Endotoxin shock in calves from intravenous injection of rumen bacterial endotoxin

A 2-year comparison of the production, health and fertility of dairy cows given concentrates either twice daily in the parlour or through out-of-parlour dispensers

Milk production, reproduction, blood composition and health were studied in two groups of British Friesian cows given food either twice daily in the parlour (IPF group) or through automatic out-of- parlour food dispensers (OOPF group) in the first 14 weeks of two consecutive lactations. The numbers of cows in the IPF and OOPF groups were 28 and 29 respectively in year 1 and 40 and 35 in year 2.

There were no differences in milk production or reproduction in year 1 but in year 2 the OOPF group had significant proportional increases in the yield of fat (+0·079) and protein (+0·072) and the median time from calving to conception was reduced by 43·5 days. In the IPF group body condition score was lower than in the OOPF group in year 1 (2·27 v. 2·59; P < 0·001) and in year 2 (2·37 v. 2·57; P < 0·01); as were serum total protein (75·8 v. 77·5 g/l; P < 0·05) and (73·9 v. 75·8 g/l; P < 0·01) and plasma glucose concentration (215 v. 2·32 mmol/1; P < 0·001) (2·28 v. 2·42 mmol/l; P < 0·01). In year 2 only, serum urea was lower (5·52 v. 6·07 mmol/l; P < 0·001) and serum copper higher (131 v. 11·9 μmol/l; P < 0·001) in the IPF group; the activities of aspartate amino transferase (1·66 v. 1·62 logm i.u. per 1; P < 0·05) and of glutamate dehydrogenase (1·00 v. 0·70 logm i.u. per 1; P < 0·001) were higher, despite no significant difference in fat deposition in the liver. The only significant difference in the incidence of disease was fewer cases of mastitis in the OOPF group in the second year (21 v. 12 cases).

The similarity in concentrate intakes, together with higher concentrations of blood glucose and total protein and better condition score, indicate either a more efficient utilization of energy in the OOPF group or a lower consumption of forage in the IPF group. The increased activities of liver enzymes and the high serum copper coupled with the increased incidence of mastitis and poorer fertility may indicate the release of endotoxin following chronic lactic acidosis in the IPF group.

Ruminal acidosis in beef cattle: the current microbiological and nutritional outlook

Ruminal acidosis continues to be a common ruminal digestive disorder in beef cattle and can lead to marked reductions in cattle performance. Ruminal acidosis or increased accumulation of organic acids in the rumen reflects imbalance between microbial production, microbial utilization, and ruminal absorption of organic acids. The severity of acidosis, generally related to the amount, frequency, and duration of grain feeding, varies from acute acidosis due to lactic acid accumulation, to subacute acidosis due to accumulation of volatile fatty acids in the rumen. Ruminal microbial changes associated with acidosis are reflective of increased availability of fermentable substrates and subsequent accumulation of organic acids. Microbial changes in the rumen associated with acute acidosis have been well documented. Microbial changes in subacute acidosis resemble those observed during adaptation to grain feeding and have not been well documented. The decrease in ciliated protozoal population is a common feature of both forms of acidosis and may be a good microbial indicator of an acidotic rumen. Other microbial factors, such as endotoxin and histamine, are thought to contribute to the systemic effects of acidosis. Various models have been developed to assess the effects of variation in feed intake, dietary roughage amount and source, dietary grain amount and processing, step-up regimen, dietary addition of fibrous byproducts, and feed additives. Models have been developed to study effects of management considerations on acidosis in cattle previously adapted to grain-based diets. Although these models have provided useful information related to ruminal acidosis, many are inadequate for detecting responses to treatment due to inadequate replication, low feed intakes by the experimental cattle that can limit the expression of acidosis, and the feeding of cattle individually, which reduces experimental variation but limits the ability of researchers to extrapolate the data to cattle performing at industry standards. Optimal model systems for assessing effects of various management and nutritional strategies on ruminal acidosis will require technologies that allow feed intake patterns, ruminal conditions, and animal health and performance to be measured simultaneously in a large number of cattle managed under conditions similar to commercial feed yards. Such data could provide valuable insight into the true extent to which acidosis affects cattle performance.

Acidosis in Feedlot Cattle

Mortality from digestive diseases in feedlot cattle is second only to that from respiratory diseases. Acidosis is a major digestive disorder and is likely to continue because of ongoing attempts to improve the efficiency of beef production by feeding more grain and less roughage. Subacute acidosis is the most prevalent form of acidosis in feedlots but is difficult to diagnose because of the absence of overt clinical signs. Control of acidosis is achieved largely by sound nutritional management. No single strategy or solution exists; however, an effective management strategy should factor in dietary formulation, a consistent feeding program, prudent bunk management, use of nonstarch by-products, and feed additives to minimize pen-to-pen and animal-to-animal variations in feed intake.

