Enzymes Sériques pour le Diagnostic de la Nécrose Hépatique Aigüe Expérimentale

The activity of certain serum enzymes ornithine carbamyl transferase (OCT), serum isocitric dehydrogenase (SIC-D), total serum lactic dehydrogenase (LDH) and its isoenzymes (LD₁ and LD₅) was evaluated as a mean of assessing experimental hepatic necrosis on dogs treated with CCl₄. Measurement of activity levels of these enzymes, seldom carried out in veterinary clinical pathology, was made together with tests commonly used in our laboratories: serum glutamic pyruvic transaminase (SGPT), serum glutamic oxalacetic transaminase (SGOT) and serum alkaline phosphatase (SAP), cholesterol, bilirubin and prothrombin time. Measurement of the level of OCT was useful in the diagnosis of liver necrosis. The SIC-D level was important during the first four days of the experiment, but on subsequent days, the enzymatic activity was practically normal. Because of the wide variations of LDH serum levels in normal animals and since many factors influence its activity, the measurement of this enzyme and its isoenzymes was not a good index in the diagnosis of canine liver necrosis. The evaluation of cholesterol and bilirubin was judged of secondary importance because these metabolites are not specific to hepatic problems.     

Characterization of the humoral immune response in alpacas (Lama pacos) experimentally infected with Fasciola hepatica against cysteine proteinases Fas1 and Fas2 and histopathological findings

A characterization of the humoral immune response of alpacas to Fasciola hepatica Fas1 and Fas2 antigens, two abundant cysteine proteinases in the excretory/secretory (E/S) products, was performed over the course of 6 months of experimental infection. Six adult alpacas aged 1-2 years old received a single dose of 200 F. hepatica metacercariae; two non-infected alpacas were kept as control group. All infected animals shed eggs 8 weeks post-infection (PI) and the number of flukes recovered at necropsy averaged 41+/-4. The livers of infected animals showed regions with chronic inflammation, granuloma containing parasite eggs, necrosis and cirrhosis. Peripheral eosinophilia in infected animals was greatly enhanced 6 weeks post-infection and later. A single peak of serum glutamic piruvic transaminase (SGPT) was observed 4 weeks PI and serum glutamic oxalacetic transaminase (SGOT) elevated 3 weeks PI and later. Circulating IgG Abs against Fas1 and Fas2 were measured by enzyme-linked immunosorbent assay (ELISA). Fas2-ELISA detected the infection 10 days PI reaching to highest titer on 7-8 weeks PI and kept elevated, until the end of infection. Fas1-ELISA detected the infection 2 weeks PI and followed the same pattern as Fas2-ELISA. Anti Fas2 IgG Abs were in higher titers and showed stronger avidity than anti Fas1 IgG Abs. In addition, rabbit IgG antibodies raised against cysteine proteinase Fas2 showed infiltration of this parasite antigen associated to the degradation of bile ducts and liver parenchyma of infected alpacas. In the present study we have established a F. hepatica experimental infection of alpacas, Fas2 appears to have a role in the pathogenesis of the liver damage in alpacas caused by the liver fluke. Infected alpacas elicited a strong humoral immune response against fluke cysteine proteinases Fas1 and Fas2, which might be considered as candidates for immunodiagnosis and vaccine development against fasciolosis in alpacas.     

Serological changes in goats experimentally infected with Fasciola gigantica in Buea sub-division of S.W.P. Cameroon

Based on the recent increase in the rearing of West African Dwarf (WAD) goats in this environment, a study of biochemical parameters was carried out in healthy and infected goats to obtain baseline data for monitoring the health and productive indices in breeding programmes for the goats. The results revealed variations in some of the parameters studied. The serum minerals potassium, chlorine and bicarbonate did not show any significant differences (P>0.05) between the infected and control groups of goats, but there was a significant difference (P<0.0001) in sodium, calcium and urea levels. For serum lipids cholesterol and triglyceride, there were significant (P<0.0001) differences between the infected and control group. This goes same for serum proteins, albumin and total proteins. However, serum enzymes, serum glutamic oxaloacetic transaminase (SGOT) and gamma glutamyl transferase (GGT) were not significantly different (P>0.05) between the infected and control groups. There was a significant difference (P<0.0001) in alkaline phosphatase (ALP) and serum glutamic pyruvic transaminase (SGPT) between the infected and control groups.     

