Research Article

# Prevalence of selected metabolic diseases in dairy herds in eastern Poland

Piotr Guliński

Siedlce University of Natural Sciences and Humanities, Faculty of Natural Sciences, Department of Cattle and Sheep Breeding and Milk Testing, ul. Prusa 14, 08-110 Siedlce, Poland

Abstract. The aim of the paper is to investigate the prevalence of metabolic diseases in selected dairy farms. The metabolic status of the Polish Holstein-Frisian dairy cows (PHF) was assessed using the fat to protein ratio (F/P ratio). The chemical quality of raw milk produced between 2014 and 2017 in ten herds located in eastern Poland (counties: Łosicki, Radzyński, Sokołowski and Ostrów Mazowiecka) was studied in the research. Based on 4838 daily observations, milk performance of 491 cows was assessed. The following indicators were determined: milk F/P ratio, milk daily yield and the content of protein, fat and dry matter. Several factors influenced basic milk composition and milk F/P ratio were tested. There were 4 lactation number groups (1 – first; 2 – second; 3 – third and fourth; 4– fifth to ninth lactations), 10 herd number (1–10), 4 stage of lactation groups (1 – 3, 4 – 6 , 7 – 10, 11 – 18 months), 4 classes of daily milk yield ( ≤ 15 kg, 15.1 – 25 kg, 25.1– 35 kg, >35 kg), 4 calving seasons (summer – JUN–AUG, autumn – SEP–NOV, winter – DEC–FEB, spring – MAR–MAY) and 4 milk F/P ratio groups ( ≤ 1 indicating rumen acidosis (SARA); 1.1 – 1.4 optimal; 1.41 – 1.7 indicating subclinical ketosis (SCK); >1.7 indicating clinical ketosis (KET). The average milk fat to protein ratio was 1.26, but it varied considerably within individual groups. The results also showed that 3313, i.e. 68.5%, of milk samples had the F/P ratio ranging from 1.1 to 1.4, indicating adequate nutrition with well-balanced daily rations. However, 8.2% of the observations indicated the occurrence of acidosis (SARA) in the cow population, 19.9% of the observations suggested the occurrence of subclinical ketosis (SCK) and 3.3% of milk samples were from cows affected with clinical ketosis (KET).

Keywords: cows, ketosis, acidosis, Fat/Protein ratio

## INTRODUCTION

Ketosis is the most important metabolic disease of high-yielding dairy cows. For the diagnosis of the disease the assessment of β-hydroxybutyrate acid (BHBA) is most commonly used. Its level alongside the concentration of acetone and acetylacetic acid in the body fluids is the most characteristic of ketosis symptoms []. It is assumed that the critical point for the occurrence of ketosis is the BHBA level in blood of 14.4 mg · dL–1 (>1.4 mmol · L–1). For clinical ketosis, a critical level of BHBA above 29.0 mg · dL–1 (ca. 3.0 mmol · L–1) in blood is used.

The current consensus is to consider a cutoff point of BHBA at least of 1.2 mmol · L–1 for subclinical ketosis []. The SCK is defined as concentrations of BHBA ≥1.2 to 1.4 mmol · L–1 in blood and it is considered as a gateway condition for clinical ketosis [].

Buttchereit et al. [] reported that milk F/P ratio reflects the energy balance status of a cow in early lactation. In breeding practice, the primary indicator of the occurrence of subclinical ketosis is high fat content in milk, higher than the standard. Another important consequence of ketosis is also an increase in the proportion of saturated acids in milk fat. Subclinical ketosis also leads to a decrease in milk yield. It can be lower up to 300 kg during one lactation [].

According to Gravert [], the ideal range for milk F/P ratio is 1–1.25, while according to Duffield [], 1.33 is the upper margin. According to Haas and Hofírek [], F/P ratio that is higher than 1.4 shows energy deficit and, if ketone bodies are present, subclinical ketosis. Richardt [] determined a 1.5 value of F/P ratio as the risk level for subclinical ketosis, while Eicher [] considered beside the F/P ratio, the daily milk production as well, in order to find the indication of metabolic disorders (acidosis, ketosis).

In recent years cattle breeders have become more and more interested in the milk F/P ratio, especially in the early stages of lactation. The main reason is the possibility of its use as an important energy balance criterion in assessing cow feeding. It is assumed that normal protein content in the milk of PHF cows ranges from 3.2 to 3.6%. Normal fat content in the milk of this breed ranges between 3.5% and 4.5%, but in the case of high-performance cows it is about 4% []. The milk F/P ratio of a healthy cow fed with a well-balanced daily ration should ranged from 1.1 to 1.3. The F/P ratio above 1.4 means the possibility of subclinical ketosis. When the F/P ratio exceeds 1.7, it means the clinical form of ketosis, especially with low protein content in milk and relatively high fat content. If the F/P ratio is too low (<1), it may be indicative of subclinical acidosis, which is most commonly found when excessive feeding or abnormal physical structure of the ration is administered. In herds affected by acidosis there is a decrease in the milk yield, deterioration of health and, in effect, increased cow culling.

