Two experiments were conducted with three types of polyethylene particles to establish their retention time in castrated male cattle (steers) offered diets which contained predominantly cereals ad libitum. The particles were (1) ‘Ruff Tabs’, a corrugated particle of dimension 1·27 × 0·63 × 0·95 cm3 and subsequently referred to as RT and (2) and (3) plain plastic rods of 1·27 cm length and 0·32 cm (BP) or 0·63 cm (RBP) diameter.
In the first experiment with steers weighing 170 or 260 kg, 1 kg of RT particles were excreted in the faeces at a similar rate by the steers of different weights whereas BP particles passed out in the faeces more slowly in the lighter steer.
In the second experiment 30 steers weighing 440 kg were slaughtered at 7, 14, 28 and 42 days after dosing with 1 kg of BP, RT or RBP. The recovery of RT was significantly lower (P < 0·05) than that of BP 7 days after dosing and this difference was also found at 14 and 28 days. RBP behaved like BP up to 14 days but thereafter the rate of passage of RBP was faster than tha t of BP and recovery from the rumen approached that of RT.