Hepatotoxicity of stanozolol in cats

OBJECTIVE: To determine hepatotoxicity of stanozolol in cats and to identify clinicopathologic and histopathologic abnormalities in cats with stanozolol-induced hepatotoxicosis. DESIGN: Clinical trial and case series. ANIMALS: 12 healthy cats, 6 cats with chronic renal failure, and 3 cats with gingivitis and stomatitis. PROCEDURES: Healthy cats and cats with renal failure were treated with stanozolol (25 mg, i.m., on the first day, then 2 mg, p.o., q 12 h) for 4 weeks. Cats with gingivitis were treated with stanozolol at a dosage of 1 mg, p.o., every 24 hours. RESULTS: Most healthy cats and cats with renal failure developed marked inappetence, groomed less, and were less active within 7 to 10 days after initiation of stanozolol administration. Serum alanine transaminase (ALT) activity was significantly increased in 14 of 18 cats after stanozolol administration, but serum alkaline phosphatase activity was mildly increased in only 3. Four cats with serum ALT activity > 1,000 U/L after only 2 weeks of stanozolol administration had coagulopathies; administration of vitamin K resolved the coagulopathy in 3 of the 4 within 48 hours. All 18 cats survived, and hepatic enzyme activities were normal in all cats tested more than 4 weeks after stanozolol administration was discontinued. Two of the 3 cats with gingivitis developed evidence of severe hepatic failure 2 to 3 months after initiation of stanozolol treatment; both cats developed coagulopathies. Histologic evaluation of hepatic biopsy specimens from 5 cats revealed diffuse hepatic lipidosis and cholestasis without evidence of hepatocellular necrosis. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that stanozolol is hepatotoxic in cats.     

Detection of biofilm formation and nanobacteria under long-term cell culture conditions in serum samples of cattle,goats, cats,and dogs

OBJECTIVE: To determine the prevalence of biofilm formation under long-term cell culture conditions in serum samples of dairy cattle, goats, cats, and dogs, and to determine whether there is an association between nanobacteria and biofilm formation. SAMPLE POPULATION: Serum samples of clinically normal animals (313 dairy cattle, 48 goats, 140 dogs, and 44 cats) and animals with various medical conditions (60 dogs and 116 cats). PROCEDURE: Serum was incubated under cell culture conditions and observed for biofilm formation by use of light microscopy, electron microscopy, and spectroscopy. A polymerase chain reaction assay was developed to identify 16S rRNA gene sequences of nanobacteria. RESULTS: Biofilm formation developed in serum samples of 304 of 313 (97%) cattle, 44 of 48 (92%) goats, 44 of 44 (100%) cats, and 126 of 140 (90%) dogs. Prevalence of serum samples with positive results for biofilm formation was not significantly different between cats or dogs with and without medical conditions associated with pathologic extraskeletal calcification processes. Scanning electron microscopy and spectroscopy of biofilm samples revealed small coccoid particles consisting mainly of calcium and phosphate. Polymerase chain reaction assay failed to amplify sequences of nanobacteria. CONCLUSIONS AND CLINICAL RELEVANCE: Under long-term cell culture conditions, biofilm made up of aggregates of calcium and phosphate crystals does form in serum samples of clinically normal dairy cattle, goats, cats, and dogs. Disease, however, does not predispose to biofilm formation in serum samples of dogs and cats. Our findings did not support the existence of nanobacteria in serum samples of cattle, goats, cats, and dogs.     

A Comparison of Serum Creatine Phosphokinase and Serum Glutamic Oxalacetic Transaminase in Skeletal Muscle Necrosis

Rabbits were poisoned by the intraperitoneal injection of plasmocid dihydroiodide at a dosage of 80 mg. per kg. body weight. Animals were euthanatized 1, 2, 5, 7, 9, 12, 24 and 48 hours after plasmocid injection and serum and diaphragmatic muscle collected. The serum was examined for its serum glutamic oxalacetic transaminase (SGOT) and creatine phosphokinase (CPK) concentrations. The diaphragm was sectioned and examined for the progression of morphologic alterations. It was found that SGOT and CPK concentrations were similar in their time and duration of elevation and that the serum CPK elevations closely paralleled the occurrence and degree of morphologic muscle degeneration. It appears that CPK is the most specific clinical biochemical test for the detection of muscle necrosis available at this time.     