Protein content is an essential element affecting the buying-in price of milk. Milk protein price has doubled in the payment systems worldwide due to its higher suitability of this component for milk processing. In recent years, a number of dairies have introduced a payment system based on protein content in the milk following diet changes observed in the world when consumers prefer lower fat food. Currently in most countries of the world cow breeders put the main emphasis on improving cow's milk by increasing protein concentration and its efficiency and by ameliorating the fat to protein ratio [].

In breeding practice, cows whose milk F/P ratio is lower are assessed as being more easily impregnated. Research of Löf et al. [] showed that the fat to protein ratio could be a good indicator for diagnosing cows at risk of poor fertility in order to determine where preventive measures could be taken.

As concluded by Negussie et al. [] milk F/P ratio is easily available from routine milk-recording schemes. It can be used as a low-cost monitoring tool of poor health and fertility in the most critical phases of lactation and as an important indicator trait to improve robustness in dairy cows through selection. In the study by Heringstad et al. [], posterior means of heritability of liability in first, second, and third lactations were for ketosis respectively 0.14, 0.16, and 0.15.

The aim of the paper is to analyze the prevalence of ketosis and acidosis in selected herds of dairy cattle located in eastern Poland.

## MATERIAL AND METHODS

The chemical quality of raw milk produced between 2014–2017 in ten herds located in eastern Poland (counties: Łosicki, Radzyński, Sokołowski and Ostrów Mazowiecka) was studied in the research. The data were test-day milk yields from Polish Holstein – Frisian (PHF) dairy cows registered in the Polish national recording system (SYMLEK). With 4838 daily observations, the studies involved the evaluation of milk performance parameters of 491 PHF dairy cows. The following characteristics of milk performance were determined: milk daily yield, the content of protein, fat, dry matter and the fat to protein ratio in milk.

Several factors influenced basic milk composition and F/P ratio were tested. There were 4 lactation number groups (1 – first; 2 – second; 3 – third and fourth; 4 – fifth to ninth lactation), 10 herds numbers (1–10), 4 stage of lactation groups (1–3, 4–6 , 7–10, 11–18 months), 4 classes of daily milk yield (≤15 kg, 15.1–25 kg, 25.1–35 kg, >35 kg), 4 calving seasons (summer, JUN–AUG, autumn, SEP–NOV, winter, DEC–FEB, spring, MAR–MAY) and 4 F/P ratio groups (≤1, indicating rumen acidosis; 1.1–1.4, optimal; 1.41–1.7, indicating subclinical ketosis; >1.7, indicating clinical ketosis).

The linear model containing fixed effects of lactation number groups, herd number, lactation month, calving season, daily milk yield class and F/P ratio groups effect was used. The results were statistically processed applying the multifactor analysis of variance. The following linear model was used:

$$Y_{ijklmno} = \mu + a_i + b_j + c_k + d_l + f_m + g_n + e_{ijklmno}$$

where:

$$Y_{ijklmno}$$ – the value of the trait,

$$\mu$$ – general mean,

$$a_{i}$$ – effect of the lactation period ($$i$$ = 1, 2, 3, 4),

$$b_{j}$$ – effect of the herd number ($$j$$ = 1, 2 .. 10),

$$c_{k}$$ – effect of calving season ($$k$$ = 1, 2, 3, 4),

$$d_{l}$$ – effect the lactation number groups ($$l$$ = 1, 2, 3, 4),

$$f_{m}$$ – effect of the daily milk yield ($$m$$ = 1, 2, 3, 4),

$$g_{n}$$ – effect of the milk F/P ratio ($$n$$ = 1, 2, 3, 4),

$$e_{ijklmno}$$ – random error.

Significance of differences between means was estimated with the Duncan test at the level of P = 0.01. To carry out calculations GLM and FREQ procedures (with use of chi-square test (χ2) at P ≤ 0.01) of the SAS statistical package were used [].

## RESULTS AND DISCUSSION

### Assessment of the milk capacity in the cow population

Table 1 presents data on the milk performance of the cow population. The daily production of 491 cows was determined using 4838 periodic observations. The average daily yield of milk varied considerably, and in 10 herds of the cattle it amounted to 22.1 kg and ranged from 15.9 kg (herd No. 2) to 30.4 kg (herd No. 6). Data on fat and protein content and the milk F/P ratio confirmed the well-known fact of high variation in the level of these parameters in PHF dairy cows. The highest fat content was in milk produced by herd 9 (4.53%), with the highest protein content in herd 1 (3.51%). The lowest level of fat was in the milk of cows in herd 8 (4.02%), and the lowest protein content was in herd 5 (3.20%).

