The chicken in the story suggests the idea that hunger, while difficult to deal with, is temporary and can be satisfied with food. The satisfaction with KFC chicken is, to Junior, a sort-of religious moment, or a moment in which a long-desired need is satisfied.
In his cartoon, he calls the KFC the "shroud of chicken," a humor he doesn't share when his dog Oscar gets sick, again suggesting the idea that hunger is temporary.
Overall, while Junior begins with the idea of hunger being satisfied with the chicken, he quickly moves away from that idea, instead focusing on the death of his dog because his parents could not afford to get him help. Chicken works as the salve to Junior's hunger, but there is no salve for the death of his dog.
In America, we often think of poverty as people lacking something—a car, a job, cable television. But the most basic type of poverty is the inability to eat. But for Junior, the worst part of being poor is the inability to take care of a loved one's health, in this case his dog, Oscar.
The the lack of food symbolizes the abject poverty Junior's family experiences.
For most of us, eating is an ordinary activity we experience every night. While we might say we are "hungry" or "starving," our stomachs are probably just telling us, "Well, you usually eat at this time, so might as well send your brain the signals for hunger."
Junior experiences real hunger. He says that "sometimes my family misses a meal, and sleep is the only thing we have for dinner." In fact, Junior says eating, when really and truly hungry "can make anybody believe in the existence of God."
Although this chapter is really about the emotional pain poverty inflicts on people, the food reminds the reader that there is physical pain when it comes to being poor as well.