الفهرس 
Factors affecting mil yieldOnly 14 pages are availabe for public view
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Abstract
Data used in this study were obtained from milk records of Friesian cows kept at two locations, first Dalla farm which is it far from Cairo to Alexandria City by 130 kilometres, Egypt.in Egypt and 130 km from Cairo city, during the period from 1987 to 1992. A total of 2422 lactation records of cows producing for at least 100 days were used. The number of cows, sires and number of daughters per sires were 706, 308 and 7.8, respectively. Second, German farms in one sub-region in Osnabriick, which it is in Germany, during the period from 1979 to 1993. A total number of 27756 lactation records of cows producing 100 days were used. Number of cows, sires and number of daughters per sires were 9069, 659 and 39.72, respectively. The purpose of this study were: (1) to estimate non-genetic factors affecting initial milk yield (IMY), 305 day milk yield (305dMY), total milk yield (TMY), lactation period (LP) and calving interval (CI) such as month or season of calving, year of calving and parity, (2) to estimate phenotypic and genetic parameters for the same traits studied, (3) to estimate sire transmitting ability for the different traits studied and (4) to estimate genetic and phenotypic for different traits. The results obtained from the analysis of the data could be summarised as foIIows: I- Dalla Farm 1- Least squares means of IMY, 305dMY, TMY, LP and CI were 881 kg, 4530 kg, 5032 kg, 3 15 d and 380 d, respectively. 2- Month of calving had a significant effect on different traits studied. In addition, winter and spring calvers had the higher values in all traits studied than summer and autumn calvers. 3- Year of calving had a highly significant effect on different traits studied. 4- Parity had a highly significant effect on different traits studied. The present results indicate that IMY, 305dMY and TMY reached maximum level in the fourth lactation. Also, the longest LP obtained in the same lactation, while the longest CI obtained in fifth lactation.