1. Introduction

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Currently the success in the systems of animal production are not based on the quantity, but if in the quality of the produced, just in this point where the animal welfare has a key role to obtain a safe product for human consumption., “Animal friendly” production system (Frewer et al., 2005). The harmonious genotype-environment interaction in all animal production systems is the basis for the sustainability of animal production. The adaptation of a living organism to a given environment is characterized by a slow process, even more in severe environments like the tropics. An animal in welfare conditions will live and produces more and better, if all organs of the body are healthy, especially the liver, which plays a key role, as it is responsible for the processes of gluconeogenesis, biliary secretion, production of certain noble proteins and detoxification or metabolism of xenobiotics and all drugs that enter the body (Jeong et al., 2013), malfunction of this organ will cause susceptibility, weakness and loss of productivity in the individual.

Liver enzymes as ALP (alkaline Phosphatase), AST/GOT (Aspartate aminotransferase/ Glutamic Oxaloacetic Transaminase), ALT/GPT (Alanine aminotransferase/Glutamic Pyruvic Transaminase) and Bilirubin are quantified in serum and routinely used as elements of reliable hepatic diagnostic (Koide et al., 1959; Wang et al., 2006; Tu et al., 2007; Kang et al., 2008; Quintela et al., 2011; Jeong et al., 2013) in all kinds of animals such as pigs (Wang et al., 2006), fish (Kavitha et al., 2011), sheep and goats (Tibbo et al., 2008); and cattle (Quintela et al., 2011; Noro et al., 2013). It is known that the normal range of these liver enzymes is affected by internal and external factors such as the animals age and stage of lactation (Doornenbal et al., 1988; Otto et al., 2000), diet, season and management (Hawley and Peden., 1982: Quintela et al., 2011); and sex (Tibbo et al., 2008). The balance animal-environment allows serum levels of these enzymes to be normal and will determine an optimal liver diagnosis as, therefore, of him; but, what about those animals subjected to permanent environmental stress conditions, such as the Bos Taurus, managed to the level of the humid tropic that have to face the heat and humidity, submitted to the permanent presence of internal and external parasites (FAO 2004) and subject to a management that blocks their free movement on the grass in looks for refuge from environmental threats (Young et al., 1989).

The Amazon Region of Southern Ecuador (RAEsur), is an area dedicated to dairy cattle farming with a population composed primarily by Holstein cattle, carried to this environment from the high places in the Andes Mountains and have a slow process of adaptation, thereby having to endure the constant and excessive application of drugs to control health problems and parasites that affect them, so, the present study aimed to determine on cows in the postpartum period, the values of these liver enzymes and thereby establish whether the bovine Bos Taurus is affected by such tropical environment.

2. Material And Methods

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This study was developed in the places of Zamora, Centinela del Condor, Paquisha, Yanzatza, El Pangui, Yacuambi and Chinchipe, belonging to the province of Zamora Chinchipe-Ecuador, South America, localized at 4° 04’09’’S and 78°57’24’’W, 900 m above the sea level, with an average temperature of 25°C and characterized by humid tropical equatorial climate, classified in the Köppen scale as Af. 95 healthy crossbred Holstein cows in the postpartum period, from 32 herds from Zamora Chinchipe (feed is basically grass), were used in the study; being the pastures established exclusively of gramineous, prevailing in a 87 percent the Setaria or merkeron (Setaria sphacelata) and a 13 percent the purple or white gramalote (Axonopus scoparius). Animals were identified with a plastic tag and blood samples were taken (jugular vein) serially four times from each cow at intervals of 50 days from the postpartum up to 180 days. The blood samples were collected in an amount of 5 to 10 cc in Vacutainer tubes without anticoagulant, being maintained between 12 to 24 hours in a thermos with cooling gel (4 - 8°C) until they get to the Veterinary Diagnostic Laboratory of the National University of Loja for the corresponding analysis, conducted during the period of study 380 blood tests belonging to 95 postpartum cows that participated in the investigation, determining the values of liver enzymes ALP, AST, ALT and Bilirubin pigment liver. The Photometric System DiaSys® (Diasys Diagnostic Systems GmbH/Germany) was used for that. For this purpose the samples were centrifuged at 3000 r/15’ and the analyzer employed the Microlab® 300, the following methods were used:

• ALP in serum, the kinetic Photometric Test (DGKC).
• AST/GOT and ALT/GPT the UV Test, improved according to IFCC (International Federation of Clinical Chemistry and Laboratory Medicine).
• Total Bilirubin in serum, the Photometric Test 2,4-dicloroanilina (DCA).

The variables considered in this study were: grass type (n=2) in which animals are kept (Setaria sphacelata, Axonopus scoparius), because, these grasses have different growth cycles, therefore the animal has also different frequency of graze and administration of drug to control the tick all year. The height (high >1.3 m, low < 1.3 m), as higher animals are heavier and consequently receive more quantity of drugs. The other variable was the time (four) of collection of blood samples in the postpartum period. The results were analyzed using correlation-regression analysis and ANOVA, using the Statistical Analysis System program (SAS 9.3, 2010).

