Final answer:
The sentence given is a Compound sentence because it contains two independent clauses joined by the conjunction 'but'.
Step-by-step explanation:
The sentence "Mulberry leaves are silk worms' natural food preference, but silk farmers will often feed the caterpillar a specially designed artificial diet" is a Compound sentence. This is because it consists of two independent clauses joined by the conjunction 'but'. Each clause can stand alone as a complete sentence, and together they form a compound sentence that expresses two related thoughts.