BACKGROUND: Escherichia coli (E.coli) is one of the most common and important causative bacterium of urinary tract infections (UTIs) in both dogs and humans. OBJECTIVES: This study aimed to identify virulence genes and a phylogenetic group of E. coli isolated from the urine of dogs suffering from UTIs. METHODS: E. coli were isolated from urine of dogs suffering from UTIs and tested for the presence of the virulence genes using conventional polymerase chain reaction (PCR) and sequencing method. On day 60 after immunization, half of the fish in each treatment was challenged intraperitoneally and the re- maining half of fish in the oral receiving bacterin groups were challenged by bath method with 1 LD50 and 1 LC50 of a Y. ruckeri local virulent isolate respectively. RESULTS: Out of a total of 103 samples, 25 were found to be positive for E. coli, of these 20 (80.0%) were identified as aer, 14(56.0%) as pap , 12(48.0%) as sfa, 8(32.0%) as afa, 5(20.0%) as hly and 5(20.0%) as cnf1 genes. None of the isolates carried cnf2 genes. CONCLUSIONS: The study demonstrated a high occurrence of virulence genes. The phylogenetic compar- isons of these gene sequences detected in uropathogenic E. coli isolated from dogs showed high similarity to those present in the urine of humans with urinary tract infection. Phylogenetic comparisons of the virulence genes revealed that hly, sfa , cnf1 and pap matched to group B2, afa to group A and aer to group B2 and D.

BACKGROUND: Escherichia coli (E.coli) is one of the most common and important causative bacterium of urinary tract infections (UTIs) in both dogs and humans. OBJECTIVES: This study aimed to identify virulence genes and a phylogenetic group of E. coli isolated from the urine of dogs suffering from UTIs. METHODS: E. coli were isolated from urine of dogs suffering from UTIs and tested for the presence of the virulence genes using conventional polymerase chain reaction (PCR) and sequencing method. On day 60 after immunization, half of the fish in each treatment was challenged intraperitoneally and the re- maining half of fish in the oral receiving bacterin groups were challenged by bath method with 1 LD50 and 1 LC50 of a Y. ruckeri local virulent isolate respectively. RESULTS: Out of a total of 103 samples, 25 were found to be positive for E. coli, of these 20 (80.0%) were identified as aer, 14(56.0%) as pap , 12(48.0%) as sfa, 8(32.0%) as afa, 5(20.0%) as hly and 5(20.0%) as cnf1 genes. None of the isolates carried cnf2 genes. CONCLUSIONS: The study demonstrated a high occurrence of virulence genes. The phylogenetic compar- isons of these gene sequences detected in uropathogenic E. coli isolated from dogs showed high similarity to those present in the urine of humans with urinary tract infection. Phylogenetic comparisons of the virulence genes revealed that hly, sfa , cnf1 and pap matched to group B2, afa to group A and aer to group B2 and D.

BACKGROUND: Bovine leukemia virus (BLV) is an oncogenic deltaretrovirus causing a persistent lifelong infection of B lymphocytes. In addition to the domestic cattle, the virus can also infect water buffaloes. OBJECTIVES: Recent investigations have demonstrated the increasing prevalence of BLV infection among cattle population in Iran. Large populations of water buffaloes are also kept in different parts of Iran for milk and meat purposes. Considering economic losses induced by BLV infection in buffalo and more importantly the role of this species in virus epidemiology, the present study has investigated the BLV infection in Iranian water buffalo population. METHODS: Seroprevalence and occurrence of BLV was investigated in water buffalo population (n=100) in Khuzestan province, Southwest Iran by ELISA and nested PCR, targeting gp51 region in the envgene. RESULTS: In total, 52 samples were seropositive and represented the antibodies against BLV gp51 protein in ELISA test. Forty-seven out of 52 seropositive samples were confirmed by nested PCR. CONCLUSIONS: Such a high rate of BLV infection in water buffaloes is an alarming issue for both its eco- nomic impact due to the production losses and more importantly the epidemiological aspects in which the virus circulation among different host species will complicate the control and prevention strategies.