Characterization of calves exhibiting a novel inheritable TNF-α hyperresponsiveness to endotoxin: associations with increased pathophysiological complications

A subpopulation of calves, herein termed “hyperresponders” (HPR), was identified and defined by the patterns of plasma TNF-α concentrations that developed following two challenges with endotoxin (LPS, 0.8 μg Escherichia coli 055:B5 LPS/kg0.75live body wt) separated by 5 days. The principle characteristic of HPR calves was a failure to develop tolerance to repeated LPS challenge that was evident in the magnitude of the TNF-α concentrations and prolonged severity of pathological sequellae. Whereas calves failing to develop LPS tolerance were identified on the basis of their excessive in vivo plasma TNF-α concentration responses, in vitro TNF-α responses of peripheral blood mononuclear cells isolated from each calf and challenged with LPS or PMA did not correlate or predict the magnitude of in vivo plasma TNF response of the calf. Intentional breeding to obtain calves from bulls and/or cows documented as HPR resulted in offspring displaying the HPR character when similar progeny calves were tested with LPS in vivo, with extensive controls in place to account for sources of variability in the general TNF-α response to LPS that might compromise interpretation of the data. Feed intake, clinical serology and hematology profiles, and acute-phase protein responses of HPR calves following LPS were significantly different from those of calves displaying tolerance. These results suggest that the pattern of plasma TNF-α changes that evolve from a low-level double LPS challenge effectively reveal the presence of a genetic potential for animals to display excessive or prolonged pathological response to LPS-related stress and compromised prognosis for recovery.

Experimental induction of pneumonic pasteurellosis in calves by intratracheal infection with Pasteurella multocida biotype A:3

The study aimed to establish an experimental model to investigate the pathogenesis of lung infection by Pasteurella multocida, an important cause of bovine respiratory disease. An experimental model is required to assist the development of an effective vaccine. Sixteen 8-week-old calves were challenged intratracheally with 10(9) or 10(10) colony forming units of P. multocida in either 60 or 300 ml saline in a 2 x 2 factorial experiment. All animals became dull within 2-6h post-infection (p.i.) and two calves were killed humanely because of suspected endotoxic shock. Remaining animals showed increased respiratory rates by 15-20 h p.i. and, at 23 h p.i., calves given the high dose, high volume challenge showed higher (P < 0.05) rectal temperatures. From 24 to 36 h p.i., clinical signs decreased in a majority of animals. Plasma haptoglobin concentrations increased (P < 0.05) in calves given the high volume challenge irrespective of the number of bacteria. At post-mortem examination (4d p.i.), lung lesions, mainly in the apical lobes, were found in all calves. Histopathological examination showed areas of purulent pneumonia with a tendency to abscessation and inflamed interlobular septa characterised by accumulation of neutrophils and oedema. The clinical and pathological responses described were typical of bovine pneumonic pasteurellosis.

Effects of oral and intravenous administration of endotoxin in prepubertal gilts

The effect of oral intake of endotoxins was studied in 12 prepubertal gilts. The animals were given 30 or 100 mg of ET each in their regular morning feed ration. Blood samples were collected periodically during 24 h and the clinical status, including rectal temperature, was recorded at the same time. Hematological and clinical chemical analyses that included serum bile acids, glutamate dehydrogenase, alkaline phosphatase, calcium, iron, zinc and a blood plasma metabolite of prostaglandin F2 alpha, were done. The animals showed no obvious clinical symptoms following endotoxin feeding. The major findings were increased bile acid and glutamate dehydrogenase values with the most prominent rises being recorded 10-12 h after endotoxin intake. In a later experiment, 6 animals were injected i.v. with endotoxin in doses in the range 0.1-0.5 micrograms/kg b.w. Blood samples were taken and analysed as in the endotoxin-feeding experiment. Within 1 h of injection, all animals showed symptoms such as vomiting, fever and dyspnea. The clinical signs disappeared within 2-5 h. The injections were followed by increases in bile acids, glutamate dehydrogenase and prostaglandin F2 alpha metabolite. To conclude, this study indicates that clinically healthy prepubertal gilts react to ingested endotoxin in feed but that no apparent clinical disturbances ensue.

