Asymmetric time interval between evening and morning milking and its effect on the total daily milk yield

摘要

Samples of milk obtained in the course of evening and morning milking performed in variable time intervals of either 11 and 13 hours (n = 1.282) or 10 and 14 hours (n = 370) were collected with the aim to quantify the effect of the length of a variable (asymmetric) time interval between evening and morning milking on the total amount and composition of daily milk production of dairy cows. Milk samples were analysed in an accredited (EN ISO 17025) laboratory in Brno-Tu?any (Czech Republic) and the following contents of individual milk components were estimated: fat (F; g.100gsup?/supsup1/sup), total protein (TP; g.100gsup?1/sup), lactose (L; lactose monohydrate; g.100gsup?1/sup), and somatic cell counts (SCC; 10sup3/sup.mlsup?1/sup) were estimated in. It was found out that with the increasing total daily milk production the shares of evening and morning milk yield increased as well; however, the percentages of evening and/or morning yields in the total yield remained practically unchanged and represented 43.5?% and 56.5% or 40.4?% and 59.6?% in variants with intervals of 11 and 13 hours and/or 10 and 14 hours, respectively. In the variant with the milking interval of 11 and 13 hours, values of correlation coefficients between the above parameters (i.e. F, TP, L, SCC, and log SCC) of evening and morning milk yields on the one hand and the total milk performance on the other ranged from the minimum r = 0.896 (F) to the maximum r = 0.980 (TP). In the variant with the interval of 10 and 14 hours, the corresponding values of correlation coefficients were r = 0.848 (F) and r = 0.983 (TP). These correlations were statistically highly significant in all cases (P ≤ 0.001). Further, linear regression equations enabling the estimation of milk parameters of the total milk yield on the base of results obtained in evening and morning milking was calculated as well. Values of coefficients of determination (Rsup2/sup) of these equations ranged from 0.803 (F) to 0.960 (TP) and from 0.718 (F) to 0.966 (TP) for intervals of 11:13 hours and of 10:14 hours, respectively.