For ingested foods, the first opportunity for enzymatic digestion occurs in the see concept 41.3 (page 903)

Answer;

The mouth

For ingested foods, the first opportunity for enzymatic digestion occurs in the mouth.

Explanation;

The digestion of food starts in the mouth.

There is both mechanical and enzymatic digestion of food in the mouth. Mechanical digestion involves the mechanical break down of food using teeth to smaller particles thus increasing the surface are for the activity by enzymes.

Enzymatic digestion in the mouth involves enzyme salivary amylase which acts on starch to form maltose.

the concept of nucleosome occupancy, which reflects the fraction of cells from the population in which a given region of dna is occupied by a histone octamer

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.