Microbial characteristics of ruminal fluid from feedlot bloat beef cattle.

Abstract

Rumen samples from bloating steers had volatile fatty acids (VFA) concentrations high in acetate and low in propionate so that the acetate/ propionate ratio was consistently higher in bloating animals than in healthy ones. The ruminal pH values in bloated steers were compatible with those in healthy steers. Ammonia concentrations were higher in bloated steers than in healthy ones. There were no essential differences in the rates of gas production in vitro by rumen fluid between bloated and healthy steers. The total count and generic composition of rumen ciliates were similar in all steers and not likely to correlate with bloat. In contrast, although the total counts of bacteria in bloated steers were of the same order as those from healthy steers, the constitution of microflora was greatly affected by the development of bloat: gram-negative cocci (0.3-1.0 µm), gram-positive cocci (0.5-1.1 µm) and gram-positive small rods {(0.45-0.65 µm) x (0.65-1.2 µm)} increased, while gram-negative small rods {(0.35-0.7 µm) x (0.9-2.0 µm)} decreased in bloating steers.Bloat is a common and costly disorder of ruminants caused by retention of gas in the stomach. Although there are no official statistics on the incidence of feedlot bloat in Japan, the losses from sickness and death have been estimated to be Y7,200 millions annually (1-3). The tremendous economic losses from bloat in the U.S.A., Australia, New Zealand and Canada have been described in a recent review by CLARKS and RECD (4).It is well established that most of the gas in the rumen is produced by microbial fermentation and acidification of bicarbonate, and is eliminated normally by eructation without difficulty. However, the elimination of gas being prevented for some reason or other leads to gross distention of the rumen and the animal becomes bloated. Bloat is classified into foamy and free-gas types according to the physical nature of the rumen contents. In the foamy type, a large portion of the rumen gas is trapped within the rumen contents and the transfer of the gas to the esophagus is impaired. The contributions of plants, animals, and microbial factors to the bloat foam were reviewed (4).

An Evaluation of the Physicochemical and Biological Characteristics of Foaming Swine Manure

“…However, the ratio of acetic to propanoic acid was significantly (p < 0.05) higher in the foam itself than in layers B, C, or D of foaming and non-foaming storages. This may be significant, as Sakauchi and Hoshino (1981) found that rumen fluid from bloated steers had a higher acetic to propanoic acid ratio than rumen fluid from healthy steers, suggesting some similarities in the mechanisms of foam formation in deep-pit storages and bloat in feedlot cattle.…”

Particle breakdown and rumen digestion of fresh ryegrass (Lolium perenne L.) and lucerne (Medicago sativa L.) fed to cows during a restricted feeding period

“…rumen fill and particle size reduction, and those which have been implicated in the aetiology of bloat, i.e. degradation of plant leaf and release of chloroplasts (Howarth et al 1982;Majak et al 1985), fermentation (Clarke & Reid, 1974), and volatile fatty acid (VFA) production (Sukachi & Hoshino, 1981).…”

Recent advances in research in the rumen bloat of ruminant animals fed high-concentrate diets

“…As mentioned above, the rumen foam agent and foam stabilizer can only originate from feeds and rumen microorganisms. Numerous studies have found that rumen bloat occurs only in some animals, even when fed the same feed ( 32 , 33 ). The reason for this phenomenon may be related to individual differences in the structural composition of rumen microbes, suggesting that rumen microbes play an important role in the development of rumen bloat.…”