BACKGROUND: Bovine leukemia virus (BLV) is an oncogenic deltaretrovirus causing a persistent lifelong infection of B lymphocytes. In addition to the domestic cattle, the virus can also infect water buffaloes. OBJECTIVES: Recent investigations have demonstrated the increasing prevalence of BLV infection among cattle population in Iran. Large populations of water buffaloes are also kept in different parts of Iran for milk and meat purposes. Considering economic losses induced by BLV infection in buffalo and more importantly the role of this species in virus epidemiology, the present study has investigated the BLV infection in Iranian water buffalo population. METHODS: Seroprevalence and occurrence of BLV was investigated in water buffalo population (n=100) in Khuzestan province, Southwest Iran by ELISA and nested PCR, targeting gp51 region in the envgene. RESULTS: In total, 52 samples were seropositive and represented the antibodies against BLV gp51 protein in ELISA test. Forty-seven out of 52 seropositive samples were confirmed by nested PCR. CONCLUSIONS: Such a high rate of BLV infection in water buffaloes is an alarming issue for both its eco- nomic impact due to the production losses and more importantly the epidemiological aspects in which the virus circulation among different host species will complicate the control and prevention strategies.

BACKGROUND: Comprehensive studies in blood values t have been somewhat reported in wildlife animals but this study is the first one in Iranian red sheep. OBJECTIVES: The present study was aimed to reveal alterations of some biochemical and hematological parameters in Iranian red sheep (Ovis. Orientalis gmelini) in the Zanjan province (Sorkhabad protected  area), Iran. METHODS: Blood samples were obtained from 52 clinically and para-clinically healthy Iranian red sheep with different age (under 2 years, 31 sheep and over 2 years, 21 sheep) and sex (37 male and 15 female). Thereafter, some hematological parameters such as RBC, PCV, Hb, MCH, MCV, MCHC, WBC, Differen- tial leukocyte count along with biochemical parameters (T3, T4, glucose, total protein, albumin, cholesterol, HDL, LDL, triglyceride, creatinine, urea, calcium, phosphorus, magnesium, ALT, AST, GGT, ALP, CK) were analyzed. RESULTS: The results indicated significant alterations (p<0.01) of T3, T4, phosphorous, magnesium, GGT and ALP in both sex and age groups, significant alterations in glucose and creatinine only in sex group and significant changes based on age in cholesterol, HDL and LDL. No significant changes were observed in the other parameters. CONCLUSIONS: In Iranian red sheep, some parameters of serum biochemistry indicate significant chang- es based on gender and age that should be considered in laboratory tests of animal health. Meanwhile, fur- ther research should be performed in this regard.

BACKGROUND: Comprehensive studies in blood values t have been somewhat reported in wildlife animals but this study is the first one in Iranian red sheep. OBJECTIVES: The present study was aimed to reveal alterations of some biochemical and hematological parameters in Iranian red sheep (Ovis. Orientalis gmelini) in the Zanjan province (Sorkhabad protected  area), Iran. METHODS: Blood samples were obtained from 52 clinically and para-clinically healthy Iranian red sheep with different age (under 2 years, 31 sheep and over 2 years, 21 sheep) and sex (37 male and 15 female). Thereafter, some hematological parameters such as RBC, PCV, Hb, MCH, MCV, MCHC, WBC, Differen- tial leukocyte count along with biochemical parameters (T3, T4, glucose, total protein, albumin, cholesterol, HDL, LDL, triglyceride, creatinine, urea, calcium, phosphorus, magnesium, ALT, AST, GGT, ALP, CK) were analyzed. RESULTS: The results indicated significant alterations (p<0.01) of T3, T4, phosphorous, magnesium, GGT and ALP in both sex and age groups, significant alterations in glucose and creatinine only in sex group and significant changes based on age in cholesterol, HDL and LDL. No significant changes were observed in the other parameters. CONCLUSIONS: In Iranian red sheep, some parameters of serum biochemistry indicate significant chang- es based on gender and age that should be considered in laboratory tests of animal health. Meanwhile, fur- ther research should be performed in this regard.

BACKGROUND: Neurotransmitters (NTS) are endogenous chemicals secreted from neural terminals into the synaptic cleft of the chemical neurons in order to affect their receptors. NTS play vital physiological role as stimulatory, inhibitory or modulatory compounds. OBJECTIVES: This review was aimed to summarize the roles of the most important NTS which regulate food intake in the avian species. RESULTS: Over 40 neurotransmitters are known as regulatory agents that control ingestion behavior in mammals and birds. Acetylcholine (Ach), epinephrine (EP), norepinephrine (NEP), histamine, gamma amino butyric acid (GABA), glycine, serotonin and glutamate have been identified as the mediatory agents about regulation of feeding behavior in birds. Based on the molecular weight and the type of efficacy, NTS have been categorized into the two main groups including “the small molecular weight fast-effective NTS and the large molecular wieght slow-effective neuropeptides. Various physiological functions have been presented for NTS and it seems many other unknown effects and even possible interactions among them are still questionable. Appetite control, mediatory role of ingestion behavior and regulation of food intake have recently been highlighted among various roles of NTS in chicken. CONCLUSIONS: Food intake regulation is a complex physiologic process that is under the control of the central and environmental signals. Considering of the involvement of feeding behavior in other major physiological processes such as the growth, immunity and production, it is necessary to realize the role of different mediators which are affecting and modulating food intake in avian species.

