Wpływ produkcji dobowej w wybranych fazach laktacji na skład i cechy serowarskie mleka krów rasy holsztyńsko-fryzyjskiej

It was decided to analyze the daily milk production in selected lactation periods of Holstein-Friesian cows and to determine its impact on the basic milk components as well as parameters determining its cheese-making usefulness. The lactation was divided into six phases considering subsequent days of lactation after calving: 1st phase up to 30 days, II31-60, III- 61-100, IV- 101- 200, V- 201-300, VI >300. In each phase, considering daily milk production, two production groups were selected. The study results suggest that the intensity of daily milk secretion has a significant impact on the share of ingredients commonly assessed for cheese-making utility. Increased daily production of milk may favor a higher protein and casein level, however, there is not such a strong correlation with κ-casein concentration. As a result, it may affect the quality and efficiency of cottage cheese production. At the same time, it should be noted that changes in the content of the analyzed milk components were related to the changes in the chloride level, and their share was dependent on the daily milk production (P<0.05). The consequence of this was degradation of important cheese-making features: the reduction of curd amount and the prolongation of coagulation time.Analizowano wielkość produkcji dobowej mleka u krów rasy holsztyńsko- fryzyjskiej. Określono jej wpływ na zmiany poziomu podstawowych składników mleka a także parametrów jego przydatności serowarskiej. Laktację podzielono na 6 faz: I faza do 30 dnia laktacji, II- 31-60, III- 61-100, IV– 101-200, V– 201- 300, VI>300. W każdej z badanych faz, uwzględniając dobową produkcję mleka (DMP) wyodrębniono dwie grupy produkcyjne. Podział ten oparto na wartościach granicznych DMP wyliczonych w obrębie każdej fazy. Otrzymane wyniki badań sugerują, że intensywność wydzielania mleka w ciągu doby ma istotny wpływ na udział składników, które powszechnie określają przydatność serowarską mleka. Zwiększona produkcja dobowa mleka może sprzyjać większej zawartości białka ogólnego oraz kazeiny, jednak nie ma już tak silnego związku z koncentracją κ-kazeiny. Należy jednocześnie zauważyć, że zmiany zawartości analizowanych składników mleka, powiązane były z kształtowaniem się poziomu chlorków, a ich udział był uzależniony od dobowej produkcji mleka (P<0.05). Konsekwencją tego było pogorszenie ważnych cech serowarskich mleka, zmniejszenie ilości twarogu oraz wydłużenie czasu koagulacji

PRÓBA ZWIĘKSZENIA EFEKTYWNOŚCI WYTWARZANIA SERA POPRZEZ SELEKCJĘ MLEKA ZBIORCZEGO W ZALEŻNOŚCI OD ZAWARTOŚCI KAZEINY

Socio-economic conditions compel the milk industry and producers to undertake measures aimed at increasing production profitability. Above all, the specifics of long-ripened cheese production requires augmenting the casein content in milk. This is however obstructed by the lack of an established economically justified threshold value for this ingredient that would guarantee the efficiency of cheese production and correct settlement of accounts with the breeders. The presented study results for the 45th batch of milk refer to ingredients that decide the efficiency of the production of cheese from milk with different casein levels. The raw milk with a higher casein content contained 0.20% more protein (P ≤ 0.014) and 0.08% more k-casein (P ≤ 0.047). In comparison to the milk with a lower casein content, the obtained whey and cheese slurry contained 0.09% less protein (P ≤ 0.035) and 1.92% more dry non-fat matter (P ≤ 0.049). This milk also yielded 0.4% more cheese (P ≤ 0.039). It can be assumed that the selection of milk pools on the basis of their casein contents can improve production efficiency and set new trends in assessments of processing milk usability

The Effect of Energy Metabolism up to the Peak of Lactation on the Main Fractions of Fatty Acids in the Milk of Selected Dairy Cow Breeds

