INVESTIGATIONS ON THE REPRODUCTIVE STATUS OF DAIRY-COWS - 1 - UNIVARIABLE ANALYSIS OF RESULTS AND CLASSIFICATION OF OBSERVATIONS

Fifteen commercial dairy farms housed in cowsheds and which met a lact ational yield criterion were visited five times at regular intervals o ver a period of one year: Data were obtained to describe fertility in terms of the service period, the open period and the number of service s pel conception as dependent variables. Independent variables compris ed once recorded clinical and biochemical blood parameters, the concen tration of sodium in urine and the antibody titers of relevant infecti ous agents which were monitored at each visit. The data recorded were classified into observation classes 1 to 10, with 1 to 4 representing non-pregnant cattle and 5 to 10 pregnant cattle. The mean open period (143.6 +/- 1.56) were favourable when compared to published data. Excl uding the antibody titers, the majority of the quantitative and qualit ative parameters showed significant interactions between classes and f arm site. There were also significant interaction between farm site an d class. Significant differences between the global mean values and th e mean values of the clinical and biochemical parameters for classes 1 to 4 and class 10 were observed, particularly in class 1 and 2. Blood urea was distinctly lower during the first 40 days post partum which may indicate a lack of protein supply or a failure of protein mobilisa tion to yield further energy.