Germinating plant seeds can convert stored fatty acids into oxaloacetate and a variety of carbohydrates. Animals cannot synthesize significant quantities of oxaloacetate or glucose from fatty acids. What accounts for this difference?

The reason why animals cannot synthesize oxaloacetate is because the fatty acids which they produce, are not able to create glucose (oxaloacetate).

Explanation:

The fatty acids in animals need to be converted to acetyl-CoA first, but this acetyl won't convert into oxaloacetate, in comparison to plants, that use the glyoxylate cycle, that allows them to produce the mentioned glucose.