Prevalence of Listeria monocytogenes in intestinal contents of healthy animals in Japan.

A total of 1,705 fecal specimens or ileo-cecal contents of cattle, pigs, dogs, cats, chicken and rats were submitted for the isolation of Listeria monocytogenes by the use of the combination of Oxford-LPM agar plates after the cold enrichment in PBS at 4 degrees C for 4-6 weeks. Prevalence of L. monocytogenes was found to be 1.9% in cattle, 0.6% in pigs, 0.9% in dogs and 6.5% in rats. However, none of L. monocytogenes was isolated from chicken or cats. Among 26 isolates of L. monocytogenes, 13 strains (50%) were classified into types 1/2a (3 strains), 1/2b (5 strains) and 4b (5 strains) and were often associated with human listeriosis. The majority of the Listeria spp. other than L. monocytogenes isolated from these animals was found to be L. innocua.     

Effect of ruminally protected methionine on body weight gain and growth of antlers in red deer (<Emphasis Type="Italic">Cervus elaphus</Emphasis>) in the humid tropics

Sixteen male red deer (Cervus elaphus), with an initial weight of 93.83 ± 4.38 kg were used to study the effect of the dietary level of ruminally protected methionine (RPM) on growth, antler morphometry and serum metabolites. The deer were allowed to graze and were individually supplemented with concentrate to provide 0, 2.5, 3.5 or 4.5 g/day of RPM for 65 days. There was a quadratic effect on daily weight gain (0.163, 0.098, 0.147 and 0.172 kg/day; P < 0.005) and antler beam length (59.7, 63.6, 63.0 and 57.2 cm; P < 0.02) for RPM levels of 0 to 4.5 g/day, respectively. The brow tine length and the number of points were similar across all treatments. Serum glutamic pyruvate transaminase (SGPT) was reduced (quadratic effect; P < 0.02; 22.0, 29.6, 18.0 and 17.8 IU/l) to RPM levels of 0 to 4.5 g/day, respectively, whereas other metabolites (glucose, cholesterol, urea, creatinine, total protein and serum glutamic oxaloacetic transaminase [SGOT]) were unchanged. Increasing the RPM dose did not affect weight gain or antler growth. Methionine supplementation reduced the activity of SGPT.     

Alterations in selected serum biochemical constituents in equids after induced hepatic disease

Effects of induced cholestasis and hepatocellular necrosis and of fasting on serum biochemical constituents including bile acids, IgA, bilirubin, alkaline phosphatase, gamma-glutamyltransferase (GGT), arginase, and the clearance of sodium sulfobromophthalein were studied in 4 groups of equids. The reference value for serum bile acids, as determined by an enzymatic colorimetric procedure for horses and ponies was 5.94 +/- 2.72 mumol/L, there being no statistical difference for horses and ponies. Sample collection at time of feeding had no effect on serum bile acid concentration. Seemingly, serum bile acids, arginase, and GGT were the most sensitive indicators of cholestasis and/or hepatocellular necrosis and would form an essential minimum effective battery of tests to diagnose and prognose hepatic disease in equids. These tests provided a measure of hepatobiliary transport function (bile acids), cell necrosis (arginase), and cholestasis (GGT and bile acids).     

Blood cellular and biochemical studies in canine dirofilariasis

Haematological studies in heartworm-infected dogs revealed low haemoglobin concentration, increased erythrocyte sedimentation rate and a marked increase in lymphocyte percentage. Biochemical analysis of serum of dogs infected with heartworm showed increases in serum total bilirubin, serum globulin, chloride, phosphorus, serum glutamic oxaloacetic transaminase and serum glutamic pyruvic transaminase values and a decrease in albumin content.     

