Breeding against bloat may be possible

Press, 25 February 1977, Page 15

Breeding against bloat may be possible

It may be possible to breed cattle that are resistant to bloat.

Speaking to the annual conference of the New Zealand Veterinary Asociation in Christchurch last week

Dr D. G. Edgar, director of the Ruakura animal research centre, said that most bloat under New Zealand conditions was caused

by the formation of a stable foam in the rumen. This was believed to be associated with high protein in the feed and might result from “complexing” of pasture and salivary proteins. The latter proteins might differ in cattle differing in susceptibility to bloat. It seemed certain that both plant and animal factors were involved in causing bloat and New Zealand Dairy Board data suggested a level of heatability of susceptibility to bloat •which would make selective breeding well worthwhile. Two herds of dairy cattle were being selected for high and low susceptibility to bloat, he said. Their saliva was being sampled and separated into bands of various proteins and glycoproteins. So far it had been shown that a particular band (band 4) was in higher proportions in the

saliva of cows of higher I susceptibility, while band 7 1 was associated with lower t susceptibility and it ap- I peared that selective breed- s

ing might be changing its proportion. Low susceptibility cows also had a greater salivary flow and stimulation of the flow rate with acetic acid led to a large increase in the proportions of band 7. “It appears possible that biochemical testing of saliva proteins could lead to the selection of bulls likely to leave bloat resistant offspring,” Dr Edgar said.