The analysis of serum mineral profile of cows before and after calving: A case study

Focusing on high efficiency of dairy cows constantly deviates the parameters of the internal environment out of the optimal standard. It is also thought that this may significantly affect immune function (Gross et al., 2011). In large dairy farms, metabolic disorders that cause significant losses often occurs. Highly produced dairy cows are most affected. Disorders are referred to production diseases where the causes are nutritional deficiencies, imbalance between energy intake and expenditure, unilateral feeding (Prodanovi et al., 2010), reduced biological value of feed (Šimko et al., 2009), abnormal rumen function (Hanušovský et al., 2017), etc. From the diagnosis point of view, individual disorders, clinical examination remains an important method in the conditions of field practice. However, this method is not sufficient for the overall etiopathological conclusion in production diseases. For a more thorough examination of the herd or individual animals, by taking biological samples is possible to detect production diseases. By analysing are used laboratory diagnostic methods, which are ranked among the metabolic profile test (MPT), we can determine The analysis of serum mineral profile of cows before and after calving: A case study


Introduction
Focusing on high efficiency of dairy cows constantly deviates the parameters of the internal environment out of the optimal standard. It is also thought that this may significantly affect immune function (Gross et al., 2011). In large dairy farms, metabolic disorders that cause significant losses often occurs. Highly produced dairy cows are most affected. Disorders are referred to production diseases where the causes are nutritional deficiencies, imbalance between energy intake and expenditure, unilateral feeding (Prodanovi et al., 2010), reduced biological value of feed (Šimko et al., 2009), abnormal rumen function (Hanušovský et al., 2017), etc. From the diagnosis point of view, individual disorders, clinical examination remains an important method in the conditions of field practice. However, this method is not sufficient for the overall etiopathological conclusion in production diseases. For a more thorough examination of the herd or individual animals, by taking biological samples is possible to detect production diseases. By analysing are used laboratory diagnostic methods, which are ranked among the metabolic profile test (MPT), we can determine The analysis of serum mineral profile of cows before and after calving: A case study the exact cause of production disorders (Bertoni et al., 2009). The metabolic profile test is an important diagnostic method for the detection of preclinical stages of metabolic disorders, especially in dairy farms (Kantíková and Balážik, 2003). The metabolic profile test provide the possibility to sensitively monitor changes in the internal environment of animals caused by various factors. Metabolic disorders can occur latently, especially in the initial period (Hofírek et al., 2009).
They cause serious economic losses in productivity, worsen the feed efficiency, negatively affect the reproductive process and the viability of young animals. The later clinical stage already has clear manifestations and is accompanied by culling of animals or death (Kraft, 2005). The selection of animals for the metabolic profile test should reflect the purpose for which the test is intended to be performed. According to (Kantíková and Balážik, 2003) the most stressful periods for dairy cows are dry period and during third month after calving. This study was therefore aimed to describing the changes in the serum mineral profile during this period.

Material and methods
The mineral profile in the blood serum of dairy cows at 4 th week after drying and 12 th week after calving was determined. In the experiment, 12 dairy cows of Holstein Friesian breed were randomly selected from the herd at VPP-Oponice (Slovak University of Agriculture in Nitra, Slovakia). Dairy cows were on their 4 th lactation on average. Dairy cows were fed with a feed ration corresponding to the given category. During 4 th week after drying diet composition was as follows (in original matter): 12.0 kg alfalfa silage, 7.0 kg maize silage, 3.0 kg barley straw, 1.0 kg rape seed meal, 0.2 kg mineral premix. During 12 th week after calving diet composition was as follows (in original matter): 21.5 kg maize silage, 15.0 kg alfalfa silage, 9.0 kg concentrate feed mixture, 2.0 kg corn grain, 0.25 kg mineral premix. The mineral profile expresses the basic elements in the respective reference values of Ca 2+ , P, Na, K, Mg 2+ and chlorides (Cl -). The blood of dairy cows was collected at 12 th hour after morning feeding. Blood collection was performed by a veterinarian using Hemos (Gama Group, Czech Republic) collection kits from the vena caudalis mediana in an amount of 10 ml. After collection, the blood was cooled to 5 °C and processed within 24 hours of collection to obtain the serum. Serum was obtained by centrifuging the blood in a centrifuge (MPW 370, Poland), 2500-3000 rpm. for 10 minutes. The obtained serum was stored in "eppendorf" tubes at -20 °C in a freezer. Serum minerals were determined using biochemical kits according to manufacturer instruction (BIO-LA-TEST, Erba Mannheim). After thawing, blood serum was diluted with the appropriate reagent according to the methodology of the element to be measured. The colour change was measured with a spectrophotometer (UviLine 9400, Reasol). The results were compared with reference values according to the standard for dairy cows (Kahn, 2005), as well as between samplings (4 th week after drying vs. 12 th week after calving). Statistical processing and evaluation of the results were performed in Microsoft Excel and IBM SPSS v. 20. The significance of the differences in the mean values between the samplings was tested by t-test at a significance level of 0.05.