Bile acid concentrations in the diagnosis of hepatobiliary disease in the cat

The clinical usefulness of measuring serum bile acid concentrations as a diagnostic test for hepatobiliary disease was examined in 80 cats that were suspected of having hepatic disease. Serum values of total bilirubin, alkaline phosphatase (ALP), alanine transaminase (ALT), and aspartate transaminase (AST) also were measured. Fasting serum bile acid values were determined by use of solid-phase radioimmunoassay for total conjugated bile acids or by a direct enzymatic spectrophotometric method. A definitive diagnosis was established by histologic examination of the liver, and on the basis of these findings, cats were assigned to groups (1 to 8, respectively) including: extrahepatic bile duct obstruction, hepatic lipidosis, cirrhosis, intrahepatic cholestasis (cholangiohepatitis, cholangitis), neoplasia, hepatic necrosis, portosystemic vascular anomalies, and miscellaneous. Cats in group 8 had no morphologic evidence of hepatobiliary disease or had hepatic lesions that were mild. Test efficacy of fasting serum bile acids, total bilirubin, ALP, ALT, and AST were expressed by use of 4 indices: sensitivity, specificity, positive predictive value, and negative predictive value. The diagnostic efficacy of fasting serum bile acids was examined alone and in combinations with the other tests. There was wide overlapping of values of fasting serum bile acids, total bilirubin, ALP, ALT, and AST among cats in groups 1 to 7. The specificity of fasting serum bile acids for the diagnosis of hepatic disease exceeded 90% at values greater than or equal to 5 mumol/L and reached 100% at greater than or equal to 15 mumol/L.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevalence and risk factors of Japanese encephalitis virus (JEV) in livestock and companion animal in high-risk areas in Malaysia

Japanese encephalitis (JE) is vector-borne zoonotic disease which causes encephalitis in humans and horses. Clinical signs for Japanese encephalitis virus (JEV) infection are not clearly evident in the majority of affected animals. In Malaysia, information on the prevalence of JEV infection has not been established. Thus, a cross-sectional study was conducted during two periods, December 2015 to January 2016 and March to August in 2016, to determine the prevalence and risk factors in JEV infections among animals and birds in Peninsular Malaysia. Serum samples were harvested from the 416 samples which were collected from the dogs, cats, water birds, village chicken, jungle fowls, long-tailed macaques, domestic pigs, and cattle in the states of Selangor, Perak, Perlis, Kelantan, and Pahang. The serum samples were screened for JEV antibodies by commercial IgG ELISA kits. A questionnaire was also distributed to obtain information on the animals, birds, and the environmental factors of sampling areas. The results showed that dogs had the highest seropositive rate of 80% (95% CI: ±?11.69) followed by pigs at 44.4% (95% CI: ±?1.715), cattle at 32.2% (95% CI: ±?1.058), birds at 28.9% (95% CI: ±?5.757), cats at 15.6% (95% CI: ±?7.38), and monkeys at 14.3% (95% CI: ±?1.882). The study also showed that JEV seropositivity was high in young animals and in areas where mosquito vectors and migrating birds were prevalent.     

Neutralizing antibody to bovine rotavirus in various animal species

A total of 288 serum samples were collected from 12 species of animals in various localities of Japan from 1975 to 1977. Neutralizing antibody to bovine rotavirus was found in serum samples from all the species, viz., horses, cattle, sheep, goats, pigs, dogs, rabbits, guinea pigs, rats, mice, chickens and human beings. The incidence of neutralizing antibody in titers of 1 : 2 or higher ranged from 31 to 100%, and high incidences exceeding 70% were obtained in horses, cattle, sheep, pigs, dogs, rabbits and human beings. High titers were most common in horses, cattle, sheep and pigs. These serological results suggest that rotaviruses occur commonly in these species of animals.     

A multipronged approach for the detection of leptospirosis in captive sloth bears (Melursus ursinus) in Agra and Bannerghatta sloth bear rescue centers in India

