Liver abscesses in feedlot cattle: a review

Liver abscesses in slaughtered beef cattle result from aggressive grain-feeding programs. The incidence, averaging from 12 to 32% in most feedlots, is influenced by a number of dietary and management factors. Liver abscesses represent a major economic liability to producers, packers, and ultimately consumers. Besides liver condemnation, economic impacts include reduced feed intake, reduced weight gain, decreased feed efficiency, and decreased carcass yield. Fusobacterium necrophorum, a member of the ruminal anaerobic bacterial flora, is the primary etiologic agent. Actinomyces pyogenes is the second most frequently isolated pathogen. Ruminal lesions resulting from acidosis generally are accepted as the predisposing factors for liver abscesses. F. necrophorum possesses or produces a number of virulence factors that participate in the penetration and colonization of the ruminal epithelium and subsequent entry and establishment of infection in the liver. However, only a few virulence factors have been characterized well. Control of liver abscesses in feedlot cattle generally has depended on the use of antimicrobial compounds. Five antibiotics (i.e., bacitracin methylene disalicylate, chlortetracycline, oxytetracycline, tylosin, and virginiamycin) are approved for prevention of liver abscesses in feedlot cattle. Tylosin is the most effective and the most commonly used feed additive. Tylosin feeding reduces abscess incidence by 40 to 70%. The mode of action of antibiotics in preventing liver abscesses is believed to be via inhibition of ruminal F. necrophorum. Protective immunity against F. necrophorum induced by a variety of antigenic components has ranged from ineffectual to significant protection.     

A review of bloat in feedlot cattle

Improvements in feedlot management practices and the use of various feed additives have reduced, but not eliminated, the occurrence of bloat in feedlot cattle. Feedlot bloat reduces the profitability of production by compromising animal performance and more directly by causing fatalities. In feedlots, bloat is associated with the ingestion of large amounts of rapidly fermented cereal grain and destabilization of the microbial populations of the rumen. An abundance of rapidly fermented carbohydrate allows acid-tolerant bacteria (e.g., Streptococcus bovis and Lactobacillus spp.) to proliferate and produce excessive quantities of fermentation acids. As a result, ruminal pH becomes exceedingly low, and this impairs rumen motility. Further, the excessive production of mucopolysaccharide or "slime" increases the viscosity of ruminal fluid and stabilizes the foam implicated in frothy feedlot bloat. Although protocols have been developed to treat feedlot bloat, the most profitable approach is to use management strategies to reduce its likelihood. Amount of roughage, grain processing techniques, selection of cereal grain (e.g., corn, barley, and wheat), dietary adaptation periods, and various additives (e.g., ionophores) can influence the occurrence of bloat in feedlot cattle. Successful management of these factors depends on a thorough understanding of the behavioral, dietary, and microbial events that precipitate bloat in feedlot cattle.     

Acidosis and bone

Acidosis has important effects on the bone mineral which can be investigated utilizing neonatal mouse calvariae in organ culture. When calvariae are cultured for 3 h in physiologically acidic medium produced by a reduction of the bicarbonate concentration, a model of acute metabolic acidosis, there is net calcium efflux from bone in addition to net proton influx into bone which lessens the severity of the acidosis. Utilizing a high resolution scanning ion microprobe to study the bone during acidosis we have found that the protons exchange for sodium and potassium on the bone surface. In acute experiments the calcium efflux is the result of mobilization of carbonated apatite through an alteration in the physicochemical driving forces for bone mineral accretion and dissolution. In the more chronic cultures (greater than 48 h) metabolic acidosis induces calcium efflux by stimulating osteoclastic bone resorption and inhibiting osteoblastic bone formation. When calvariae are cultured for 3 h in acidic medium produced by an increase in the partial pressure of carbon dioxide, a model of respiratory acidosis, there is also calcium efflux; however, at the same decrement in pH the net flux is far less than that observed during metabolic acidosis. During acute respiratory acidosis there is no measurable influx of protons into bone and during chronic studies there is no measurable calcium efflux.     

