Early prediction of lactation milk yield enables more efficient herd management. Therefore, this study attempted to predict lactation milk yield (LMY) in 524 Polish Holstein–Friesian cows, based on information recorded by the automatic milking system (AMS) in the periparturient period. The cows calved in 2016 and/or 2017 and were used in 3 herds equipped with milking robots. In the first stage of data analysis, calculations were made of the coefficients of simple correlation between rumination time (expressed as mean time per cow during the periparturient period: second (14–8 days) and first (7–1 days) week before calving, 1–4, 5–7, 8–14, 15–21 and 22–28 days of lactation), electrical conductivity and temperature of milk (expressed as means per cow on days 1–4, 5–7, 8–14, 15–21 and 22–28), amount of concentrate intake, number of milkings/day, milking time/visit, milk speed and lactation milk yield. In the next step of the statistical analysis, a decision tree technique was employed to determine factors responsible for LMY. The study showed that the correlation coefficients between LMY and AMS traits recorded during the periparturient period were low or moderate, ranging from 0.002 to 0.312. Prediction of LMY from the constructed decision tree model was found to be possible. The employed Classification and Regression Trees (CART) algorithm demonstrated that the highest lactation yield is to be expected for cows with completed lactations (survived until the next lactation), which were milked 4.07 times per day on average in the 4th week of lactation. We proved that the application of the decision tree method could allow breeders to select, already in the postparturient period, appropriate levels of AMS milking variables, which will ensure high milk yield per lactation.

The study has been carried out on 16 Polish Holstein-Friesian dairy cattle herds across Poland. A change in the milking system from the conventional to the automatic system was implemented in these herds between 2010 and 2013. The purpose of the study was to indicate potential changes in milk production traits after automatic milking had been introduced. Milk yield and composition (fat and protein content, %) were monitored as part of the study in cows in their first (2620 cows) and second (1339 cows) full lactations between 2008 and 2015. The material used in analyses of production traits was extracted from the SYMLEK data registration system. The analysis indicated that for a majority of traits the main sources of variability of production performance in primi- and multiparous cows included the milking system, the herd and the interaction of milking system x herd. The study indicated that after the milking system had been changed from conventional to automatic the milk yield obtained from primiparous cows increased by 15%, whereas for second-lactation cows - by 9%. These changes were accompanied by a gradual decrease in fat content in milk for both lactations, while in the case of protein content it was only in the first lactation.

The aim of the work was to discuss the role and importance of longevity in Holstein-Friesian cows and to present the impact of various factors and their interactions on their life expectancy and use. Understanding the determinants of longevity seems to be key to its improvement. The results of many studies show that for many years there has been a worldwide trend towards the decreasing lifespan of dairy cows. It results from the intensification of milk production and from paying inadequate attention to animal welfare issues. Actual herd life depends on breeders, who make decisions based on cow productivity and the general state of health indicating the chance for survival. The existing knowledge has to be continuously updated due to the complexity of issues arising from cow longevity and the need to understand contributing factors, which is important from both a scientific and practical point of view.

The new techniques for automation of the milking process allow for early diagnosis of mastitis. Diagnosis of subclinical mastitis should be a priority for every producer aiming to obtain raw milk of highest possible cytological quality. The analyses were performed based on herd milking data for Polish Holstein-Friesian cows yielding an average of 9500 kg milk. The herd consisted of 180 lactating cows, data from almost 152 000 milkings were obtained. Correlations were calculated between milk electrical conductivity vs. daily yield and milking ability of primiparous and multiparous cows. The numerical data were statistically analysed using multifactorial analysis of variance. An increase in milk electrical conductivity and thus deteriorating udder health were paralleled by a significantly lower milk yield in both primiparous and multiparous cows. In primiparous cows, the decrease was 4.7 kg (from 32.0 with milk electrical conductivity of ≤5.50 mS/cm to 27.3 kg with conductivity of >7.00 mS/cm). A notably greater reduction in productivity was observed for multiparous cows (5.5 kg) between the extreme ranges of milk electrical conductivity. In both primiparous and multiparous cows, milking time increased progressively with increasing range of milk electrical conductivity (from 366 to 372 s and from 369 to 379 s, respectively). Milk yield per minute decreased by 0.41 kg (from 2.23 to 1.82 kg/min.) in older cows and by 0.32 kg (from 2.05 to 1.73 kg/min.) in primiparous cows. The deteriorating udder health caused a significant decrease in daily milk yield of the primiparous and multiparous cows in every lactation period. For both primiparous and multiparous cows, the highest milk yields per minute (2.08, 2.20, 2.20 and 1.88; 2.57, 2.37, 2.18 and 1.96 kg/min., respectively) in all lactation periods were observed when milk electrical conductivity (≤5.50 mS/cm) was indicative of very good udder health. In summing up, it is concluded that throughout lactation, in both primiparous and multiparous cows, daily milk yield decreased with increasing electrical conductivity of the milk and thus with deteriorating udder health. Furthermore, milk electrical conductivity had a significant effect (in the interaction with lactation period and daily milk yield of the cows) on milkability traits.