During early lactation in dairy cows, metabolic processes are adopted to provide energy and nutrients for the synthesis of milk compounds. High milk production potential includes sudden changes in energy metabolism (negative energy balance (NEB)) that can induce uncontrolled lipomobilization and high blood free fatty acid (FFA) levels. Destabilization of cows’ energy may interfere with endocrine homeostasis, such as the secretion of leptin, a co-regulator of the appetite center. Therefore, it is important to analyze the physiological aspects of the maintenance of energy homeostasis in various dairy breeds. Usually it is crucial for the health of cows, influences the production cycle and lifetime yield, and determines the profitability of production and milk quality. The aim of this study was to analyze the energy metabolism of selected breed groups of cows and its variability in different stages of early lactation. The analysis was performed using data on the following parameters: body condition score (BCS), fatty acid (FA) fractions, basic milk constituents, and serum parameters (BHBA, glucose, and leptin). These results were analyzed in relation to parameters of energy metabolism during the stage up to the peak of lactation. An earlier peak of lactation was shown to be conducive to an increase in the content of non-esterified fatty acids (NEFAs) and of casein and κ-casein. During the study period, parameters characterizing the maintenance of energy homeostasis were usually lower in the Simmental and Black-and-White Lowland cows. Compared to the group with the highest production, their yield was from 2.8 to 4.7 kg lower, but the milk had a more beneficial fatty acid profile and nutrient content, determining suitability for cheese making. At the same time, they had lower levels of NEFAs and β-hydroxybutyrate in the blood, which indicates less spontaneous lipolysis of fat reserves. Concentrations of the appetite regulator leptin in the blood were correlated negatively (p ≤ 0.05) with the glucose concentration (–0.259) and positively with NEFA (0.416). The level of NEFAs was at the same time positively correlated with the content of saturated fatty acids in the milk (0.282–0.652; p ≤ 0.05). These results contribute to our knowledge of the effect of production intensity on the maintenance of homeostasis up to the peak of lactation in dairy breeds with differing production potential. In practice, this may increase the possibilities of improving milk quality and the profitability of production

The Occurrence of a Negative Energy Balance in Holstein-Friesian and Simmental Cows and Its Association with the Time of Resumption of Reproductive Activity

Intensive lactation (lactogenesis) in cows is conducive to a negative energy balance (NEB), so the search for traits associated with the physiological capacity to cope with its consequences is a current area of research. This is especially important because NEB overlaps with the resumption of the reproductive cycle, which determines the profitability of herds. This study analysed the relationship between NEB and the time of resumption of reproductive activity in cows with varying genetic potential (Simmental and Holstein-Friesian), fed a similar diet (TMR). The aim of the study was to analyse the dependencies between NEB markers and changes in progesterone levels between 25 and 31 days postpartum. A strong positive correlation was shown between daily milk production (DMP) and loss of body condition (LBCS; 0.772; p &le; 0.05). These parameters were associated with the levels of NEB biomarkers. Higher values of NEB indicators (LBCS, C16:0, C18:1, NEFA, and BHBA) were usually noted during periods with higher DMP (II and III). The trends observed were confirmed by positive correlation coefficients (r), which ranged from 0.324 to 0.810 (p &le; 0.05). The reverse trend was noted for glucose and leptin, which decreased as productivity increased, as confirmed by r values from &minus;0.368 to &minus;0.530 (p &le; 0.05). In both breeds, the glucose and leptin levels decreased as DMP increased. Higher values for NEB indicators were shown to be negatively correlated with progesterone levels (r from &minus;0.300 to &minus;0.712; p &le; 0.05), and a lower progesterone level was associated with a longer calving-to-first-service interval and calving-to-conception interval. The rate of postpartum triglyceride release depends on daily milk production, and therefore the adaptability of the liver should be considered an important element of mitigation of the consequences of NEB. This may have practical applications by extending productive life, which is often shortened due to deteriorating reproductive performance