A review of nonpesticide phosphate ester-induced neurotoxicity in cattle

Nonpesticide phosphate esters induce delayed neurotoxicity in cattle. The most common exposures are to complex mixtures of triaryl phosphate used in lubricating oils. Oral ingestion is most common, but dermal exposures have also occurred. Clinical signs of cholinesterase (ChE) inhibition may or may not be seen. Depending on the biochemical targets, the percent reduction in blood ChE is variable and can be < 30% of normal activity. Organophosphate ester-induced delayed neurotoxicity cannot be predicted by inhibition of blood ChEs. Signs of delayed neurotoxicity occur 2 to 25 d after exposure; these signs are neurologic deficiencies of the antigravity muscles and the muscles of the urinary bladder and larynx. Affected cattle may dribble urine and some may be mute. Signs of ChE inhibition generally are not observed in animals with neurological deficiencies. Pathologic findigs are axonopathy and myelin degeneration of nerves with long axons located in both the peripheral and central nervous systems. In the spinal cord, location of the affected nerve tracts is variable. Degenerative changes occur in motor neurons. Calves are less susceptible to organophosphate ester-induced delayed neurotoxicity than cows. A dose of 500 mg triaryl phosphate/kg body weight will produce complete paralysis in a mature cow in 26 d.     

The effect of grain source and grain processing on performance of feedlot cattle: a review

Effects of grain species and grain processing method on DMI, rate and efficiency of gain, and feeding value for cattle fed high concentrate diets were appraised by statistically compiling results from 605 comparisons from feeding trials published in North American journals and experiment station bulletins since 1974. Metabolizable energy (ME) values for each grain and processing method were calculated by quadratic procedures from DMI and animal performance. Averaged across processing methods, ME values for corn, milo, and wheat grain (3.40, 3.22, and 3.46 Mcal/kg DM) fell within 9% of ME estimates from NRC (1996) for beef cattle. In contrast, ME values for barley and oats grain (3.55 and 3.46 Mcal/kg DM) were 24% and 17% greater than NRC (1996) estimates. Compared with the dry rolled forms, high moisture corn and milo resulted in lower ADG and DMI. Compared with dry rolling, either steam rolling or flaking of corn, milo, and wheat decreased DMI without decreasing ADG and improved feed efficiency by 10, 15, and 10%, respectively. Compared with dry rolled grain, steam flaking increased (P < .05) body weight-adjusted ME of corn and milo grain by 15 and 21%, respectively; body weight-adjusted ME for whole corn was 9% greater (P < .05) than for rolled corn grain. Steam flaking was surprisingly effective (13%) at increasing (P < .05) the body weight-adjusted ME of wheat, but steam flaking failed to increase the ME of barley and oats. Higher moisture content of high-moisture corn decreased dry matter intake without depressing ADG and improved efficiency and increased ME of the grain. Compared with steam flakes of moderate thinness, processing milo or barley to a very thin flake tended to reduce ADG and failed to improve feed efficiency. The ideal roughage source and roughage moisture content for maximum ME and ADG varied with grain processing method. Feeding corn silage rather than alfalfa and wet rather than dry roughage depressed (P < .01) ADG of cattle and reduced (P < .01) body weight-adjusted ME of cattle fed high-moisture corn grain but tended to increase both with steam-flaked corn or wheat.     

