Abstract
A total of 8426 dairy records were randomly selected from 11 dairy herds which had been accepted the request to participate in this study to explore the influence of herd size on the productivity and economic efficiency of the Holstein dairy cows. Records were collected during the period started from 1st January 2016 to 30 January 2017. The localities which the dairy farms were located are El-Beheira, Alexandria and Kafr El-Sheik provinces. All the investigated farms were belonged to the private management system. Herd size was classified into three categories: small (from 100 to 500 cow), medium (501 to 900 cows), and (more than 900). The obtained results showed that total milk yield of the medium size herd (5001-900 cow) was significantly (10080.02±55.51 kg; P<0.05) greater than the herd size for small and large size herd which yielded 8232.79±100.32 kg and 9380.60±58.89 kg, respectively. However, 305-milk yield of large herd size was significantly (8743.95±44.23 kg; P<0.05) greater than the comparable small and medium size herds. In terms of the reproductive performance, small and medium size herds required number of service per conception more than (3.36±0.08 and 3.53±0.06; P<0.05) the large herd size. In terms of the return parameters, total returns and net return of medium size herd were greater than those for small and large size herd.

Key words: Holstein cows, Herd size, Economic, Productive, Efficiency