The role of endotoxins in induced ruminal acidosis in calves

Experimentally induced ruminal acidosis was carried out in 4 calves to investigate the possibility of resorption of endotoxins from Gram negative bacteria originating from the gastro-intestinal tract. The ruminal acidosis was induced by overfeeding of oats and the effect was evaluated by clinical and blood biochemical changes. Blood samples were collected every 2 h for 60 h before and after experimental feeding. The animals showed signs of ruminal acidosis and also the clinical and blood biochemical changes were similar to those seen after experimental endotoxaemia. However, although being less dramatic the changes in many relevant parameters such as an increase in prostaglandin F metabolite levels, body temperature, endotoxins and a decrease in iron indicate that an endotoxaemic state had occurred. The results of the present study show that ruminal acidosis/stasis is linked to resorption of endotoxins from the gastro-intestinal tract causing endotoxaemia/endotoxicosis.

Antigenic homology of endotoxin with a coliform mastitis vaccine strain, Escherichia coli O111:B4 (J5)

This study examined recognition of heterologous Gram-negative endotoxin by antibodies recognizing common lipopolysaccharide core antigens. Gram-negative endotoxins from 11 heterologous bacterial strains were tested for recognition by antibodies against common lipopolysaccharide core antigens. Serum was harvested from a calf immunized with the Rc mutant, Escherichia coli O111:B4 (J5), and affinity purified against endotoxin derived from an Ra mutant, Salmonella typhimurium, producing an antibody reagent recognizing homologous Gram-negative core antigens present in the Rc mutant vaccinal antigen. This reagent demonstrated reactivity against 11 chemically purified Gram-negative endotoxins. Included were endotoxins derived from 3 smooth E. coli species, 2 Salmonella spp., Shigella flexneri, Klebsiella pneumoniae, Pseudomonas aeruginosa, Serratia marcescens, and lipid A. Endotoxin derived from K. pneumoniae had significantly higher ELISA reactivity with core antigen specific antibodies than did endotoxin derived from either E. coli O111:B4 (J5) or P. aeruginosa. These results suggest immunization with R mutant bacterins may have utility in the prevention of Gram-negative mastitis even when whole bacteria react poorly with antibodies recognizing common core antigens.

Investigation of the possible role of endotoxin, TXA2, PGI2 and PGE2 in experimentally induced rumen acidosis in cattle

Rumen acidosis was induced experimentally with 70 g barley/kg b.w. in 2 rumen fistulated cows. The cows were followed for 80 h after the grain engorgement. Endotoxin was monitored in cell-free ruminal fluid and peripheral plasma together with inflammation mediators TXA2, PGI2 and PGE2 and several clinical and clinical-chemical parameters. The results do not support the theory of systemical endotoxemia due to a large increase in rumen endotoxin concentration in cattle suffering from rumen acidosis. However, both clinical and clinical-chemical data suggest that an endotoxicosis developed, but the levels of inflammation mediators TXB2, FGI2 and PGE2 were not significantly elevated in the peripheral circulation. An absorbtion of endotoxins and synthesis of inflammation mediators are therefore suggested to take place prehepatically.

A clinical and endocrine study on the effect of orally administered bacterial endotoxin in adult pigs and goats

Endotoxin of Gram-negative bacteria was orally administered in 5 female pigs and 8 male goats. Two of the gilts were pregnant. A solution of lipopolysaccharide (LPS) of Enterobacter agglomerans was mixed into the feed ration of the pigs (40 mg/animal), and given by gastric tube into the rumen of the goats (1-20 mg/animal). Jugular venous blood was collected and clinical signs, rectal temperature and WBC counts were recorded for 12-24 hours. Plasma concentrations of the major plasma metabolite of PGF2 alpha, 15-keto-13,14-dihydro-PGF2 alpha were determined in both species, progesterone concentration only in pigs. The pigs showed slight to severe signs of endotoxemia. Increases in rectal temperature and levels of the PGF2 alpha metabolite occurred in 3 gilts. Progesterone level and the total WBC counts remained unchanged. Differential counts followed irregular patterns mostly within the normal range. The goats showed slight signs of discomfort. Temperature increased in one animal. No other parameters were altered after the intake of LPS. The observations in pigs indicate that endotoxin either penetrated the intestinal barrier causing systemic endotoxemia or induced inflammatory reactions in the intestine activating inflammatory mediators.

Nutritional and metabolic diseases involving the nervous system

This article will discuss eight diseases that alter normal nervous system function: hypovitaminosis A, water deprivation/salt toxicity, ammonia toxicosis, hypomagnesemia, hypocalcemia, nervous ketosis, hepatoencephalopathy, and rumen metabolic acidosis.