Acidosis reduces neuronal apoptosis

Multiple factors are thought to influence the level of circulating angiotensinogen (AGT). We showed previously that the serum AGT concentration was significantly related to body mass index (BMI) in a cohort of young people. In the present study, we studied whether levels of the gonadal hormones estradiol and testosterone might also predict the AGT level and might contribute to the BMI effect, since both the production of these hormones and BMI increase with age. In boys (n=127; mean+/-SD age, 14.7+/-1.9 years) and girls (n=104; age, 14.8+/-1.9 years) studied as a single group, we found a significant association of AGT level with level of estradiol (P=0.015) after adjustment for haplotype, age, race, testosterone concentration, and BMI. In girls studied alone, the level of AGT showed a significantly positive relation to level of testosterone (P=0.043), possibly a result of peripheral conversion of testosterone to estradiol, after adjustment for haplotype, age, race, estradiol concentration, and BMI. In boys, on the other hand, the level of testosterone was inversely related to AGT concentration (P=0.019), again after making adjustments for the other variables. Finally, in pairs of subjects matched for BMI, age, race, and gender where 1 member of each pair had either 1 or 2 copies of an AGT gene haplotype (T235 and -1074t) and the other member had no copy, the level of AGT was higher in the carrier of a haplotype in 24 of the 34 pairs (P<0.001). In conclusion, gonadal hormones are an additional influence on the circulating level of AGT in growing young people. In addition, with matching for BMI and other covariates, there is a strong association of AGT genotype with the serum level of AGT, emphasizing the importance of AGT gene expression as a determinant of the circulating level of AGT.     

Selection for economic efficiency of dairy cattle using information on live weight and feed intake: a review

The objective of this study was to review some of the latest evidence of genetic variation in feed intake and feed utilization and to determine how this variation might be used. The most important sources of genetic variation in gross efficiency are likely to be the quantities of feed eaten and used for yield or maintenance and the extent to which body tissue is mobilized. Accounting for just one of these components when selection is for improved feed efficiency might result in undesirable genetic changes. For example, in an ad libitum feeding system, the heritability of body condition score is reported to be 0.43 for heifers; genetic correlations of body condition score with milk production and live weight were -0.46 and 0.66, respectively. Also, the genetic correlation between milk yield and live weight depends on lactation stage. For example, over the first 26 wk of lactation, this correlation was reported to be -0.09, but, after genetic adjustment for body condition score, the correlation was 0.29. When economic values are being derived, energy norms or genetic correlations can be used, and double counting of the feed costs needs to be avoided. An index that contained linear type traits, however, gave high accuracy of selection. Hence, although there appears to be great potential to improve economic efficiency by selecting for feed intake and live weight or by possible indicator traits, there is still uncertainty about some of the genetic parameters, especially among traits related to health, reproduction, and energy balance.     

Acidosis and hyperlactatemia in acute sodium valproate poisoning

OBJECTIVES: We searched for signs of metabolic acidosis and associated hyperlactatemia in case of sodium valproate overdose. PATIENTS AND METHODS: A retrospective study was conducted in the toxicology intensive care unit at the Fernand Widal hospital from 1990 to 1995. Patients retained for study had sodium valproate levels above the therapeutic range (> 600 mumol/l). Data collected included past history, intubation for mechanical ventilation, administration of catecholamines and infusion of bicarbonate or sodium lactate, and blood pressure. Laboratory tests included serum sodium valproate, pH, PCO2, bicarbonate, anion balance and lactate. RESULTS: The study included 22 consecutive patients. None had a history of liver disease. Thirteen patients were intubated before admission to intensive care. Two received catecholamines. None of the patients received bicarbonate or sodium lactate. Mean blood pressure was 118 +/- 16 mmHg, mean serum sodium valproate was 2668 +/- 2437 mumol/l, mean pH was 7.41 +/- 0.08, mean PO2 35.6 +/- 8.0, mean anion imbalance 23.2 +/- 6.0 mmol/l and mean lactate 5.0 +/- 2.1 mmol/l. There was a significant correlation between lactase and pH (p < 0.003). CONCLUSION: We found metabolic acidosis with major anion imbalance and high lactate levels in patients with acute sodium valproate intoxication. Hyperlactatemia could be due to the direct effect of sodium valproate or to an unknown mechanism.     