The variation of the chemical composition of cows' milk is the result of a number of factors which consistently differentiate the level of individual components at the production level. The production conditions include the season of the year, the cow's age, the lactation stage and the pregnancy, the cow’s condition during milk production, the disease (mainly metabolic and udder) and feeding [, , , , ]. In view of the high variation in milk chemical composition, some authors point out that the impact on the above factors should be taken into account when determining it. Guliński and Kłopotowska [] suggest including somatic cell count, nutrition level and the milk yield in studying PHF-typical milk chemical composition.

### Effect of selected factors on the milk F/P ratio

Table 2 presents the distribution of the milk F/P ratio, according to the effects of factors listed in Materials and Methods. Based on 4838 observations the average value of the ratio amounted to 1.26, but it ranged from 0.01 to 3.06. A high statistically significant (P = 0.01) effect of the lactation period, the herd and the production level on the formation of the milk fat to protein ratio were noted in the research. The highest values of the ratio were found in milk produced during the first months of lactation, but also in the milk of cow herd 2 and in the milk of cows with the production level of 15–25 kg, with 1.32, 1.32 and 1.29, respectively.

Currently, in Poland the average milk F/P of PHF cows is 1.23 []. After a 15-year assessment of cow population in southern Podlasie Guliński et al. [] found only a slight increase of this ratio. Similarly, only a slight variability of the F/P ratio was observed both throughout lactation and over the productive lifetime []. The lowest average ratio reaching 1.15 was recorded by Barłowska et al. [] for Simmental and Jersey cows, and the highest (1.29) for Red-and-White cows. In other Simmental populations studied by Grega et al. [] and Barłowska et al. [] this ratio was even lower and ranged from 1.07 to 1.19. In contrast, Litwińczuk et al. [], studying Black-and-White PHF milk, as well as the authors of many other studies [, , ] carried out on cows with varying amount of PHF blood recorded the similar average F/P ratio of 1.20.

In their studies of 1693 Holstein-Friesian cows in Germany, Buttchereit et al. [] recorded the average milk F/P ratio within the first 180 of lactation of 1.13. They estimated the heritability of the ratio at 0.30.

### Distribution of the milk F/P ratio

Effect of selected factors on the distribution of the milk F/P ratio is presented in Table 3. According to the data in 68.5% of milk samples the fat to protein ratio ranged from 1 to 1.4, indicating that they came from cows fed with fully balanced food rations. In 19.9% of milk samples the F/P ratio ranged from 1.41 to 1.7, suggesting that they were from cows with subclinical ketosis. In 3.3% of total milk samples the fat to protein ratio was above 1.7, indicating clinical ketosis. Additionally, 8.2% of milk samples with the F/P ratio below 1 suggested that they came from animals affected with acidosis.

A detailed analysis of the effects of various factors revealed that the highest percentage of milk samples indicating subclinical ketosis was during the first three months of lactation (29.2% of the total), in the milk of herd 2 (31.9%) and the primiparous group (21.0%) and in the group with a daily yield of 15–25 kg (22.2%). The results showed that regarding the prevalence of clinical ketosis the greatest risk in the conditions of eastern Poland is associated with the first lactation trimester. During this period the F/P ratio of 7.7% of milk samples exceeded 1.7. It was also found that increasing milk yields of the cow population to a higher degree was accompanied by a higher risk of lactic acidosis than ketosis. In the group of cows with the average daily yield of milk of over 35 kg, 25.6% suffered from acidosis and 12.2% from ketosis (subclinical and clinical).

Generally, data on the prevalence of SCK vary considerably, depending on their source. The problem is mostly observed in poorly-fed animals with high milk production potential. In Poland among cows that were assessed for β-hydroxybutyrate acid the level exceeding 1.4 mmol · L–1 was found in at least 10% of the animals. However, according to Słoniewski after Guliński [], 20% of cows in the first lactation, 16% in the second and 23% in the third and subsequent lactation were affected in a similar way. In the USA and Canada, the prevalence of subclinical ketoses in bovine herds ranged from 30 to 50% [].

