Warming temperatures and increased moisture levels (if you have been fortunate enough to receive some useful rainfall) correspond with the growth of lush grasses and legume pasture species.
Cattle and sheep producers with stock transitioning from winter fodder to pasture, need to be mindful that changes in diet can increase the risk of bloat.
Nigel Brown, District Vet, Northern Tablelands Local Lands Services, warns that a sudden intake of lush, green pasture can result in the production of large amounts of gas in the rumen (chamber of the stomach). If the animal is not able to get rid of it by belching, the rumen blows up – ‘bloat’.
The rumen contains a mixture of different organisms including bacteria, protozoa, fungi, yeast and others, whose role is to break down the fodder consumed. A balance of organisms is required to digest different foodstuffs. Bacteria multiply very quickly and the products of their activity in the rumen can cause serious effect.
Gas is normally produced during fermentation in the rumen (just like the head on beer). However, the rapid fermentation in bloat increases gas pressure that inhibits breathing and soon causes heart and lung failure – death follows.
Nigel Brown maintains that understanding how bloat occurs helps in implementing the necessary steps to prevent it. He recommends changes in diet be introduced gradually to avoid bloat.
“Rumen microflora require approximately 10 – 14 days to adapt to a new diet. It is recommended that animals be fed hay or winter fodder in the morning before being put out to pasture for the first time. Grazing time should be limited to approximately 1 – 3 hours in the early afternoon, before stock are removed and returned to high fibre,” he said.
Nigel recommends that this should be undertaken daily for a week to ten days before stock are allowed to graze permanently.
Signs that an animal may be affected include a reluctance to move, a distended left abdomen and rapid breathing.
“Animals experiencing symptoms should be kept moving. A stomach tube can be used to relieve the gas build-up. In severe cases, vegetable oil (or mechanical oil if vegetable is not available) can be administered to break down the gas in the rumen,” said Nigel.
“In severe cases where an animal has gone down, a hole can be made into the rumen high on the left flank (where the swelling is greatest.) In these cases it is important to seek veterinary advice, but often there isn’t time,” he said.
At this time of year, animals should also be vaccinated with 5-in-1 or 8-in 1 for clostridial diseases which include tetanus, pulpy kidney and others.
“Animals should be vaccinated at least 10 – 14 days before being challenged by a new diet. In spring, animals should also receive a booster after 2 – 3 months,” said Nigel.