Leptospirosis is an exacerbating factor responsible for the drastic decline of sloth bear population in India. In this study, a multipronged approach based on antigen detection using Polymerase Chain Reaction (PCR) employing G1/G2 and LigBF/LigBR primers, antibody detection using Microscopic Agglutination Test (MAT) and recombinant LigBCon1-5 antigen based Latex Agglutination Test (rLigBCon1-5 LAT), serum biochemistry using hepatic (serum glutamate oxalo acetic transaminase (SGOT) and serum glutamate pyruvic transaminase (SGPT) and renal biomarkers (blood urea nitrogen (BUN) and Creatinine) and gross/histopathological evidence in liver and kidneys were employed to investigate leptospirosis in captive sloth bears. A total of 133 serum samples collected from Agra (n=113) and Bannerghatta (n=20) sloth bear rescue centers were screened using MAT and rLigBCon1-5 LAT. A total of 87 and 78 sera tested positive by MAT and LAT respectively. Pyrogenes was the leading serovar obtained using MAT followed by Icterohaemorrhagiae, Javanica, Grippotyphosa, Canicola and Tarassovi. The relative sensitivity, specificity and accuracy of rLigBCon1-5 LAT in comparison to MAT were 89.66%, 100% and 93.23% respectively. PCR performed on hepatic and renal tissues showed amplicon of 285 and 219 base pairs for G1/G2 and LigBF/LigBR primers respectively. Gross evidence (icteric liver, severely engorged hepatic sinusoids, congested kidneys with necrotic white spots on sub capsular surface), histopathology (severe hepatic degeneration and tubulointerstitial nephritis) and elevated hepatic/renal biomarkers were suggestive of leptospirosis. This study suggests that rLigBCon1-5 LAT can be employed as a pen-side test for detecting leptospirosis in sloth bears.     

Distribution and genetic variability among Campylobacter spp. isolates from different animal species and humans in Switzerland

In Switzerland, a national database with 1028 Campylobacter isolates from poultry, pigs, cats, dogs, cattle, humans, zoo animals and water has been created. The database contains the genetic fingerprint and background information of each Campylobacter isolate. Dominant species could be identified in the different sources with a majority of Campylobacter jejuni in poultry (73%), humans (79%), cattle (95%), zoo animals (40%) and water (100%), of Campylobacter coli in pigs (72%), and of Campylobacter upsaliensis/helveticus in cats and dogs (55%). The comparison of three genotyping methods, amplified fragment length polymorphism (AFLP), pulsed field gel electrophoresis and restriction fragment length polymorphism, revealed that AFLP allows discrimination between the different Campylobacter species and is the most appropriate method to distinguish specific strains within the same species. Genotyping analysis demonstrated that the Campylobacter population is heterogeneous among the different sources and that no dominant clone is spread in the country. Genotyping and the resulting database are useful tools to trace back future Campylobacter infections.     

Investigation of domestic animals and pets as a reservoir for intimin- (eae) gene positive Escherichia coli types

Domestic animals belonging to seven different species (cattle, sheep, dogs, cats, pigs, chicken and goats) were investigated as natural reservoirs for attaching and effacing Escherichia coli (AEEC). For this, 2165 E. coli strains from faeces of 803 animals were examined for the presence of the intimin -(eae) gene as a characteristic of AEEC strains. Ten percent of the animals were found to excrete AEEC, most frequently found in sheep (19.2%) and pigs (17.6), followed by cattle (10.4%), dogs (7.2%), cats (6.5%) and poultry (2.3%). The 97 AEEC strains from animals were grouped into 44 serotypes. Only four E. coli serotypes (O2:H8, O26:[H11], O109:[H25] and O145:[H28] were found in more than one animal host species. AEEC O26:[H11] strains were most frequently isolated (13.4%) being present in cattle, poultry, pigs and sheep. A search for virulence markers associated with enterohemorrhagic E. coli (EHEC) revealed Shiga-toxin genes in three (3.1%) AEEC strains from sheep. Bundle forming pili genes as a trait of typical enteropathogenic E. coli (EPEC) were detected in four (4.1%) strains from dogs and cats. The remaining 90 AEEC strains were classified as atypical EPEC. Typing of intimin genes revealed intimin beta being present in 51.5% of the strains, followed by intimins theta (23.7%), epsilon (6.2%), kappa (5.2%), zeta (5.2%), alpha, eta and iota (each 1.0%). Our data indicate that domestic animals and pets constitute an important natural reservoir of AEEC strains, and some of these (O26:[H11], O103:H2, O128:H2, O145:[H28] and O177:[H11]) are known to occur as pathogens in humans.     

