Toxicity of Riddell's groundsel (Senecio riddellii) to cattle

The toxicity of Riddell's groundsel (Senecio riddellii) fed to calves in gelatin capsules, by gavage, or mixed in their hay ration was determined. Dosages were varied according to the pyrrolizidine alkaloid (PA) content of the plant, and the calves' responses were measured by clinical signs, serum enzyme changes, survival time, and histopathologic changes. Calves fed S riddellii to provide 10 mg of PA/kg of body weight/day in capsules or by gavage for 20 consecutive days did not develop clinical signs of seneciosis and did not have meaningful serum enzyme changes. However, feedings of the plant that provided 15 to 20 mg of PA/kg/day or more (gavaged or fed in capsules for the same time period) resulted in high mortality. The Senecio plant mixed in calves' hay ration was eaten slowly and reluctantly and was tolerated at dosages greater than 20 mg/kg/day, emphasizing that the toxicity was dependent on the rate at which the dosage was consumed and that mortality was not necessarily dependent on the cumulative dosage. Because of its high PA content, S riddellii presents a great hazard to cattle managed under conditions where they can consume quantities of the plant in short periods of time.     

Failure of mineral-vitamin supplements to prevent tansy ragwort (Senecio jacobaea) toxicosis in cattle

The efficacy of 2 mineral-vitamin supplements in preventing or alleviating initial pyrrolizidine alkaloid (PA) toxicosis in cattle was tested. Three groups of calves were fed 1 of the 2 supplements plus tansy ragwort (Senecio jacobaea) containing PA and 2 groups of calves were fed tansy ragwort without the supplement. Toxicity comparisons were based on differences in observed clinical signs, serum enzyme changes, survival time of calves, and histopathologic examination of hepatic tissue. Typical tansy ragwort toxicosis terminating in death developed in all calves. There were no marked differences in responses of the groups of calves. Seemingly, the supplements did not afford protection or alleviate tansy ragwort-related PA toxicosis in calves.     

Milk transfer of pyrrolizidine alkoloids in cattle.

A study was conducted to determine if pyrrolizidine alkaloids from Senecio jacobaea (tansy ragwort) are passed into milk of lactating cows. Four cows were given dried tansy ragwort via rumen cannula at a dosage of 10 g/kg/day for 2 weeks. Chemical assay of pyrrolizidine alkaloid content in the dried plants averaged 0.16% by weight. By use of thin-layer chromatography, 5 alkaloids were isolated from the plant materials. The only alkaloid isolated from the milk was jacoline. Condition of the cows and nursing calves was monitored via measurement of blood leukocyte count, and serum protein, albumin, and globulin content. Sorbitol dehydrogenase values and liver biopsy specimens were used to assess liver function. In the cows, marked changes were observed in blood leukocyte count, sorbitol dehydrogenase values, and liver biopsy findings. No changes of any type were observed in the calves. Pyrrolizidine alkaloid content of the milk ranged from 9.4 to 16.7 mug/100 ml of milk.     

Serum liver enzyme and histopathologic changes in calves with chronic and chronic-delayed Senecio jacobaea toxicosis.