BACKGROUND: Neurotransmitters (NTS) are endogenous chemicals secreted from neural terminals into the synaptic cleft of the chemical neurons in order to affect their receptors. NTS play vital physiological role as stimulatory, inhibitory or modulatory compounds. OBJECTIVES: This review was aimed to summarize the roles of the most important NTS which regulate food intake in the avian species. RESULTS: Over 40 neurotransmitters are known as regulatory agents that control ingestion behavior in mammals and birds. Acetylcholine (Ach), epinephrine (EP), norepinephrine (NEP), histamine, gamma amino butyric acid (GABA), glycine, serotonin and glutamate have been identified as the mediatory agents about regulation of feeding behavior in birds. Based on the molecular weight and the type of efficacy, NTS have been categorized into the two main groups including “the small molecular weight fast-effective NTS and the large molecular wieght slow-effective neuropeptides. Various physiological functions have been presented for NTS and it seems many other unknown effects and even possible interactions among them are still questionable. Appetite control, mediatory role of ingestion behavior and regulation of food intake have recently been highlighted among various roles of NTS in chicken. CONCLUSIONS: Food intake regulation is a complex physiologic process that is under the control of the central and environmental signals. Considering of the involvement of feeding behavior in other major physiological processes such as the growth, immunity and production, it is necessary to realize the role of different mediators which are affecting and modulating food intake in avian species.

BACKGROUND: In dogs, Achilles tendon rupture is an important clinical issue. Treatment of the ruptured tendon remains a controversial problem. However, surgical intervention, by the using of different biological scaffolds, has been recognized as the most effective approach for the repair of such cases. OBJECTIVES: The current study aimed to evaluate the efficiency of platelets-plasma rich protein (PRP) and autogenous peritoneal scaffold to improve the healing process of ruptured Achilles tendon in dogs. METHODS: Eighteen healthy dogs of the local breed were randomly allocated into three equal groups. Achilles tendon of the hind limbs were prepared aseptically and transected transversely. In the control group, the tendon was reconstructed with the traditional suture using modified Kessler techniques. In the peritoneal scaffold group, a combination of traditional suture and the autogenous peritoneal scaffold was used to augment the defected tendon. In the peritoneal scaffold with the PRP group, the induced rupture was treated as similar to the peritoneal scaffold group and supported by a topical application of PRP. In addition to the gross observation, the healing process was evaluated with histopathological and sonographic investigations at 15, 30, and 60 days post-operative. RESULTS: By comparison with control, the utilizing of autologous peritoneum scaffold augmented with PRP revealed a valuable impact on Achilles tendon healing. This impact was manifested by improved fibroblastic proliferation, reduced adhesion, and improved mechanical function of the tendon. Also, the sonographic examination of the fibrosis site demonstrated the presence of hyperechoic spots. CONCLUSIONS: We concluded that utilizing both the peritoneal scaffold augmented and PRP along with the traditional suture revealed remarkable optimistic effects on healing of the ruptured Achilles tendon in dogs.

BACKGROUND: In dogs, Achilles tendon rupture is an important clinical issue. Treatment of the ruptured tendon remains a controversial problem. However, surgical intervention, by the using of different biological scaffolds, has been recognized as the most effective approach for the repair of such cases. OBJECTIVES: The current study aimed to evaluate the efficiency of platelets-plasma rich protein (PRP) and autogenous peritoneal scaffold to improve the healing process of ruptured Achilles tendon in dogs. METHODS: Eighteen healthy dogs of the local breed were randomly allocated into three equal groups. Achilles tendon of the hind limbs were prepared aseptically and transected transversely. In the control group, the tendon was reconstructed with the traditional suture using modified Kessler techniques. In the peritoneal scaffold group, a combination of traditional suture and the autogenous peritoneal scaffold was used to augment the defected tendon. In the peritoneal scaffold with the PRP group, the induced rupture was treated as similar to the peritoneal scaffold group and supported by a topical application of PRP. In addition to the gross observation, the healing process was evaluated with histopathological and sonographic investigations at 15, 30, and 60 days post-operative. RESULTS: By comparison with control, the utilizing of autologous peritoneum scaffold augmented with PRP revealed a valuable impact on Achilles tendon healing. This impact was manifested by improved fibroblastic proliferation, reduced adhesion, and improved mechanical function of the tendon. Also, the sonographic examination of the fibrosis site demonstrated the presence of hyperechoic spots. CONCLUSIONS: We concluded that utilizing both the peritoneal scaffold augmented and PRP along with the traditional suture revealed remarkable optimistic effects on healing of the ruptured Achilles tendon in dogs.