3. Results And Discussion

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In Table 1, the biochemical elements investigated showed fluctuation in values that is different during the four postpartum times analyzed (P< 0,05), all of which are especially the ALP over the normal range for this species (Peter et al., 2002). Some studies, manifested that serum ALP levels fall during lactation (Doornenbal et al., 1988; Otto et al., 2000; Tibbo et al., 2008), but in our work they remained high at this stage. The height had a significant influence on the values of ALP, small size animals had higher values (327.7±118.7U/l) than the ones of higher height (260.0±71.2U/l), the values of AST, ALT and Bilirubin were similar for this variable. As it concerns the effect of the ration, Hawley et al. (1982), Tibbo et al. (2008), Quintela et al. (2011), indicated that the type of food is one of the factors affecting the serum concentration of these elements and effectively affected (P< 0,05) our results because the animals kept in Setaria grass showed values of the three liver enzymes higher than those kept in Axonopus grass.

Table 1

The analysis by percentiles (Table 2) showed that only between 17.5% and 23% of the population presented values considered normal in the four biochemical elements analyzed while the rest of animals had high levels of ALP and Bilirubin negatively associated with the functional state of the liver parenchyma and degree of obstruction of the biliary tract (Gutman, 1959; Wang et al., 2006) and transaminases relating to liver damage (Tibbo et al., 2008; Kavitha et al., 2011; Noro et al., 2013), constituting all in biochemical markers for the diagnosis of liver diseases.

Table 2

When performing an analysis of the relationship between the variables considered in the investigation (Table 3), significant correlation was not found in the group of cows kept on pastures of Axonopus, between height and variables: ALP, GOT/AST, GPT/ALT, Bilirubin; but in the group of animals kept on pastures of Setaria a negative dependency ratio between height and ALP (P< 0.05) and between height and GPT/ALT (P< 0.10) was determined.

Table 3

These results are explained in a very common situation that occurs in that environment with animals Bos Taurus that graze Setaria sphacelata, because this grass has a fast growth cycle between 30 – 40 days (Ramírez et al., 1996), which facilitates the early return of the animals to its consumption, thereby not causing disruption of the biological cycle of ecto and endoparasites present in abundance in the tropics (Cardoso et al., 2013) and thereby causing a greater frequency of drugs administration for their control. While with the grass Axonopus this frequency decreases because the cycle of plant growth is slow and therefore the return of animals to its consumption is late between 150 and 180 days (personal communication with farmers).

Another factor to consider in this negative dependency ratio between height and levels of ALP and GPT/ALT is the weighing of the animals for dosage of drugs, because in the absence of bascules or not using barimetrica tapes, the same is made by a “subjective” criteria of the farmer or technician, causing errors of notorious underestimation of body weight (Machilla et al., 2008) and thus causing under-dosing and resistance to anthelmintics (Soutello et al., 2007; Kaplan and Vidyashancar, 2012), especially macrocyclic lactones such as Ivermectin widely used for tick control (Castro-Janer et al., 2011), leading to use of Ivermectin of high concentration and intervals of diminishing time (Cotter et al., 2014; Cruz et al., 2014; Muniz et al., 2015). This has come to the fact that small animals receive higher amounts of drugs and bigger animals receive lower amounts just because of those errors of live weigh estimates.

Figure. 1 and 2 can see the scattering of data ALP and GPT/ALT, whose serum levels decrease as the height increases, it is showing that the person who is dosing the drug takes into consideration a criteria of overdosing for “the drug to act better”, this causes levels of the cytosolic enzymes to be increased in blood by the high and continuous administration of corticosteroids (Gutman, 1959), therapeutic use of all kinds of chemical drugs (Koide and Oda, 1959; Lemaire et al., 1991; Manna et al., 2006; Kavitha et al., 2011), causing liver cytolysis due to the release of oxidative radicals resulting from the splitting of these xenobiotics (Peter et al., 2002; Ashworth et al., 2006, Jeong et al., 2013). Bilirubin also increases because of this liver damage and by the cholestasis because of the liver fluke, very common in this type of environment (Noro et al., 2013).

Figure 1    Figure 2

4. Conclusion

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Considering the susceptibility of Bos Taurus to health problems present in these humid tropic environments and the poor technical handling of chemical products to control these problems, it can be concluded by the high values of these biomarkers, especially ALP of a diagnosis of liver damage by probably continuous use of drugs that affect to it and causes malfunction for the process of glycogenesis, leading to malabsorption of nutrients, decreasing productive and reproductive performances, and longevity in the animals, being the most affected those with little height and also those maintained on grassland of Setaria sphacelata.

Acknowledgments

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The National University of Loja-Ecuador financed the accomplishment of this research and the farmers and technicians of RAEsur, who collaborated with their farms and animals.

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