Progressive changes in serum enzyme activity and liver histologic features were monitored in calves fed tansy ragwort (Senecio jacobaea)-contaminated pellets. The experiments were designed to simulate natural intoxicant ingestion conditions in relationship to the dose and duration of exposure to the toxic plant to correlate early laboratory diagnostic changes with the natural progression of the disease, thereby facilitating early diagnosis and intervention by veterinary clinicians. Eight calves were fed tansy ragwort and 4 additional calves served as controls. In group 1, 4 calves were continuously fed dried tansy ragwort mixed in a pelleted feed at a 5% concentration by dry weight until terminal liver disease developed. Serum liver enzyme (alkaline phosphatase, glutamate dehydrogenase, and gamma-glutamyltransferase) activities were monitored at weekly intervals in these calves and in the 2 controls. In group 2, 4 calves were fed the same contaminated feed for only 60 days, with return to normal feed for the duration of the trial. Two additional calves served as controls. Their liver enzyme activities were monitored every other week in conjunction with percutaneous liver biopsies. All 8 calves fed tansy ragwort-contaminated pellets developed terminal hepatopathy in either a chronic pattern (n = 6) or a chronic-delayed pattern (n = 2), with the onset of a moribund state or sudden death at 11 to 17 weeks and 27 to 51 weeks, respectively. The calves were euthanatized when classic terminal signs of hepatic encephalopathy first became evident. The clinicopathologic patterns of chronic and chronic-delayed toxicoses were typical of over 5,000 cases of field tansy toxicosis diagnosed at the diagnostic laboratory. Serum glutamate dehydrogenase was the first enzyme to increase in most animals, with a short-term increase to peak values followed by a rapid return to normal. This enzyme change was followed by increases in alkaline phosphatase and gamma-glutamyltransferase. Serum enzyme changes preceded development of recognizable histologic lesions. Vacuolar changes in hepatocyte nuclei, biliary hyperplasia, and fibrosis sequentially developed in liver biopsy specimens from each animal, whereas megalocytosis was not a predominant feature until necropsy. On the basis of our findings, we suggest that the optimal tests for diagnosis of pyrrolizidine alkaloid intoxication should consist of liver biopsy and determination of concurrent serum liver-enzyme activities.     

Pyrrolizidine alkaloid-induced liver disease in horses: an early diagnosis

Nine adult horses were fed alfalfa hay cubes containing approximately 10% Senecio vulgaris until all horses had consumed approximately the same amount of toxic components of S vulgaris, pyrrolizidine alkaloids (PA). The amount of PA consumed was determined by the amount that induced clinical signs of PA toxicosis in 3 horses. The 6 other horses were given similar amounts per kilogram of body weight. An initial decrease of feed intake was observed when horses' diets were changed from alfalfa cubes to alfalfa/Senecio cubes, and feed intake was decreased further over 89 to 98 days. From 50 to 159 days, body weight decreased in all horses. Liver disease was induced in all 9 horses after they ate an average of 233 +/- 9.2 mg of PA/kg of body weight. Eight horses died or were euthanatized. Treatment with branched chain amino acids had no effect on mortality, but appeared to reduce neurologic problems. Clinical signs of PA-induced liver disease included ataxia, head pressing, and decreased feed intake. Other clinical signs of toxicosis were observed individual horses, but did not develop in most horses. Megalocytic hepatopathy developed. Liver abnormalities proceeded as PA was consumed and were severe in 8 of 9 horses before clinical signs of toxicosis appeared. Sulfobromophthalein sodium clearance did not decrease until PA-induced liver disease was advanced. Bile acid (BA) concentrations increased to greater than or equal to 50 mumol/L, in the 8 horses that died. One horse had hepatopathy and increased BA concentration, but survived. In this horse, BA concentration peaked at 33 mumol/L and then decreased.(ABSTRACT TRUNCATED AT 250 WORDS)     

SENECIO LAUTUS TOXICITY IN CATTLE

Mortalities and a poor growth syndrome in cattle in the Hunter River valley of New South Wales were associated with pyrrolizidine alkaloid toxicity caused by Senecio lautus (common fireweed). A clinical problem of poor growth rate on a large property, where S. lautus was very common, was associated with consistent evidence of some degree of hepatic pyrrolizidine alkaloid lesions in young growing cattle and cows. S. lautus subsp maritimus from this property caused the death of 2 experimentally fed calves within 77 days and depressed growth rate in a third calf. Pyrrolizidine alkaloidosis was evident histopathologically in the liver, biliary tree and gall bladder and other organs, especially kidney, of these calves. Histopathology of liver biopsy samples was the most sensitive monitoring technique of those used to indicate exposure to pyrrolizidine alkaloids in this investigation.     

