During the heat wave experienced in November 2009, Dorper ewes and lambs as well as weaned lambs were moved to the yards at midday on an irrigation property.
To encourage their quick movement to the yards a heavy trail of faba beans was placed on the track leading to the yards. The owner observed that the weaned lambs rushed onto this trail and many of them rushed onto water in a channel just before the yards.
Two hours later the owner returned to the yards and found six of the weaned lambs recumbent or standing in apparent distress with 'grunting' respiration. Affected sheep were blown up on the left hand side.
The number of affected weaners grew rapidly to 50 clinical cases and 6 dead. The dead ones were autopsied and a large volume of thick frothy rumenal contents containing faba beans and dry ingesta was the main finding. The findings were consistent with a frothy bloat. Samples were collected for lab analysis. Rumen pH was found to be within normal range when tested later (however owner could not remember which lambs he had already drenched with sodium bicarbonate).
Treatment of affected sheep with diluted Eskalin® wettable powder was commenced starting with the worst affected sheep. Many of the weaners were by that stage extremely moribund. Within approximately 15 -30 minutes of an Eskalin drench lambs started to show signs of recovery characterised by improved posture, rising from recumbent position and improved respiration. Following treatment, two further weaners died and a further five required a repeat dose. 48 ex 50 treated weaners recovered.
Handling stress, extreme heat and rapid consumption of both faba beans and water could all be considered as factors contributing to the development of the frothy bloat . It is recognised that microbial factors contribute to the stability of foam inside the rumen in frothy bloat . The response to treatment with virginiamycin as an oral drench is assumed to be due to its detrimental effect on bacteria present in the rumen. The rapid response is difficult to explain given that a frothy bloat significant enough to cause death was already present.