The objective of this study was to reveal the effect of milk urea levels on the fertility of dairy cows, taking into account their age, herd production level, number of cows, season of first insemination, which were analyzed using data from the SYMLEK national system. The study included data on milk urea levels in 88,745 test-day yields of 55,685 Holstein?Friesian cows, which were milked up to 30 days before first insemination, during the period preceding 180 days of first and second lactation. The GLM procedure of the SAS package was used in the statistical calculations. Considering the observed significant relationships and tendencies, a milk urea level higher than 300 mg/L was found to negatively affect reproductive efficiency in dairy cows, although the effects of the urea level could be masked by the more profound impact of environmental factors. Regardless of the factors, an increased milk urea level was paralleled by decreased cow fertility, with statistically significant differences occurring only for the interactions with herd production level and with herd size. The unfavorable effect of the increase in the level of urea in milk (from ≤150 to >300 mg/L) on cow fertility was particularly evident in the highest producing herds (>9000 kg milk).

The objective of the study was to analyse the effect of age at first calving (AFC) on first lactation milk yield, lifetime milk production and longevity of dairy cows. The study used SYMLEK data on the milk yield and culling of 111 857 Polish Holstein-Friesian cows from the active population in Pomerania and Kujawy, Poland. The cows first calved during 2000-2009 and were used or removed from the herds until the end of 2015. For each cow, calculations were made of first lactation milk yield, lifetime milk production, first lactation milk yield per milking day, lifetime milk production per day, as well as the lifespan (length of productive life, duration of rearing) and number of calvings. Based on the age at first calving (duration of the rearing period), the cows were grouped as follows: <= 22, 22.1-24.0, 24.1-26.0, 26.1-28.0, 28.1-30.0, 30.1-32.0 and >32 months. The GLM, CORR PEARSON and FREQ procedures from the SAS package were used in the statistical calculations. Considering first lactation milk yield, lifetime milk production and longevity, it is recommended that the cows should be first milked between 22.1 and 26.0 months of age. This is supported by the approximately 24% higher lifetime milk production in relation to the latest calving cows (P<0.01). Late commencement of the first milking (especially after 28 months) causes a considerable decrease in the first lactation milk yield and lifetime milk production, shortens the productive period, reduces the number of calvings, and increases culling rate due to low milk yield and udder diseases.