The toxicity of Senecio inaequidens DC

This study was designed to confirm the toxicity of a plant implicated in an outbreak of poisoning of stock in Frankfort, Free State Province, South Africa. Cows died acutely after being introduced into a camp, where an abundant, green shrublet was noted to be heavily grazed. This plant was subsequently identified as Senecio inaequidens DC. (Asteraceae) by the South African National Biodiversity Institute (SANBI). Extraction and chemical analyses for pyrrolizidine alkaloids (PAs) in Senecio inaequidens revealed the presence of 4 different compounds, namely retrorsine and senecionine (known to be hepatotoxic) and 2 unidentified compounds. The average total PA (free base plus N-oxide) concentration in plant parts of S. inaequidens collected at Frankfort during the outbreak was 0.81%, compared with the total alkaloid content in the dried, milled S. inaequidens plant material, collected 7 weeks after the outbreak, of only 0.18%. Male Sprague-Dawley rats (n = 4), aged 8-9 weeks, were dosed per os. Each rat received a different dose of the crude Senecio inaequidens extract, ranging from 0.049 mg/g body weight (b.w.) to 0.25 mg/g b.w. No clinical signs were observed in the rat receiving the lowest dose. Rats receiving higher doses showed depression, an unsteady gait, pilo-erection and jaundice, which was particularly noticeable in the ears. Clinical chemistry evaluation revealed an increase in the activities of ALP (except Rat 4), AST and GGT in all animals. Total serum bilirubin, creatinine and urea concentrations were also elevated. All rats had low serum globulin concentrations with an A/G ratio above 1.2. Post mortem examination of the rats revealed marked hepatic lesions. Histopathologically, these changes were characterised by necrosis (variable in extent) of the centrilobular and midzonal hepatocytes (but sparing the portal hepatocytes), with extensive haemorrhage and congestion. Proliferation of the bile ducts, fibrosis and oedema were also present. Ultrastructural changes in affected rats were characterised by margination of chromatin, the presence of numerous autolysosomes in necrotic hepatocytes, intramitochondrial woolly inclusions and changes in the endoplasmic reticulum. A sheep, also dosed with the crude extract, failed to exhibit clinical signs, clinical chemistry aberrations or macroscopic lesions; however, examination of the liver of this sheep revealed histopathological and ultrastructural changes similar, though milder, to those displayed by the rats. Pyrrolizidine alkaloids were extracted from the liver and kidneys of the rats and the sheep. In the case of the sheep, retrorsine was also detected in the lungs, urine and bile.     

Selenium effects on glutathione peroxidase and the immune response of stressed calves challenged with Pasteurella hemolytica

The present study was conducted to determine whether a marginal Se deficiency affects health, blood characteristics and the immune response of calves subjected to stresses associated with weaning, shipping (332 km) and Pasteurella hemolytica inoculation. Treatments were 1) -Se, 2) -Se/P. hemolytica, 3) +Se (.1 mg Se/kg feed) and 4) +Se/P. hemolytica. Previous Se intake was controlled; dams of -Se calves were fed diets marginally deficient in Se (.03 to .05 mg/kg), whereas dams of +Se calves received a s.c. injection of 30 mg Se (as sodium selenite) every 60 d. Calves were inoculated with P. hemolytica intratracheally on d 3 following weaning and transport. Inoculation with P. hemolytica increased (P less than .05) body temperatures, platelet counts, serum IgM concentrations and serum antibody titers and decreased serum albumin concentrations at 4 to 7 d postinoculation. Weight gains for the 21-d study were not affected by Se status, although whole blood and plasma glutathione peroxidase (GSH-Px) were higher (P less than .05) for +Se calves. Plasma GSH-Px increased (P less than .01) in calves showing signs of morbidity. Increases in plasma GSH-Px were correlated positively with body temperature. Serum IgM concentrations were higher (P less than .05) in +Se calves on d 17, but Se-supplemented calves had lower (P less than .05) anti-P. hemolytica titers on d 17 than -Se calves. Selenium status did not affect body temperatures, plasma creatine phosphokinase or serum IgG and albumin concentrations. These results indicate that Se status can affect IgM concentrations following stress.     

