Ketosis is the most common metabolic disease in high-performance dairy cows during the first 6-8 weeks of lactation. Its main symptoms include an excessive amount of so-called ketone bodies in a cow's body fluids. Ketone bodies consist of β-hydroxybutyric acid (βHBA), acetoacetic acid, and acetone. βHBA is the main component with its share of the total volume of ketone bodies in the blood of about 70%. Clinical symptoms of ketosis in cows include loss of appetite, preference for forage to concentrated feed, and acetone odor in their mouth and urine. Those symptoms are accompanied by a production drop, an increase of concurrent illness (mastitis, metritis, and displaced abomasum), and poor reproductive performance. One of the ketosis characteristic effects is an increase in the level of fat in milk (>5%), while protein levels decrease (<2.9%). In the case of subclinical ketosis (SCK), the fat–protein ratio in milk is increased to above 1.4:1. The current consensus for SCK is to consider a cutoff point of βHBA to be at least 1.2 mmol/L in blood plasma. Ketosis prevention is based on keeping perinatal cows in good condition, that is, with around 3.5 points in the five-point body condition scoring, carefully balancing food doses during the first 2 months of lactation with the correct energy–protein ratio. Glucose precursor products should be administered orally, in particular to at-risk herds. Ketosis occurs in 7-14% on average of the total number of cows in a herd. In general, data on the prevalence of SCK vary considerably, depending on their source. Moreover, the problem is mostly observed in poorly-fed animals with high milk production potential. The objectives of this review are to reveal the current situation of ketosis prevalence, the possibility of diagnosis, consequences in dairy cows and to provide some recommendations for ketosis treatment and prevention.

Investigation of antimicrobial resistance and genetic relatedness of staphylococci from milk of cows with mastitis and cowshed environment was the aim of this study. Antimicrobial resistance against 14 antimicrobials were determined by using a disc diffusion method. Genetic similarity between the most frequently isolated species was analysed by PFGE (pulsed-field gel electrophoresis). Haemolytic activity, DNase, protease and esterase production was also investigated. Coagulase-negative Staphylococcus species were isolated from 30.8% of milk samples from cows with mastitis. The most frequently isolated species was Staphylococcus xylosus and yield of these organisms was significantly associated with milk of mastitis cows. S. epidermidis was a predominant penicillin-resistant species. High frequency of resistance to lincomycin was observed among isolates of S. sciuri (54.2%) and S. xylosus (25.9%) from cows with mastitis. PFGE (pulsed-field gel electrophoresis) analysis of 29 Staphylococcus aureus isolates showed the presence of 17 PFGE pulsotypes. Isolates of S. sciuri (n=36) had unique PFGE patterns. Some S. xylosus isolates from milk and milker's hands had the same PFGE pulsotypes, and this observation could indicate that dairyman may be a potential source of the infection. The pulsotype of each of the remaining isolates of S. xylosus suggested that they might have come from common environmental sources; however, these isolates differed in antibiotic resistance pattern or virulence traits. Therefore, knowledge about antibiotic sensitivity pattern and virulence factors of a CNS isolate, besides its genotype, may be informative in tracking the source of the infection.

The aim of this paper is to develop a method for determining the typical chemical composition of the milk of Polish Holstein-Friesian (PHF) cows. The paper uses data collected from 1329 test-day milking records from 20 herds of PHF dairy cattle in Sokołów County, from 2009 to 2015. The effect of the following factors on the chemical composition of milk was determined: lactation stage (15 one-month stages); age of cows (lactations 1, 2, 3–4, and 5–7); genotype (share of PHF breed: less than 50%, 50–75%, 75–82.5% and more than 82.5%); somatic cell count (SCC) in 1 ml of milk (in thousands: 0–200, 200–400, 400–1000 and more than 1000); feeding level (fat to protein (F/P) ratio): ≤1.0, 1.0–1.4, 1.4–1.7 and >1.7); calving season (autumn/winter, spring/summer) and daily milk yield (milk yield in kg: ≤15, 15–25, 25–35 and >35). Nutrition and udder health status were found to be the main factors influencing the chemical composition of milk. For selected cows with optimally balanced feed rations (F/P ratio in milk from 1.1 to 1.4) and a low somatic cell count (SCC ≤200,000/ml), daily yield was the main factor affecting the chemical composition of the milk. It was also concluded that government and scientific publications on the PHF breed should take into account the impact of the F/P ratio, SCC and yield of milk on its composition.

The aim of the study was to analyse the concentration of immunoglobulins in colostrum produced by Polish Holstein-Friesian (PHF) cows in relation to selected factors. An important element of the study is the analysis of colostrum yield and density. The research was conducted between April 2017 through April 2018. The yield and selected traits of colostrum obtained from the first 9 milkings from 20 PHF cows calving during this period were analysed. A total of 180 measurements were made. The average immunoglobulin content in the 180 observations was 37.7 g • L -1 , ranging between 7 and 140 g • L -1 . The study showed a significant effect of time after calving on the content of immunoglobulins. The highest content of the antibodies was found in colostrum obtained immediately after calving. Its average level at that time was 90.2 g • L -1 and in 20 assessed cows it ranged within the wide limits of 32-140 g • L -1 . The quality of colostrum radically deteriorated soon after calvong. The lowest level of immunoglobulins was found in the 96th hour after parturition and it was on average 10 g • L -1 . The average yield of colostrum was 10.3 kg. The yield of colostrum increased with time elapsing after calving. The lowest colostrum yield was observed within 2 hours, the highest within 96 hours after calving, respectively, 6.9 and 12.4 kg. The average specific density of colostrum was 1.041 g • cm -3 . The study showed that the highest density was characterized by colostrum obtained in the first milking post-partum. Its specific weight was 1.059 g • cm -3 . In subsequent milkings, the calcareous density of colostrum systematically decreased to 1.030 g • cm -3 in the 90th hour after calving.

The average somatic cell count in the milk analysed was 326,000 cells/ml. For the 4 groups of cows distinguished in the study, with daily milk yield of ≤15 kg, 15-25 kg, 25-35 kg and >35 kg, the somatic cell count was 771,000, 393,000, 240,000 and 180,000 cells/ml, respectively. Statistical analysis revealed significant differences in the somatic cell count in milk from cows with different productivity. A highly significant correlation coefficient was obtained for the daily milk yield of the cows and the somatic cell count in the milk (r=−0.81). The negative coefficient indicates that an increase in the quantity of milk was accompanied by a decrease in the somatic cell count in the milk. The regression equation obtained suggests that in the study population a decline in somatic cell count of 100,000 cells/ml was accompanied by an increase in daily milk yield of 3.8 kg. The analysis showed that there is a negative correlation between SCC and milk yield of cows. An increase in milk yield was found to be accompanied by a decrease in the number of somatic cells in 1 ml of milk, which indicates an improvement in its quality.