BACKGROUND:Due to the large proportion of iodine present in milk and dairy products, they have been one of the important sources of nutritional iodine in several countries. Information about variation in milk iodine concentration in Iran is limited. OBJECTIVES:The present study was conducted to determine the iodine concentration in Iranian milk and dairy milk products. METHODS: In the first step, 10 commercial dairy farms (five located in tropical and other located in cold region) were included in the study. In the second step, the iodine concentration of six samples of different milk products from the retail market was determined by Sandell-Kolthoff (acid-digestion) reaction. RESULTS: The average iodine concentration of milk samples from cold region was significantly lower (50.7 ± 24.3 %) than the iodine concentration of milk samples from the tropical region (P<0.05). Sterilized milk (282.0 ± 111.0 µg/l) had higher and raw milk (224.3 ± 116.9 µg/l) had lower iodine concentration  (P<0.05). There was no effect of milk fat class (whole and semi-skimmed) on milk iodine concentration (P>0.05). CONCLUSIONS: Based on Iranian dairy product intake, raw, pasteurized and sterilized milk provides on average, 74.6, 84.6, 96.0 µg of iodine, approximately 29.8, 33.8, 37.6 % of the adult recommended dietary allowance for this nutrient, respectively.

BACKGROUND:Due to the large proportion of iodine present in milk and dairy products, they have been one of the important sources of nutritional iodine in several countries. Information about variation in milk iodine concentration in Iran is limited. OBJECTIVES:The present study was conducted to determine the iodine concentration in Iranian milk and dairy milk products. METHODS: In the first step, 10 commercial dairy farms (five located in tropical and other located in cold region) were included in the study. In the second step, the iodine concentration of six samples of different milk products from the retail market was determined by Sandell-Kolthoff (acid-digestion) reaction. RESULTS: The average iodine concentration of milk samples from cold region was significantly lower (50.7 ± 24.3 %) than the iodine concentration of milk samples from the tropical region (P<0.05). Sterilized milk (282.0 ± 111.0 µg/l) had higher and raw milk (224.3 ± 116.9 µg/l) had lower iodine concentration  (P<0.05). There was no effect of milk fat class (whole and semi-skimmed) on milk iodine concentration (P>0.05). CONCLUSIONS: Based on Iranian dairy product intake, raw, pasteurized and sterilized milk provides on average, 74.6, 84.6, 96.0 µg of iodine, approximately 29.8, 33.8, 37.6 % of the adult recommended dietary allowance for this nutrient, respectively.

BACKGROUND: A limited number of studies have investigated the inclusion of amino acids in calf starter. OBJECTIVES: This study was aimed to evaluate different levels of crude protein in starter and supplement- ing some protected amino acids on efficiency, health status and blood metabolites of dairy calves and to com- pare it with unprotected amino acids. METHODS: Forty-eight 3-day-old Holstein calves were randomly allocated to four treatments in a complete- ly randomized design. Dietary treatments were (1) 18% Crude Protein starter without Amino Acid, (2) 18% Crude Protein with 0.0340% protected lysine and 0.016% protected methionine, (3) 18% Crude Protein starter with 0.215% un-protected lysine and 0.012% un-protected methionine, (4) 22% Crude Protein without Amino Acid. All calves received the same amount of whole milk, weaned on day 56; the study was finished on day 70. RESULTS: Calves in treatment 4 had the greatest starter intake, weaning weight and final weight (P<0.05) but their feed efficiency was not different among treatments. There were no significant differences in Immu- noglobulin G, total protein and Lysine and Methionine concentration in blood (P>0.05). Health score (eye, ear, nose and respiratory score), was not different among treatments but the fecal score revealed a significant difference (P<0.05). Starter diet with 22% Crude Protein resulted in higher serum urea concentration (P< 0.05) CONCLUSIONS: Results of the present study indicate that, the performance of calves received protected or un-protected amino acid in starter was not different. Also, higher Crude Protein levels in diet did not lead to a better gain to feed ratio.