Brunner et al. [] studied the prevalence of SCK and production-related clinical diseases in early lactating cows in various countries across the world, other than those in North America and Western Europe. Twelve countries of South and Central America (Argentina, Brazil, Chile, Colombia, Mexico), Africa (South Africa), Asia (Thailand, China), Eastern Europe (Russia, Ukraine), Australia, and New Zealand were assessed. Data from a total of 8,902 cows from 541 commercial dairy farms were obtained. A minimum of five cows per farm were blood sampled and examined once after parturition up to day 21 of lactation. Across all investigated countries, the SCK prevalence was 24.1%, ranging from 8.3% up to 40.1%. Despite differences in production systems across countries and variation between individual farms within a region, the authors pointed out that data on SCK prevalence aligned with observations in Western European and North American dairy herds []. Data from 1693 Holstein-Friesian primiparous cows in Germany recorded within the first 180 days of lactation by Buttchereit et al. [] indicated that disease frequencies (percentage of cows with at least one case) was 9.7% for metabolic disorders.

Fiorentin et al. [] evaluated a total of 299 Holstein cows during early lactation (from calving to 30th day of lactation) in 15 herds located in the western region of Santa Catarina state in Brasil. Blood samples were collected for the measurement of BHBA. In that research, the cut-off point for SCK was when serum BHBA concentration was over 1.2 mmol · L–1. The results showed a 9% occurrence of subclinical ketosis. Although no significant differences were observed in subclinical ketosis prevalence among cows with different production levels. The rate of this disorder was almost double in cows yielding more than 30 L per day than in cows producing 15–30 L per day, with 14.9 % and 6.9%, respectively.

Asl et al. [] found that the prevalence of SCK was greatest in high-yielding dairy cows and in those with two or more lactations. Vlček et al. [] studied 208 Holstein cows from 3 dairy farms in west Slovakia calved between 2012 and 2015. The research included 908 test-day records of the yield from cows with 5 to 150 days in milk (DIM). The sample of cows produced 35.25 ±11.55 kg of milk daily. The average F/P ratio was 1.19 ± 0.25, and 19.71% of all observation were at risk of acidosis with 8.92% at risk of ketosis. The occurrence of ketosis risk decreased from 5 to 150 DIM. In the first month of lactation the proportion of ketosis risk was 22%, and in the fifth month it was 2.78%. The occurrence of acidosis risk increased and the occurrence of ketosis risk decreased from early to mid-lactation. Following Eicher’s recommendations [], subclinical disorder (ketosis/acidosis) was determined using the F/P ratio and the daily milk production. Additionally, the F/P ratio ≥1.5 in cows that yielded between 33 to 50 kg per day was used as an indicator of subclinical ketosis, while F/P ratio <1.0 in cows that yielded between 20 to 43 kg per day was used as an indicator of subclinical acidosis.

Gantner et al. [] studied first-parity cows of Holstein breed in Croatia and found that ketosis prevalence was highest in the first 15 days of lactation, with 33% of affected cows, while in cows with more lactations the prevalence peak was on the 25th day. Regarding acidosis prevalence, high values were determined at the beginning of lactation with a decreasing trend until mid-lactation, then the prevalence increased up to 22%. A significant negative effect of subclinical ketosis on daily milk yield for each parity was noted. A decrease in milk yield of 4.21, 2.73, 2.78, 2.83 and 3.72 kg per day in each parity (i.e., parities 1, 2, 3 and 4+) was found within 35 days after the detection of subclinical ketosis.

Table 4 presents the effect of the milk F/P ratio on selected milk production traits. There was a significant effect of the ratio on the daily milk yield and fat, protein and dry matter content. The highest content of fat and dry matter was in milk with the highest F/P ratio (>1.7), with its average level of 5.78% and 14.2%. respectively. The lowest level of fat was in milk with the lowest F/P ratio (≤1), with the average of 3.08%. A strong relationship was noted between the F/P ratio and the milk production traits. An increase in F/P ratio was accompanied by a decrease in the concentration of protein and an increase in the amount of fat and dry matter in milk. In milk with milk F/P ratio ≤1, 1.1–1.4, 1.4–1.7, >1.7 the levels of protein were 3.46, 3.49, 3.32, 3.07, the levels of fat: 3.08, 4.22, 4.97, 5.78 and dry matter: 13.7, 13.1, 13.6, 14.2, respectively.

## CONCLUSIONS

According to 4838 observations the average milk F/P ratio was 1.26, but large variation within individual factors was recorded. It was observed that in 3313 milk samples, i.e. 68.5%, the milk F/P ratio ranged from 1.1 to 1.4, indicating adequate nutrition and daily rations. However, 8.2% of the observations indicated the prevalence of acidosis in the cow population, 19.9% of the observations suggested the occurrence of subclinical ketosis and 3.3% of the milk samples were from cows affected with clinical ketosis. In addition, the analysis of the fat to protein ratio showed that cows in the first three months of lactation were particularly susceptible to metabolic problems. In this group the share of animals affected by acidosis or ketosis was close to 45%.

## ACKNOWLEDGEMENT

The work has been financially suported within the project no. 474/16/S – UPH Siedlce.

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