Clinical effectiveness of tulathromycin, a novel triamilide antimicrobial, for the control of respiratory disease in cattle at high risk for developing bovine respiratory disease

The efficacy of tulathromycin in decreasing the incidence of morbidity and mortality due to bovine respiratory disease (BRD) in 1,239 high-risk cattle was investigated at four US feedlots. Calves not exhibiting clinical signs of BRD received one of three treatments administered subcutaneously in the neck: physiologic saline at 0.02 ml/kg, tulathromycin at 2.5 mg/kg, or tilmicosin at 10 mg/kg. Each treatment group consisted of 413 calves. Calves with clinical signs of BRD and rectal temperatures of 104 degrees F or higher on days 1 through 14 were considered treatment failures (BRD morbidity). Nasopharyngeal swabs from saline-treated morbidities were submitted for isolation and identification of BRD organisms. Respiratory disease morbidity was highest in calves treated with saline and significantly (P < or = .0001) lower in calves administered tulathromycin or tilmicosin. Morbidity from BRD was significantly (P < or = .0001) higher in calves treated with tilmicosin than in calves treated with tulathromycin. Under conditions of this study, tulathromycin, given to calves at high risk of developing BRD, was significantly more effective in reducing BRD morbidity when compared to both saline- and tilmicosin-treated calves.     

Effects of dietary supplementation with butylated hydroxyanisole, cysteine, and vitamins B on tansy ragwort (Senecio jacobaea) toxicosis in ponies

Dried tansy ragwort, which contains pyrrolizidine alkaloids, was fed as 10% of a complete diet to ponies, with and without a mixture of additives. The additives provided a dietary supplement equivalent to 1% cysteine, 0.75% butylated hydroxyanisole, 200 micrograms of vitamin B12/kg of feed, and 5 mg of folic acid/kg of feed. The additives did not alter tansy ragwort toxicity, as assessed by survival time, liver changes, sulfobromophthalein (BSP) clearance rate, serum gamma-glutamyl transpeptidase activity, and plasma amino acid patterns. In ponies fed tansy ragwort, BSP clearance rate was a sensitive indicator of liver damage, and decreased to about 20% of control values. gamma-Glutamyl transpeptidase activities showed considerable variability, but generally were elevated in animals fed tansy ragwort. Liver iron and copper concentrations increased, and liver zinc concentrations decreased in tansy ragwort-fed ponies. Plasma amino acid patterns in tansy ragwort-fed ponies showed changes typical of those observed in liver disease.     

Influence of supplemental selenium on humoral immune responses in weaned beef calves

Influence of supplemental Se on humoral immune response was measured in 60 weaned beef calves with marginal blood Se status. Calves were fed a Se-deficient diet consisting of corn silage, corn grain, and soybean meal. Blood Se concentrations, primary and secondary humoral immune responses to hen egg lysozyme inoculation, and weight gain were determined in a 70-day trial. Calves fed 20 mg of Se/kg of mineral mixture ad libitum had lower antibody responses (P less than 0.02), compared with calves fed 20 mg of Se/kg of mineral mixture and given 0.1 mg of Se and 0.22 IU of vitamin E/kg of body weight, IM, or with calves fed 80, 120, 160, or 200 mg of Se/kg of mineral mixture. Calves fed 80, 120, 160, or 200 mg of Se/kg of mineral mixture had higher (P less than 0.001) blood Se concentrations on day 70, compared with calves fed 20 mg of Se/kg of mineral mixture and given 0.1 mg of Se and 0.22 IU of vitamin E/kg of body weight, IM. Selenium supplementation had no effect on weight gain.     

Hound's-tongue (Cynoglossum officinale) poisoning in a calf

Cynoglossum officinale was believed to be responsible for the death of one calf and possibly 5 other calves in a group of 9 calves being fed chopped hay contaminated by this plant. The plant, commonly known as hound's tongue, contains pyrrolizidine alkaloids and has been determined to be toxic to horses fed contaminated hay, but was fed to cattle at the same time with no effect.     