The aim of the study was to analyse the relationship between the somatic cell counts in the milk (the udder health status indicator) and the cow's fertility, taking the influence of the selected factors into account. The udder health status was determined based on the somatic cell count of the milk from 88 745 test-day records from 55 685 Polish Holstein-Friesian cows. The test-day measurements were made up to 30 days before the first insemination, during the period up to 180 days of the first and second lactation. Because the somatic cell count showed high variation and is not normally distributed, the data were transformed to the natural logarithm scale. Based on the results of the statistical analysis, it was shown that with the increase in the number of somatic cells in the milk, the calving intervals were extended by 11 days (P ≤ 0.01), the service period by around 4 days (P ≤ 0.05), the increase in the services per conception by 0.11 (P ≤ 0.01). There was a statistically significant correlation, weak on the Guilford scale, between the natural logarithm of the somatic cell count and the fertility of the cows: the calving interval - CI (r = 0.050**, P ≤ 0.01), service period - SP (r = 0.016**) end services per conception - SPC (r = 0.019**). Monitoring the number of somatic cells in the milk could contribute to improving the fertility of the cows in particular: in the second lactation in the double lactation (for the CI (r = 0.059**)); in herds with a production level of 7000-9000 kg of milk (for the CI (r = 0.055**), the SP (r = 0.022**) and the SPC (r = 0.024**)); the daily productivity of > 40 kg (for the CI (r = 0.052**), the SP (r = 0.033**) and the SPC (r = 0.029**)), the number of cows in the herd of > 200 (for the CI (r = 0.061**), the SP (r = 0.034**) and the SPC (r = 0.033**)), in the autumn season of the first insemination (for the CI (r = 0.072**), the SP (r = 0.027**) and the SPC (r = 0.031**)). The magnitude of these correlations varied within the classes of the factors such as the daily production level, the age of cows´ lactation number, the season of the first insemination, the herd production level, and the herd size. It appears that the somatic cell count results obtained from the periodic milk recording, considered as an indirect measure of the udder health and used when deciding on the mastitis treatment, could be a useful tool for controlling the fertility in the cows.

Decreasing fertility in dairy cows, especially in the highest yielders, may be due to excessive metabolic burdens placed on their bodies. Many authors attribute decreasing reproductive efficiency in high-yielding cows to energy deficiencies in early lactation and to associated metabolic and hormonal disorders. The complexity of the issues involved in the efficient reproductive management of cows and the scientifically and practically important understanding of factors affecting fertility in high-producing cows mandate continuous updating of existing knowledge. The aim of this study was to present the effect of postpartum endocrine function, metabolism, and mastitis on fertility in high-yielding cows. Gaining insight into these mechanisms and their relationships with factors such as nutrition and milk yield appears to be crucial for improving dairy cow fertility.

The study, performed in January 2017 on a group of 271 consumers, used data obtained from an anonymous internet survey concerning the consumption frequency of different fermented milk drinks and the criteria which determine consumer purchase decisions.Consumption of fermented milk beverages was declared by 83.8% of the respondents regardless of their socio-demographic status (sex, residence, education, social status).The most frequent consumption was recorded for yoghurt (40% of those surveyed, 3-5 times per week), followed by kefir and buttermilk (less than once a week).Respondent purchase choices were most influenced by product quality, in particular flavour (4.48 pts.), shelf life (4.27pts.), nutritive value (3.82 pts.) and health-promoting value (3.53 pts).Advertising was of marginal importance (1.94 pts.).When creating new types of fermented milk drinks, it is worth focusing on improving their flavour and making them more attractive while paying attention to product shelf life.

The aim of the study was to evaluate relations between feto-pelvic proportion and further fertility of milk cows, select proportions and critical values of disproportion best predicting cows with lower fertility as a result of difficult calving as well as to evaluate fertility of cows selected on the basis of chosen criteria. The study was carried out on black-and-white and red-and-white Polish Holstein-Friesian cows in six farms diversified by the number of livestock (from 10 to 20 to over 180 cows) and milk yield (from 6.563 –

The effects parity, herd production level, number of cows per herd, insemination season and lactation stage on the relationships between daily milk and first insemination success of 55 685 cows were examined. The statistical analysis was performed using the chi(2) test and the decision tree technique. The chi(2) test showed that all the experimental factors affected the insemination success as a function of the daily milk yield of the cows; as it increased from <= 20 kg to > 40 kg, first insemination success decreased by more than 7% in primiparous cows, and by as much as over 16% in second lactation cows. With the herd production level going up from <= 7000 kg to > 9000 kg, the unfavourable effect of the increasing daily milk yield on fertility decreased almost 4-fold. Summer was the least favourable period for insemination. Cows yielding > 40 kg milk/day were particularly sensitive to heat stress, as evidenced by their first insemination success decreasing by over 13% in relation to the cows producing <= 20 kg milk. In winter this difference was 9.5%. Considering the lactation stage, as daily milk yield increased, first insemination success decreased by around 9% when performed up to 60 days of lactation, and by as much as over 15% during 151-180 days of lactation. Cows in bigger herds exhibited lower fertility, but the increase in daily milk yield caused first insemination success to decrease by 16% in very small herds (<= 20 cows) and by 4.6% in larger herds. Classification tree analysis showed that similar factors (lactation period, number of cows per herd, daily yield, parity) were moderating the first insemination success in cows. At the same time, the applied methods showed that the determinants of fertility in cows are highly complex. This complexity may be well explained using the classification tree technique.