BACKGROUND: A limited number of studies have investigated the inclusion of amino acids in calf starter. OBJECTIVES: This study was aimed to evaluate different levels of crude protein in starter and supplement- ing some protected amino acids on efficiency, health status and blood metabolites of dairy calves and to com- pare it with unprotected amino acids. METHODS: Forty-eight 3-day-old Holstein calves were randomly allocated to four treatments in a complete- ly randomized design. Dietary treatments were (1) 18% Crude Protein starter without Amino Acid, (2) 18% Crude Protein with 0.0340% protected lysine and 0.016% protected methionine, (3) 18% Crude Protein starter with 0.215% un-protected lysine and 0.012% un-protected methionine, (4) 22% Crude Protein without Amino Acid. All calves received the same amount of whole milk, weaned on day 56; the study was finished on day 70. RESULTS: Calves in treatment 4 had the greatest starter intake, weaning weight and final weight (P<0.05) but their feed efficiency was not different among treatments. There were no significant differences in Immu- noglobulin G, total protein and Lysine and Methionine concentration in blood (P>0.05). Health score (eye, ear, nose and respiratory score), was not different among treatments but the fecal score revealed a significant difference (P<0.05). Starter diet with 22% Crude Protein resulted in higher serum urea concentration (P< 0.05) CONCLUSIONS: Results of the present study indicate that, the performance of calves received protected or un-protected amino acid in starter was not different. Also, higher Crude Protein levels in diet did not lead to a better gain to feed ratio.

BACKGROUND: Phenobarbital is one of the most commonly used drugs to treat epilepsy and other seizure disorders in dogs and cats. Hepatotoxicity following phenobarbital administration is dose-dependent. OBJECTIVES: The present study aimed to evaluate the protective action of silymarin on phenobarbital-in- duced hepatotoxicity in cats. METHODS: For this purpose, twenty-four healthy adult cats were randomly allotted to four equal groups. Cats in group A were given phenobarbital with dosage 16 mg/kg orally for 28 days; group B received silymarin (30 mg/kg/day for twenty-eight days) orally concurrent with phenobarbital; groups C and D were treated like group B, but silymarin was administered 3 and 48 h after administration of phenobarbital, respectively, and continued up to twenty-eight days. The serum concentrations of alanine aminotransferase, aspartate amino- transferase, alkaline phosphatase, lactate dehydrogenase, total and direct bilirubin, blood urea nitrogen and creatinine were measured before administration of phenobarbital and after 24 h, 72 h and 28 days. RESULTS:Phenobarbital elevated significantly serum concentrations of liver enzymes (in all cases), and total and direct bilirubin in two cats of group A, after 24 h (P <0.001). In groups, B and C, levels of serum enzyme activities and total and direct bilirubin remained within the normal range up to 28 days (P>0.05), while in group D, levels of serum enzyme activities (in 4 cases) were higher than the normal values (P<0.001). CONCLUSIONS: The results showed that silymarin can protect liver tissue against oxidative stress in cats with phenobarbital intoxication especially in the first 3 h post-exposure.

BACKGROUND: Phenobarbital is one of the most commonly used drugs to treat epilepsy and other seizure disorders in dogs and cats. Hepatotoxicity following phenobarbital administration is dose-dependent. OBJECTIVES: The present study aimed to evaluate the protective action of silymarin on phenobarbital-in- duced hepatotoxicity in cats. METHODS: For this purpose, twenty-four healthy adult cats were randomly allotted to four equal groups. Cats in group A were given phenobarbital with dosage 16 mg/kg orally for 28 days; group B received silymarin (30 mg/kg/day for twenty-eight days) orally concurrent with phenobarbital; groups C and D were treated like group B, but silymarin was administered 3 and 48 h after administration of phenobarbital, respectively, and continued up to twenty-eight days. The serum concentrations of alanine aminotransferase, aspartate amino- transferase, alkaline phosphatase, lactate dehydrogenase, total and direct bilirubin, blood urea nitrogen and creatinine were measured before administration of phenobarbital and after 24 h, 72 h and 28 days. RESULTS:Phenobarbital elevated significantly serum concentrations of liver enzymes (in all cases), and total and direct bilirubin in two cats of group A, after 24 h (P <0.001). In groups, B and C, levels of serum enzyme activities and total and direct bilirubin remained within the normal range up to 28 days (P>0.05), while in group D, levels of serum enzyme activities (in 4 cases) were higher than the normal values (P<0.001). CONCLUSIONS: The results showed that silymarin can protect liver tissue against oxidative stress in cats with phenobarbital intoxication especially in the first 3 h post-exposure.