Economic analysis of feeding pasteurized nonsaleable milk versus conventional milk replacer to dairy calves

OBJECTIVE: To determine growth, morbidity, and mortality rates in dairy calves fed pasteurized nonsaleable milk versus commercial milk replacer and compare economics of feeding pasteurized nonsaleable milk versus commercial milk replacer in dairy calves. DESIGN: Clinical trial. ANIMALS: 438 dairy calves. PROCEDURE: Calves were assigned at 1 to 2 days of age to be fed pasteurized nonsaleable milk or a commercial milk replacer until weaned. Body weight was measured at the time of study enrollment and at the time of weaning, and any medical treatments administered and deaths that occurred prior to weaning were recorded. A partial budget model was developed to examine the economics of feeding pasteurized nonsaleable milk versus commercial milk replacer. RESULTS: Calves fed conventional milk replacer had significantly lower rates of gain (-0.12 kg/d [-0.26 lb/d]), lower weaning weights (-5.6 kg [-12.3 lb]), higher risk for treatment during the summer and winter months (odds ratio [OR], 3.99), and higher risk of death during the winter months (OR, 29.81) than did calves fed pasteurized nonsaleable milk. The estimated savings of feeding pasteurized nonsaleable milk, compared with milk replacer, was dollars 0.69/calf per day. The estimated number of calves needed to economically justify the nonsaleable milk pasteurization system was 23 calves/d. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that dairy calves fed pasteurized nonsaleable milk have a higher growth rate and lower morbidity and mortality rates than do calves fed conventional milk replacer. Feeding pasteurized nonsaleable milk could be an economically viable strategy for dairy calf producers.     

Effects of dietary supplementation with ethoxyquin, magnesium oxide, methionine hydroxy analog, and B vitamins on tansy ragwort (Senecio jacobaea) toxicosis in beef cattle

Dried tansy ragwort containing pyrrolizidine alkaloids was fed as 2.5% of a complete (control) diet to Hereford steers, with and without (basal) a mixture of additives. The additives provided a dietary supplement equivalent to 0.1% ethoxyquin, 1% methionine hydroxy analog, 2% MgO, 2.7 mg of vitamin B6/kg of diet, 50 micrograms of vitamin B12/kg of diet, 0.45 g of folic acid/kg of diet, and 0.2 g of cobalt/kg of diet. The additives did not alter tansy ragwort toxicity substantially, as assessed by liver histologic changes, sulfobromophthalein clearance rate, and serum gamma-glutamyl transpeptidase activity. After 281 days, 1 of 4 steers fed the basal diet was alive, whereas 3 of 4 steers in the basal plus additives group were alive, suggesting some protective activity. The chronic lethal dose of tansy ragwort in steers was 3.6% of initial body weight.     

Pyrrolizidine alkaloids and seneciosis in farm animals. part 1: occurrence, chemistry and toxicology

Pyrrolizidine alkaloids belong to a class of phytotoxins which are present in more than 6000 plant species. The disease seneciosis in farm animals represents the severe poisoning by pyrrolizidine alkaloids from plants of the genus Senecio. This form of poisoning has been known since the end of the 19th century in Germany, the USA, Canada and New Zealand, and is mainly caused by Senecio jacobaea and related Senecio spp. in farm animals, including poultry. Animal poisoning by pyrrolizidine alkaloids is of worldwide importance. In Germany poisoning of horses and cattle by Senecio jacobaea, which was earlier named Schweinsberg disease, is of renewed relevance for veterinary medicine. The disease occurs almost entirely as a consequence of chronic poisoning and in general ends fatally. The ultimate cause is the formation of toxic metabolites of pyrrolizidine alkaloids in the liver, and their covalent binding to nucleic acids and proteins leading to liver cirrhosis. Because many pyrrolizidine alkaloids possess mutagenic, and a few also carcinogenic properties, European and international authorities are concerned about possible residue levels in food of animal origin. The review addresses in its first part several aspects, being the occurrence, the chemistry, and the toxicology of pyrrolizidine alkaloids as well as animal intoxications by poisonous plants. In the second part (46) clinical characteristics of animal seneciosis, the therapeutic interventions, the significant species differences and a critical assessment of so-called nontoxic amounts of Senecio plants in animal fodder with reference to cumulative lethal toxin doses are presented.     

