In nautical slang, a “donkey's breakfast” was the slang term used to describe the straw-stuffed mattresses used on board ship well into the 20th century. As one might imagine, straw-stuffed mattresses were not terribly comfortable, especially by the end of a long trip; it is doubtful that any donkey would have wanted to sample the innards of a sailor's mattress after an ocean crossing. These uncomfortable and unsanitary mattresses were used up through the Second World War on some parts of ships.
The concept of a straw-stuffed mattress is quite old. Early humans undoubtedly used straw in their bedding, along with furs and skins for additional padding. Straw stuffed mattresses known as straw ticks were used everywhere from the chambers of queens to the cottages of shepherds until someone got the bright idea of stuffing a mattress with feathers. Other mattress stuffers included horsehair and wool, until synthetics and springs were developed and the modern mattress was born.
Incidentally, the “ticking” in straw ticking is not a reference to parasites, although straw ticking undoubtedly housed a wide assortment of parasites, dust mites, and other small visitors. It is derived from the Middle Dutch tike, which means “a cloth covering for mattresses.” Like other straw ticking mattresses, a donkey's breakfast was made by sewing a sturdy canvas cover and then stuffing it with straw. Periodically the straw would be discarded and the mattress would be refilled; sailors usually emptied their donkey's breakfasts at the end of a journey.
For most of sailing history, the uncomfortable donkey's breakfast would have been the least of a sailor's problems. Sailors contended with extremely dangerous and sometimes brutal conditions on board ship. They also often shared their coarse straw ticks with other men; many ships used a hot-bunking system, in which men who were not on duty would sleep in the beds left vacant by men on duty. As one might imagine, this contributed to the spread of parasites such as body lice, and a donkey's breakfast probably would have been itchy in a number of ways by the end of the trip.
In addition to providing fodder for parasites, straw ticking also flattens out as it is used. A donkey's breakfast would have resembled a straw pancake at the end of a journey, with a thin layer of hard, scratchy straw sandwiched between the ticking of the mattress. On journeys with more concern for comfort and hygiene, the mattresses might be periodically aired and beaten on deck to freshen them up.