Investigation of milk composition in different periods of lactation

The research aims to reveal milk composition in different periods of lactation, thus providing information to breeders about which lactation periods the milk quality is better and enlightening them on how to effectively make herd projections and herd planning. For this purpose, 14 dairy cows were monitored on a private farm in Bingol province Karliova district, Turkiye where approximately 400 Simmental breeds were raised. These cows calved at the same age (5 years old) and during lactation (3rd lactation, that is, having given birth at least 3 times), at close dates to each other. Milk samples were taken from the front and rear lobes of 14 cows with these conditions during morning and evening milking in the early period (day 60 of lactation), the middle period (day 130 of lactation), and the last week before going dry, that is, in the last periods of lactation (approximately day 210). A total of 168 milk samples, 56 in each period, were collected. The part including casein, acidity, pH, coagulation time, and ash analyses of milk samples was carried out by conventional methods; Fat, protein, lactose, fat-free solids, density, water, conductivity, salt, and somatic cell count analyses were performed with a milk analyzer. Casein analyses were determined using the α-casein standard by the SDS-PAGE electrophoresis method. Multi-factor analysis of variance [Factors: lactation periods (3), morning and evening milking (2), and anterior and posterior udder lobes (2)] was used to analyze the data. Using the General Linear Model, the main effects of the data obtained in a 3x2x2 experimental design and the interactions of the factors were determined. There was a statistically significant difference in pH value in different lactation periods (P<0.05). Interactions between factors in ash values were determined to be statistically significant (P<0.05). The effect of milk taken from the anterior and posterior mammary lobes on the clotting time was found to be significant (P<0.05). The effects of the lactation period on protein, lactose, salt, non-fat dry matter, density, freezing point, conductivity, somatic cell number, and casein, excluding fat, were statistically significant (P<0.05). As a result, although the composition of milk is different in terms of mammary lobes and milking time, it has been observed that the most significant difference is in the lactation periods. Although many factors are effective in this, the differentiation of the cellular structure in the breast in the pre-and postnatal period may be effective. The fact that casein, which has an important place in dairy products such as cheese and yogurt, is high in the middle period of lactation suggests that herd management should be more sensitive to the herd population in this period.