Some Sources of Variation in Total Plasma Cholesterol Levels in Dairy Cattle

Open Access
Publisher Website
Google Scholar
Abstract
Variation in total plasma cholesterol levels was studied in four groups of dairy cattle of various ages and physiological states, in which three blood samples were collected from each of 12 animals at designated intervals during the day, on each of four alternate days. The effects due to variation among animals constituted 97.07% of the total variance. Short-term variation in blood sampling, represented by daily and diurnal rhythm effects, constituted 2.79% of the total variance; whereas, assay error effects contributed only 0.14% of the total variance. The physiological state of the animal as expressed by age, parturition, pregnancy, and lactation, had a profound influence on total plasma cholesterol levels. Daily variation in total plasma cholesterol values was highly significant statistically, yet contributed less than 1% to the total variance. No significant diurnal rhythm effect was noted, indicating that blood samples for total plasma cholesterol assay could be collected at any time during the day. One cholesterol determination per blood sample and one blood sample per animal were found to be sufficient for routine investigations. Levels of total cholesterol in 11 cows at the time of parturition were significantly lower than prepartum or postpartum levels.