Motor activity of 158 Polish Holstein-Friesian cows was evaluated 5 times (before and during milking in a DeLaval 2*10 milking parlour) for both the morning and evening milking, on a 5-point scale, according to the method of Budzynska et al. (2007). The statistical analysis used multiple logistic regression and classification trees (Enterprise Miner 7.1 software which comes in with SAS package). In the evaluation of motor activity, cows that were among the first ten to enter the milking parlour were more often given a score of 3 points before (11.5%) and during milking (23.5%) compared to the other cows. Cows' activity tended to decrease (both before and during milking) with advancing lactation. The cows' reduced activity was accompanied by shorter teat cup attachment times and lower milk yields. The criteria calculated for the quality of models based on classification tree technique as well as logistic regression showed that similar variables were responsible for the reactivity of cows before milking (teat cup attachment time, day of lactation, number of lactation, side of the milking parlour) and during milking (day of lactation, side of the milking parlour, morning or evening milking, milk yield, number of lactation). At the same time, the applied methods showed that the determinants of the cow reactivity trait are highly complex. This complexity may be well explained using the classification tree technique.

This study was designed to analyse the effect of milking behaviour (temperament) of primiparous dairy cows on their milk and reproductive performance as well as survival to the second lactation. Milk performance, reproductive performance and culling data on 12028 Polish Holstein-Friesian primiparous dairy cows were acquired from the SYMLEK database. Using the methodology of the Polish Federation of Cattle Breeders and Dairy Farmers, the temperament of the cows was assessed as: 1 - calm, 2 - normal, 3 - excitable or aggressive. Primiparous cows from the analysed population were characterized by averagely normal temperament and optimal milking speed. Daily and lactation yield depended (P <= 0.01) on the temperament of cows. Excitable (aggressive) cows had higher daily and lactation yield compared to normal and calm cows. The temperament trait was found to correlate (P <= 0.01) also with functional traits such as milking speed, survival to the second lactation, and culling level. As milking speed increased, the proportion of cows with calm temperament decreased and that of excitable (aggressive) primiparous cows increased. As the temperament score increased, so did the proportion of primiparous cows sold for further breeding. Excitable (aggressive) primiparous cows had the lowest chance of survival to the second calving.

The study involved 55 685 Polish Holstein-Friesian cows whose services per conception (SPC) averaged 2.2. Statistical analysis performed using the GLM procedure of SAS, showed significant differences in SPC value within different factors. The greatest changes were associated with daily milk yield of the cows; as it increased from ≤ 20 kg to >40 kg, the number of services required to conceive increased by 0.6. SPC value deteriorated also with an increasing number of cows in the herd (by 0.37) and with an increase in milk somatic cell count, being indicative of mastitis (by 0.11). The opposite situation existed for an increase in herd production level and lengthening of the interval between calving and first insemination (decrease of SPC by 0.31). It was also found that summer was the least favourable period for insemination and winter the most favourable (SPC=2.28 vs. 2.16). Analysis of the results demonstrates that it is necessary and appropriate to account for these factors when aiming to improve cow fertility.

The effect of first lactation yield and herd production level on longevity was studied using data from the SYMLEK database on 12045 Polish Holstein-Friesian cows in 1371 farms from the active population in Pomerania and Kujawy. The cows first calved in 2008 and were used or disposed from the herds by the end of 2015. FREQ, GLM and CORR procedures from the SAS package were used in the statistical calculations. The optimum level of first lactation milk from the viewpoint of longevity varies according to herd production level, which serves as a measure of the quality of rearing conditions. If the living conditions are not adapted to the high milk production of first calvers, there is a possibility that their productive life will be shortened and number of calvings decreased. The percentage of voluntary culling decisions by the breeder, which included the sale for further breeding, low milk yield and old age, averaged 9% and decreased with increasing herd production level from 16% to around 6%. The main reason for culling was infertility (around 40% on average). Culling due to infertility was particularly common among the cows which produced more than 11000 kg milk as first calvers.