奶牛瘤胃酸中毒的诊断与治疗

瘤胃酸中毒是威胁奶牛业生产的主要疾病之一,由于发病急、病程短、病症重、死亡率高等特点,成为近年来阻碍我国奶牛业发展的主要因素.奶牛瘤胃酸中毒是奶牛食入大量含碳水化合物的饲料、精料或酸败饲料,导致瘤胃产酸过多,引起一系列消化系统障碍,代谢功能紊乱,瘫痪、休克病症的一种代谢性疾病.本文针对奶牛瘤胃酸中毒的诊断与治疗,详细叙述了引起奶牛瘤胃酸中毒的原因,综合诊断与治疗的方法以及手术治疗的方法和步骤.在实际生产当中,可以作为兽医技术人员的参考资料     

Moxonidine: a review

Moxonidine is an imidazoline compound which acts on I1 imidazoline 'receptors' in the central nervous system to reduce blood pressure. This novel mechanism of action is claimed to lead to fewer adverse effects than the older centrally-acting agents such as clonidine. In this review we examine the drug's pharmacology, clinical pharmacokinetics, efficacy as an antihypertensive agent including comparative studies with pre-existing drugs, and adverse effect profile. With a growing number of effective antihypertensive agents already available to the clinician, it is not yet clear whether moxonidine represents a significant advance in hypertension management.     

Noma: a review

Cancrum oris or noma is a condition not well known in western Europe and North America. It is, however, a relatively common cause of mortality and disability in children of undeveloped areas of Africa, Asia, and South America. This paper describes the experience at Galmi Hospital, in the sub-Saharan region of South Africa in the Niger Republic, with 50 operative patients out of a group of 300 who were referred. An extensive review of the literature is presented describing the epidemiological impact of the disease, the characteristics of the lesions, the pathogenesis, symptoms, sequelae, differential diagnosis, and preoperative preparation. Additionally, we review approaches to anesthesia, methods of reconstruction, and the most common causes of complications and mortality. Numerous photographs illustrating the devastating consequences of this problem are presented.     

Myocarditis: a review

BACKGROUND AND OBJECTIVES: Although pediatric sedation (PS) is widely used in emergency departments (ED), the practice of PS in general community hospital (GH) ED has not been described. We surveyed PS practice patterns in pediatric hospitals (CH) and GH and compared frequency and usage between the two groups. METHODS: All CH (n = 115) and 400 randomly selected GH were surveyed. Alcohol and drug detoxification, psychiatric, chronic care, rehabilitation, and specialty facilities were excluded. Data were collected on hospital type (pediatric or community), location (urban, suburban, rural), annual visits, academic affiliation (presence of an emergency medicine residency or pediatric emergency medicine fellowship in the hospital), and sedation agents used. RESULTS: Of 515 hospitals surveyed, 238 responded [84/115 CH (73%), 154/400 GH (39%)] yielding an overall response rate of 46%. Of the responding CH the majority were urban [57 (68%) were urban, 15 (18%) suburban, and 12 (14%) rural]. GH were more evenly distributed by location [44/153 (29%) were urban, 49/153 (32%) suburban, and 60/153 (39%) rural]. Eight (5%) GH had emergency medicine residencies, while 39 (46%) CH had pediatric emergency medicine fellowships. The mean annual pediatric volume was 38,000 for CH and 6500 for GH. For the four specified clinical scenarios, representing the most common ED procedures using sedation (laceration repair, fracture reduction, radiologic imaging), GH performed significantly fewer sedations than CH when matched for pediatric volume. PS was less frequently used among rural GH compared to suburban (P < 0.01) and urban GH (P < 0.01). Midazolam was listed as the most frequently used drug in all three geographic locations for both CH and GH. CH listed fentanyl as a second agent, while GH preferred meperidine. Fentanyl and ketamine were listed as preferred agents only in CH. For cranial computerized tomography, chloral hydrate was listed as the drug of choice by both CH and GH. Both CH and GH listed "relief of pain and anxiety" as the first and "agitation control" as the second most common reason for using sedation. CH and GH listed "the risks outweigh the benefits" as the primary reason and "ED too busy/takes too much time" as the secondary reason for not using sedation. CONCLUSIONS: GH performed fewer sedations than did CH when matched for pediatric volume in all geographic locations and for the most common ED procedures using sedation. Since 1989, sedation patterns have shifted in CH to include the short-acting agents, while GH (with the exception of midazolam) continue to prefer the long-acting agents. Midazolam is now the most frequently used sedation agent for ED procedures in both CH and GH.     

