Kibble is a kind of animal feed. It can only be made by a cook at a butcher table. No minimum cooking skill is required to create it. The recipe requires 1 unit of nutrition from vegetarian items (20 vegetables or haygrass) and 1 unit of nutrition from meat and/or animal products. A completed bill produces 50 kibble (only 35 at a butcher spot). Kibble restores only 0.05 saturation each, but up to 20 can be consumed in one sitting. Kibble never spoils if it is under a roof, so kibble is a long-term and easily stored way to feed a large number of animals. (In 1.0 unstable, kibble now does deteriorate outdoors even when roofed.)
The most efficient way to create Kibble is to use haygrass for the vegetable, as it is the most plentifully generated vegetable component. Kibble is also an effective way to use insect or human meat, both of which will give your colonists bad thoughts if incorporated into their diets. However, if you happen to lack both of these, Kibble is generally not very cost-effective with a mere 25% net nutrition gain from its ingredients, and only really useful as it's made in bulk. Otherwise, Pemmican has a net nutrition gain of 80% over its ingredients, although it doesn't last indefinitely and requires significantly more work to make.
Kibble is consumable by humans, but will provide a strong negative moodlet. This is the only way for humans to eat hay. It will not counter the negative effects of eating human or insect meat.