Pakistan Journal of Biological Sciences1028-88801812-5735Asian Network for Scientific Information10.3923/pjbs.1999.60.64AtilHulya 1199921A total of 2897 lactation records of Holstein Friesian cattle from the fields of Dena Farm in Egypt from 1987 to 1993 were used to study relationships of days open (DO) and days dry with milk production. The effect of month and year of calving, sire and cow within sires were also investigated. Month of calving, year of calving, sire and cow within sires significantly influenced milk production. Including DO and dry period (DP) as a polynomial of second degree of production were significant. The partial linear and quadratic regression coefficients of 305 day milk yield on DO and DP were significant being 7.59±0.40 kg/d and -0.37±0.00 kg/d2, respectively for DO and -9.37±0.54 kg/d and 0.02±0.00 kg/d2, respectively for DP. Therefore, reduction of DO and DP are a desirable goal of dairyman. Heritability (h2) estimates for 305 day milk yield, DO, DP were 0.13±0.05, 0.00 and 0.00, respectively. Adjustment of lactation milk yield for DO will not involve genetic influence on milk yield.]]>Abdel-Bary, H.H., M.M Mahmoud, H.I. Zaky and A.A. Mohamed,199229229253Afifi, A.E., M.H. Khalil, M.F. Abd El-Glil and Z.A. Sultan,199229197214Bar-Anan, R. and M. Soller,197929109119Berger, P.J., R.D. Shanks, A.E. Freeman and R.C. Laben,198164114122Dias, F.M. and F.R. Allaire,198265136145El-Chaife, O.M.,19811981Everett, F.W., D.V. Armstrong and L.J. Boyd,196649879886Funk, D.A., A.E. Freeman and P.J. Berger,19877023662373Ghanem, Y.S., M.A. Mandour, K.M. El-Bayomi and A.E. Badran,1991810711071Hansen, L.B., A.E. Freeman and P.J. Berger,198366293305Henderson, C.R.,19539226252Harvey, W.Y.,19871987Kaya, L.,19661966Khattab, A.S. and A.A. Ashmawy, 1988105300305Khattab, A.S. and A.A. Ashmawy,199027161170Khattab, A.S. and Z.A. Sultan,1991108349354Khattab, A.S., M.M. Mabrouk and A.M. El-Hakim,198713286297Khattab, A.S., M.F. Abdel Glil and A.Y. Salem,19942483498Laben, R.L., R. Shanks, P.J. Berger and A.E. Freeman,19826510041015Lobo, R.B., F.A.M. Duarte, A.A.M. Goncalves, J.A. Oliveira and C.J. Wilcox,198439157163Louca, A. and J.E. Legates,196851573583Makuza, S.M. and B.T. McDaniel,199679702709Mansour, H.,1992378594McDowell, R.E.,1972Pages 711Pages 711Abdel-Glil, M.F.,19962134793492Mostageer, A., Y.A. Afifi, M.A. Morsy and A.A. Nigm,1987104383390Olds, D., T. Cooper and F.A. Thrift,19796211401144Onenec, A.,19971997Ragab, M.T., A.S. Abdel Aziz and H.M. Morad,197313119Sadek, M.H. and A.E. Freeman,199275279287Sallam, M.T., F.M. El-Feel and A.S. Khattab,199012521539 Schaefer, L.R. and C.R. Henderson, 197255107111Soliman, A.M., I.F. Marai and S.M. EI-Menshaway,19943214891510Swiger, L.A., W.R. Harvey, D.O. Everson and K.E. Gergory,196420818826Thompson, J.R., A.E. Freeman and P.J. Berger,19826515621577Weller, J.I., M. Han and S. Bar Anan,19861986Yener, S.M., N. Akman and A.S. Khattab,19981998Yener, S.M., N. Akman and A.S. Khattab,19981998