Background and Aim: Milk yield (MY) is one of the main factors that affect the economic profitability of dairy farms. Thus, increasing the MY per animal and decreasing the feed cost can lead to economic gains, so the objective of this study was to evaluate the effect of dry period length (DPL), days open (DO), and days in milk (DIM) on the productivity and profitability of dairy cow farms.

Materials and Methods: Data used in this study were taken from 3095 lactation records of Friesian dairy cows of private and governmental sectors. The data were classified into 4 DPL categories: DPL₁ <45 days; DPL₂ 45-60 days; DPL₃ 61-75 days, and DPL₄ >75 days, 3 DO categories: DO₁ ≤90 days; DO₂ 91-110 days and DO₃ >111 days, and 8 DIM categories: DIM₁ 180-210 days; DIM₂ 211-240 days; DIM₃ 241-270 days; DIM₄ 271-300 days; DIM₅ 301-330 days; DIM₆ 331-360 days; DIM₇ 361-447 days; and DIM₈ >447 days.

Results: The average net profit (NP) was significantly different (p<0.05) among different categories of DPL, DO, and DIM in both production sectors, where high estimates of NP were calculated for DPL₃ (30667.3 EGP), and it was the lowest for DPL₁ (19690.6 EGP). DO₂ had the highest NP (30754.1 EGP), while DO₃ had the lowest NP (24875.5 EGP). DIM₃ had the highest NP (29569.3 EGP), while DIM₈ had the lowest NP (19528.4 EGP).

Conclusion: Finally, we can conclude that DPL 61-75 days, DO 91-110 days, and DIM 241-270 days had the highest level of total MY, total return, and NP. Private dairy cow farms achieve a higher level of NP than governmental ones under subtropical Egyptian conditions.

Keywords: 305-milk yield, days in milk, days open, dry period length, Holstein Friesian, profitability.