higher risk if inbreeding and linebreeding if millions of animals of one breed were used. Inbreeding and linbreeding may be the only option to increase the population of that one breed within that particular country. With increased inbreeding, more offspring with genetic mutations, fatal or otherwise, would arise. Smaller calves result with each consecutive breeding of relatives, which is highly inefficient for the cattle industry.