Final answer:
The #1 bovine GI helminth is Ostertagia ostertagi, a stomach-dwelling nematode that causes ostertagiosis in cattle, leading to reduced growth and productivity in infected herds.
Step-by-step explanation:
The #1 bovine GI helminth is Ostertagia ostertagi, which is the correct answer b to the student's question. This helminth is particularly significant in cattle populations and is known for residing in the stomach of its bovine hosts, causing a condition known as ostertagiosis or parasitic gastroenteritis. Ostertagia ostertagi affects the animal's ability to digest food and absorb nutrients, often leading to poor growth and productivity in infected herds.
Ostertagia ostertagi is a helminth that is often found feeding from its host, fitting into the broader category of parasitic worms that can cause infections in the gastrointestinal (GI) tract. It's important to differentiate this from other parasites such as protozoa, flukes, or hookworms, as proper identification helps in managing and treating infections in livestock.