| The present study consisted two parts. The first part studied the effects of energy sources and calcium salt of conjugated linolic acid (CaCLA) supplemented in the diet of dairy cows on milk fat yield and fatty acids composition. The second part investigated the effects of parities on production trait in Holstein cows and estimated lactation curves by Wood models.Part one: Four Holstein cows were utilized in a two factorial 4×4 Latin square design. The four treatments were supplementing corn + CLA, calcium fatty acids (CaFA) + CLA, CFA, or corn in the basal diet of the cows. The results indicted that the responses of milking performance varied with the two supplemental energy sources. Milk yield (P<0.01), protein yield (P<0.01), milk protein content (P<0.01), and lactose yield (P<0.01) increased significantly when corn was supplemented, while milk fat content (P<0.01) and yield ( P<0.05 ) was increased significantly when FACa was supplemented. Yield of long-fatty acids in milk fat was increased significantly (P<0.05) by adding CaFA to diet. Milk fat percentage and yield were not altered greatly by adding CaCLA to the diet.Part two: Sample day observations of Holstein cows in dairy farm of Jiabao Group Jinan were evaluated to determine contributions to variation among milk, fat, and protein yields; fat and protein percentages; and somatic cell score. Milk, fat, and protein yield lactation curves were estimated by Wood model. The results indicted that mean yields for sample days were the greatest during the second parity and were earlier than the normal milk peak parities. Somatic cell score for sample days increased with parity. Milk peaks were ahead of schedule and persistency decreased in lactation with parity. Milk yields lactation curves were well estimated by Wood model and Goodness of fit was 0.87 to 0.91, whereas estimated milk fat and protein yields lactation curves were not so goog as milk yield, Goodness of fit was 0.65 to 0.91.
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