The effects of poloxalene on ingestion by cattle grazing Lucerne

The mechanisms that terminate meals of cattle grazing lucerne (Medicago sativa L.) are not well defined. Sub‐acute bloat may lead to cessation of grazing and, consequently, surface active substances used in the treatment and prevention of bloat, such as poloxalene, may extend grazing meals and increase herbage intake. Twelve mature Angus cows (Bos taurus) were offered 0, 12·5 and 25·0 g poloxalene in 0·5 kg of crushed maize (Zea mays L.) kernels each day, immediately before two consecutive 1‐h measured parts of a grazing meal on 21‐ to 24‐day‐old lucerne swards with a herbage dry matter (DM) mass (> 5 cm) of 2·03 t ha−1 and herbage DM mass allowance of 3·55 kg hd−1h−1. Total herbage DM intake was 2·52 kg hd−1 during the first hour and 1·54 kg hd−1 during the second hour of the 2‐h grazing meal. Differences in herbage intake were attributable to a cessation of grazing. Mean rates of biting were 26·3 and 14·8 bites min−1 and mean DM intakes per bite were 1·82 and 4·38 g during the first and second part of meals, respectively. Poloxalene treatments caused a small linear decline in grazing time during the first part of meals and a larger increase in grazing time during the second part of meals. Lower rates of DM intake caused by poloxalene were offset by increases in grazing time. It was concluded that poloxalene moderated ingestive behaviour within grazing meals of immature lucerne and this response may have been at least partly due to the relief of sub‐acute bloat.