Compositions providing increased energy content of animal feed using plant crop biomass which include a polyhydroxyalkanoate have been developed. In one embodiment, the compositions can be prepared using conventional techniques for harvesting and processing plant crops into forms useful as animal feed, wherein the plant, or parts thereof, have accumulated PHA, preferably in excess of 2% by dry weight of the plant tissue. In a preferred embodiment, the PHA is accumulated in corn or an oilseed. The feed compositions can include the PHA-containing meal byproduct from corn or oilseed processing. In another embodiment, the PHA can be provided with the green tissue of plants, such as clover, alfalfa, sorghum, and silage corn.