The study attempted to estimate the lactation curves of primiparous dairy cows in relation to their feeding management. Therefore, the first aim of the study was to determine and compare the lactation curves of primiparous dairy cows using Wood’s model and to estimate the association between the lactation curves and feeding management. The second objective was to investigate the effect of the culling rate on improvement in the milk yield of primiparous dairy herds. The study was conducted on four commercial dairy farms of Polish Holstein–Friesian cows using different feeding systems (TMR—total mixed ration and PMR—partial mixed ration) and management (T1—one TMR throughout lactation; P1—one PMR throughout lactation; T2 and T3—three feed periods such as FRESH, TMR I and TMR II according to days in milk). The data used for the study were obtained from monthly milk performance evaluations of 1662 primiparous cows conducted by the Polish Federation of Cattle Breeding and Dairy Farmers throughout the year 2015. Wood’s lactation model was used to plot curves for milk yield, fat and protein content, lactose content, and milk urea contents. The highest milk yield for the whole lactation and in the peak lactation phase was recorded for cows in herd T1. This herd reached peak lactation on day 105 of milking, with an average milk yield of 42.1 kg, which was about 5 kg more milk than in the other herds. The study showed that the culling of primiparous cows in herd T1 after 30, 60 and 90 days of lactation prevented a significant reduction in milk yield in a 305-day lactation. It also increased average milk production by 1586.9 kg per primiparous dairy cow.

The aim of the study was to carry out a research on the use of milking robots compared to utilization of milking parlors. There was no such study in literature on the milking farms in Poland and abroad. The presented study, except for scientific knowledge, provides also practical utilization as a good agriculture practice on the farm. Tests were carried out simultaneously in two barns belonging to the same farm. In barn K, milking was used in the rib bone milking parlor, and in barn N with milking robots. The results covering three years of research from 2016 to 2018 were presented. It was concluded that the milk yield of young cows in both barns was almost identical, while in the second and subsequent lactation, cows in barn N had higher yield. In barn N, about 3% more milk was obtained from LKS below 400 thaus. ml−1, compared to barn K. Time of cows’ utilization in both cowsheds was similar, while in barn N the life efficiency of culled cows was higher by about 1,000 kg of milk. The level of deficiency and its structure, due to the number and stage of lactation, were very similar in both barns. In barn N, the uniformity of milk production throughout the year was more even compared to barn K. There were reserves in the use of the milking robot due to the low number of cows per milking stand and the need to better adaptation of milking times to current cow performance. The milking robot improves cow welfare and ensures high milk yield and good cytological quality of milk.

Abstract. A study was conducted on the effect of separated manure as bedding material on milk quality as manifested in the somatic cell count. Cows were maintained in a loose barn in cubicles bedded with fresh separated cattle manure (SCM) with 40 % solids content. Analyses were conducted on 242 primiparous Polish Black and White Holstein-Friesian cows in the course of a 305-day lactation. Mean milk yield in that period amounted to over 9000 kg per cow. Somatic cell counts, daily milk yields and chemical composition of milk were analysed. Data were obtained from analyses of 2324 milk samples. It was found that 93.3 % of samples contained less than 400 000 somatic cells per 1 mL milk. Approximately 4.3 % of milk samples contained the number of somatic cells indicating subclinical mastitis (200 000 cells mL−1), while in 2.4 % it was clinical mastitis (> 800 000 cells mL−1). The incidence rate for both forms of mastitis was similar in the beginning and at the end of lactation. Mean daily milk yield of cows producing milk classified according to quality (SCC) grades 1 (< 25 000 cells mL−1) and 2 (< 25 000; 50 000 > cells mL−1) was statistically significantly greater than the yields of other cows. For analysed milk constituents a relationship was found between SCC classes and contents of milk fat and solids. Conducted analyses showed that SCM as bedding in cow cubicles had no effect on somatic cell counts in milk of primiparous cows. The study was conducted in a single holding, in one lactation, on cows calving in 2014.

We researched the influence of two methods of housing primiparous cows on meeting estimated energy requirements. In herd A primiparous cows were kept in a separate technological group during the whole lactation period, whereas in herd B they were kept in technological groups together with multigravid cows. The whole herd A consisted of 400 cows, where the average annual yield was 10,200 kg of milk per cow. Herd B consisted of 250 cows, where the average annual yield was 8,500 kg of milk per cow. In 2010 and 2011 there were 200 primiparous cows in herd A, whereas in herd B there were 165 primiparous cows. The milk yield for 100 and 305 days of lactation was analysed. Meeting the cows' demand for energy was determined on the basis of the percentage of protein in milk. In both herds primiparous cows were divided into milk yield classes for 100 days of lactation. Both the trend and the amount of variation in the content of protein in milk were found to be identical in both herds. The content of protein in milk increased as the milk yield decreased. This regularity could be observed at both lactation stages under analysis and the differences between the classes were statistically confirmed. During the first 100 days of lactation the estimated energy deficit comprised a much larger percentage of the cows than in the 305-day lactation period. The system of maintenance of primiparous cows (separately or together with multigravid cows) was not found to influence the milk yield or the estimated demand for energy.

The aim of the study was to determine factors influencing the balance of energy and protein in high-yielding cows. Daily milk yield, lactation number and month of lactation were analysed. The study was carried out in a herd with yield of 11,000 kg milk/year, on 517 lactating cows. The cows were divided into four feeding groups. They were fed TMR calculated for levels of milk production, as follows: group 1 – for 45 kg, group 2 – for 35 kg, group 3 – for 26 kg and group 4 – for 20 kg. The actual mean milk yield for these groups was 49.1 kg, 38.1 kg, 26.3 kg and 17.5 kg per day. Each group consisted of cows in their first to sixth lactation and in their first to tenth month of lactation. No significant differences were noted in daily milk yield between lactation numbers or months of lactation. As milk yield increased in the groups, the content of fat and protein decreased. The estimated balance of energy, based on the protein percentage in the milk, was negative for nearly the entire lactation in group 1, for the first four months of lactation in group 2, for the first two months in group 3, and in the second month of lactation for group 4. Group 1 was divided into three subgroups according to yield: up to 45 kg, 45-50 kg and 50 kg or more. Energy was estimated to be wellbalanced only in the first subgroup. The balance of energy in the cows was strongly determined by daily milk yield, and to a lesser degree by the month of lactation. Protein, based on the concentration of urea in the milk, was well-balanced in groups 1 and 2. In groups 3 and 4, the recommended level of protein in the rations was exceeded by 10-20%.