Results and discussion
Examination of blood serum from dry cows, at 4 th week after drying, confirmed differences in calcium and phosphorus (Table 1), compared to reference interval published by Kahn (2005). The average value for calcium was 2.11 mmol/l, which not reached the down value of reference interval of cows. The highest concentration of serum calcium from all analysed dry cows was 2.56 mmol/l. Within the physiological range of serum calcium were only 4 dry cows. The average concentration of phosphorus was 1.79 mmol/l. Only two dry cows had phosphorus concentration under the physiological range. Concentration of other analysed serum minerals was within physiological interval. Blood serum mineral profile of the same cows was analysed also after calving, during 12 th week of lactation (Table 1). Similar as in blood serum of dry cows, in serum of cows during 12 th lactation week the deviation from physiological interval was detected for calcium and phosphorus. Serum calcium concentration under the physiological range had 5 lactating cows and the lowest calcium concentration was 1.96 mmol/l. On the other site, the highest serum calcium concentration of lactating cows was 2.82 mmol/l. On average, serum concentration of calcium was higher (P <0.05) in cows during 12 th week of lactation. Serum phosphorus concentration had under the physiological range three from twelwe analysed lactating cows and the lowest concentration was 1.42 mmol/l. Difference in phosphorus concentration between sampling times was insignificant (P >0.05). Other analysed serum minerals of lactating cows were within the physiological range, with moderate change. Mg (P <0.01), Na (P >0.05) and Cl -(P <0.05) concentration was higher in cows' serum at 12 th week after calving, compared to serum of dry cows. Between serum of dry cows and cows at 12 th week after calving a decrease was detected for K (P <0.05). http://www.acta.fapz.uniag.sk © Slovak University of Agriculture in Nitra Faculty of Agrobiology and Food Resources  (Kahn, 2005); P-value indicate the significance of difference of mean values between 4 th week after drying and 12 th week after calving Phosphorus is presented almost in all tissues, and similar as calcium provides transfer of nutrients on cellular level. Concentration of Ca and P is regulated by parathormone, thyrocalcitonin as well as by vitamin D. Parathormone directly affects the release of Ca from bones and P excretion by kidneys and has also influence on calcinemia. Thyrocalcitonin protect resorption from bones and so decreased the concentration of Ca and P in blood serum. Hypercalcinaemia is in animals rarely and if, is related to overdosage of vitamin D, or to oncological diseases. Hypocalcaemia set in rickets, osteomalation, milk fever, deficit of vitamin D and disorders of resorption in intestine. According to data from literature, the reference interval for phosphorus in cow's blood serum is 1.81 to 2.1 mmol/l (Kaneko, 2008;Blood and Radostis, 1994). In this study some cows had concentration of phosphorus under the lower value of reference interval. Hadžimusić and Krnić (2012) found significant effect of cow's reproductive cycle sage on the concentration of phosphorus, which is in discrepancy with results of this study. The presence of hypophosphatemia is common in time around calving. But Palmer and Eckles (1927) reported hypophosphatemia in animals fed in phosphorousdeficient regions. If occur hypophosphatemia, the muscle weakness, rickets and osteodynia is detected. Occurrence of hypophosphatemia is accompanied with metabolic alkalosis (Šamanc et al., 2010). Similar as in this study, Hadžimusić and Krnić (2012) found significant difference in magnesium concentration between dry cows and lactating cows. Other analysed parameters were within reference intervals published by other authors (Slanina et al., 1991;Aiello, 1998). Beside intake of minerals through feed, according to Hadžimusić and Krnić (2012) also season have significant effect on average values of cows serum mineral profile.

Conclusions
Results shown, that main problem of dry and lactating cows was the hypocalcaemia and partly the hypophosphatemia, from blood serum mineral profile point of view. For reduction of presence of hypocalcaemia and hypophosphatemia is important direct feeding and continual monitoring of cows from each group. In the future will be better to determine the mineral profile of also in urine and rumen fluid.