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 this study was to compare daily yield, milk composition and somatic cell count after increasing milking frequency from twice to three times a day. The study also includes the effect of other factors such as: the sequence of lactation (1, 2, ≥3) and the period of lactation (100 days, 101-200 days, 201-300 days, and more than 300 days). In conclusion, it should be noted that increasing the frequency of cow milking had a positive effect both on the milk yield (P≤0.01), causing a substantial increase, as well as on the cytological quality of produced milk. The somatic cell count (1000/mL) was lower in the group of cows milked three times a day. All the data regarding farming records of this farm came from the SYMLEK system maintained and made available by Polish Federation of Milk Producers and Cattle Breeders (PFHBiPM). Analysis of useful milk traits included: daily yield, fat, protein, dry matter and somatic cell count in milk.

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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.