Effects of lasalocid on coccidial infection and growth in young dairy calves.

Effects of lasalocid on coccidial infection and on calf growth were examined in 16 Holstein bull calves. Calves were assigned randomly to a 2 x 2 factorial arrangement of starter ration containing 0 or 40 mg of lasalocid/kg of starter, beginning when calves were 3 days old (SE = 0.046), and single oral inoculation with 0 or 30,000 sporulated oocysts (Eimeria bovis) at 28 days. Pelleted calf starter was fed ad libitum from day 1; milk replacer was fed at a rate of 3.6 kg/d until day 28. Mean daily gain, dry-matter intake, and body weight were increased in calves fed lasalocid and decreased in those inoculated with coccidia. Addition of lasalocid to the feed improved gains by 8% in uninoculated calves and by 50% in inoculated calves. Fecal oocyst numbers were reduced when lasalocid was fed to inoculated calves. Feces were more abnormal in calves inoculated with coccidia. Respiration rates, rectal temperatures, PCV, and serum sodium and potassium concentrations were unaffected by treatment. On the basis of findings in this study, lasalocid minimized effects of coccidial challenge inoculation and increased growth of calves.     

Nutritional and toxicological evaluations of kochia hay (Kochia scoparia) fed to lambs

Kochia foliage that had tested positive to Dragendorff's reagent (presumptive alkaloids) and had elicited chronic toxicosis when fed to rats was fed to sheep to characterize early stages of kochia toxicosis and evaluate treatments that might improve tolerance. Twelve fine-wool lambs (46 +/- 9 kg BW) were fed chopped kochia hay (35%) mixed with chopped alfalfa hay (65%) for 4 wk. The kochia diet had 14.3% CP and 39.9% ADF. Dry matter intake averaged 3.4% of BW/d. Body weight did not change during 4 wk and blood serum components were not changed from values at the onset. Thereafter, kochia was increased to 50% of diet for five more weeks, during which four treatments were imposed randomly (three lambs/treatment): 1) none; 2) N-acetyl-L-cysteine plus trans-stilbene oxide, 21 and 52 mg/kg of BW, respectively, given i.p. twice weekly; 3) retinyl palmitate, 275 mg, plus alpha-tocopherol, 300 mg/lamb dosed i.m. twice weekly; and 4) zinc sulfate mixed in the feed to provide 500 mg daily. Kochia contained 4.8% oxalate. The diet with 50% kochia had 16% CP and 36% ADF, and digestibility coefficients were 59% for DM, 72% for CP, and 59% for ADF. After 5 wk, blood glucose was elevated slightly, total bilirubin was increased about 1.5-fold (P less than .05), alanine aminotransferase was elevated slightly (P less than .05), and inorganic phosphorus and urea (blood urea N) were diminished (P less than .05); other serum components, including calcium, were unchanged from initial levels (P greater than .10). Treatments had negligible effects for modifying serum signs of mild chronic toxicosis associated with kochia hay fed as 50% of diet.     

