Effect of Dietary Protein and Sunflower Meal on Blood Serum Cholesterol of Dairy Heifers

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Abstract
Effects of dietary protein and protein supplement on cholesterol in blood serum of Holstein heifers were determined in 2 replications of a 2 .times. 2 factorial study on 16 animals. Treatment variables were 2 crude proteins, either low (12%) or high (20%) and 2 protein supplements with soybean meal or sunflower meal. Rations contained 21% acid-detergent fiber supplied by sunflower hulls. Free serum cholesterol (17.9 mg/100 ml) from heifers consuming high protein rations was lower than that of animals on low protein (28.2 mg/100 ml). The same degree and direction of interaction between quantities of protein and sources of protein were exhibited by total and esterified cholesterols. Concentrations of total cholesterol were not different among treatment groups but quadratic responses with weeks of trial were significant. Lowest free cholesterol (16.4 mg/100 ml) was recorded by heifers on sunflower meal on high protein ration. Composition of serum proteins was not altered by sources or amounts of protein in the ration. Weight gains and growth efficiency (gain/feed) were higher in animals on high protein, irrespective of the protein supplement.