Hysteroscopy: a review

3 chemicals were selected for mutagenicity testing from a priority list, based on production volume and available mutagenicity data. Propargyl alcohol (PA), 2-nitroaniline (2NA), and 5-methyl-1H-benzo-triazole (MBT) were selected for testing using the approach recommended in the Health Protection Branch Genotoxicity Guidelines. The battery of tests included the Salmonella/mammalian microsome mutation assay, the in vitro chromosomal aberration assay, and the bone-marrow micronucleus assay. The results indicate that 2 of the 3 chemicals, PA and 2NA, were clastogenic in vitro. Both PA and 2NA induced chromosomal aberrations in CHO cells in vitro with and without metabolic activation, while none induced reverse mutations detectable with the Salmonella/mammalian microsome assay. Because PA and 2NA were found to be in vitro clastogens, they also were tested in the mouse bone-marrow micronucleus assay. 2NA induced a small increase in micronuclei in males but not females. PA did not induce an increase in micronuclei.     

Teleradiology: a review

The Biographical Personality Interview (BPI) was applied to 179 subjects (158 psychiatric patients and 21 probands from the general population); 100 patients and 20 healthy controls served as a validation sample; the others had been interviewed during the training period or did not meet the inclusion criteria for the validation of the BPI. The acceptance of the interview was high, the inter-rater reliability of the ratings of premorbid personality structures ("types") varied between 0.81 and 0.88 per type. Concurrent validity of the typological constructs as assessed by means of the BPI was inferred from the intercorrelations of type scores and correlations of these scores with questionnaire data and proved to be adequate. Clinical validity of the assessment was indicated by statistically significant differences between diagnostic groups. Problems and further developments of the instrument and its application are discussed.     

Chlamydia trachomatis in adolescents: a review

Genital infections caused by Chlamydia trachomatis represent the most prevalent bacterial sexually transmitted disease in the United States. An estimated 3-4 million cases annually necessitate the expenditure of more than $2 billion in health care costs per year. The ramifications of infection with this organism have significant reproductive complications. The objective of this paper is to provide the reader with a review of Chlamydia trachomatis in general with particular focus on those areas that are pertinent to the adolescent population. The authors hereby provide an overview of the clinically pertinent microbiology, epidemiology, risk factors, selective screening protocols, diagnostic methods, clinical manifestations, and sequelae of C. trachomatis.     

Inclusions in wrought superalloys:a review

Inclusions in wrought superalloys significantly affect the stability of the alloy properties and limit their use and devel-opment in aeroengines and other appli...     

Delusions in Alzheimer''s disease: a review

To understand the developing processes of gamma-aminobutyric acid (GABA)-containing chromaffin cells and nerve fibers in the mouse adrenal gland, we examined the tissues in various postnatal stages by immunohistochemistry using a GABA antibody. From birth until postnatal week 1, GABA-immunoreactivity was seen in very few nerve fibers, and in none of the chromaffin cells. At postnatal week 2, GABA-immunoreactivity appeared weakly in clusters of chromaffin cells and strongly in relatively numerous varicose nerve fibers. The immunoreactive nerve fibers were densely distributed in the small immunonegative chromaffin cells and large ganglion cells, but only sparsely so in the weak immunoreactive chromaffin cells. At postnatal week 3, the number of the immunoreactive chromaffin cells and nerve fibers further increased compared to that at postnatal week 2. The staining pattern of GABA-immunoreactive nerve fibers in the medullas was similar to that at postnatal week 2. From postnatal week 4 until postnatal week 8, the distribution and frequency of the immunoreactive chromaffin cells and nerve fibers were also similar to those at postnatal week 3. These results suggest that the expression of GABA in the chromaffin cells and in the nerve fibers of the mouse adrenal gland may be completed by postnatal week 3.