Hematologic changes induced by intravenous administration of diacetoxyscirpenol in pigs, dogs, and calves

Diacetoxyscirpenol (DAS) was given IV to pigs (0, 0.5, and 1.0 mg/kg of body weight), cattle (0 and 0.5 mg/kg), and dogs (0 and 0.5 mg/kg). Blood was collected and hemograms were done at 0.5-hour intervals for 8 hours. The animals were euthanatized at 8 hours after treatment, and bone marrow samples were taken and examined by light microscopy. Moderate to severe necrosis of bone marrow hematopoietic elements was found in animals given DAS. The sequential increase in the type and number of abnormal cells in the blood suggested a successive destruction of the hematopoietic elements. A marked left shift in the neutrophil population was found in animals given DAS. Metarubricytes and large platelets were found in the blood of animals given DAS. Lymphocytes were replaced with immature cells. Pathologic changes were most severe in the pigs given a dosage of 1.0 mg of DAS/kg. The order of species sensitivity to DAS was pigs greater than dogs much greater than cattle.     

Adenocarcinoma of the extrahepatic bile duct in a cat

A scirrhous adenocarcinoma of the extrahepatic bile duct was shown by histopathological examination to be the cause of obstructive jaundice in an 11-year-old female Siamese cat. In addition to icterus, the cat's clinical signs included depression, anorexia, vomiting, constipation, weight loss and dehydration. Symptomatic therapy relieved the anorexia, constipation, dehydration and depression, but jaundice, weight loss and occasional vomiting continued during the 2-month course of illness. Serum cholesterol and serum glutamic pyruvic transaminase (SGPT) remained elevated and serum bilirubin and serum alkaline phosphatase (SAP) values progressively increased from the cat's initial presentation to its death 2 months later. At necropsy the tumour was found to involve only the extrahepatic bile duct. Neoplasia of the extrahepatic biliary system has been reported only twice in domesticated animals (Patnaik et al., 1975; Feldman, Strafuss & Gabbert, 1976).     

Mechanisms of infection in the respiratory tract

Related to its potential vulnerability the respiratory tract has a very complex and effective defence apparatus. The interaction between these defence mechanisms and certain characteristics of aetiological agents results in a pattern in which initial infections by these agents tend to occur at specific sites in the tract. Infections in which the primary portal of entry is in the upper respiratory tract include Bordetella bronchiseptica and Haemophilus spp in pigs; Pasteurella spp in cattle, sheep, pigs; Mycoplasma spp in cattle, sheep, pigs and poultry; equine herpesvirus 1 in horses; infectious bovine rhinotracheitis in cattle; parainfluenza 3 in cattle and sheep; infectious laryngo-tracheitis and infectious bronchitis in poultry; feline viral rhinotracheitis and calicivirus in cats; Aujeszky's disease virus and swine influenza in pigs; and equine influenza in horses. Infections in which the primary portal of entry is in the lower respiratory tract include Aspergillus fumigatus in poultry and mammals, respiratory syncytial virus in cattle, distemper virus in dogs and adenovirus in cattle and dogs. A fuller understanding of the interactions between an agent and the host at the point of entry would make it much easier to develop effective vaccines and therapeutic agents.     

A simple way to reduce heat stress in laying hens as judged by egg laying, body weight gain and biochemical parameters

This study was designed to test the effects of feed withdrawal and darkening on the performance, triiodothyronine (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), and some blood serum metabolite and mineral concentrations of laying hens reared at high ambient temperatures ranging from 25 to 35 degrees C. Ninety, 16-week-old hens (Ross Brown) were divided into 3 groups, 30 hens each. The first group was used as control. Hens in the second group (feed withdrawal) were subjected to feed removal from 14:00 to 18:00, and hens in the third group (darkening) were subjected to light restriction from 14:00 to 18:00 using black curtains. Liveweight, feed intake, and egg production were higher (P < 0.01) in the feed withdrawal and darkening groups, particularly in the darkening group, than in the control. Water intake was higher in the control group compared with the feed withdrawal and darkening groups (P < 0.01). T3, T4, and TSH concentrations in the serum were higher (P < 0.01), whereas ACTH serum concentration was lower (P < 0.01) in the feed withdrawal and darkening groups compared with the control. The haematocrit was higher in the feed withdrawal and darkening groups compared with the control (P < 0.01). Darkening and feed withdrawal treatments increased serum glucose, urea-N, uric acid, albumin, triglyceride, cholesterol, Ca, P, Na, and K concentrations, also the activities of amylase and alkaline phosphatase, but did not influence the activities of serum glutamic-oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT). The present study found that feed withdrawal and darkening, particularly darkening, at high temperatures during the summer months offer a good management practice to reduce heat stress related depression in feed intake and egg production in laying hens.