Effect of dietary chromium-L-methionine on glucose metabolism of beef steers

Thirty-six crossbred steers (288 +/- 3.7 kg initial BW) were used to determine the effect of Cr, as chromium-L-methionine, on glucose tolerance and insulin sensitivity in beef calves. Calves were fed a control diet or the diet supplemented with 400 or 800 microg Cr/kg of diet as chromium-L-methionine. Calves were kept in drylots (six calves/pen; two pens/dietary treatment). Steers were caught twice a day in locking headgates and individually fed their respective diets for a period of 22, 23, or 24 d prior to the metabolic challenges. Calves received a totally mixed diet containing 54% corn, 38% cottonseed hulls, and 5% soybean meal. On d 21, 22, and 23, four calves/dietary treatment were fitted with an indwelling jugular catheter. Approximately 24 h after catheterization, an intravenous glucose tolerance test (500 mg glucose/kg of BW), followed 5 h later by an intravenous insulin challenge test (0.1 IU insulin/kg of BW), was conducted. There was no effect (P > 0.10) of dietary treatment on ADG or ADFI. During the intravenous glucose tolerance test, serum insulin concentrations were increased by supplemental chromium-L-methionine (linear effect of Cr, P < 0.05). There was a time x treatment interaction (P < 0.05) on plasma glucose concentrations after the glucose infusion. Plasma glucose concentrations of calves fed 400 microg Cr/kg of diet were lower than those of controls and calves supplemented with 800 microg Cr/kg of diet (quadratic effect of Cr, P < 0.05) 5 and 10 min after the glucose infusion. Supplemental chromium-L-methionine increased the glucose clearance rate from 5 to 10 min after the insulin challenge test (linear effect of Cr, P < 0.05). Glucose half-life from 5 to 10 min after the insulin infusion was also decreased by supplemental chromium-L-methionine (linear effect of Cr, P < 0.10). These data indicate that supplemental Cr, as chromium-L-methionine, increased glucose clearance rate after an insulin infusion and increased the insulin response to an intravenous glucose challenge in growing calves with functioning rumens.     

Influence of dietary protein on blood cholesterol and related metabolites of growing calves

Forty male, Holstein calves were utilized to evaluate effects of either low (12%) or high (25%) dietary protein on growth and serum metabolites, with a particular concern for serum cholesterol. All diets contained 19% acid detergent fiber and consisted of corn silage, alfalfa hay and grain mixtures. Average concentration of total serum cholesterol was depressed (P = .001) for calves on the high-protein diets (58.8 mg/dl) as compared with their low-protein counterparts (67.9 mg/dl). Calves fed the high-protein diet had lower (P = .002) free serum cholesterol but elevated high-density lipoprotein cholesterol as a percentage of total cholesterol. Calves receiving the high-protein diets showed increases (P = .206) in lecithin cholesterol acyltransferase activity compared with low-protein counterparts. Serum urea nitrogen was increased (P = .001) for calves fed high-protein diets, while serum protein and glucose remained unchanged. Calves fed the high-protein diets consumed less dry matter with improved (P = .09) growth efficiency (gain/feed).     

Effects of intermittent and continuous administration of decoquinate on bovine coccidiosis in male calves

Male Holstein calves were each inoculated with 350,000 sporulated oocysts of Eimeria bovis. Two calves were given decoquinate (0.5 mg/kg of body weight) continuously in dry feed for 29 days, and 2 calves each were given 0.5, 1, or 1.5 mg of decoquinate/kg on an every 2nd-or 3rd-day schedule for 29 days. Calves given decoquinate continuously did not discharge oocysts but had slightly loose feces. In general, the number of oocysts discharged increased and fecal consistency decreased as the time between feeding of medicated feed increased. Calves given 0.5 or 1.5 mg of decoquinate/kg every 3rd day discharged more oocysts and had more diarrhea than did calves given 1 mg of decoquinate/kg every 3rd day. At postinoculation day 29, calves were euthanatized. At necropsy, intestinal tissues of calves given decoquinate were mostly normal. Apparently, reduced infections along with the elapsed time were sufficient to resolve most intestinal lesions caused by the coccidia. Decoquinate was most effective when fed continuously at 0.5 mg/kg. However, when fed at 1 or 1.5 mg of decoquinate/kg every 2nd day or 1.5 mg of decoquinate/kg every 3rd day, oocyst production was reduced and clinical coccidiosis was prevented.