Dermatofibroma is a common skin benign cutaneous tumor with many variants based on alterations in the morphology and composition of its diverse elements. The cause of dermatofibroma is unknown, it was his- torically attributed to being a reactive response to some traumatic lesion to the skin which is associated with itching and pain. This tumor usually appears on the limbs, especially the end extremities, in young adults. In the present study, a middle-aged Persian leopard was accidentally killed because of a car incident in the Golestan National Park, Iran. Following necropsy, skin mass on the right toe was observed and after sam- pling was transferred to the laboratory. After routine histopathological and immunohistochemical processes, Dermatofibroma was diagnosed microscopically with non-capsulated, circumscribed, hypocellular dermal nodule in a spiral pattern. According to the results of this study immunohistochemical staining revealed positivity for CD34. There is limited information about the Dermatofibroma in leopards. To our knowledge, this is the first report of Dermatofibroma in the Persian leopard.

Dermatofibroma is a common skin benign cutaneous tumor with many variants based on alterations in the morphology and composition of its diverse elements. The cause of dermatofibroma is unknown, it was his- torically attributed to being a reactive response to some traumatic lesion to the skin which is associated with itching and pain. This tumor usually appears on the limbs, especially the end extremities, in young adults. In the present study, a middle-aged Persian leopard was accidentally killed because of a car incident in the Golestan National Park, Iran. Following necropsy, skin mass on the right toe was observed and after sam- pling was transferred to the laboratory. After routine histopathological and immunohistochemical processes, Dermatofibroma was diagnosed microscopically with non-capsulated, circumscribed, hypocellular dermal nodule in a spiral pattern. According to the results of this study immunohistochemical staining revealed positivity for CD34. There is limited information about the Dermatofibroma in leopards. To our knowledge, this is the first report of Dermatofibroma in the Persian leopard.

reducing production and death. The disease in endemic areas would be mild or subclinical in indigenous cattle and clinically acute in exotics. OBJECTIVES: This study was conducted to evaluate the resistance of indigenous cattle in comparison with Holstein and crossbred cattle against Theileria annulata through assessment of clinical signs and response to treatment. METHODS: For this purpose, the data history and clinical examination were observed on 51 naturally affected cattle with T. annulata (17 Holstein, 17 crossbred and 17 indigenous cows). Examination of blood smears was used for diagnosis. Detection of schizonts in lymph node punctured smears confirmed validity of the suspect samples. All three groups of cows were treated with buparvaquone along with oxytetracycline. Their clinical signs and the results of blood smear examinations were recorded before and 48 hours after treatment. The severity of clinical signs, parasitemia rates and response to treatment were compared among the groups. RESULTS: The results showed significant difference (p <0.05) in severity of fever, intense and abnormal lung sounds, mucosal changes (pallor, jaundice, petechiae) and ruminal hypomotility among the groups. There was no significant difference in parasitemia rate and response to treatment among the groups. CONCLUSIONS: This study indicated that Iranian indigenous cattle in comparison with Holsteins and crossbreeds had milder clinical manifestations and no significant difference in response to treatment for tropical theileriosis.

reducing production and death. The disease in endemic areas would be mild or subclinical in indigenous cattle and clinically acute in exotics. OBJECTIVES: This study was conducted to evaluate the resistance of indigenous cattle in comparison with Holstein and crossbred cattle against Theileria annulata through assessment of clinical signs and response to treatment. METHODS: For this purpose, the data history and clinical examination were observed on 51 naturally affected cattle with T. annulata (17 Holstein, 17 crossbred and 17 indigenous cows). Examination of blood smears was used for diagnosis. Detection of schizonts in lymph node punctured smears confirmed validity of the suspect samples. All three groups of cows were treated with buparvaquone along with oxytetracycline. Their clinical signs and the results of blood smear examinations were recorded before and 48 hours after treatment. The severity of clinical signs, parasitemia rates and response to treatment were compared among the groups. RESULTS: The results showed significant difference (p <0.05) in severity of fever, intense and abnormal lung sounds, mucosal changes (pallor, jaundice, petechiae) and ruminal hypomotility among the groups. There was no significant difference in parasitemia rate and response to treatment among the groups. CONCLUSIONS: This study indicated that Iranian indigenous cattle in comparison with Holsteins and crossbreeds had milder clinical manifestations and no significant difference in response to treatment for tropical theileriosis.