الفهرس 
Lactation curve of milk productionOnly 14 pages are availabe for public view
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Abstract
Data for the present study were obtained from 1955 – 2201 lactation records during the years from 2005 – 2007, at Dina Farms which lactated eighty kilometers north of Cairo, Egypt. The data were analyzed statistically and results showed that: Order of lactation and year of calving had a significant effect on all factors affecting the shape of lactation curve, its components and persistency estimates measured by ratio methods. Age at first calving, calving interval and days open had a significant effect on all traits except persistency measured based on ration of partial 200 days. Dry period and season of calving had a significant effect on all traits and persistency except the rates of ascending and descending of the lactation curve. Low heritability estimates were obtained for age at first calving, while high and moderate heritability estimates were obtained for lactation length and total milk yield. Phenotypic and genetic correlations between different factors affecting the shape of lactation curve, its components and persistency were estimated, high positive genetic and phenotypic correlation was obtained between total milk yield and days open, while this correlation was negative as correlation between age at first calving and 305 – day mature equivalent milk yield and weak correlation was obtained between age at first calving and low milk yield.